Ion-Propulsion Craft Reaches The Moon

Rollie Hawk writes "It ain't warp speed, but it's exciting new technology at work! The European Space Agency put an ion-propelled rocket into lunar orbit today. While not much horsepower is generated, this method of propulsion could be ideal for travel in near-weightless space as it does not require any combustion to occur."

Comments

Warp ?

[Killjoy_NL]

"It ain't warp speed"

But to me, it's a good step forward :)

Re:Warp ?

[uberdave]

I guess that would make it impulse, then :-)

Peak of eternal light

[Rei]

I think what is most interesting is one of the destinations they're going to visit - the peak of eternal light. Perfect spot for a moonbase - constant sunlight instead of 2 weeks of light and 2 of darkness, water ice likely in nearby craters, and temperatures warm enough that you might be able to get by with passive solar heating alone.

Re:Peak of eternal light

[binarybum]

man, screw your moon base. Perfect place for a five-star resort. This sounds like prime realty. The europeans should stake a claim to it and auction it off as land for when the moon is colonized. The price this would go for would probably fund a colonization project, oh and a moonbase - somewhere else.

Re:Peak of eternal light

[RebelWebmaster]

I'm pretty sure there are international treaties banning any country from claiming extraterrestrial land for their country.

Re:Peak of eternal light

[Colonel Cholling]

I'm pretty sure there are international treaties banning any country from claiming extraterrestrial land for their country.

International treaties? BWAHAHAHAHAHA!

Re:Peak of eternal light

[Naffer]

I'm also pretty sure that no one could do anything about it if the U.S. built a base and claimed to own 10 miles in every direction around it.

Re:Peak of eternal light

[AstroDrabb]

Sure they could. China could send up a "scientific mission" that just happens to fail and crash into the US Moon base. Do you really think the USA would start WWW (III/IV/V) over it? Humm, if the president at that time happens to be a Bush, maybe "we" would.

Re:Peak of eternal light

[Richard_at_work]

Country yes, corporation or person, no. Get up there and plant your stake, no international treaty is in your way.

Re:Peak of eternal light

[daniel23]

Unless, of course, it was a Chinese/European consortium who built the base.

Re:Peak of eternal light

[uncoveror]

No one on earth could do anything about it, but not everyone who goes to the moon is from earth. The Zhti Ti Kofft would probably destroy any U.S. base in no time, or at least conquer it, and say ALL YOUR BASE ARE BELONG TO US!

Re:Peak of eternal light

[yobbo]

You honestly think the US will remain the leading superpower forever?

You poor thing.

Re:Peak of eternal light

[Lally Singh]

We'll see what my nukes say about that! ha!

Re:Peak of eternal light

[Jaywalk]

I'm pretty sure there are international treaties banning any country from claiming extraterrestrial land for their country.

Sorta. You're probably thinking about the Lunar Treaty. While that treaty only prohibits the actions of states, I doubt that a private industry would be able to claim moon land with any authority. Still, Article 9 specifically grants the authority to build moon bases provided "that they do not impede the free access to all areas of the moon by personnel, vehicles and equipment of other States Parties conducting activities on the moon."

Sure, you can build your luxury hotel, but you're never going to be able to keep out the riff-raff.

Re:Peak of eternal light

[PKPerson]

When the U.S. makes plans to set up a moonbase, it will certainly claim a large section of moon-realty. What will happen when we are fighting over land on the moon, or will the U.S. just take it all, and sell it to others. Now, some orginization like like UN should split it up fairly, mabey giving plots of land based on contry size or population.

I wonder if they geet good pings from the moon?

Re:Peak of eternal light

[TheDugong]

You forgot...

<bushvoice>Now watch this drive!</bushvoice>

Re:Peak of eternal light

[tonyr60]

That would be the same international treaties that prohibit aggression against other countries with good cause and the backing of the UN?

Re:Peak of eternal light

[phoenix321]

Of course there's no army to back this up. But if you built a base on the moon and claim anything inside plus 5 km around the perimeter your own property, it *should* be yours.

It's as simple as that: if you made new land habitable, it should be yours. Maybe I'm a little romantic here, but making some land habitable comes first, then it becomes your property, then you defend it against possible intruders.

As long as there is enough land left on the moon, there will be no conflicts, if the people involved have the slightest hint of moral obligatons left. What they may or may not have anymore, considering this will be 20 years from now at a minimum.

In general, humans all alone on a vast amount of land, totally devoid of people, in a situation of need and struggle, they tend to build friendly relationships instead of murdering each other for a piece of land. Supply and demand. If there's enough resources, land in this case, left, people don't value that land high enough to commit crimes against their moral standards. Example: Australia. Even outlaws built a society, because they couldn't survive otherwise.

Sooner or later, people will fight their wars in space, of course. But not as long as there's millions of square kilometres left for anyone to take.

Re:Peak of eternal light

[MrScience]

I don't think that little agreement matters anymore...

Re:Peak of eternal light

[drpatt]

The moon doesn't even have a real estate commission. How am I supposed to get licensed to sell property up there?

Re:Peak of eternal light

[sadler121]

I wonder if they geet good pings from the moon?

Hell, we can't even get good pings from satallites, and those are in orbit, the moon is a lot further out...

Re:Peak of eternal light

[Anonymous Coward]

Example: Australia. Even outlaws built a society, because they couldn't survive otherwise.

In general, humans are arrogant, self-interested and convinced of their own superiority.

Example: Australia. Landing immigrants once considered the indigenous people nothing more than animals, destroyed their hunting grounds, forced them off their lands, killed them and stole their children (this last thing was still happening in the mid-1900's).

I'm sure I could name a few other terrestrial countries where similar things have happened. In a few hundred years, as a space-faring species, we might be able to name a few extra-terrestrial sites as well - unless we come across a more-powerful adversary who kicks our collective asses back into the Stone Age.

Re:Peak of eternal light

[corbettw]

You honestly think the US will remain the leading superpower forever?

Well, if we established a moon base, it would go a long way to keeping us on the scene for much longer than we could expect to now.

Of course, even Rome eventually fell, so it's a given that we'll pass the torch to someone else someday.

Re:Peak of eternal light

[Scott7477]

Here is the text of the following link(www.iafastro-iisl.com/additional%20pages/Stat ement_Moon.htm) which quotes the relevant part of the 1967 Outer Space Treaty: Of the International Institute of Space Law (IISL) On Claims to Property Rights Regarding The Moon and Other Celestial Bodies Claims to own the Moon or parts thereof by private parties have been made for many years, but so far such claims have not been taken very seriously. However, this could change, as "deeds to lunar property" have started to appear, raising the opportunity for individuals to be misled. In addition, the scope of such claims has been extended recently to other celestial bodies. Thus, the Board of Directors of the International Institute of Space Law (IISL) has concluded that there is a need for a statement regarding the current legal situation concerning claims to private property rights to the Moon and other celestial bodies or parts thereof. While this issue is only a small part of a much broader context surrounding private sector activities on the Moon and other celestial bodies, this statement is limited only to the topic of claims to private property rights to the Moon and other celestial bodies or parts thereof. Article II of the 1967 Outer Space Treaty states that "Outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means." The object and purpose of this provision was to exclude all territorial claims to outer space, including the Moon and other celestial bodies. As of March 2004, the Outer Space Treaty has been ratified by 98 nations, and signed by an additional 27 countries. Article VI of the Outer Space Treaty provides that "States bear international responsibility for national activities in outer space, including the Moon and other celestial bodies, whether such activities are carried on by governmental agencies or by non-governmental entities", that is, private parties, and "for assuring that national activities are carried out in conformity with the provisions set forth in the present Treaty". Article VI further provides that "the activities of non-governmental entities in outer space, including the Moon and other celestial bodies, shall require authorization and continuing supervision by the appropriate State Party to the Treaty." Therefore, according to international law, and pursuant to Article VI, the activities of non-governmental entities (private parties) are national activities. The prohibition of national appropriation by Article II thus includes appropriation by non-governmental entities (i.e. private entities whether individuals or corporations) since that would be a national activity. The prohibition of national appropriation also precludes the application of any national legislation on a territorial basis to validate a 'private claim'. Hence, it is not sufficient for sellers of lunar deeds to point to national law, or the silence of national authorities, to justify their ostensible claims. The sellers of such deeds are unable to acquire legal title to their claims. Accordingly, the deeds they sell have no legal value or significance, and convey no recognized rights whatsoever. According to international law, States party to a treaty are under a duty to implement the terms of that treaty within their national legal systems. Therefore, to comply with their obligations under Articles II and VI of the Outer Space Treaty, States Parties are under a duty to ensure that, in their legal systems, transactions regarding claims to property rights to the Moon and other celestial bodies or parts thereof, have no legal significance or recognised legal effect. Note: Notwithstanding matters covered in the above Statement, the Board of Directors of the IISL recognises that other private activities on the Moon and other celestial bodies are permitted. Article VI of the Outer Space Treaty affirms that non-governmental entities, including private indivi

Re:Peak of eternal light

[fr2asbury]

So basically we need to dig our moon bases into the ground, because if they have walls, suddenly you're impeding the free access of vehicles and the like to parts of the moon.

"I'm sorry, you can't drive through our dining hall."
"But the treaty says . . . !"

Re:Peak of eternal light

[JudgeFurious]

Well of course nobody thinks the US will remain the leading superpower forever. Nobody who gives it any thought at least. At one point damned near ever real "power" on the earth was located in Europe. Now there's not a single nation in Europe that equals the United States. Together they do the job quite nicely though.

That's just it. Despite what we've seen from the former USSR there is life after being a superpower. Most Americans aren't living under the impression that the ride's going to last forever and only the small percentage of real paranoids think it has to at any cost.

I can't wait for us to return to being one of the pack so to speak. Then maybe our leaders wouldn't feel like it's necessary to station troops all over the planet. A military that can protect the United States is fine by me. An economy in the upper half of the world is more than many could ask for. Damn I'd like to see us get out of the world police business and back to the "working on making America better" business.

Re:Peak of eternal light

[hey!]

It's as simple as that: if you made new land habitable, it should be yours. ...

As long as there is enough land left on the moon, there will be no conflicts, if the people involved have the slightest hint of moral obligatons left.

The words you are looking for here are: Lockean proviso. According to Locke, it is permissible to privatize a resource that you improve, provided you leave as much of the same (unimproved) quality for others. For example, you can privatize an oasis in the desert, so long as it is not the only one within reach of a caravan route.

Of course Locke then went on to argue that money changes this basic moral prinicile, but that's a story for another day.

Re:Peak of eternal light

[CaptBubba]

Given that the closest a point on the earth and a point on the moon come to each other is around 370,000km that's a round trip time of around 2.5 seconds, plus any routing lag.

On a more serious note, what would this mean for those on the moon as far as interaction with the world? During Apollo you had a couple of people there for a few days with rigourously defined schedules, but how about long term or civilian astronauts? I wonder if the whole internet would be accessable, or if they limited the data to a predefined set of things, such as the New York Times, updated daily.

Re:Peak of eternal light

[Anonymous Custard]

Of course, even Rome eventually fell, so it's a given that we'll pass the torch to someone else someday.

Maybe so, but Rome didn't have no moon base did they now?

Re:Peak of eternal light

[mi]

I can't wait for us to return to being one of the pack so to speak.

So, do you want your country to become weaker, or its competitors (friendly and otherwise) to become stronger?

Then maybe our leaders wouldn't feel like it's necessary to station troops all over the planet.

It is never necessary, but often desirable. As long as it is possible, we'll keep doing it. As Romans did, BTW -- our relationship with Europe is not unlike that of Romans and Greeks.

Re:Peak of eternal light

[Dr. Spork]

I think you're right, and I know it's off topic, but though I detest our present foreign policy, I don't want some other country to be a superpower either. Well, maybe some sane country like Norway or Canada, but China or India seem far more likely candidates.

I think after USA falls apart, the world should get together and have a "no superpowers" rule. But then again, there were no superpowers at the 70 years ago, and things didn't turn out so well. Europe sort of punched itself out, somebody else took over. We might not be far from that right now.

Re:Peak of eternal light

[freedom_india]

I wish some good-natured extra-terrestrial civilisation land on Earth, kick our asses, teach us to respect each other first before we again dare to send out Pioneers or Voyagers...

But then Bush would push for a ET-PATRIOT Act, Ashcroft would be back again in Job and powell would go abegging the UN for an attack on K'laatu....sigh... some things never change...like
1. Bush is a texas tiger.
2.Bush is NOT a UN pussy...

Re:Peak of eternal light

[sonicattack]

Well, maybe some sane country like Norway or Canada,

And just how long would they remain "sane" when living with the status as "superpower"? How long before they too turned paranoid, or pissed off somebody and really got something to worry about?

Has there been studies on how even being targeted with nuclear weapoins for prolonged periods affects human psychology, and in the extent, foreign politics?

There was said something about how power corrupts.... Perhaps every state should have plans for how _not_ to grow too large or powerful. An international agreement to keep world domination in check. (No, a perpetual state of war isn't it. :)

Re:Peak of eternal light

[shaitand]

I thought the US already claimed the moon when we first planted our flag there? Just as explorers did in times of old when discovering and claiming new lands for their nation?

Also to the best of my knowlege the only ones to dispute this claim were the Russians, and the Russians lost the cold war buddy.

If you think we USians can't hold that much territory you obviously haven't read the new airforce "space superiority" proposals (which are also in contradiction to your pittly international treaties).

Re:Peak of eternal light

[mcrbids]

Well of course nobody thinks the US will remain the leading superpower forever

So... what's next? India? China?

The thing about the US is that it's... damn big. I read a statement once that makes it clear.

In the US, they think 100 years is a long time. In Europe, they think 100 miles is a long way.

Just to highlight a detail, it takes 12 full hours averaging at good highway speeds (65 M.P.H.) to cover the 786.5 miles (1,265.74 kilometers for you Europeans) just to travel the length of ONE U.S. state.

It's a trip comparable to traveling from Paris, France all the way to Vienna, Austria! How many countries would you travel on such a trip?

Some more facts:

Europe 3,837,000 Sq Miles (9,938,000 Sq. Km)
North America 9,365,000 Sq. Miles (24,256,000 Sq. Km)
USA (not Candada or Mexico) 3,618,770 Sq Miles (5, 823,845.79)

In short, the US of A covers a landmass similar to all of Europe. In area, only the USSR and Canada have more, and much of their land is desolate and cold.

Let's not get into politics or economics. Eventually, I'm quite certain that someday the USA will no longer be a "super power". All things come to an end, someday. But, it will probably take a while.

Re:Peak of eternal light

[shaitand]

"Now there's not a single nation in Europe that equals the United States."

True enough.

"Together they do the job quite nicely though."

That's fairly amusing, even if far from true.

"Then maybe our leaders wouldn't feel like it's necessary to station troops all over the planet."

My friend, I truely hope you aren't as a snowed as you sound. Even most of those who call us warmongers these days haven't gotten the big picture. All of those places that we've "policed" we are OCCUPYING not policing, there is a rather substantial difference. The switch in terms keeps the rest of the world from getting in an uproar and calling us war mongers.

Think about the pattern, we "try to help" a small strategic (in some fashion, economics, advantageous location, threating to us, resources, etc) nation. Oh goodie us, we are such good dudely do rights we are. So we send troops to "help", next thing you know we are "helping" oversee a new puppe... err democratic government.

Oddly enough, our troops actually NEVER leave. Oh their numbers reduce once the pup... err democratic government is established and in power but our presence is always kept in place. Hell we still keep massive deposts of military resources in GERMANY.

We aren't merely the super power of the moment my friend, we are Rome and more or less rule the known world. Rome didn't rise in a day, and Rome didn't fall in a day, rather it took centuries for it's power to be chipped away.

Like Rome we are sure to fall, I'd prefer it sooner than later but don't see it as being something likely to happen during the lifetime of anyone alive today.

"A military that can protect the United States is fine by me. An economy in the upper half of the world is more than many could ask for."

Agreed on that.

"Damn I'd like to see us get out of the world police business and back to the "working on making America better" business."

I can not exactly say I'd like to see us get "back" to it, since that would imply that was the aim of our nation at some previous point in time. But in general I think that would be a good direction to start going at some point.

Re:Peak of eternal light

[cHiphead]

Yet eventually you DO run out of unprivatized area with this principle, do you not? It is self defeating and the common good is more important than the profit of one man/group.

Basic moral principles taught from birth: be nice, share.

cheers.

Re:Peak of eternal light

[cHiphead]

I disagree, I think it REALLY stopped mattering when THIS happened.

Cheers.

Re:Peak of eternal light

[Anonymous Coward]

Unfortunately this small percentage of real paranoids are the ones calling the shots in the white house right now...

Re:Peak of eternal light

[JollyFinn]

SOMEBODY SET UP US THE BOMB.

Re:Peak of eternal light

[LucidBeast]

Some comparisons

• Currently European Union has more citizens (~400M) than United States (~280M), but US I think has younger population. Europeans aren't having enough immigration or kids.
• European Unions economy is a bit bigger than US economy, but US has still more GDP per capita. US spends larger portion of its GDP on Defence (or Offence I guess now days), also Europeans have longer vacations and shorter work weeks that eat up the GDP a bit. Quality of life for citizens is hard to measure.
• Europe doesn't have unity on what it should be: lose pack of nations concentrating on economic issues or more of a federation counter balancing United States.
• All Europeans have health care of some sort. 40 million US citizens don't
• EU citizens have higher life expectancy than US citizens despite US spending more on health care per capita
• EU kids score better in math and science than US kids
• EU economy has been growing slower than US economy

I'm don't think US is a failing empire, but unless the emphasis in US politics changes from gay rights, abortion, religion vs. science and god in pledge I think it will run into trouble. Also the huge military emphasis and spending is a taxing even to a rich nation like US.

Also Europe has its problems and it's not a Utopia, so please don't take this comparison that way.

Re:Peak of eternal light

[dcw3]

Oddly enough, our troops actually NEVER leave. Oh their numbers reduce once the pup... err democratic government is established and in power but our presence is always kept in place. Hell we still keep massive deposts of military resources in GERMANY.

Ummm, didn't we leave the Phillipines, France, and Iran?...I'm sure that there were others. As a cold-war vet. who spent six yrs. in Germany, I find your assertion that we're still "OCCUPYING" simply naive. Most of the places I used to work at have been shut down because there's no longer a need for them. Others are still necessary, and the Germans are smart enough to understand that they need us there (FWIW, I've got German relatives), and if we were asked to leave, we would. In many places where locals protest the remaining presence of the U.S. military (Seoul Korea, Okinawa Japan for a couple of examples) it's more about economics than anything else...the land has become so valuable that they want it back. Having also spent six years in Korea, I'd hardly call the number of troops we've got there "OCCUPYING"...it's barely a presence (currently ~34000...few of which are in combat roles).

Re:Peak of eternal light

[R.Caley]

When the U.S. makes plans to set up a moonbase, it will certainly claim a large section of moon-realty.

Consider what happened in the antarctic. The US is the one player who didn't make a land claim. The antarctic is a far more useful bit of terretory than the moon.

In the modern world you don't need to hold terretory. Indeed, that is basicly why the European empires disolved -- they became far more expensive to hold and run than they were worth. The USA's effective empire in central and south America has given them the advantages of empire (consider where the phrase banana republic came from) for a relatively small expendature in gunboat diplomacy, bribary, political intervention etc.

Basicly, if the USA found something worthwhile having on the moon (be it raw materials or an observation platform or whatever), it could just go for it. They wouldn't need to claim ownership of the land, just make sure they had the strength on-earth to dissuade anyone from putting their oar in.

Re:Peak of eternal light

[dkleinsc]

How about a theme park instead?

"We're whalers on the moon, we carry a harpoon ..."
With no apologies to Matt Groening

Re:Peak of eternal light

[kimmo]

Oh yes, there are international treaties for demilitarization of space, environmental matters, international trade, international laws, universal human rights etc.

Then again, there are certain countries which interpret stuff quite liberally and shortsightedly, on a we-want-this-and-that now basis.

Re:Peak of eternal light

[ViolentGreen]

I'm don't think US is a failing empire, but unless the emphasis in US politics changes from gay rights, abortion, religion vs. science and god in pledge I think it will run into trouble.

That's not the emphasis on politics. Those are polarizing issues which the parties try to use to their advantage. They are small issues in the overall picture.

Re:Peak of eternal light

[JudgeFurious]

On the US being big I know exactly what you're talking about. Before the first Gulf war a friend of mine and I drove out to San Diego to pick up a bunch of stuff for his sister who was in the navy and had her discharge halted at the last moment. She of course had an apartment off base and a pile of personal posessions that she had no place to store. There were a bunch of better solutions than going to get the stuff but my friends dad asked us to go pick it up and we were up for a road trip.

Turned out to be a semi-bad plan. We live in Houston Texas. Know what? When you drive from Houston to San Diego and you reach the halfway point you're still in Texas.

Re:Peak of eternal light

[JudgeFurious]

I don't really care how it happens (The US gets weaker or the rest of the world becomes stronger) because in the end it's the same thing.

I simply believe that a US military presence in countries like South Korea, Japan, and of course Germany is no longer needed. Prior to WWII we didn't have soldiers stationed in those countries (though of course we had them in the Philipines as we owned them at that time) and now that things in those areas are more than stable I see no reason to continue it.

Sure North Korea is a friggin nightmare but honestly isn't that the problem of the nations in that particular region? What keeps their army from coming south again? Is it the physical presence of US troops stationed in the south? I no longer think that's true. The players in that part of the world are interdependant now. NK's biggest (and maybe only) friend is China. China's biggest market is the US. SK's biggest friend is of course the US and economically we're tied tightly to China. Nothing is going to happen and if anyone should be hard at work keeping a lid on Kim Il it's China, not the United States.

Japan and Germany can easily defend themselves and both do. The defense budget in the US has been exceedingly large for far too long. I'm not espousing isolationism either. One can be involved in the affairs of the rest of the world to a reasonable and not inflamatory degree without keeping soldiers around the globe. The money spent doing this would be better spent elsewhere.

Re:Peak of eternal light

[PMuse]

It's as simple as that: if you made new land habitable, it should be yours. Maybe I'm a little romantic here, ...

To be sure, when Europe conquered the New World, the greatest tragedy was the near-erradictation of native peoples. However, there were also wars among the settlers and among the parent nations over territory and resources. Those wars alone are reason enough not to repeat that history on the moon.

Left to a free for all, colonists will first settle on the best land. Then on the second-best. Perhaps next even on the third-best. But before anyone accepts the fourth-best, they will have a fight over the first-best.

Re:Peak of eternal light

[PMuse]

As long as there is enough land left on the moon, there will be no conflicts, ...

The Parable of the Milk Bottle

Once upon a time, there was a colony of bacteria living in a milk bottle on a porch step. Because they lived in a land of milk (if not honey), they were fruitful and multiplied. They doubled their number every hour.

The bacteria were also very wise. When they had consumed 25% of all their resources, their leaders began to plan for what their society would do when they ran out of space in the milk bottle. The leaders sent explorers out to find new territory.

The explorers were wildly successful. In only 1 hour, they discovered that there were in fact four milk bottles sitting on the porch step. The people rejoiced at the news of these vast new territories -- 4 times as much space and food as they had in all their history. They promptly colonized the three new bottles.

Question: How long did the bacterial civilization survive? Answer: Exactly 2 hours longer.

Re:Peak of eternal light

[PMuse]

The point is this: Vast new areas of resources are never as vast as they seem. 640K is not enough for everyone. And, unless we want Jeff Goldblum and Wil Smith to plant a virus in our mothership 300 years from now, we had bettered learn that expansion is not a sustainable business plan for humanity.

Re:Peak of eternal light

[bpowell423]

I'm tired of people saying things like 40 million US citizens don't have health care. In reality, the situation is that something like 40 million US citizens don't have health INSURANCE. Now, in many cases, maybe that means they don't get as good of health care as they should. HOWEVER, I DON'T HAVE HEALTH INSURANCE, BECAUSE IT'S TOO FRIGGIN EXPENSIVE! YET, my kids have all their immunizations and regular checkups, my wife has all her regular annual female exams, etc. We have all the health care we need, and, btw, all of our health providers (family doctor, ob-gyn, etc.) give us CASH DISCOUNTS. I DON'T HAVE HEALTH INSURANCE, BUT DON'T THINK FOR A MINUTE THAT I DON'T HAVE HEALTH CARE. IMHO, health insurance isn't the solution to high health care costs, it's the cause. Why else would my health providers give a cash discount... we're both saving money by cutting out the middle man, the health insurance company who is trying to screw us both.

This wasn't a personal rant against the parent poster, I just had to get it out of my system.

Re:Peak of eternal light

[AGMW]

good highway speeds (65 M.P.H.)

Well it's nice to know you're not the tops at everything eh!

You drive so slow, you could drive Miss Daisy.

Re:Peak of eternal light

[sylvandb]

Turned out to be a semi-bad plan. We live in Houston Texas. Know what? When you drive from Houston to San Diego and you reach the halfway point you're still in Texas.

Yeah, Texas is a big state. Of course, Alaska is BIG! Alaskans like to talk about splitting Alaska in two, and making Texas the 3rd biggest state. :)

sdb

Re:Peak of eternal light

[sylvandb]

To be sure, when Europe conquered the New World, the greatest tragedy was the near-erradictation of native peoples.

Oh, stop the politically correct BS!

None of the people living in North or South America when the spanish (or other europeans) arrived had evolved here. They just immigrated earlier. And what did they do with the people that were living here before them? They wiped them out (for the most part) and assimilated the survivors until they disappeared.

sdb

Re:Peak of eternal light

[mi]

The trouble with your (already insightful) thinking is that -- by your own discourse -- our removing of military bases from parts of the world will happen only as a result of the relative weakening of our might.

If we can not afford to keep the bases, yes, we will withdraw them, but then there would be no money to "better spend elsewhere".

Your true motivation -- conscient or sub- such -- however, appears to be more about the "inflammatory" aspect of these bases, rather than their budgetary costs. In other words, your true concern is about the feelings of the foreigners, rather than the needs of the United States. You may be right in that the interests of both are aligned, but do get your priorities straight.

As far as the "need", well, you are right to question the decisions of the generals who -- honest and loyal as they are -- will never voluntarily decide to reduce their domain. But I tend to agree with them. Japan may or may not be able to defend itself, but Taiwan will certainly have a hard time facing off China. 17,600 US Marines in Okinawa present a good counterweight. In Europe, yes, the threat of USSR is gone for now, but Middle East is much closer to Germany, than to Virginia and even if the Iraq war is the last shooting one over there, the cold war with Iran and Syria is not ending soon... The matter with North Korea is also far from over...

Of the places you listed, only the base on the now-Japanese Okinawa causes tensions of any significance. Both South Koreans and Germans are quite content with US military presence despite occasional incidents involving US troops.

The news you should be welcoming, is that we are reducing our presence at those bases without visible deterioration of the might -- much to the chagrin of the hundreds of locals employed by bases.

Re:Peak of eternal light

[corbettw]

Maybe so, but Rome didn't have no moon base did they now?

They also didn't have sharks with frickin' lasers on their heads. What's your point?

Re:Peak of eternal light

[subl33t]

There is also a treaty prohibiting the militarization of space, but that isn't stopping the 800 lb gorilla (USofA) from doing it anyway.

Th US will just ignore any treaty it pays lip service to.

Re:Peak of eternal light

[shaitand]

The troops there aren't in a police capacity, they are there in the capacity of a threat. It wouldn't be much of a farse if the common grunt on the field knew what was going on either.

Re:Peak of eternal light

[PMuse]

...what did they do with the people that were living here before them? They wiped them out...

We cannot justify the killing of the remote children of killers merely because of their ancestors' crimes. Were it so, the next invader of the Americas would be justified in slaughtering me for the crimes of the 1500-1900 colonists.

Killing a people is a bad thing.

Re:Peak of eternal light

[Anonymous Custard]

They also didn't have sharks with frickin' lasers on their heads. What's your point?

My point is that if Rome had established a strategic moon base staffed by ninjasharks with head mounted laser cannons, then we'd all be speaking hyper-talian today.

Re:Peak of eternal light

[OwnedByTwoCats]

I, as an American, think the world would be much better off if the USA were weaker.

Fortunately, the Bush Administration is pursuing fiscal policy aimed at this goal. Cutting the deficit in half by increasing military spending and cutting taxes. We fell for that before. Now the chickens are coming home to roost.

Re:Peak of eternal light

[OwnedByTwoCats]

My wife was somewhat surprised earlier this year; she went to her GP complaining of indigestion and expecting a script for one of the new pills.

What she got, three days later, was a triple bypass operation.

Do you have $60,000 lying around? If your choice is to spend that kind of money, or risk a family member suffering a heart attack at any point in time, which do you choose?

Re:Peak of eternal light

[JudgeFurious]

How is that?

Hypothetical time of course but if the United States chose to close those bases down and bring those soldiers back to the United States, stationing them at some of the many bases inside our borders why would that happen as a result of the weakening of our might?

I can see how an argument might be made that doing this could result in a weakening of our relative might or of our ability to project that might but nothing in the world says that we could not close those bases down for no other reason than "we want to". That's what I'm saying and that's what you're missing.

Close them today, spend the money here in the United States. Simple as that. The size of the military and the amount of money it sucks from US coffers is my primary motivation. Trust me on that.

I do indeed place some concern on the feelings of people in other countries. I don't believe that there's a carved in stone rule out there saying that a large part of the rest of the world must inevitable hate the United States. I know (how could I not know) that "x" number of people across the globe will always have or find some reason to hate America. Someone hates everything. Someone hates puppies and cotton candy somewhere, I swear they do.

Still, there's no reason to go about actively prodding that hatred. No reason to go giving people and nations a reason to be pissed off at us all the time. The United States doesn't "need" a free South Korea. A free South Korea is a good thing. It's the best thing next to a free Korea from top to bottom but it's not one of our needs. Graduating students who are educated is for example one of our needs.

And I'm not saying that the US shouldn't be prepared to stand with those countries if they are threatened. Coming to the aid of a free nation or nations is a good thing to do but those nations should be able to defend themselves first. Providing a military umbrella for other countries at no cost to those countries is a losing proposition.

Japan can defend itself make no mistake about that.

Taiwan is not a country. It's a part of China and eventually Taiwan is going to have to accept that. The war ended long ago and the communists won it. The best they can hope for is a solution not unlike the one Hong Kong managed. They should be hoping that their new "Red flag bearing overlords" want to make every effort not to kill the goose that laid the golden egg and that's about as good as it gets. Maybe, just maybe there's an outside chance that they can prolong this far enough and slip off China's plate but they've got decades to go before that's even on the horizon.

I don't really care if Japan and Germany are good with a US military presence. It doesn't belong there. A German military presence should be enough for Germany. A Japanese military presence ought to take care of Japan.

The Middle East is a whole other can of worms entirely. This is nothing more than the primary view of one shortsighted American I'm sure but I want my country to have nothing to with the Middle East aside from the purchase of crude oil. This is in all reality the only thing that region produces with any value.

I don't want to enslave muslims, I don't want to steal their oil, I don't want to step a dirty western foot on their precious "holy land". I just want to do business with them for a commodity we need that they have. In return they get fat cash and we get "go-juice". End of story. To quote Marsellus Wallace from Pulp Fiction "There is no you and me".

Why in the world we're in the process of trying to turn Iraq into a civilized nation I will never understand. Who the hell cares if Saddam was filling mass graves with the Iraqi people? I certainly don't and obviously niether did they. They'd take a brutal dictator killing them hand over fist over a democracy that we helped build so why bother to try? The answer of course lies with Israel (another extraordinary can of worms).

Re:Peak of eternal light

[mi]

How is that?

Well, you started this subthread with:

I can't wait for us to return to being one of the pack so to speak. Then maybe our leaders wouldn't feel like it's necessary to station troops all over the planet.

This led (and continues to make) me to believe, you want to see US weaken (just relatively or indeed absolutely -- you don't care) as means to achieve the change of mind of our leaders -- the ends that you desire.

Why, in most ages past and even in most places present this kind of opinion would be considered Treasonous... But in our age and place, this view is a sure way to get one a '4 Insightful'. How much better a place do you want US to be?

For your other points, let me be quick. I disagree, that Taiwan is part of China. I wish them the best of luck in their quest for independence and am willing, nay, eager to see US help them at that. Especially since they can and do pay handsomely for the weapons, they are forced to purchase by the unyielding China.

Countries should be able to defend themselves, but facing off the hostile superpowers like ex-USSR or the future China requires the help of a friendly superpower like America.

We need to project might into Middle East to defend all our allies over there (Iraq, Kuwait, Saudi Arabia, Israel) and to prevent them from going at each other. Iraq tried to break the balance, got spanked, but kept contemptuously reneging on its cease-fire obligations, so we had to finish off its regime. Having done that a year ago, we are now trying to establish a Democracy over there because, left ungoverned, Iraq may continue to require invasions often, while Democracy is the sort of government we like and naturally select -- having to start from scratch anyway.

Yes, all we want from Middle East is the ability to buy oil, but -- as the 1970ies crisis has shown -- it is possible for the sellers to agree to stop selling it -- at any price. Our ability to project might into the region helps ensure, that no a-holes with delusions of grandeur will again threaten the world economy to advance a petty cause of theirs.

Last time the cause was the fate of Palestinians, next time it may be France's ban on scarves, Dutch filmmaking, or Germans' pork-ladden (thus un-Islamic) cuisine...

Re:Peak of eternal light

[LucidBeast]

I hope you have insurance that covers catastrophic illnesses like cancer or heart problems so you don't lose your house due to medical bills.

I'm currently living in Europe and I have private insurance here too, but because of the national health care it only costs me about $300 / year, while in states our family of 2 adults and 3 kids had insurance through my wifes job university that cost as $400 / month.

Re:Peak of eternal light

[virtual_mps]

The players in that part of the world are interdependant now. NK's biggest (and maybe only) friend is China. China's biggest market is the US. SK's biggest friend is of course the US and economically we're tied tightly to China. Nothing is going to happen and if anyone should be hard at work keeping a lid on Kim Il it's China, not the United States.

You seem to be laboring under the misconception that wars begin for rational reasons. Do you know who Germany's largest trade partner was prior to WWI? France--and their economic "interdependency" did nothing to avert that war. Both countries burned themselves out and the conflict pretty much ended European dominance in world affairs. Was that war rational? Wars start because some leader is too stupid, scared or short-sighted to not attack somebody. The reality of the situation is that if someone decides for some stupid reason to launch an attack on, e.g., South Korea, it will be too late after the fact to say "gee, we should have had some troops there".

Re:Peak of eternal light

[dsoltesz]

I think the point was that the Lockean proviso can be called up as a justification for wiping out an existing civilization in order to "improve" a resource. The European "improvements" to the Americas is cited as an example. It's not about "political correctness" - it's about learning from history. If the Lockean proviso is a valid justification, then we could have Japan improve the U.S., Germany improve Europe, Israel improve Palestine, the Brits improve Africa, India improve IT, and the Chinese improve what's left...

better article

[teridon]

Nature has a better article here.

Re:better article

[macdaddy357]

That one's pretty good, but I think this one says it all.

Re:better article

[UnholySauce]

This generates charged ions that are accelerated through a magnetic field and ejected from the rear of the spacecraft, producing a gentle thrust equivalent to the weight of two pennies resting on the palm of your hand.

Perhaps I should RTFA more carefully, but does anyone know how the thing got into orbit in the first place? It sure as heck didn't get off the ground on two pennies' worth of acceleration.

Re:better article

[nofx_3]

Only in an environment with no or little gravity. The problem is that from the surface of earth there is friction and gravity to deal with. Ion propulsion does not have a high enough specific impulse to get something as massive as this probe (or really anything for that matter) into orbit. If you were to actually read the acrticle you would see that it reached orbit on an Ariane IV (a traditional liquid fueled rocket) launched from French Guiana.

-kaplanfx

Is it regular speed?

[xanthines-R-yummy]

Does anyone know how the trip time compared other expeditions? I realize that the longer the flight, the more efficient and speedy this method would be, but I was just trying to get an idea of how fast this thing moves. Could cryogenics and this propulsion technology together land humans on other planets?

Re:Is it regular speed?

[Rei]

Well, apollo took a little over 3 days to accomplish what this craft took a year to do. And it's not neessarily "the longer the flight, the more efficient and speedy this method would be". It's all about ISP. The faster the "exhaust" leaves the craft, the less mass of propellant you need to achieve a given delta-V - and it falls off fast.

In fact, ion drives tend to be rather energy-inefficient. However, they get their energy from electricity, which is renewed either by solar or RTG energy. Since RTGs are extremely energy-dense compared to conventional fuels, and solar cells constantly take in more energy, the penalty for a large amount of electrical waste and much, much larger propulsion system (for a given amount of thrust) is dwarfed by the benefits in terms reduced propellant mass.

Re:Is it regular speed?

[Moofie]

Er, you don't need people-sicles to go to Mars.

Re:Is it regular speed?

[centauri]

Could cryogenics and this propulsion technology together land humans on other planets?

No, especially if you're aiming for extrasolar planets. Ion engines are good for a small payload that can take its time getting to where it's going. Humans (even those in some kind of imagined stasis) need something with a higher thrust to get where they're going in a reasonable time (ie, before cosmic radiation carves up their DNA, or a micrometeor holes their lifesupport system).

Re:Is it regular speed?

[Metryq]

Ion propulsion would be the last drive I'd consider for human transport. It is extremely low thrust, but can maintain drive for a very long time. Take a look at nuclear thermal rockets at nuclearspace.com. The book TO THE END OF THE SOLAR SYSTEM is an excellent primer on the technology and history.

I think it was the TOS Trek episode "Spock's Brain" where Scotty commented on an ion-driven ship, "they could teach us a thing or two!" Right.

Re:Is it regular speed?

[purfledspruce]

The high radiation environment of space keeps us from using this method for humans.

However, it would be quite useful to use this technology to bring cargo to the Moon for possible astronauts to use. For instance, it's possible to deploy an entire habitat--crew quarters, energy producer, perhaps even in-situ resource production ("mining" water-ice for oxygen and hydrogen to feul your return vehicle)--all before we launch humans on a high-energy tracjectory that will get them there in three days, thus avoiding high radiation exposure.

You could do similar things with Mars. Here's a reference done by the Revolutionary Aerospace Systems Concepts part of NASA:

OASIS

It will take a suite of technologies to get safely to other planets, and possibly another suite of technologies to get back.

Re:Is it regular speed?

[AndresFerraro]

I thought one of the key advantages of an ion engine was that the speed of the exhaust would enable it to travel (eventually) at near light speed velocities (ok, maybe 3/4ths). And one of the key drawbacks was that acceleration was painfully slow.

Re:Is it regular speed?

[Locutus]

looks like this took quite a bit longer than the last trip to the moon but, IIRC, wasn't this same tech considered to keep Mir up in orbit? I thought they were considering bolting on a couple of Ion-Propulsion units and shuttle up some fuel ever now and then. I thought there was even a concept of a very long Ion absorbsion line they might extend down toward Earth to almost elimate the need for external fuel. Or I was just dreaming....

LoB

Re:Is it regular speed?

[Rei]

No, nowhere near light speed. SMART-1's ion drive, for example (which was actually a Hall effect thruster, which is a little less ISP-efficient, but not that much) launched xenon atoms at 16,000 m/s. Deep Space 1 did the same at 35,000 m/s. Light travels at 299,792,458 m/s. It's not realistic to go up to relativistic speeds with an ion drive.

Acceleration is painfully slow, but again, that's not necessarily a requirement of an ion drive. It may prove to be a practical limitation, however; we'll have to see.

You can make a (very inefficient) ion drive at home on earth with commodity items - they're called "lifters" (an ironic name, since they typically can barely lift themselves). Lifters work through ionization of air via coronal discharge.

Re:Is it regular speed?

[glenebob]

I thought I understood that any propulsion system can get you to near light speed provided you can keep it in operation long enough. The propellant velocity has no bearing on top speed. Am I all wet here?

Re:Is it regular speed?

[Rei]

Sorry... sometimes I forget that many people here aren't very familiar with rocketry.

ISP is specific impulse. Roughly, ISP in a general (Earth) context is velocity/~9.8. So, given a hydrogen-oxygen rocket with an ISP of 450, this means that its exhaust is leaving at 450*9.8=4410 meters per second, or roughly half of the velocity for a LEO orbit. Compare this to a good ion drive which may give you ~40,000 m/s exhaust (still far from the ~300,000,000 m/s speed of light, mind you).

Re:Is it regular speed?

[bcrowell]

Apollo 11 took 73 hours from the burn that took it out of Earth orbit to the burn that inserted it into lunar orbit. This is actually very close to the time it would take to free-fall to the surface of the Earth from a distance equal to the radius of the moon's orbit. This is pretty much always the case with chemical rockets, which work by doing short burns followed by very long periods of free fall: the time to get there is the time it takes to orbit from here to there. To go to Mars, you can use Kepler's laws, and you find that the time to get to Mars in an elliptical orbit is 0.70 years.

The problem with getting to Mars is fundamentally the radiation. If you send astronauts to Mars on a 0.70-year orbit, without any shielding against penetrating radiation, their radiation dose ends up being on the same order of magnitude as the dose that kills you. This is Not Good :-) There is a variety of ways to get around this:

1. Use electromagnetic shielding. (There was recently a Slashdot article on this. The idea is to use a quadrupole field, which discriminates between high-mass and low-mass particles.)
2. Use really thick material shielding. This requires either a really really really thick layer of rock, steel, ... (very heavy), or a really really thick layer of liquid hydrogen. Either way, it's a lot of mass.
3. Cut the trip time dramatically.

Solar-powered ion drive could make method #2 practical, because it would theoretically allow very large masses to be moved around without having to lift huge amounts of propellant off of the Earth's surface. However, a ship with a nuclear reactor aboard (not just a passive RTG) could accomplish both #2 and #3.

Fundamentally, I don't see the justification for sending humans to Mars in the forseeable future. The really exciting science task would be to find out of there is unicellular life on Mars (with a positive result probably qualifying as the most important scientific result of the last 200 years). This can be accomplished with an uncrewed sample return mission.

Want to send humans to Mars? Great! Please dream up either (a) a valid scientific reason, or (b) a valid commercial reason. I don't think either exists presently, and I don't think either will exist within the next 100 years.

Re:Is it regular speed?

[Rei]

No, you're completely right, but the amount of propellant needed rises geometrically (excluding relativistic effects). So, it is completely unreasonable with low-ISP fuels.

Re:Is it regular speed?

[Rei]

The problem with all shielding methods proposed is that none that are lightweight handle GCR well. Electromagnetic shielding, mind you, does have some very promising applications concerning the Van Allen belts and other lower-energy particles. Right now, it looks like either liquid hydrogen or heavily saturated plastics (HDPE, for example) are going to be the best way to shield a craft on long trips.

While I agree that there *currently* isn't a good reason to send people to Mars, I think that once we can demonstrate some cost-effective mix of ability to mine low-G bodies, grow realistic amounts of food outside of Earth, create bulk raw structural materials outside Earth, and to produce fuel outside Earth, there is ample reason to work on colonizing Mars. Not only would being able to do these reduce the costs of operation, but even high costs could be justified by the future-potential of using Mars as a triangle trade with Earth and the asteroid belt (one of the few things I agree with Zubrin on). So, I would argue in favor of working on the technology with the goal of eventually having it become a realistic course of action.

Re:Is it regular speed?

[Rei]

Yeah! And networking people shouldn't say ISP, they should say "Internet Service Provider!" And programmers shouldn't say "args" they, should say "arguments". And database people shouldn't say "db", they should say "database". How pompous of them....

(/sarcasm)

Re:Is it regular speed?

[djmurdoch]

Other people have pointed out that the Apollo missions got there in much shorter times.

However, an interesting oddity is that the SMART mission averaged a significantly higher speed than Apollo did: It spiralled out from the Earth, and travelled around 80,000,000 km, according to the Nature article someone posted. Apollo went to the moon pretty much by the shortest route.

Doing the math, I find the SMART average speed was around 8500 km/H, while Apollo averaged around 5500 km/H.

Re:Is it regular speed?

[nofx_3]

There is no friction in space so inertia will carry they ship at a constant velocity, that is unless its constantly accelerating as is the case with the Ion drive. It would take a long time but you should eventually be able to reach near relativistic speeds seeing as you are accelerating constantly albiet at a very slow pace.

-kaplanfx

Re:Is it regular speed?

[Rei]

Ion drives are subject to the same limitation as regular engines (they just hit it later): geometric fuel requirement growth. The xenon mass will soon take up 50% of the craft's mass, then 90%, then 99%, etc, long before you get to relativistic speeds.

Re:Is it regular speed?

[fredrik70]

well, it might be enough for trips within the solar system, it's still far faster than conventional methods, mind you, you're right about the size, a proper manned space vehicle might have too much mass for an ion drive. if only we dared using something like orion for manned crafts....

Re:Is it regular speed?

[spike hay]

There is no friction in space so inertia will carry they ship at a constant velocity, that is unless its constantly accelerating as is the case with the Ion drive. It would take a long time but you should eventually be able to reach near relativistic speeds seeing as you are accelerating constantly albiet at a very slow pace.

Unless you want to carry a few solar masses worth of xenon, you cannot get to relativistic speeds with an ion engine. The exhaust velocity of DS1 was 30km/sec. Now, C is 300,000 km/sec. This means that the stuff travelling out the back of the ion thruster is going a mere 1/3000 of lightspeed. Using Newton's laws, you can see that it is completely impractical to reach such a speed with an ion thruster.

A better idea would be a laser sail, in which a multi-terrawatt orbital laser would propel a spacecraft many miles wide composed of gold film. Due to the fact that it would carry no fuel, it could reach near lightspeed. Other, slower options, include very advanced fusion engines, although that might not be that efficient in practice.

Re:Is it regular speed?

[GileadGreene]

Uh, it's unlikely that anyone is going to use RTGs to power an ion engine. They simply produce too little power. For example, all three of Cassini's RTGs combined produce a mere 890 W (at BOL) - ion engines need on the order of several kilowatts to produce anything approaching a useful amount of thrust. Plus the plutonium needed to build RTGs is very expensive.

There is a lot of interest in so-called "Nuclear-Electric Propulsion" (NEP) right now, but no one is talking RTGs. Every NEP proposal I'm familiar with makes use of some form of space-going reactor (i.e. energy production by fission rather radioactive decay), such as the Russian Topaz reactor (5+ kW electrical output).

Re:Is it regular speed?

[cicadia]

Without considering the constant acceleration, the 55-year figure is worthless -- you're calculating as if every 14 months, the craft came to a dead stop, and started accelerating again.

A rough calculation is that the craft started from 0 speed, and travelled ~384,000 km in ~415 days, giving a constant accelleration of 4.46 km / day / day.

The closest mars has been to us in recent years is about 55,760,000 km (last August.) At that rate of acceleration, a spacecraft could reach it in 5000 days, or about 13.7 years. Still not as fast as the 9 months you mentioned, but a far cry from 55 years.

Re:Is it regular speed?

[DeputySpade]

What about ludicrous speed? Is that possible with an ion drive?

Re:Is it regular speed?

[uberdave]

It also did it with a mere 70Kg of propellant.

Re:Is it regular speed?

[twiddlingbits]

4) a type of suspended animation ( such as a year long coma, I don't think "freezing" will ever work) with shielding only around the small area for the crew.You could use LH and LO and combine them in a fuel cell for electricity and water. That way the shielding is fuel. But you have to have enough left to come back too. Suspended animation would require tremendous advances in medical science, but maybe in 50 yrs it might work. Combine that with #3 and you just might have the solution.

Re:Is it regular speed?

[MrFreshly]

"Want to send humans to Mars? Great...dream up a...reason"

Dreamed up reason(s): Science and exploration. You mentioned that we need to come up with a solution that keeps people alive in extended space missions...If we launch such a mission and develop such technologies then we will have the push for a Human/Mars mission to thank for it.

True, robotic exploration could probably get us what we need from Mars / Saturn / wherever.

I believe the mission is not just about finding what we're looking for, but also about getting to the point where we can survive without the Earth or it's resources. Would be nice...

Re:Is it regular speed?

[Rei]

Hmm, actually, I was thinking that JIMO was scheduled to use an RTG, but they're looking to use a somewhat more complex reactor. So, you're right that there are no RTG missions on the drawing board right now. However, you're wrong on several factors. Apart from the fact that NASA is developing higher power stirling cycle RTGs, the ESA already had an RTG-powered ion-drive craft under development - the Europa Orbiter, which was cancelled to be replaced by JIMO. Additionally, you're wrong about the power requirements. Deep Space 1, for example, operated its ion drive for months at 520 watts (its maximum power was 1.9 kW). Hall effect ion thrusters are generally lower power devices; for example, the T-40 HET engine which uses 200 watts.

Now, you can argue that low-power ion drives don't produce the sort of thrust needed for deep interplanetary space missions. However, they'd do it better than solar powered thrusters would. At jupiter, the sun's light is 4% what it is at Earth; at Saturn, it's around 1%. Solar powered ion drives are a crazy notion at that distance. RTGs, however, remain equally feasable.

Re:Is it regular speed?

[whatgives]

Hmm, maybe I don't get it right, but this article: nature says "Its epic 80-million-kilometre journey has taken 13 months, compared with the four days taken to cover 400,000 kilometres by Apollo 11 during the first Moon landing mission.".. If it has taken 13 months to do 80 million kilometres, then it would have taken.. like 2 days to do 400,000 kilometres?

Re:Is it regular speed?

[shaitand]

ISP is an abbreviation for Internet service provider. DB is an abbreviation for Database.

Programmers do NOT in my experience use args rather than arguments when they are not specifically talking/writing to/for other programmers. Also args is still just an abbreviated form of the word arguments and can easily be figured out if used in context by someone who would understand the full word used in the same context.

Abbreviating is a common practice in internet communications and is used extensively in virtually all areas of communication. It works well because the reader can generally figure out the meaning.

Delta-v on the other hand bears NO relation to it's meaning whatsoever. It is NOT an abbreviation, rather it's a randomly chosen piece of jargon which serves no actual purpose. All of the above examples could be interpreted easily in place of the full terms, if used in context, by an individual of reasonable intelligence who would understand the full terms used in the same context.

Delta-v on the other hand must be defined before anyone understands it, attempts to decipher it's meaning when used in context do NOT have a benefit of any association to said meaning. You could as well decide to attach that meaning to the word "bob" and the choice would be no less arbitrary.

In short, ISP is a practical shortening of a long term and if anything is easier to understand than the full term. Delta-v is the creation of a pompous ass to make it easier to distinguish the initiated from the unwashed masses. In this way it shares common ground with many other things in the physics and scientific world in general. If you want further evidence of this, look to astronomy and the naming of extraterrestrial bodies.

Re:Is it regular speed?

[StikyPad]

Finding life on Mars of any sort would be "neat," but only important insomuch as it shows that life is more ubiquitous than we thought. It depends how you define important, I suppose.. I tend to think things are important if they are directly relevant to my life, or the lives of many people. If it turned out that there was bacteria on Mars that cured cancer, that would be "important." But I think most people believe that life exists outside of our planet, so I don't think such a discovery would be revolutionary. It might have a big wow factor, but that doesn't make it important.

What would be far more important are both the expected and unexpected benefits of the technology developed to make such a trip.

Furthermore, I'd venture to say that the great majority of scientific discoveries were accidents. It's difficult, if not impossible, to predict the benefits or lack thereof beforehand.

Re:Is it regular speed?

[maxwell demon]

Delta-v on the other hand bears NO relation to it's meaning whatsoever.

That's wrong. Every physicist when seeing or hearing Delta-v will immediatly know that it is a velocity difference, even if he never was exposed to rocket science at all. That's because the greek letter Delta is commonly and quite universally used to denote differences (for example, the energy difference between two quantum states will usually be names Delta-E), and the letter v is also quite universally used to denote velocity (as in, v=dx/dt, a=dv/dt, p=mv, E_kin = mv^2/2, ...).

Re:Is it regular speed?

[Grab]

Way back when, there were people like Magellan and Raleigh who went out exploring. They were funded by governments. No-one knew what they'd find out there, but chances were that it'd be interesting and often profitable. If a couple of your missions don't find much, maybe a third will hit the jackpot. Drake didn't bring much back with him, but Raleigh brought back the potato which revolutionised European farming, and the Spanish found gold mines in Mexico which basically financed Spain as a superpower for a couple of hundred years. (Note that I don't count Columbus, who had a fixed commercial reason of getting to India more easily.)

This is the venture capital principle - fund it with the intention of seeing what you can get back. And even if you don't make anything back off the trip itself, maybe you've learnt something from what you did that'll be of use - British funding of seafaring turned them into a superpower by having better ships and sailors than anyone else (rather like air superiority these days).

So what's the extra-terrestrial equivalent of Cathay and the Indies? Answer: asteroid mining. You can pick up a lot of metal very easily up there, but the problem is getting out there and back cheaply enough to make the trip worthwhile. If you have a space elevator to get you to the top of the gravity well, and a solar-powered spacecraft to get you around, spaceflight becomes relatively cheap.

Mars in itself isn't much of a prize. But Mars as an intermediate target on the way to true space exploration (and, let's be honest, exploitation) is very valuable. And if you're going to be mining asteroids, you might as well live on Mars instead of Earth, simply bcos it's closer and has less gravity well to overcome (even space elevators take energy).

And finally, don't discount the lure of pure investigation and "something new". The prime drive of humans is curiosity. Not long back, NewScientist had an article about travelling to Mars that suggested cutting down the cost of the expedition by making it one-way - if ppl couldn't survive there then they'd die. And a survey of ppl involved in space research found that a massive number of them would be up for that, even though the odds were they'd not live out the year.

Grab.

Re:Is it regular speed?

[stanmann]

So colonization it is then... 70-80% mortality in the first year for many of the "new world" colonies.

Re:Is it regular speed?

[PMuse]

The really exciting science task would be to find out of there is unicellular life on Mars (with a positive result probably qualifying as the most important scientific result of the last 200 years).

Are we really still excited by this question? We now know beyond a shadow of a doubt that there is no intelligent life on Mars. That's what the 1950s masses cared about. Unicellular life isn't all that interesting to the non-scientist. Except, perhaps, for whatever use it may have in the tiresome debate with the religious creationists.

Re:Is it regular speed?

[PMuse]

Want to send humans to Mars? Great! Please dream up either (a) a valid scientific reason, or (b) a valid commercial reason. I don't think either exists presently, and I don't think either will exist within the next 100 years.

Agreed. I'd like to see us go to Mars as much as the next geek, but there are criteria for a "valid" reason, right?

something we can't get without sending humans to Mars

something important enough to justify the expense and danger

Re:Is it regular speed?

[CrimsonAvenger]

Drake didn't bring much back with him

He didn't? He took 70 tons of silver from one of the ships he captured. And back then, 70 tons of silver was a lot of money.

Re:Is it regular speed?

[CrimsonAvenger]

To put some numbers on it:

Assume Isp ~3000 for an ion drive. Could be lower, could be higher.

Assume a deltaV of 10% of lightspeed. Not really relativistic, but it'll give you an idea.

Assume a 10 Kg spacecraft, before you load the reaction mass aboard.

mass ratio = e^(deltaV/(9.8 * Isp)), which, in this case, is about 7x10^442. So your 10 Kg spacecraft would need 7x10^443 Kg reaction mass.

It's been a long time since I checked, but that's about a bazillion times the mass of the entire universe (10^394 times, give or take a couple-three orders of magnitude).

If by relativistic speeds, you mean 80% or so of lightspeed, then increase the reaction mass to something like 10^3550 Kg or thereabouts.

So, as has been said, ion drives (at least as currently conceived, won't be doing relativistic trips anytime soon).

Re:Is it regular speed?

[GileadGreene]

Hmm, actually, I was thinking that JIMO was scheduled to use an RTG, but they're looking to use a somewhat more complex reactor.

JIMO has, AFAIK, always been baselined to use a reactor. It's the only thing that makes sense. Particularly since they are talking in terms of hundreds of kW of power.

Apart from the fact that NASA is developing higher power stirling cycle RTGs

If it's Stirling Cycle it's not and RTG - RTG stands for Radioisotope Thermoelectric Generator, and uses Peltier-type devices to directly convert thermal energy into electrical energy. The drawback is that the conversion process is not very efficient (although it does avoid the need for moving parts). The reason that NASA is looking into Stirling Cycle Radioisotope Generators is that they can boost the energy conversion efficiency to maybe 20%. But you still only get a relativle small amount of pwoer out of a Radioisotope Generator of this kind (I believe that they are talking about 55 We from ~500Wth). AFAIK Europa Orbiter was a NASA (not ESA) mission that used chemical (not electric) propulsion, so it's not really relevant to this discussion.

Deep Space 1, for example, operated its ion drive for months at 520 watts

That's nice, but what are you supposed to run the rest of the spacecraft on? DS1 had solar arrays that produced ~2.5 kW at BOL, so even at max power on the ion thruster they still had a bunch of power left over to run the other spacecraft systems. I won't dispute that HET's are somewhat more power efficient, but not enough to make a significant difference compared to electrostatic ion thrusters.

I'm not arguing that low-power ion thrusters powered by an RTG won't produce more thrust in a Jovian orbit that a SEP system (although it depends a lot on the size of your solar arrays). I'm arguing that the thrust levels that you can achieve using any power source that produces only a few hundred Watts for both spacecraft and thruster is insufficient to perform a deep-space mission - the resulting trip times become unimaginably long. Now, perhaps if you were to combine traditional ballistic gravity-assists with RTG-based propulsion for say minor stationkeeping maneuvers you might be on to something. But somehow I doubt the (high!) cost and complexity of using an RTG would be worth the minor gains that you might make in propellant savings.

Re:Is it regular speed?

[leeward]

Perhaps you could site a source for the claim of such high amounnts of radiation? The sources I have seen all say otherwise, including this one on Space.com.

Re:Is it regular speed?

[Suidae]

Is there an upper limit to the exaust velocity possible with an ion engine? Are these craft anywhere near that limit?

Re:Is it regular speed?

[Rei]

Yes, a stirling cycle isn't technically an RTG, however neither are what we call "RTGs" (discussed below); however, it works on the same energy input (simple nuclear decay, not self-sustaining fission like JIMO's proposed reactor - note that I didn't say that JIMO changed its reactor plans, just simply that I had misread what they were).

Where did you get your power ratios? Stirling cycle engines can get near the maximum Carnot cycle 50% efficiency - usually 30-45% efficiency. Thermoelectrics used to be limited to about 10%, but the newest types get 17%, and should be scalable to 25%. Also, RTGs don't use Peltier-type devices (thermoelectrics) - they're actually thermionic. Thermoelectric ("Peltier-type") devices use a junction in electrically conductive/heat insulating materials. Thermionics use a vacuum between two extreme-heat-differential plates, where the hot-plate acts like a cathode and emits electrons.

> but what are you supposed to run the rest of the spacecraft on?

In-transit? You don't need much insturment power for the dozen or so years to the outer planets. What, do you think they're gathering nonstop radar images of deep space while flying?

> I'm arguing that the thrust levels that you
> can achieve using any power source that
> produces only a few hundred Watts for both
> spacecraft and thruster is insufficient to
> perform a deep space mission

As I mentioned, DS1 *did* use just a couple hundred watts for its ion engine for a good portion of its flight, so it clearly is a reasonable option. Hall effect thrusters use even less electricity for the same total amount of thrust, with a penalty of lower ISP (but still far greater than chemical rockets).

> Now, perhaps if you were to combine
> tradditional ballistic gravity assists

Why exactly would you not? Ion thrusters have plenty of time (months to years) to line up the craft for planetary assists. You might have trouble getting assists from moons when in orbit around a planet due to the short differences in time between encounters, but that's about it.

> But somehow I doubt the (high!) cost

Given standard launch cost rates (~25k$/kg for escape velocity), it would cost about 140 million dollars to launch Cassini. 78 million of that would go to launching just its propellant. RTG costs are trivial in comparison to propellant launch costs.

> minor gains that you might make in propellant savings

10x the ISP is *NOT* minor gains. 10x the ISP is a huge gain.

Re:Is it regular speed?

[spike hay]

Yes. There is an upper limit. No hard and fast one, but you cannot scale it up so the exhaust hits relativistic velocities. In ion engines, particles are accelerated by electrostatic potential. They have more in common technologically with a HEPA filter than a sci-fi ion engine.

Re:Is it regular speed?

[GileadGreene]

Where did you get your power ratios? Stirling cycle engines can get near the maximum Carnot cycle 50% efficiency - usually 30-45% efficiency.

From a NASA report describing their Stirling Cycle radioisotope generator - real efficiencies, not theoretical numbers.

Also, RTGs don't use Peltier-type devices (thermoelectrics) - they're actually thermionic. Thermoelectric ("Peltier-type") devices use a junction in electrically conductive/heat insulating materials. Thermionics use a vacuum between two extreme-heat-differential plates, where the hot-plate acts like a cathode and emits electrons.

I don't know where you are getting you're information from. There may be a few "RTGs" that use thermionics for energy conversion (I haven't heard of any though). The majority of RTGs do use thermoelectrics. For example, Cassini's RTGs make use of SiGe unicouples for energy conversion. Thermionics are much more common in space-going reactors, such as Topaz, Topaz II, and the US SP-100.

In-transit? You don't need much insturment power for the dozen or so years to the outer planets. What, do you think they're gathering nonstop radar images of deep space while flying?

It's not instrument power that's the issue. It's power for the comm system, the onboard computers, the attitude control system, and the thermal control system. Yes, you can reduce the amount of pwoer that these things draw, but you cannot make it zero, and we are still talking about a significant number of Watts.

As I mentioned, DS1 *did* use just a couple hundred watts for its ion engine for a good portion of its flight, so it clearly is a reasonable option. Hall effect thrusters use even less electricity for the same total amount of thrust, with a penalty of lower ISP (but still far greater than chemical rockets).

And as I mentioned, DS1 had a power source that produced far more than the amount of energy that it needed for the thruster - running both spacecraft systems and thruster off of "a few hundred watts" is not practical. The DS1 spacecraft, excluding the thruster, used about 400-500 W of power (see my points above about other subsystems that require power).

Why exactly would you not? Ion thrusters have plenty of time (months to years) to line up the craft for planetary assists. You might have trouble getting assists from moons when in orbit around a planet due to the short differences in time between encounters, but that's about it.

There is plenty of work being done on combing low-thrust trajectories and gravity-assist trajectories. I don't dispute that there is a lot of potential there. The question is whether or not the RTG-based design that you are proposing would be worthwhile in such a mission. I am saying no. See below.

Given standard launch cost rates (~25k$/kg for escape velocity), it would cost about 140 million dollars to launch Cassini. 78 million of that would go to launching just its propellant. RTG costs are trivial in comparison to propellant launch costs.

Actually, it cost closer to $450 million to launch Cassini, since they used an ultra-expensive Titan LV. The problem with your math is that launches aren't sold by the kg, they're sold by the launch vehicle. Would Cassini have been light enough to get to a smaller launch vehicle if you switched to ion thrusters? Hard to say - yes, you will get some propellant mass savings due to better Isp. But, either you use the existing power system, which means very low thrust, a seriously extended mission duration, and a greater need for redundancy, or you beef up the power system (use something other than RTGs). The latter approach being the one the JIMO has taken.

10x the ISP is *NOT* minor gains. 10x the ISP is a huge gain.

Yes, it is. But you are failing to account for the additional mass of the power processing infrastructure that is necessary to support an ion thruster, or the extra thermal radiators you will need due to the inefficiencies of

Re:Is it regular speed?

[Rei]

Oh come on, now. Voyager 1 and 2 each need only 215 watts, and that was launched in 1977. You're saying that we've 2.5xed our idle power load since the 70s (I can't find the idle power req's for DS1; if you can cite a reference, please do)? It really doesn't make sense that a craft would require anywhere near that much power idling anyways, either, especially if you use nuclear heating elements. I can run a graphing calculator for a day on a couple double a batteries that has 10 times the processing power of these craft (and you don't need to be transmitting continuously)

The actual launch cost of Cassini is irrelevant, since any given spacecraft is just as likely to come close to using an entire launch vehicle's capability as any other. But you agree with my point, I assume? That the cost of the plutonium is completely dwarfed by the cost of launching the fuel?

> VERY low thrust

Nope. Hall effect thrusters, while having ISPs of "only" around 2,500 (compared to ~450 for a good LOX/LH engine) give power/thrust ratios of near .65-.70 newton per kwH in the case of the T-220 (assumedly the T-40 performs similarly). A 200W T-40 HET, therefore, would well outperform DS1's engine operating at full power, and yet use a tiny fraction of the propellant of a chemical engine.

> But you are failing to account for the
> additional mass of the power processing
> infrastructure that is necessary to support an
> ion thruster or the extra thermal radiators

Lets say that Cassini's engine (ignoring all of its huge fuel payload) was 100kg. That's probably being kind, but lets go with it. To replace that:

Your power module can be There is a reason that JIMO and other NEP
> proposals are all focusing on reactors rather
> than RTGs ... and it's not about thrust, at least not primarily (check the JIMO website). It's about the insturments, specifically high powered ground-penetrating radar capable of penetrating 10s of kilometers through Europa's ice, high powered communications links to carry the data of that and other high-data rate components (including a 200 channel spectrometer that will be mapping at less than 100 meters per pixel), 10 meter resolution laser mapping, etc, simultaneously.

In short, the situation we have: a single Cassini RTG could power a T-40 HET with power to spare (you can bring more RTGs as you want for insturments) and produce over 100 millinewtons of continuous thrust. Over a year, it could impart, to a 1000 kg spacecraft, over 3000 m/s delta-V**. Seing as it took Gallileo 5 years to get to Jupiter, that's 15k m/s delta-V** - I.e., you could get to Saturn using *no* gravity assists as fast as Gallileo did *using* gravity assists.

** - Ok, I cheated here to make the math easier. Even with a high ISP, the mass of the spacecraft still changes. So, it's not really going to impart 15k delta-V to the craft, but I'm sure it'd at least be enough to get to Jupiter.

P.S. - I'd be interested in seing the paper you mentioned on NASA stirling cycle engines. I'm curious as to why they'd be getting such poor efficiency; you might as well just keep it simple and use bismuth telluride thermoelectrics (or any of the other recently-developed high efficiency thermoelectrics) if that's all the efficiency you're going to get.

Re:Is it regular speed?

[Rei]

Blah. .65-.70 N/kw, not N/kwh. That's what I get for not proofreading. :P

Re:Is it regular speed?

[GileadGreene]

Voyager 1 and 2 each need only 215 watts, and that was launched in 1977. You're saying that we've 2.5xed our idle power load since the 70s (I can't find the idle power req's for DS1; if you can cite a reference, please do)?

Voyagers 1 and 2 were deliberately built simple and rugged, and were tightly constrained by the power available from their RTGs. Modern spacecraft are more complex and often consume more energy. Spectrum Astro's DS1 factsheet gives the bus orbit average power as 500 W. Admittedly, that probably isn't with all systems "idled" (whatever that means), but there is a limit to how much you can switch off on a spacecraft in mid-flight.

I can run a graphing calculator for a day on a couple double a batteries that has 10 times the processing power of these craft

A graphing calculator is not an internally redundant rad-hard flight computer (30+ W), with its associated I/O interfaces. It does not have a comm system (which will draw power even when not transmitting - you always want to be able to receive). It does not have attitude sensors. It does not have attitude actuators (which can be large power consumers on a 3-axis stabilized spacecraft, as you would want to be with a low-thrust system since spin-axis precession is probably infeasible). These things all take power. 500 W? Not necessarily. Several hundred W. Quite probably.

That the cost of the plutonium is completely dwarfed by the cost of launching the fuel?

The cost is not just the cost of plutonium itself, but the additional cost and complexity that results from flying a radioactive (and toxic) substance. Cassini cost $1.2 billion just to develop - the launch cost is a small fraction of the development cost, let alone the total mission cost. Admittedly, not all of Cassini's cost was driven by the RTGs, but they definitely contribute to a higher cost than you would otherwise see.

Hall effect thrusters, while having ISPs of "only" around 2,500 (compared to ~450 for a good LOX/LH engine) give power/thrust ratios of near .65-.70 newton per kwH in the case of the T-220 (assumedly the T-40 performs similarly). A 200W T-40 HET, therefore, would well outperform DS1's engine operating at full power, and yet use a tiny fraction of the propellant of a chemical engine.

Unfortunately, electric propulsion system performance doesn't tend to scale linearly. There are economies of scale that come with larger systems. Quoting from the Pratt & Whitney website:

The T-40 operates at 0.1 to 0.4 kW and produces 5 to 20 mN of thrust, with specific impulse values varying between 1,000 and 1,600 seconds, depending on operational conditions.

a single Cassini RTG could power a T-40 HET with power to spare (you can bring more RTGs as you want for insturments) and produce over 100 millinewtons of continuous thrust. Over a year, it could impart, to a 1000 kg spacecraft, over 3000 m/s delta-V**. Seing as it took Gallileo 5 years to get to Jupiter, that's 15k m/s delta-V** - I.e., you could get to Saturn using *no* gravity assists as fast as Gallileo did *using* gravity assists.

Since you have overestimated HET performance you are getting numbers that are unrealistic (which is exacerbated by the exponential dependence of propellant mass on Isp). Using your numbers (which are optimistic) we get:

Isp 3800 s
dv 15 km/s
mdry 1000 kg
thrust 0.1 N

mprop 496 kg
TOF 5.8 years

However, if we use realistic (but still optimistic - I'm assuming the upper end of the quoted T-40 performance range, which requires closer to 400 W) numbers for low-power HET performance, we get**

Isp 1600 s
dv 18.84 km/s
mdry 1000 kg
thrust 0.02 N

mprop 2325 kg
TOF 57.8 years

Re:Is it regular speed?

[Rei]

> Voyagers 1 and 2 were deliberately built simple and
> rugged, and were tightly constrained by the power
> available from their RTGs. Modern spacecraft are more
> complex and often consume more energy.

They were also built with *1970s electronics*. Surely you, as a poster on slashdot, know how much electronics have improved since the 1970s.

> Spectrum Astro's DS1 factsheet [spectrumastro.com]
> gives the bus orbit average power as 500 W.

Just ignoring that you can't tell what they're running, a search for "orbit average power" gives you much lower numbers for other spacecraft - for example, the first hit, SAMPEX, gives 60 watts. SWAS is 150W. FAST is 33W. SMEX is 50-200 watts. Now, these are all in earth orbit, so they need less power for communications, and are somewhat light (i.e., less stabilization force needed, although the fact that they're in a non-uniform gravity well with a variety of other forces will somewhat negate this), but not only were they running various insturments with this power, but they at the very least show how little power one needs for internal components apart from communications.

> A graphing calculator is not an internally redundant
> rad-hard flight computer (30+ W), with its associated I/O
> interfaces.

It was an example of how electronics have improved. To put it another way, you can get a cell phone whose processing power easily dwarfs that of a VAX (same time period as the Voyager probes). Neither are hardened, so that excuse is irrelevant.

The situation comes down to: 1970s electronics vs. 2000s electronics.

> It does not have a comm system (which will draw power
> even when not transmitting - you always want to be able
> to receive).

Not really. Why would you design a craft to constantly be expecting to receive when you have a delay time of hours? Scheduled command receipt times make far more sense, unless you've just got power to burn.

> These things all take power. 500 W? Not necessarily.
> Several hundred W. Quite probably.

The fact remains that with 1970s tech, the Voyager craft idled on minimal power. Now you're trying to say that it's not realistic with 2000s tech. That rings incredibly hollow.

> Cassini cost $1.2 billion just to develop - the launch cost
> is a small fraction of the development cost, let alone the
> total mission cost.

You're hurting your point even more; I was being kind by only discussing launch costs. Your argument was that plutonium is expensive. I think we can agree that that argument is dead? Shall we move on to "there are hassles with nuclear powered spacecraft"?

> Isp 1600 s
> dv 18.84 km/s
> mdry 1000 kg
> thrust 0.02 N
> mprop 2325 kg
> TOF 57.8 years

Do you know what the TOF for Cassini would be to get to Saturn without gravity assists?

*Infinite* - it never would have gotten there. Launching on a direct Hohmann transfer to Saturn is completely unreasonable using chemical propellants; at least it is possible here without having 95% or so of the spacecraft as propellant. I was being kind and comparing flight without gravity assists to flight with gravity assists. 0.02 Newtons thrust should be plenty for lining the craft up for gravity assists. If it's not enough for you, then we can upgrade the power supply; Cassini, after all, launched with ~750W of RTG power (of which a peak load is only needed during flybys) - and there, we're not even talking about a craft that powered its propulsion via electricity. If you want to devote even a small fraction of that saved propellant mass to RTG power, you can get a T-140 without having to launch an unreasonable amount of plutonium (i.e., the costs of the plutonium will still be insignificant compared to the costs of the entire project). Then, with your remaining propellant savings, you can fill it with insturments, and you can have your insturments make use o

Re:Is it regular speed?

[Grab]

Hey, it's still a lot of money now! :-)

As you say though, he took it from a ship he captured. As far as discovering anything new himself, he didn't get much - just spread a bit of "brand recognition" for Britain.

Britain *did* discover that a useful form of income was beating the crap out of the Spanish and Portugese (through naval superiority) and stealing from them, which provided a lot of extra finance for Britain back then when pirates were legalised as privateers. But that wasn't really a "discovery" bcos sailors had been doing piracy for ages, just a different business model for government really.

Grab.

Re:Is it regular speed?

[Rei]

BTW - the T-40 is hardly the only low-power Hall effect thruster - it was just the first that I ran into. The KM-32 uses 150-400W power, has a reported specific impulse of 2000s at 400W, and a thrust efficiency of about 45%. Again, this probably isn't the best on the market, but is just another example; I'm sure there are even better ones out there.

Re:Is it regular speed?

[GileadGreene]

They were also built with *1970s electronics*. Surely you, as a poster on slashdot, know how much electronics have improved since the 1970s.

The problem is that spacecraft power consumers consist of more than just electronics. And yes, electronics have improved since the 70's, but they also do a lot more than their 70's ancestors do. You will consume 60-70 W in comm system alone (transponders plus amplifiers), even neglecting high-rate transmissions. Your onboard computer (plus associated interface circuits) will consume upwards of 30 W (for a non-redundant system - more for a redundant system). Survival heaters will probably consume anywhere from 70 W up to 200 W (yes, you can use some isotope-based heaters, but they cannot be switched on and off, so they are of limited use). Between reaction wheels, star trackers, IMUs, and the like, your attitude control system will consume 70+ W at a minimum. None of this includes the inevitable inefficiencies in DC-DC conversion and power distribution. These are real estimates, based on real deep-space (as opposed to near-earth) missions (NEAR, DAWN, ACE, etc).

...less stabilization force needed, although the fact that they're in a non-uniform gravity well with a variety of other forces will somewhat negate this

"Non-uniform" gravitation has little or nothing to do with it. The prinicipal disturbance torques acting on a spacecraft are gravity-gradient (which has little to do with the non-uniformity of the field), magnetic, solar radiation, and aerodynamic torques. Aerodynamic torques are negligible even for high LEO orbits. GG torques will not affect a deep sapce mission. The other two are still a concern. Plus, you are constantly turning your spacecraft to keep the thrust vector pointed in the appropriate direction.

Not really. Why would you design a craft to constantly be expecting to receive when you have a delay time of hours? Scheduled command receipt times make far more sense, unless you've just got power to burn.

[sigh] Look, no one (or at least no one I am aware of) designs spacecraft that switch their command receiver on and off - there's too much chance that it won't get switched on again at the right time (or ever). Plus, if you are constantly thrusting you are going to want to get regular telemetry, just to amke sure everything's still operating correctly.

The fact remains that with 1970s tech, the Voyager craft idled on minimal power. Now you're trying to say that it's not realistic with 2000s tech. That rings incredibly hollow.

See above - we're talking at least 200 W, probably more. And these are not subsystem you can switch off: if you are constantly thrusting you need to be controlling your attitude - which means ACS on, flight computer on, comm system on for telemetry and command updates. You can't "idle" at 0 W, or even close to it.

If it's not enough for you, then we can upgrade the power supply; Cassini, after all, launched with ~750W of RTG power (of which a peak load is only needed during flybys) - and there, we're not even talking about a craft that powered its propulsion via electricity. If you want to devote even a small fraction of that saved propellant mass to RTG power, you can get a T-140 without having to launch an unreasonable amount of plutonium (i.e., the costs of the plutonium will still be insignificant compared to the costs of the entire project). Then, with your remaining propellant savings, you can fill it with insturments, and you can have your insturments make use of your higher power supply as well. It's a win-win situation.

The T-140 requires a minimum of 1.8 kW. If you're going to try to supply that much power (plus whatever you need for spacecraft power), why not just use a reactor? You are now attempting to fly almost of 500 kg of RTGs, versus a reactor that could weigh less than 500 kg, and produce significantly more power output (while using cheaper uranium, instead of plutonium). That's been my point al

Re:Is it regular speed?

[Bob Uhl]

70 tons is 2,240,000 ounces; silver is currently $7.65/oz. I'd say that $17,136,000 is still a lot of money.

The latest score just in...

[Electronik]

SMART-1
BEAGLE-0

Re:The latest score just in...

[Luigi30]

Maybe it'll find Beagle while it's over there.

Re:The latest score just in...

[uncl_bob]

Why would it? Beagle = Mars, SMART = Moon.

Re:The latest score just in...

[roadrunnerro]

woooosh!... hey, a joke just passed by you...

I don't get it

[centauri]

this method of propulsion could be ideal for travel in near-weightless space as it does not require any combustion to occur

What were you trying to say here? That combustion rockets are not a good way to travel through space? Maybe they're not the best, but it's going to be some time before anyone seriously considers getting people to the moon with ion engines.

Re:I don't get it

[Headw1nd]

Ok.. the reason this is noteworthy, despite it's lethargic speed, has to do with reaction mass. Ion propulsion and rockets are similar in that both require reaction mass for propulsion- the craft goes forward because something goes back. The speed which the craft goes forward is proportional to the speed that something is ejected out back. Ion drives have ejection speeds far above that of conventional rockets, thus are far more efficient in their use of their propellant.

So?

So this is crucial on the long haul. With a reaction drive, when you run out of reaction mass, you're done. The craft becomes inert. The trick here is that the saturn V was out fuel within 15 minutes, wheras this craft is still accelerating a year later. Concievably, it could run for another year, or a dozen. (I don't know how much reaction mass it has) An ion drive craft might be made that could with enough reaction mass for an interstellar voyage, where a chemical rocket could not. (esp. considering the mass needed to decelerate at the ead!)

Re:I don't get it

[mark-t]

it's going to be some time before anyone seriously considers getting people to the moon with ion engines.

Well, at least 13 months, at any rate.

Re:I don't get it

[Anonymous Coward]

Understood, but a long time ago in a galaxy far far away, we've had space vehicles running on Twin Ion Engines. Efficient? Hell yeah! The price of that efficiency, though, was the apparent lack of a deflector shield.

Re:I don't get it

[w42w42]

I *think* what they were saying is that because there is constant thrust during the entire trip as opposed to a massive amount at just the very beginning, that constant thrust would in effect simulate gravity. This might be the intent, but the reality is it would be very low, and I would love to see someone calculate the actual generated g's.

Re:I don't get it

[centauri]

I'm not so sure. I think the earth's or at least the sun's escape velocity is faster than you can throw something.

Re:I don't get it

[npross]

I doubt you'd be able to throw hard enough to escape earth's gravity well.

Re:I don't get it

[Anonymous Coward]

Actually, if you maintain any constant acceleration you can outrun light (you have to do the math, but basically, it's like a variation on Zeno's paradox of Achilles and the tortoise). Given a sufficiently large distance, constant acceleration will always win. Interstellar distances, and in some cases, interplanetary distances are likely to be sufficient to ensure that the constantly accelerating vehicle arrives first.

Re:I don't get it

[Headw1nd]

A chemical rocket could reach another star, but in talking about a voyage, a shorter timespan is implied. Say something in the less than 1,000 year range. For this you need more sustainable acceleration.

To showcase what I mean, the current fastest human object is Voyager 1. It was launched via chemical rocket and is currently traveling at 3.4 AU/year. The closest star, Alpha Centauri, is currently 275725 AU away. While something that speed would eventually reach another star, there would be little point in sending it there.

Re:I don't get it

[Rubyflame]

Umm, no. You can accelerate at one gee forever and never reach light speed relative to your starting point.

Re:I don't get it

[Anonymous Coward]

You will never reach light speed, but you can still outrun light, as long as you start accelerating at more than a distance of c^2/A away from the light source, where A is your proper acceleration and c is the speed of light (assuming constant proper acceleration). Consider this spacetime diagram; any light emitted beyond the indicated Rindler "event horizon" (blue 45-degree line) will never intersect the worldline of the accelerated observer (red hyperbola).

Re:I don't get it

[CrimsonAvenger]

Alright. 2x10^-4 m/s^2 is ~2x10^-5 G. I'd weigh about 1/14th of an ounce. Most of you would be a bit lighter.

To give a real-world reference, you'd weigh about 2/3 the weight of an American dime.

Which is another way of saying you'd be effectively weightless. Note that if you were in such an acceleration field, and dropped your coffee cup, you'd have a couple minutes before it reached the deck. Letting go of your coffee cup while you typed a quick post to /. and getting it back in hand before it spilled would be quite practical.

So when do we get to see the US flag?

[rsborg]

On one hand, showing the US flag on the moon would make for very good press...

[conspiracy] On the other hand, if they can't find it... [/conspiracy]

Re:So when do we get to see the US flag?

[ari_j]

The flag was almost certainly burned when the LEM ascent stage lit up.

Re:So when do we get to see the US flag?

[RajivSLK]

burned? whith what oxgen?

Re:So when do we get to see the US flag?

[ari_j]

Despite your 50% spelling and 0% capitalization rates, I'm going to respond. The definition of "burned" involving combustion is not the first definition of the word. There are ways to burn things that don't involve oxygen, at all. The looser definition I'm going under, for the sake of rhetorical readability, would include any destruction by heat or fire. I assure you that there was enough heat from the ascent stage's ignition to destroy the flag.

Re:So when do we get to see the US flag?

[fredrik70]

Well, the flag which the crew from apollo 11 apparently got toasted a bit, IIRC the planted the flag a bit further away on the later missions

Re:So when do we get to see the US flag?

[ari_j]

What later missions? Apollo 11 is the only one that they've spent a lot of time rebutting the conspiracy theories, so as far as I'm concerned 11 happened but 12-17 never did. ;)

Re:So when do we get to see the US flag?

[lavaface]

Offtopic, but . . . can you see the flag on the moon with a telescope? I would think that you could and a simple peep verifying that a flag is up there should silence conspiracy theorists. So, where are the telescopic pictures of evidence left behind from the Apollo missions? Seriously . . . I'm curious.

Re:So when do we get to see the US flag?

[Guppy06]

"On one hand, showing the US flag on the moon would make for very good press..."

I can't seem to find it right now, but I've seen people suggest that all that direct sunlight may have bleached those flags white by now.

Re:So when do we get to see the US flag?

[maxwell demon]

And of course, even if you would make an image with Hubble, the conspiracy theorists would probably claim that you faked it. After all, how do you proof that it's really an image taken by Hubble?

Re:So when do we get to see the US flag?

[NardofDoom]

First, Any conspiracy nut will just say the flag was photoshopped into the frame.

Also, if they don't believe now, they never will. You will never get everyone to believe anything.

Re:So when do we get to see the US flag?

[apanap]

There are mirrors left on the moon by the Apollo 11 astronauts that were put there to be able to measure the distance to the moon by laser. It's mentioned here for example. But the conspiracy theorists won't listen to that...

Re:So when do we get to see the US flag?

[WWWWolf]

No. Hubble could theoretically pick up items the size of over 125x125m from moon surface, everything else is too small. You'd better not even bother with terrestrial telescopes, unless you come up with some completely amazing advances in optics.

So... Let's hope Chinese go to the moon and paint the entire surface red, after which Americans go there and paint huge Coca-Cola logo on it with white paint. That ought to make the conspiracy theorists stumped for at least a few seconds =)

Re:So when do we get to see the US flag?

[fredrik70]

aha, I think They [que Twilight zone theme] found errors in all missions. However bad astronomy will sort you out when it comes to defuse the conspiracy minded! ;-)

It REALLY Ain't warp speed

[guitaristx]

Considering that Apollo 8 made it around the moon in less than a week, and this mission took over a year, we're not dealing with lots of speed here.

I'm interested in seeing some comparisons with project cost, energy consumption, etc.

Re:It REALLY Ain't warp speed

[Anonymous Coward]

No, but compare the prices of this craft vs appolo 8.

Appolo 8 technology can't go very far because you quicky get to the point where the fuel needed to carry the fuel needed to get anywhere reaches infinity.

Re:It REALLY Ain't warp speed

[Ianoo]

Yes, but Apollo 8 didn't accelerate all the way, and couldn't accelerate all the way from here to halfway to Alpha Centauri. You'd get there a lot faster on ion drive.

Re:It REALLY Ain't warp speed

[anethema]

I wonder how much faster since you'd have to spend half your trip decelerating, assuming you have a given thrust.

Re:It REALLY Ain't warp speed

[WillWare]

Apollo 8 ... couldn't accelerate all the way from here to halfway to Alpha Centauri. You'd get there a lot faster on ion drive.

To maintain the acceleration, you need sunlight hitting the solar panels. When you get that far out, the sunlight's going to be very weak. By then you might have picked up plenty of speed (I haven't done the math) but at the halfway point you won't have the acceleration you had near the inner planets.

Re:It REALLY Ain't warp speed

[exp(pi*sqrt(163))]

Constant velocity => time taken is proportional to distance Constant acceleration => time taken is proportional to square root of distance (taking into account deceleration) For long journeys constant acceleration will generally win, even for small accelerations.

How long will it take to reach Mars?

[jerichohol]

Warp 0.0001 more like it, Picard would say"E....N.....G....A....G......E"

Re:How long will it take to reach Mars?

[adam31]

"Prepare ion thrusters for - Retarded Speed!"

Re:How long will it take to reach Mars?

[iceburn]

Ha ha ah, that's good stuff. "...close all shops in the mall... secure the animals in the zoo..."

wrong link

[Anonymous Coward]

it's http://www.esa.int/ not http://www.esa.in/

Re:wrong link

[boule75]

Mod this up pls

An official Esa site about SMART is here (in English)
Some information in French.

The Washington Times deals with a Moon too, but another one: Rvd Moon's "church" owns it and it has been recently frequently used to promote US Pentagon anonymous sources' views. It is soooo strange to see it pointed by /. in the same article where the "old Europe's ESA" link is broken!!!

Re:wrong link

[apanap]

There's also a lot of info at the main contractors site. Swedish Space Corporation

(ok, I just did that to brag about the fact it's swedish ;)

Plasma technology is the space enabler

[QuantumG]

Although it's called an "ion engine", it's really just the first step in the progression of plasma propulsion. Next up we have the VASIMR which they've been talking about testing on the space station. It can produce slow thrust like an ion engine, or it can produce hard thrust like a chemical rocket. You can power it with solar panels, or you can power it with a nuclear reactor. Eventually, almost the exact same design will be used in fusion rockets, and possibly even antimatter rockets. Then we're in Startrek country with plasma power distribution and ships which you can actually live and work on.

Re:Plasma technology is the space enabler

[WolfWithoutAClause]

Next up we have the VASIMR ... it can produce hard thrust like a chemical rocket.

'Fraid not. To do that requires an enormous, lightweight, electrical power source. No current powerplant, solar, nuclear, chemical or other can provide enough power to generate high thrust when used with VASIMR.

VASIMR is a wannabe fusion power drive. Trouble is, fusion doesn't work well enough right now to use it for this; and they are stuck with trying to powering it the old fashioned ways. It works, but not noticeably any better than ion drive- if you were to get VASIMR to work with a new power supply, you can pretty much just gang up any of the existing ion drive thrusters and get about the same thrust.

VASIMR has theoretical advantages of being able to vary the exhaust velocity to increase the thrust, but even on the lowest settings I've seen them talk about, ion drives usually give better thrust.

Re:Plasma technology is the space enabler

[QuantumG]

For some reason I think a 190MWt nuclear submarine engine would be more than adequate for heating plasma. There simply isn't a big enough dedication to making space colonisation happen. It's such a shame that we need militarisation to see innovation in technology.

Re:Plasma technology is the space enabler

[WolfWithoutAClause]

It's not designed for absolutely minimum weight is it? Weight totally matters in space work. A heavy power source takes away from payload or equivalently makes you accelerate really slowly.

Re:Plasma technology is the space enabler

[DeputySpade]

s/weight/mass/g

We _are_ talking about space here, afterall.

Re:Plasma technology is the space enabler

[ryanmfw]

So, getting it up there isn't a problem? OK then, just lend me your Saturn V, and I'll launch it up there for ya. :-)

Re:Plasma technology is the space enabler

[WolfWithoutAClause]

No, he's just saying that when I said 'weight' I meant 'mass'. Which is precisely true.

The cost of launch is mostly related to how heavy the vehicle is, which is very roughly proportional to how massive the payload is.

Re:Plasma technology is the space enabler

[ryanmfw]

Yes, and as you said, nuclear reactors are massive. I was talking about how easy it would be to launch that nuclear reactor into space, which would not be easy at all.

Re:Plasma technology is the space enabler

[rssrss]

When she was upset, my grandmother used to say VASMIR a lot. She would also say OY and OY VASMIR.

Not the best source in the world.

[Anonymous Coward]

Isn't the Washington Times the same paper that is owned by the Moonies?

http://www.realjournalism.net/times.htm

Re:Not the best source in the world.

[MillionthMonkey]

Isn't the Washington Times the same paper that is owned by the Moonies?

Yep... if you're uncomfortable getting your news from Rev. Moon (a.k.a. God himself) there are plenty of non-cult-affiliated links for this story.

short answer: yes

[Anubis350]

don;t know about actual nums (though I'm sure some arma whore'll dig 'em up) but ion is more efficient for longer distances (i.e. the farther you go the faster you go). This is due to the fact that its a constant acceleration requiring little/no fuel. It doesnt give great initial thrust as compared to normal engines, but it can build its speed gradually to approach (though of course not reach) the speed of light. for stopping at your destination you could do a burn of a fuel based engine.

so the short answer to you question is yes, thoug cyogenics are even farther from usefulness right now than this is for such type of travel.

Re:short answer: yes

[Paster Of Muppets]

"Uptime" = approx. 3648 hours
Final velocity = approx. 2737 km/s (about 10,000 km/h)
Fuel consumed = 58.8kg Xe

Assuming constant acceleration and no retarding forces, if the initial velocity on leaving the Earth's atmosphere was 11.2 km/s, then the acceleration is (change in velocity)/(change in time) = (2737 - 11.2)km/s * 3600s / 3648h = 2725.8 * 3600 / 3648 km/h^2 = 2690 km/h^2 = 2.08e-4 km/s^-2 = 2.08e-7 m/s^2.

Rather slow accelaration, at that rate it'll take 29683seconds to travel the length of an American Football pitch (from a stationary start), approximately 8.25 hours. That's slow.

Data taken from here.

Re:short answer: yes

[vadim_t]

Question: What does escape velocity have to do with this, unless the satellite is shot from a cannon? From what I understand, escape velocity is the velocity needed for an object without propulsion to fly off to space despite gravity.

However, if you've got a rocket, that shouldn't matter. If you have something that keeps pushing you'll eventually get to space, even if it's ascending at 1 KM/h.

Or I'm missing something here?

Re:short answer: yes

[Paster Of Muppets]

Oh, and I calculate that as roughly 5000 miles per (UK) gallon. A fighter jet will do about 1 mile per gallon, a car about 30. Fuel efficient or what!

Correction to parent, it won't actually cross a football pitch, the resistive forces would be far greater than the thrust of the "engine", so it would stay where it is. The calculation above was assuming no resistive forces.

Re:short answer: yes

[nofx_3]

Yep you are missing something. The Ion rocket cannot lift a satelite into orbit, the specific impulse is much to low, you just don't have the thrust to weight ratio to go anywhere in an environment with gravity and friction due to the density of the atmosphere. You need to piggyback on a tradition rocket to get into a frictionless, low or apperent zero gravity environment.

-kaplanfx

Re:short answer: yes

[spike hay]

don;t know about actual nums (though I'm sure some arma whore'll dig 'em up) but ion is more efficient for longer distances (i.e. the farther you go the faster you go). This is due to the fact that its a constant acceleration requiring little/no fuel. It doesnt give great initial thrust as compared to normal engines, but it can build its speed gradually to approach (though of course not reach) the speed of light. for stopping at your destination you could do a burn of a fuel based engine.

so the short answer to you question is yes, thoug cyogenics are even farther from usefulness right now than this is for such type of travel.

Ion engines cannot get anywhere near the speed of light, although they can be over ten times as efficient as chemical engines.

Re:short answer: yes

[spike hay]

Question: What does escape velocity have to do with this, unless the satellite is shot from a cannon? From what I understand, escape velocity is the velocity needed for an object without propulsion to fly off to space despite gravity.

However, if you've got a rocket, that shouldn't matter. If you have something that keeps pushing you'll eventually get to space, even if it's ascending at 1 KM/h.

Or I'm missing something here?

If I take my rocket, and go up 200,000 miles vertically from the surface of the earth, I will fall back down again. Escape velocity is needed to leave the orbit of a body. It does applies to rockets, as well as everything else in the universe. If you push something at 1 km/hr towards space, it will just fall back down again.

Rockets actually just propel their payloads to greater angular velocities, which puts them in higher orbits.

Re:short answer: yes

[twiddlingbits]

Assuming enough fuel to provide constant acceleration by the time this thing hit the edge of the Solar System it would be hitting a fraction (5-6%) of c. Of course hitting a tiny spec of space dust at that speed would destroy the craft so there are practical limits to how fast something should go. I doubt that even with massive fuel you would never get more than 10-15% of c, since increasing the velocity takes more and more fuel since e=mc2. It's not a practical means of propulsion unless you got LOTS of time to get there. But it does get good gas mileage ;)

Re:short answer: yes

[Dyolf Knip]

Recheck your numbers. You're using 2737 kps, not meters per second. And at 2.08e-7 m/s^2, it would take a year just to change velocity by 6m/s. The answer you should be getting is dv/dt = (11.2kps - 2.737kps) / (3648sec *3600sec/hr) = 8463mps / 13,132,800s = 6.44e-4 m/s^2. You're off by 3 orders of magnitude.

Now, with that kind of acceleration, the first football field would be crossed in 531 seconds of acceleration, approximately 9 minutes. Slow by interstellar standards, but with constant acceleration each successive football field is crossed in 41% of the time. Each hour of thrust yields 2.3 m/s of delta-v in exchange for (on this craft) a lousy 10 grams of propellant. When your fuel is chump change payload, you can afford decent environmental systems to keep you alive until you arrive.

Re:short answer: yes

[spike hay]

I couldn't get anywhere near 5% the speed of light. The engines aren't that fuel efficient at all. I'm too lazy to do a real calculation, but to accelerate one ton that fast, not taking into account fuel weight, would require 500 tons of fuel using a Deep Space 1 ion engine. That means that in reality, a .05 craft weighing in a mere one ton empty would need a mass of xenon much greater than a supertanker.

Re:short answer: yes

[spike hay]

I=it, by the way. However difficult it would be to get deep space one to such a velocity, it would even be more difficult to accelerate me that fast.

Re:short answer: yes

[Dyolf Knip]

Pride goeth before a fall, it was running for a lot more than 3648 hours. More like 10224. So 2e-4 m/s^2, which I believe is the result someone else posted.

Re:short answer: yes

[vadim_t]

No, it doesn't apply to rockets. Escape velocity refers only to objects without any kind of propulsion, and rockets have one.

I can't see why you couldn't leave Earth's gravitational field at any speed you wanted. Now, at 200,000 miles you might fall down, if you run out of fuel. But at that point the escape velocity would be much lower than on the surface.

Re:short answer: yes

[vadim_t]

Right, but the thing here is that they're not shooting the satellite from a cannon. They're lifting it from a rocket, which can leave earth as fast or slowly as it wants.

Say, a helicopter ascends much slower than escape velocity, and still has no problem with doing because it has *propulsion*. Of course it can't leave Earth's gravitational field due to lack of air, but that's about the only thing that stops it from doing that.

Re:short answer: yes

[twiddlingbits]

50ish Kg of fuel to go to the MOON isn't efficient? Beats the crap out of chemical engines. If you read my post I said it would take A LOT of fuel, I too was too lazy to calculate it. Another post said a few solar masses of fuel would be needed to get close to C. The whole problem is really how to get that huge mass accelerating even the tiniest amount with a engine with such low thrust. But if you can get it moving and keep it moving then the mass gets smaller and smaller, eventually you have a very light craft going very fast but it would take centuries to get to there due to the time required to get up to speed.

Re:short answer: yes

[another_henry]

Right.. now, a question I've never found an answer to: Why can't you do the same thing with a black hole? Henry

Boeing has some power...

[domenic v1.0]

Boing has developed the PAS-5, the world's first commercial satellite with an ion thruster.

Re:Boeing has some power...

[DarthWiggle]

I don't know if I'd trust a satellite made by a company called "Boing".

Re:Boeing has some power...

[mowler2]

And in soviet/russia they have been using ion engines for decades.

Aha, I get it, it is the *commercial* part that is the big thing here, truly revolutionary, eh? ;)

This is not the first ion drive...

[meringuoid]

... JPL's Deep Space 1 demonstrated the potential of such an engine back in the 20th century. Now we're seeing the first missions to rely on ion propulsion.

It'll be interesting to see, if the Pluto probe ever flies, whether that uses ion propulsion. An ion drive could really make a difference on such a long-haul flight.

Re:This is not the first ion drive...

[ari_j]

It'll be interesting to see, if the Pluto probe ever flies, whether that uses ion propulsion. An ion drive could really make a difference on such a long-haul flight.

Yes, it really could make a difference. Specifically, it'd make the difference between how many times you'll have to say "great" before you get to the "grand-father was alive when they launched that thing" part of the conversation your descendants will have when it gets there.

meanwhile....

[sponga]

our friendly Russian comsmonauts will prepare another rocket to be sent to the moon and topple the flag.... again!

George Lucas should sue...

[Guitar Wizard]

That's very cool...I'm sure that it's a lot cheaper to power that sort of craft in comparison to a solid-based rocket fuel (which I hear is absurdly costly).

Now we need to start making TIE fighters (Twin Ion Engine fighters from Star Wars). :D

Re:George Lucas should sue...

[Clay Pigeon -TPF-VS-]

This is gonna hurt my karma, but what the heck. I'd take a y-wing. Its main propulsion (sublight) is an ion drive, it has a hyper drive, proton torpedo launchers, shields, armor, can seat two (plus droid), and has greater range than the x-wing. Of course, it actually has an atmosphere inside its cockpit (unlike the TIE series), and has a top light ion turret.

Re:George Lucas should sue...

[cjameshuff]

I don't see why it would be so costly...mostly a butyl polymer (synthetic rubber, basically), solids like aluminum powder, catalysts such as iron oxide, and an oxidizer...probably ammonium perchlorate. They are very compact, simple, and powerful. You just can't turn them off once they're started, and the solid fuel-oxidizer mixture is far more dangerous to handle than a couple tanks of unmixed cryogenic liquid. (Spark hits a cryogenic vessel...nothing happens. Spark his a fuel core...trouble.)

The main advantage of ion engines is that, once you get them into orbit, they'll get you a lot further than an equivalently sized chemical rocket. This means you don't need to lift as much, and a greater portion of what you lift will be the more interesting stuff.

Cheap Technology!

[jd]

Give me a Bussard Ramjet any day! Well, that and an extremely good handbrake.

Re:Cheap Technology!

[cryptochrome]

I think plasma sails are more likely in the short term.

Re:Cheap Technology!

[WolfWithoutAClause]

Actually, analysis of Bussard Ramjet showed that it is a good handbrake!

Inspite of early promise it turned out that the thrust/drag of the ramjet against solar wind and interstellar gas turned out to be below unity. That's bad- you don't go anywhere.

This lead to a concept called M2P2, which is an 'inflatable' plasma. You turn it on and it expands out to a few tens of kilometers, the solar wind pushes on it, and a few months later you are leaving the solar system at high speed, dragged along by the plasma. Basically they ditched the drive system, and just used the collection field.

It worked in a small scale lab test, but nobody knows whether it will really expand out to a few tens of kilometers, and there were a few potential problems, such as tending to vapourise the vehicle due to the very high temperatures of the plasma, still it shows some promise, it's similar to the way the Earths magnetosphere operates.

TIE Fighers?

[ecliptik]

Isn't this how TIE Fighers from Star Wars worked? Their wings were solar panels, and TIE stood for Twin Ion Engine.

Re:TIE Fighers?

[jfengel]

That's right. What the movie doesn't make clear is that it was sped up by a factor of 10,000, because solar panels that size result in only a trivial amount of thrust.

Re:TIE Fighers?

[Anonymous Coward]

Why did I just have a flashback to a scene in Austin Powers involving a steam roller and somebody screaming "Nooooooooooooo"?

Re:TIE Fighers?

[mikael]

That's right. What the movie doesn't make clear is that it was sped up by a factor of 10,000, because solar panels that size result in only a trivial amount of thrust.

No, the TIE fighters had a large bank of 48 car batteries which were kept topped up by the solar cells. Each TIE fighter had to charged up from the mains at least once every 48 hours, otherwise the battery would run flat, and you'd be stuck in space. In that case, the only way to start the engines was to plug an R2D2 unit into the cigarette lighter socket.

Re:TIE Fighers?

[glenebob]

What the hell is an "R2D2" unit??? "R2D2" was an individual "R2" unit with the designation "D2".

Now, somebody needs to explain how the maximum number of R2 units with unique ID's in the WHOLE FRIGGIN' GALAXY could only have been 1296???

Re:TIE Fighers?

[Tablizer]

Isn't this how TIE Fighers from Star Wars worked? Their wings were solar panels...

"Luke, you may get away today, but in 12,000 years my total thrust will eventually exceed yours, and you'll be MINE!" -- Darth "Quickie" Vader

Re:TIE Fighers?

[Gulthek]

Dude, you know that R2D2 sabotaged the motivator or convinced the R5 to play broken right?

R2 doesn't leave the fate of the galaxy to chance :-)

Re:TIE Fighers?

[hey!]

Which reminds me of an oldie but goodie.

How do you tell a redneck jedi?

His X-wing is painted with primer.

Re:TIE Fighers?

[Guppy06]

Yes, but unlike the ion engines of today, they were powerful enough to be heard in a vacuum.

I almost fell out of my seat laughing when Jango Fett broke out those "sonic charges" in AOTC. That one was right on up there with the Wing Commander movie...

Re:TIE Fighers?

[Suidae]

With any luck his ramscoop collection field will sweep through the leading ship, killing any inhabitants.

Sharper Image

[nick_davison]

Anyone who's anyone knows Sharper Image have been selling these for years.

There's really no end to the crap Sharper Image can add ions to and double the price for. It only stood to reason they'd release spaceships with them too. ;)

You'll find them in their catalogue next to the negative ion vacuum cleaners, negative ion air purifiers, negative ion hair driers, negative ion bikini zone razors, and negative ion pet hair brushes (the scary thing is I only made one of that entire list up).

Re:Sharper Image

[glenebob]

Double the price? That ought to get a few customers all charged up...

Re:Sharper Image

[Gulthek]

That and burltech (the wood grainy stuff). Back in my retail days at The Sharper Image we'd take bets on what product would have:

1) Those damn nature sounds added
2) The wood grain added
3) Negative Ions added

Some products would get a nature sound added, and no volume control. Brilliant work.

Wait for: the "negative ion standing fan with wood grain and 50 soothing sounds" to hit the shelves for only $399.95.

Science writing at its best

[peggus]

The engine does not combust fuel; rather it splits atoms with electricity to get ions, accelerates them at high speed, and then ejects them, driving the spacecraft forward. SMART-1 generates its electricity by converting sunlight with outsize solar arrays that give the spacecraft a 45-foot wingspan.

Brilliant science journalism there. If the smart probe was splitting atoms it wouldn't need solar panels. Not to mention you don't need to split atoms to get ions.

That reminds me of the article that was written on some research I was involved with. We were pulsing cells with high potential electric fields. The field strength was measured in MegaVolts per meter due to a very small gap between the electrodes, the actual voltage was only a kilovolt or so (over a 300ohm load for 5-15 ns). The journalist / engineer-reject thought that megavolts sounded really big and took it upon herself to proclaim that our pulse generators could power a whole city. Moan, groan....

Re:Science writing at its best

[joshv]

I will grant you that in normal scientific usage 'atom splitting' usually refers to splitting the nucleus, but technically the atom is composed of a nucleus and the surrounding electron cloud, so separating an electron from the atom could be considered 'splitting' the atom.

-josh

Re:Science writing at its best

[glenebob]

At least he got the part about the wings right. Without those, you'd fall right back to Earth!

Re:Science writing at its best

[Ruie]

Brilliant science journalism there. If the smart probe was splitting atoms it wouldn't need solar panels. Not to mention you don't need to split atoms to get ions.

Sounds ok to me. You take a neutral atom (argon most probably) and split into an ion and a few electrons.

This is not the same as splitting the nucleus.

Re:Science writing at its best

[peggus]

True.
And technically our pulse generators could power a city, for a very very short period of time.

How is weightlessnes relevant?

[mowler2]

I dont understand why they talk about the probe being (near) weightless in space in the same context as the engine beeing useful in space?

No matter where the probe is, it has got the same mass, and hence the same inertia. Low-thrust engines work good in space because of no friction and often no requirement on quick travel (if it is a non-manned spacecraft). On earth an ion engine would never work for several reasons, one beeing friction against air and ground, but none of them has to do with the weight of the vechile/probe?

Or have I misunderstood something?

Re:How is weightlessnes relevant?

[hobbesmaster]

Newton's law of universal gravitation: Fg = GMm/(r^2) where:
Fg is the force of gravity
M is the larger mass
m is the smaller mass
r is the distance between the center of hte two objects.

An object at the surface of the earth with a mass of 1 kg is subject to a gravitational force of 9.8N. At the moon, the gravitational force exerted by the earth on the 1kg mass, using newton's law of universal gravitation is 0.0026N.

So indeed, gravity and weight have a pretty big part to play in this. On the surface of the earth, an object would have to have an upward force of more than 9.8N/kg to produce and upward acceleration; as your distace from the surface of the earth increases, your gravitational attraction to the earth decreases. What is refering to here is that the ion engine is producing a small thrust, lets just say a few newtons/kilogram (no idea what it really is), so long as its thrust is greater than earth's pull of gravity, it'll keep accelerating (and that magnitude of acceleration will increase as it moves along).

Hope that makes sense and I confuse you (or inadvertantly make some obvious error).

Re:How is weightlessnes relevant?

[jmichaelg]

I think they were implying that you couldn't use one of these engines to get off the earth's surface. The thrust they generate is on the order of the weight of a single sheet of paper. If you don't have to fight earth's gravity to get the craft moving, you're set. If you're trying to get off-planet, you're not going anywhere.

JPL has an open house every year. A few years back, they were in the middle of a multi-year burn test and during the open house, you could see the engine's blue glow as it sat there chugging out ions into a vacuum chamber. It was totally silent (vacuum has that effect...) and the exhaust looked like it came off the front page of Analog.

Re:How is weightlessnes relevant?

[mowler2]

I believe you are wrong. The probe is not accelerating perpendicular to earths surface, it is accelerating in an orbit around earth. The force accelerating the probe can be anything, as long as it is more than the tiny deacceleration from friction in the thin gascloud that surrounds earth.

When a probe is in orbit around earth no force is required to eliminate the pull of gravity from earth, since this force is counteracted by the centrifugal force due to the circular motion around earth, and the probe stays in orbit (if we assume the friction from the gas in space is zero).

Using the formula you provided for gravitational force, and the formula for centrifugal force, you can calculate the necessary speed you must have to sustain a specific orbit, or virce versa. If you want to leave earth, you just simply have to increase your speed and this acceleration can be how big or small as you like.

Re:How is weightlessnes relevant?

[carambola5]

You have missed something...technically.

In a typical chemical rocket, you burn and coast. During the burn, you have micro- or macro-g conditions (depending on numerous factors). During the coast, however, you have micro-gravity...so micro, in fact, you could consider it zero-g.[1]

With these engines, however, you don't have a coast period. You are continually in a burn state and therefore are continually accelerating, producing a micro-g environment. Granted, the acceleration is near-trivial, but it's still "near-weightless." Perhaps the only zero-g period with this type of craft is halfway to its destination, bewteen when the engine is shut off, the craft is turned around, and the engine is turned back on for deceleration.

[1]Before you chastise me, floating around in orbit is not a 2-body problem. You still have the sun, moon, earth, and self....among other diminutive gravitational forces to other bodies.

Re:How is weightlessnes relevant?

[mowler2]

Hm, I seem to have written a bit stupid.

What I ment was that the weight has nothing to do with it per se (except that it can cause friction), however, if we remove friction (for example by some imaginary surface, magnetic field, or whatever) and air resistance (perfect vacuum tube) on earth, the ion engine would work just as well here on earth?

Re:How is weightlessnes relevant?

[mowler2]

>not for e.g. atmospheric flights.

In atmospheric flights you also have problem with air friction.

>you're mixing up mass and weight.

The mass of the probe is the same in a zero-g environment, or on jupiter - it is the weight that is different, we both agree on that.

However, I still dont see why weight, in it self, is (always) relevant for the acceleration of the probe. When we calculate the resulting acceleration from the engines we only consider the mass of the probe and the engine thrust. Now imagine if we have the probe on earth in a vacuum tube floating on some zero-friction surface or magnetic field (we have force equlibrium). Then if the engine are turned on, they would accelerate the probe as much as they do in empty space even though the probe has weight, right? (now the gravitational force is counteracted by the force of the magneticfield, instead of the centrifugal force in orbit)

Re:How is weightlessnes relevant?

[ryanmfw]

No! It would work, but it wouldn't do anything. It doesn't have the strength to overcome earth's gravity. Air resistance and what not, or the lack of those factors does not change it. It will work in air, just not well. It will work inside the earth's gravity well, but not very well. It only works when it doesn't have gravity pulling on it very hard.

Re:How is weightlessnes relevant?

[ryanmfw]

Weight is a measure of how much gravity is pulling down on the mass. If the weight is too large for the force of the engine, it will fall down. This is why weight is important.

Re:How is weightlessnes relevant?

[mowler2]

I mean that the surface is completely orizontal - that is, the "tunnel" lies in such a way that the probe/engine is not affected at all by gravity (there is no friction, and no air resistance, but the probe does not move until we turn on the engine). Then it would accelerate just as good as it does in space even though it has weight?

Re:How is weightlessnes relevant?

[ryanmfw]

Sure, it would just be a negligible amount of force. It probably wouldn't move as it wouldn't be able to break static friction. Of course, with a low enough amount of friction it would still work. It's just not meant to work in environments with more friction than space. It *can* work, just not very well.

Re:How is weightlessnes relevant?

[mowler2]

As I said, we have force equilibrium when the engine is not running - that is, the sum of all forces are 0. I am not talking about a vertical "launch", I am just talking about a sort of "horizontal" burn where the engine resides on a frictionless surface of some kind and there is no air. Then the engine should accelerete just as good as it does in space, even though it has "weight".

Say its mass is 1 kg and its weight is 1 million kg and the engine has a 1 N thrust. This means that the acceleration is, using a = f/m is:

1/1 = 1 m/s^2.

That weight of 1 million kg becomes a problem only if we have friction.

Re:How is weightlessnes relevant?

[ryanmfw]

Sure, but you're essentially operating in space. Sure, there's gravity, but you're operating on a tangent to the gravity so it doesn't perform any work.

Re:How is weightlessnes relevant?

[mowler2]

My point is that it is not the *weight* that makes the probe do "better" in space than on earth; but rather friction from air or the ground caused by weight and/or size/shape of the probe.

When the probe is in space, the engine is not used to overcome the gravitational force afaik. A traditional rocket places the probe into an appropriate orbit where the probe is not affected by the gravitational pull (all forces equals zero), then the probe use its engine to increase its orbital velocity, and in doing that, increasing the radius of the orbit.

Re:How is weightlessnes relevant?

[ryanmfw]

Well, most people don't use incredibly weak motors to move things on earth. You are technically right, that when moving something tangentially to the gravitational force on a frictionless surface in a vacuum, it accelerates at the same speed as in space. What you have created though is pretty much space. I thought you were talking about lifting things into orbit with ion engines, which is pretty much impossible. On a sidenote, there is still a gravitational pull in space, it's just very small compared to being near the earth. Otherwise, the probe wouldn't *stay* in orbit.

Re:How is weightlessnes relevant?

[mowler2]

With my sentence "...orbit where the probe is not affected by the gravitational pull", I ment that there is a gravitational force acting on the probe, but a equal centrifugal force acting in the opposite direction so the sum of the forces is 0. (stable orbit)

In simplified theory the probe can then stay in orbit indefinetly without burning engines, etc, which is what I ment with "not affected by gravitational pull".

However in reality gas-friction, "gravitational waves", tidal energy, other bodies, etc, will remove/add kinetic energy and ultimately destroy the orbit. :(

Re:How is weightlessnes relevant?

[ryanmfw]

OK ok, I'll grant you that. :-)

Re:How is weightlessnes relevant?

[mowler2]

Yes it does perform work, acceleration of the probe is work. Formula for work: dW = F * ds, where F is force and ds is the change in position.

Now if the acceleration would stop, there would be no forces acting on the probe, and it would continue at an unchanging velocity and there is no work performed at this time.

Re:How is weightlessnes relevant?

[ryanmfw]

I meant that the gravity wasn't doing any work. :-) And it's dW=F(cos angle)*ds, which is why the work done by gravity is zero. Of course the engine does work. All I'm saying is that the engine *works* in the atmosphere, just not very well. So poorly in fact, that it's not worth using it there. If you set up the conditions so that it will work, you're replicating space, and for it to be useful, you'd have to make a frictionless vacuum tunnel so that it is even slightly worthwhile, and even then it wouldn't be.

Re:How is weightlessnes relevant?

[ryanmfw]

Let me note that after the equation for work, I didn't mean work in the technical manner. :-) Just thought I'd add that since we're catching each other in technicalities.

Re:ideal?

[Anonymous Coward]

In case you're not clear about this... SMART1 was built by ESA, not NASA. With that out of the way... SMART1 costs less than $100M, which is pretty cheap. It was the smallest of 3 payloads on an Ariane 5 rocket. So, this is a small, R&D style mission, very much unlike what happened in 1969.

Ion drives are great in some situations, because they give you a lot more thrust (over time, of course) per pound, then chemical drives. I believe they're about 5 times as efficient. Thus, if you're not in a hurry, this is indeed useful. And NASA used an ion drive for it's Cassini mission to Saturn too...

Re:ideal?

[mark-t]

The idea is that it becomes more practical the further you need to go in space because the system can provide a constant accelleration for its trip.

While getting to Mars may not be that practical with this tech, Jupiter's or Saturn's moons might be.

Re:Master of Orion

[mdvolm]

I thought the ion pulse cannon disabled ships without damaging them. Before a game patch dissallowed them, you could build heavy ion pulse cannons on your ships, which worked wonderfully. With a couple of doomstars so equipped you could literally take out an entire enemy fleet before they even got a chance to shoot at you.

Apparently the folks at Micro Prose noticed this as well and disabled the heavy version via the patch...

origin of cosmic rays

[Anonymous Coward]

Then could the mystery of the origin of cosmic rays be explained by particles emitted by alien ion-propulsion?

Re:ideal?

[uncl_bob]

1. It is not made for human flights.

2. It is not NASA.

NASA announces it will outdo the ESA

[i41Overlord]

"After hearing the news that the ESA's slow ion-powered probe has entered Moon orbit after a record-long 13 month voyage, NASA has announced that it will launch an even slower probe that propels itself by gliding on a trail of its own mucous."

Re:Master of Orion

[meringuoid]

Yep, my mistake. I think I was confusing MoO with Stars!, where IIRC there was an ion cannon that did knock down shields.

I always liked to build ships with a bank of mass drivers to take down the shields, followed by a battery of ion cannons to wreck the ship's systems. Easy kill. But that was a middle-game strategy; by the time I was building doom stars, I preferred phasors with all the modifications. You can put shield-piercing and auto-fire on a phasor; in conjunction with the Achilles targeting unit, which bypasses armour, that's about as lethal as it ever gets. Never played the original, though; things might differ in MoO2.

Re:ideal?

[AstroDrabb]

2. The ESA did _not_ come up with an ion propulsion system. NASA had an ion propulsion system back in 1998 that was used on Deep Space 1. This is just the ESA continuing what NASA has done.

A similar proposal to go orbital

[randall_burns]

JP Aerospace has proposed using an ion drive to take a special purpose blimp orbital.

What is interesting about this approach is the high ISP might make space fairly cheap. Personally, I find the fact that travel using this means is slow somewhat interesting. Humanity might benefit by having some "wide open spaces". Communications inside the solar system would be rapid in any event. Slow transportation might act to help discourage things like rash, interplanetary wars.

Re:ideal?

[AstroDrabb]

I don't even think Jupiter or Saturn would be preacticle for an ion engine. However, compared to current technology for deep space or extra-solar voyage using gravity assist, yes, the ion engine would be better. However, I still am not very impressed by it. I think it is a shame that we (USA) would spend billions upon billions on war, and constantly strip the budget of NASA. I really hope that in my life time (I'm 31) I get to see technology that can at least get us around the solar system in weeks or months.

Re:ideal?

[QuantumG]

I'm glad that's your idea of cheap. Ya know, I really hope that it cost that much because of all the sensors because an ion propulsion engine really isn't that complicated. You could build one in your garage for a few 1000's of dollars.

Great...

[MHobbit]

Wow, the ESA was capable of doing something! Ok, really, I'm actually interested in this. Ion-propulsion rules and should be released/developed on for other technology.

Re:ideal?

[polyp2000]

While you are correct in saying that for such a short distance it seems somewhat a long time to get from point A to point B to use such a propulsion system to travel a huge distance it becomes a much more viable proposition. In terms of acceleration we are talking slow, but over a larger distance it becomes significantly more economic in terms of efficiency. You can travel large distances with greater overall speed compared to traditional means because it will just keep on accelerating.

Re:ideal?

[AstroDrabb]

I agree and that aspect of the system is good. However, I don't think it is good for our inner solar system. It may not even be good for our outer solar system. However, compared to other propulsion systems getting to the nearest star, the ion engine would be the best, but still leave much to be desired. I just hope that in my life time (I'm 31) I get to see cool technology that can get us to Pluto in like 3 months or so >:P

Ion Propulsion has been used on Deep Space 1

[Herschel Cohen]

Indeed it landed years ago on an odd shaped space rock where it remains. Moreover, it tested other features like robotic flight and other risky technologies. [Note robotic is not remote control.]

It was one of the <i>cheap</i> experimental crafts meant to test as much technology as possible. Begin here for a bit of the history: http://nmp.jpl.nasa.gov/ds1/

Re:ideal?

[exp(pi*sqrt(163))]

Constant velocity => time for trip is proportional to distance

Constant acceleration => time for trip is proportional to square root of distance

The ion drive provides constant acceleration. As you rack up distance the ion drive becomes many orders of magnitude faster than constant velocity drives.

Re:no silly, they were that fast cuz the solar pan

[Tablizer]

...fast cuz the solar panels were so dang efficent!!!

Solar panels used in space are currently about 20% efficient. Even at 100% effeciency, I doubt Tie fighters with panels that size would have much visible thrust. It would violate the laws of physics to have solar panels be 1000% efficient. (Unless maybe they hang out near gamma rays, but gamma collectors don't look the same as solar panels.)

Speed of light...

[FuzzyDaddy]

Any thrust system can get you arbitrarily close to the speed of light, as long as you don't run out of fuel. Even if your exhaust velocity was slow, it would always provide thrust.

Suppose you had an exhaust velocity of 1 m/s. Even if you were going 1000 m/s, and you pushed half your mass out at 1 m/s backwards, you would end up going 1001 m/s, despite travelling at 1000X the speed of your exhaust velocity.

Now, it IS an issue of efficiency of your propulsion mass. Energy can theoretically be stored with a vry high density, and practically is available from the sun.

Re:Speed of light...

[Rei]

Please point to where I said that it's impossible to go up to relativistic speeds with an ion drive (as opposed to whether it was *realistic*, which was your exact point).

Re:Speed of light...

[FuzzyDaddy]

Your logic is fine except for one thing: I was replying to a different comment.

Re:Speed of light...

[Rei]

Grr... I misread the slashdot indentation. My apologies to you.

It ain't warp speed, and it ain't new either.

[Lew Pitcher]

"It ain't warp speed, but it's exciting new technology at work!"

Ion propulsion isn't "new" technology at all. It's been around for fourty years or more, in one form or another. The only "new" thing about this ion propulsion is that it is being used as the motive power for a spacecraft.

See this article from the August 1964 edition of "Popular Mechanics".

Re:How slow is it?

[wcrowe]

Nope, I've got it wrong. If they travel farther in the same amount of time, they're going faster.

Still, I think I could beat them there driving my '89 Volvo.

This is what

[Anonymous Coward]

NASA should be working on developing - advanced propulsion technologies - instead of wasting its money on the shuttle and the ISS.

Unfortunately, pork politics and a generally uinformed space enthusiast community keep supporting these wasteful programs, even though almost all scientists and engineers admit both the shuttle and ISS are doing little if anything in helping us further space exploration.

Re:How slow is it?

[djmurdoch]

Read the Nature article someone posted. They went 80 million kilometres in 13 months.

That's actually faster than the Apollo missions.

Re:ideal?

[WindBourne]

This was not about speed. It was about low costs and testing of durability. The US did the testing with Deep Space one. ESA has elected to do a moon mission.

The engine has ran quite a while and has proven that it is well made. I suspect that with the next generations of satillites (micro-sats), this will be the norm for propulsion.

Who needs sun?

[zippthorne]

well yeah.. or RTG's (Radioisotope Thermoelectric Generators) I'm sure the power-plant will well outlast the propellant supply

Re:ideal?

[AstroDrabb]

It would make a good propulsion system for micro-sat. Howver, I just think it is not a good option for any space option. One year to get to the moon vs. 3 day is really _very_ sad. An ion engine as you pointed out would be great for Earth orbit. I just don't want to see 30 year missions to Jupiter or Saturn any more. I want to see a big cut in or defense budget and transfer that to something that would really help mankind like our space budget. Here is too wishing :P

Benefits of Mars Colonization

[zippthorne]

Why does everyone neglect the obvious: safeguarding our species against single-event extinction.

Why do we need any more reason than that?

Re:Benefits of Mars Colonization

[bcrowell]

Why does everyone neglect the obvious: safeguarding our species against single-event extinction.
Because there's a mismatch of time scales. The dinosaurs survived for 300 million years without an asteroid defense. Over the next 100 years, it's not the big threat to our survival as a species.

whats next

[Petrus9373r]

with this step taken, whats next? People living on the moon. oooooo i cant wait

Technical project info

[d2ksla]

The project home page can be found here: http://www.ssc.se/ssd/smart1.html

Ion propulsion for cars!

[cpghost]

Imagine ion propulsion in our cars! Just gimme some months to reach those 55 mph...

Re:Ion propulsion for cars!

[antispam_ben]

Imagine ion propulsion in our cars! Just gimme some months to reach those 55 mph... I had a 1973 VW Beetle that drove like that.

Re:Ion propulsion for cars!

[daijo78]

Since SAAB was the main contractor you might not have to wait that long;)

Re:Ion propulsion for cars!

[daijo78]

Correction: Swedish Space Corporation was the main contractor but SAAB Aerospace was involved I think.

Wikipedia link to propulsion system

[Anonymous Coward]

SMART-1 uses Hall effect thrusters, somewhat different from the ion thrusters that the U.S. usually uses.

Couple of errors

[cicadia]

Your final result would be off by a factor of 1,000,000, if everything else was valid -- 2.08e-4 km/s^2 is 2.08e-1 m/s^2, not e-7.

That seemed like a ridiculous amount of accelleration, though, so I checked further, and the spacecraft's final velocity is given by the esa as 2737 m /s, not km. Interestingly, that's actually less than the earth's escape velocity by a good margin. My best guess at this point, then, is that the 2737m/s figure is the velocity imparted to the craft by the engine, not counting the initial velocity it was given by the rocket it was strapped to.

In this case, its acceleration is just 2737m/s / (3648h * 3600s/h) = 2.08*10^-4 m/s^2

At that rate, it will cross it's first football field (91.4m) in 296s, and the next one in just 122s. (It goes by the last one in just 0.033s)

Re:Couple of errors

[CrimsonAvenger]

That seemed like a ridiculous amount of accelleration, though, so I checked further, and the spacecraft's final velocity is given by the esa [esa.int] as 2737 m /s, not km. Interestingly, that's actually less than the earth's escape velocity by a good margin. My best guess at this point, then, is that the 2737m/s figure is the velocity imparted to the craft by the engine, not counting the initial velocity it was given by the rocket it was strapped to.

Actually, it is almost twice escape speed - the spacecraft was at the moon when it reached its "final velocity". Earth escape speed is only 1400 m/s or so at the altitude of the moon.

Re:Couple of errors

[cicadia]

That is interesting -- what I meant, though, was that it must have been going faster than that when it left earth and turned its engines on for the first time, and unless it spent the whole trip decelerating from 11,200 m/s to just 2,737 m/s, that it didn't make much sense for its final velocity to be 2737m/s

Re:Couple of errors

[CrimsonAvenger]

Ahh. It didn't start at Earth escape speed, it started at Earth orbital speed (~8kps for a low orbit).

It accelerated constantly in direction of travel, thus adding to speed.

Which changed the orbit so the spacecraft went up.

Which slowed it down, as kinetic energy was converted to potential energy.

Thing to remember is it started at ~70% escape speed, and ended up at ~200% escape speed.

Unfortunately, one of the downsides of very low acceleration is that deltaV required for escape is twice orbital speed, rather than sqrt(2) times orbital speed for high acceleration mode.

Given the Isp advantages, it still makes sense to use an ion engine, so long as you aren't in a real hurry to get anywhere.

Re:How slow is it?

[ryanmfw]

Considering that Apollo got there in 3 days, I don't think so. And are you sure it's 80 million kilometers? Last time I checked, the moon wasn't that far away.

Re:ideal?

[WindBourne]

While I would like to see some interesting missions going around, I think that the microsats have to be one of the better approachs to exploring. Think of mars with about 30 different microsats. Each could have an ion engine(s) for control. In addition, it would have a small amount of solar panels and batteries. Finally, these would form a network with each other and communicate with a main satillllite that does the core communication with Earth. Each of these microsats would offer communications with mars suraface and perhaps one other function. Some might have cameras. Others might contain a unique single experiment. These could be sent in 1 mission and simply seperate after going to orbit.

Likewise, think of a 100 of these on cassini. These could be launched around various moons and structures while cassini is racing around.

Re:How slow is it?

[djmurdoch]

Apollo went there more or less directly. The SMART mission got there by gradually spiralling out from a low orbit. The total distance travelled was about 200 times further than the Apollo capsules travelled, even though the distance from starting point to ending point was the same.

Re:Extinction events

[kinzillah]

No. statistically speaking the odds are the same as they always were. Just because you flipped heads, does not make tails more likely to come up next.

Re:How slow is it?

[ryanmfw]

Oh, ok. Oops, I take it back. :-)

Re:ideal?

[uberdave]

However, this is the first time an ion engine has been used to leave orbit and re-enter orbit.

"old news"

[PipoDeClown]

this reminds me of the Zero X comics where spaceships use this technic ^_^ http://www.technodelic.pwp.blueyonder.co.uk/Upload 01/ZeroXPt1.htm

Re:One small...

[Dr. Spork]

Look, strictly speaking, the first man, woman, dog, satellite, etc. in space were all European.

Haven't been there. Done that.

[Gorimek]

You can get that on Earth already. Where I grew up, just down the street from the North Pole, we had 3 months of daylight during summer. And plenty of water ice, if that's important to you.

It's actually the one thing I miss the most. Once you've experienced life without any darkness, you realize how much the night cripples your life, and it's a hard thing to lose.

Slightly off topic...

[DaneelGiskard]

...so, is there an engine based on electricity which works both inside the atmosphere and in vacuum?

Re:Slightly off topic...

[savuporo]

Actually, yes. "Lifters" work in the atmosphere with just electricity.
Unfortunately, nobody has built them big enough just yet to lift their own power source.

Re:Extinction events

[tantrum]

well, the number of asteroids out there is astronomical as well ;)

Not that I think it is likely that an asteroid will crush us. We can take care of that ourselves.

But but but

[Hatukaze]

But B*sh said we would go to Mars!
http://news.bbc.co.uk/1/hi/sci/tech/3384697.stm

And we all know B*sh never lies!

Re:Extinction events

[maxwell demon]

That's why you should always take a bomb with you to the airplane: The probability that there are two bombs in the same airplane is very low.

Valid reason?

[pwhysall]

Because it's there.

I've seen it in action.

[abramovs]

I was on a tour of JPL a couple of years ago and they had a team testing one out. It was rigged up inside a vaccum chamber with one small window. The engine had a light blue glow and I immediately though of a Star Destroyer.

They already have

[eberry]

NASA launched Deep Space 1 back in 1998.

Welcome to the party.

From the article:
April 6, 1999: The ion propulsion system on Deep Space 1 is the culmination of over 50 years of development on electric engine systems in space. Launched on Oct. 24, 1998, Deep Space 1 will be the first spacecraft to actually use ion propulsion to reach another planetary body.

Re:How slow is it?

[wcrowe]

Well, I knew they would have to spiral out, adding considerable distance to the trip, but I had no idea the spiral was so tight. It sounds like they were essentially in Earth orbit, slowly moving farther out in small increments.

Horsepower?

[shrikel]

While not much horsepower is generated, That's good, because horses would die in the cold, airless void. Plus there's nothing for their feet to push against, so it would be pointless anyway.

Besides, a quarter-million miles is a long way to make those poor suckers walk.

Re:Extinction events

[Anonym0us Cow Herd]

The surfact of the moon is covered with the results of astronomical odds.

(Don't remember where I read that quote.)

Deep Space 1 was not the first ion drive...

[GPS Pilot]

Hughes comsats used ion thrusters for stationkeeping years before DS1.

Re:ideal?

[AstroDrabb]

I know that NASA did not build this one. I was refering to the fact that NASA came up with the ion drive and did the first lauch of one on the Deep Space 1

NASA didn't used an ion drive for the Cassini mision. It was a regular chemical rocket with gravity assist to get to Saturn. NASA would not have risked such an expensive mission to unproven ion drives. There is also the little fact that Deep Space 1 was the first spacecraft to actually use ion propulsion to reach another planetary body and was launched Oct. 24, 1998 while Cassini was launched late 1997 I think it was October 13th. I would have been _really_ stupid of NASA to use an ion engine on Cassini when they were never tested yet. A quote from the Cassini mission overview

After a seven-year voyage that includes four gravity-assist maneuvers, Cassini will enter Saturn's orbit in July of 2004.

Current ion drives would never get to Saturn in 7 years.