Next Goals For The ESA

Ion drives... by FooAtWFU · 2004-01-19 17:23 · Score: 1, Funny

Efficient, but not fast. :) 1500 hours thrust time and they're still not there? Meh.

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Re:Ion drives... by ciroknight · 2004-01-19 17:32 · Score: 5, Informative

If you RTFA'd, you would realize that the satelite isn't on a direct moonshot, it's spiralling out from an earth orbit, to a lunar orbit. This would be hella slow compaired to a direct shot, which should get it there in a few days at worst. The thing is traveling at 3850km/h, it's just not doing it with a direct vector to the moon, rather, a spiral.

--
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Re:Ion drives... by WolfWithoutAClause · 2004-01-19 17:42 · Score: 5, Insightful

Interestingly, technically neither efficient, nor fast.
But they are economical of fuel. Jettisoning the exhaust at such high speed means you need hardly any fuel; which is good, but the energy source is an issue.
The reason that they are inefficient is that the exhaust velocity is too high. It turns out that the optimum exhaust velocity for minimum energy is about 2/3 the mission delta-v- and the delta-v to get to the moon is about 4.1 km/s whereas an ion drive exhaust velocity is usually around 30km/s... hugely too high from an energetic point of view.
Ok, big deal- it's only energy right? Wrong. The solar panels end up pretty enormous, and pretty heavy, pretty quickly. Nuclear energy? Power/weight ratio is little better.
Still, it works, but it's not even as efficient as chemical rocketry; chemical rockets can hit 80+% energetic efficiency in fact (it's very high because of the high temperatures used in the combustion chamber, rocket engines are actually classed as heat engines).

--
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"
Re:Ion drives... by Plocmstart · 2004-01-19 17:46 · Score: 5, Informative

A little flash animation for those confused about ion drives: http://www.esa.int/export/esaSC/SEM3K81P4HD_index_ 0.html . Of course depends on mass, momentum, etc. too....
Re:Ion drives... by Aardpig · 2004-01-19 18:05 · Score: 3, Interesting

Still, it works, but it's not even as efficient as chemical rocketry

One word: fusion. As soon as fusion comes along, coupled with ion drives, chemical rocketry is history. Period.

--
Tubal-Cain smokes the white owl.
Re:Ion drives... by britneys+9th+husband · 2004-01-19 18:21 · Score: 3, Insightful

The reason that they are inefficient is that the exhaust velocity is too high. It turns out that the optimum exhaust velocity for minimum energy is about 2/3 the mission delta-v- and the delta-v to get to the moon is about 4.1 km/s whereas an ion drive exhaust velocity is usually around 30km/s... hugely too high from an energetic point of view.
They're not trying to minimize the amount of energy used. They're trying to minimize the weight of the vehicle. Yes, the solar panels have to be bigger if they eject the ions at a higher speed, but this is more than made up for by not having to carry as much fuel.
I don't doubt that chemical rockets have a very high energetic efficiency, but they come with the major disadvantage that you have to transport all the energy out of the gravity well and into low earth orbit. With solar energy, you can wait until you're in space to collect it, so it's OK if you can't use it as efficiently.

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Re:Ion drives... by Bigfishbowl · 2004-01-19 18:45 · Score: 3, Interesting

Perhaps they are not the most efficient for Mars travel, but much beyond that, give me a break (having not done the math for Mars, I don't know). Chemical rockets spit far too much of their inital mass out the back to be even *somewhat* considered for longer term missions (remember the rocket equation?). There are several differnt kinds of "ion" engines all of which exceed 50% efficiency. At this point it becomes a bit more important to define "efficiency" - (power in)/(power out) may not necessarly be relevent if (mass start)/(mass end is near zero [what is the point of accelerating all of your "80%" fuel if you fling the crap out the back in a somewhat effiecent matter?) I may be (ok I am) a bit baises since I'm a grad student working in Ion Propulsion but the field obviously has merit or I would not have funding.
Re:Ion drives... by Aglassis · 2004-01-19 18:50 · Score: 5, Informative

You said: "One word: fusion. As soon as fusion comes along, coupled with ion drives, chemical rocketry is history. Period.'

Unlikely.

There are two main designs for a fission rocket.
(1) To couple a semi-conventional PWR or BWR with an ion engine. The big downside to this is that you have to have a large secondary system to use the steam to make electricity. What this means is that you have to have a large heat sink (large radiators) and lots of moving parts. A design like the GT-MHR could simplify this, but not hugely so.
(2) Using a bladder of fuel (hydrogen, or water or whatever), you use this as coolant to a critical reactor that jets the superheated portion directly to space. The downside is that this doesn't make electricity, so you would have to divert some of the coolant (which requires construction of the additional secondary systems) or use solar panels or RTGs to electrically power the spacecraft (there will be additional power requirements due to reactor safety equipment).

There are two main designs for fusion power:
(1) Tokamak: basically shaped like a donut, a low atomic number elemental plasma is magnetically confined and heated (with I^2*R losses or X-rays) to the point where fusion occurs. The means of useful energy transfer is via neutrons emitted which hit a water tank surrounding the fusion reactor. From here its just like the secondary side of a normal fission nuclear reactor (ex 1 above).
(2) A pellet of low atomic number elements is simultaneously hit by energetic radition from all directions compressing it until fusion occurs. Heat transfer like above.

You could argue that either of these fusion reactions could operate like the fission reaction #2 above (with part of coolant directed to make electricity), but an important point is that a significant fraction of the energy released by fusion (if it ever produces more energy than is required to induce it) is required to sustain it. This requires the construction of a very large secondary system compared to that of the fission reactor (a lot more heat being transferred). Since a fission reactor will probably provide way more power than is needed anyways, there is no reason to build a much heavier fusion reactor.

--
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
Re:Ion drives... by spacecowboy420 · 2004-01-19 19:50 · Score: 1

Just one nit pic; I agree with you except for this point:

the field obviously has merit or I would not have funding.

All fields that have merit don't neccessarily get funding and all fields that have funding don't neccessarily have merit. I believe ion drives are good, but based on their merit not their funding.

--
ymmv
Re:Ion drives... by Anonymous Coward · 2004-01-19 22:03 · Score: 0

Pretty interesting from a theoretical point of view... Could you please point to an analysis that discusses the relationship between delta-v and exhaust velocity?

I need however to be convinced that the overall energy has much relevance in mission planning. Solar generators have a life span much greater than the duration of any orbit transfer, so the limiting factor is surely not the total energy drawn from the system but rather the available power. Besides, solar generators are seldom fitted to the propulsion unit, it's rather the other way round.
It is always possible to balance thrust and exhaust velocity for a given power, so the actual exhaust velocity usually results from a compromise between fuel economy and acceptable transfer duration, nothing else.

And while I'm here, a shameless plug to a description of Smart-I's ion drive (actually a Hall thruster).
Re:Ion drives... by Anonymous Coward · 2004-01-20 00:08 · Score: 0

Why do you fu$%ing septics always put "Period" after everything ?
Full stop.
Re:Ion drives... by Short+Circuit · 2004-01-20 00:52 · Score: 1

The idea is that it's cheap...if you're not on a tight deadline, you can afford to wait for it to get there.

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Re:Ion drives... by FooAtWFU · 2004-01-20 01:49 · Score: 1

Dude, I did RTFA. And I realize it's not on a direct moonshot. It's not fast enough to do that. Which was kind of my point. (Well, OK, raw speed isn't really the deal so much as power, but you get the idea.)

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Re:Ion drives... by Anonymous Coward · 2004-01-20 02:19 · Score: 0

You forgot one fission drive possibility, namely the use of a fission pile as in voyager, which I believe has no moving parts and has operated for a few decades, though power output is getting low now. You can power a ion drive with such a construct, which makes it usable for moderatly long voyage times in the outer solar system.

As for fusion, it won't happen anytime all to soon, the current leading edge already has more return energy then input by a considerable margin, but it's still quite some distance from general usability and to my knowledge is fairly heavy and large. Scaling things down enough will probably take some time, once they have a working system that is.

Quickshot
Re:Ion drives... by robby2 · 2004-01-20 02:23 · Score: 1

It's not fast enough to do that.

No, I think it's because the main objective is to test the ion engine. Doing a spiral around the earth they are able to test it a lot more than just a shot right to the moon.

Anyone up for the calculation if it's accually able to do a direct shot out of earths gravity?

Robby2
Re:Ion drives... by WolfWithoutAClause · 2004-01-20 07:00 · Score: 1, Funny

The good news is that fusion is only 30 years away, unlike 50 years ago, when it was 50 years away.

--
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"
Re:Ion drives... by WolfWithoutAClause · 2004-01-20 07:54 · Score: 1

Efficiency isn't the most important metric- usually cost is.
The main potential advantage that ion drives have is that the delta-v is potentially huge (although most current thrusters often wear out fairly quickly- each giving maybe 1 tonne km/s, although you can have multiple thrusters.) In practice, the fuel they can use is often very expensive.
The energetic efficiency that you mention is related to the kinetic energy of the exhaust divided by the supplied energy- that's a different number to the efficiency I'm talking about; you multiply the mission efficiency by the thruster efficiency to get the overall mission efficiency (for a fixed ISP drive).
I don't really see the point in antipathy towards chemical propulsion; ion drives are much too slow for quite a lot of applications- the energetic efficiency ultimately limits their applicability- indeed, somewhat lower ISP, say, 1000-1600 seconds, with good thruster energetic efficiency is probably more desirable.

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-WolfWithoutAClause
"Gravity is only a theory, not a fact!"
Re:Ion drives... by AKAImBatman · 2004-01-20 09:30 · Score: 1

An RTG is NOT a fission pile. It simply takes the heat from the plutonium and converts that into electricity. The most current RTGs get about 75W per 2.5 pounds of Plutonium.

As for Fusion, there are quite a few good ideas on using it for propulsion (such as firing small fusible pellets in front of a pusher plate and causing fusion by way of high powered lasers). However, fusion as an electricity source is not only far away, but would probably be bulkier than an equivalent fission reactor.

--
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Apart from the costs of launch by GonzoDave · 2004-01-19 17:24 · Score: 3, Interesting

What are the technical obstacles to Lagrange point colonies?

Re:Apart from the costs of launch by Anonymous Coward · 2004-01-19 17:32 · Score: 1, Funny

Having them thrown back at you when the colonies revolt.

Sieg Jion!
Re:Apart from the costs of launch by kfg · 2004-01-19 17:35 · Score: 5, Funny

What are the technical obstacles to Lagrange point colonies?

Mostly all that vacuum and radiation and fast moving rocks and stuff.

Ya know. The usual.

KFG
Re:Apart from the costs of launch by Anonymous Coward · 2004-01-19 17:42 · Score: 2, Interesting

Would a colony actually *stay* in the lagrange point?

I imagine that the point is moving around the earth at the moon orbit speed, and whilst within the point, the gravity of both moon and earth would have no influence on the colony -> ie it wouldn't be holding it in orbit to follow the point around as required...

I also imagine that putting a colony *near* the point would be silly as the forces on the colony structure would come from different directions at different times of the day, and thus require stronger construction techniques (for forces in any direction, instead of forces in one).

The orbit would also wander widely for the same reason, and it would thus be a bitch to dock with, and perhaps even unecessarily difficult to find...
Re:Apart from the costs of launch by kfg · 2004-01-19 17:47 · Score: 1

Would a colony actually *stay* in the lagrange point?

http://www.physics.montana.edu/faculty/cornish/l ag range.html

KFG
Re:Apart from the costs of launch by Aardpig · 2004-01-19 17:52 · Score: 4, Informative

Would a colony actually *stay* in the lagrange point?

L4 and L5 are the stable Lagrange points; these are the ones in the same orbit as the moon, but leading or trailing by 1/6th of a revolution. The other points, L1-L3, are unstable: while the effective gravitational force at these points is zero, an infinitessimal displacement away from a point will lead to a force which is also directed away from the point, leading to runaway.

So, in answer to the quesiton, a colony at L4 or L5 would stay in position without further assitance. At L1-L3, it would need positioning rockets to stop it from wandering. This in fact is how SOHO (the Solar and Heliospheric Observatory) remains in its Sun-Earth L1 position (inside the Earth's orbit, on the line between Earth and Sun).

--
Tubal-Cain smokes the white owl.
Re:Apart from the costs of launch by techno-vampire · 2004-01-19 17:52 · Score: 2, Informative

Would a colony actually *stay* in the lagrange point?
Do the Trojan Asteroids stay in, or at least near the Lagrange points in Jupiter's orbit? Yes, I believe they do. The Trojan Points are the two most stable Lagrange points. In fact, the biggest problem with L4/L5 colonies is the other "space trash" that's bound to be there: dust, pebbles, small rocks and so on.

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Re:Apart from the costs of launch by Ancil · 2004-01-19 17:55 · Score: 1

Just off the top of my head:
Food
Water
Getting there
Getting back
Getting funded
etc...
Basically, the usual suspects.
Re:Apart from the costs of launch by EmCeeHawking · 2004-01-19 17:57 · Score: 1

What are the technical obstacles to Lagrange point colonies?

Keeping CowboyNeal tied down to a single point on the surface.

Allowing him to move around displaces the actual Lagrange points enough to make it unfeasible unless he is kept stationary.
Re:Apart from the costs of launch by flewp · 2004-01-19 20:30 · Score: 1

Don't forget horribly bad movies.

Although I dunno if the SoL is at a Lagrange point.

--
WWJD.... for a Klondike bar?
Re:Apart from the costs of launch by 69charger · 2004-01-19 22:51 · Score: 1

Well, I hear it's fine if you got the time
and the ten to get yourself in.
A hmm, hmm.
And I hear it's tight most ev'ry night,
but now I might be mistaken.
hmm, hmm, hmm, hmm.

Have mercy. ;)
Re:Apart from the costs of launch by fucksl4shd0t · 2004-01-19 23:02 · Score: 1

*sigh* Time for bed.
I had to read your post three times before I placed the lyrics, and then I had to read it three MORE times to figure out how it was relevant.
I must be sleepy. There's no other explanation.

--
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Re:Apart from the costs of launch by not-my-real-name · 2004-01-20 03:21 · Score: 0

If I remember correctly, the gravity from the sun distorts the L5 & L4 points so the actual stable point wanders around that region a bit. The main practical problem with placing something at one of these points is that they would also tend to collect whatever debries wanders by.

You can place an object in orbit around the L1, L2, or L3 points. This is called a halo orbit, and if I remember correctly, is what SOHO uses.

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Re:Apart from the costs of launch by FroMan · 2004-01-20 04:25 · Score: 1

Well, I have done a large amount of research at home with working with a vacuum. It really does not seem that difficult. My test subjects were my cats, Millie and Callie.

Required supplies: vacuum, floor, two cats.
Millie hates the vacuum and runs and hides in the closet.
Callie loves the vaccum and runs around like a wild beast when the vacuum is running (I think cause she hates Millie and its the time she has to run around without being bothered by Millie).

So, all we need in space is closets. Closets will protect us from the vacuum.

--
Norris/Palin 2012
Fact: We deserve leaders who can kick your ass and field dress your carcass.
Re:Apart from the costs of launch by Brahmastra · 2004-01-20 05:15 · Score: 1

Even then, it would need some kind of rockets to keep it stable. The colony would have to jettison waste, people inside the colony may fart, etc, and these forces would cause slight drifts. Rockets will still be needed to correct wandering periodically.
Re:Apart from the costs of launch by Anonymous Coward · 2004-01-20 05:16 · Score: 0

The conclusion that objects placed at Lagrangian points will remain there depends on the assumption that there are no other forces other than gravity acting on said objects. Unfortunately there is solar wind. Without corrections, objects will eventually drift from any L-point.

Not to mention, the L-points are not so simple once you include the gravitation effects from other sources: other Sol planets, etc.
Re:Apart from the costs of launch by PhuCknuT · 2004-01-20 06:00 · Score: 2, Informative

Halo orbits will only keep the object stable in the plane perpendicular to the line between the earth and moon, any displacement out of the plane will need to be corrected still by rockets. IMHO, this is a perfect application for ion engines, making minor orbital corrections in geosync and lagrange orbits.
Re:Apart from the costs of launch by Carewolf · 2004-01-20 06:41 · Score: 2, Informative

No it's a stable point, this means that small changes are unimportant as you will be dragged back in position, unless you exceed the exit energy level.
Re:Apart from the costs of launch by kfg · 2004-01-20 09:09 · Score: 1

There are an awful lot of theories as to what seperates man from the animals, however, I've always thought it really came down to the fact that we're not afraid of vacuums.

I'd note, however, that your experiment left out the radiation and fast moving rocks. I suggest you repeat while watching the Daytona 500 on the Telly and tossing a mini superball around.

Cat behaviour can become very interesting under these conditions. Although closets still seem to figure prominently for some of them.

KFG

New pictures... by AIX-Hood · 2004-01-19 17:25 · Score: 3, Informative

Well, to give it equal footing to the Spirit, here's some new high res photos that the ESA's orbiting photo taker took. Apparently there's also one of it looking down on the crater that the Sprit is in. http://www.esa.int/export/SPECIALS/Mars_Express/in dex.html

Re:New pictures... by swm · 2004-01-19 17:34 · Score: 4, Informative

A better link

http://www.esa.int/export/SPECIALS/Mars_Express
Re:New pictures... by __aatgod8309 · 2004-01-19 18:41 · Score: 5, Informative

A better better link

This is pretty neat! by blankinthefill · 2004-01-19 17:31 · Score: 2, Informative

I had read somewhere that an 'ion drive " might be the basis for interstellar travel (not necessarily a manned mission), because it's so effiecient. I don't know the truth of that, though. On a second note, the ATV is awe-inspiring, but I wonder how Lockheeds new hybrid space-plane idea wll work in with that. (POP-Sci just ran an article in the last issue that subscribers got, feburary, I think)

Re:This is pretty neat! by GonzoDave · 2004-01-19 17:32 · Score: 1

http://www.space.com , search "Ion Drive", "Chemical Drive" and "M2P2" if you're interested
Re:This is pretty neat! by stevelinton · 2004-01-19 17:57 · Score: 4, Insightful

An ion drive is still nowhere near effective enough for a manned
interstellar probe.You need a fairly pure fusion drive, or antimatter, or some flavour of beam-rider to get interstellar journey times down to a few years or decades without completely silly mass ratios.
Re:This is pretty neat! by fucksl4shd0t · 2004-01-19 23:04 · Score: 1

I thought the problem with getting instellar journey times down to a few years or decades had everything to do with the speed of light and very little to do with anything else?

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Re:This is pretty neat! by jsebrech · 2004-01-20 01:10 · Score: 1

The closest stars are 4 lightyears away (even less? I forget). If you could build something that could deliver the ridiculously high energy requirements of getting to light speed and back again you could travel there in a matter of years. Also, remember that this would be earth time. For the people making the journey it would be a matter of weeks or months (as distance shortens as you go faster due to relativity). So, we could even send people to places hundreds of lightyears away (and have it only take a few months or years for them), provided we let them travel close enough to lightspeed. Ofcourse, the use of this for humans might be limited, but we've already sent probes on missions that take decades (which is too long to get any political payoff out of it), so maybe missions that don't arrive until 200 earth years have passed would find funding.

There's also the matter of communicating your findings back to earth, but there are a number of theorized ways on doing faster than light communication (read: instantaneous regardless of distance), as a result of research in quantum physics, so it's not quite impossible.

You've also got to take into account that at those distances you have to send entire colonies. It's not feasible to send people and have them come back (they would have nothing to come back to since all their relatives and friends would have died long before they returned). Once we colonize a planet 100 light years from here, it's just a matter of time before they colonize a planet 100 lightyears from them (200 from us), and so on. Couple that with instantaneous comms, and you have the beginnings of a galaxy-wide empire (provided we don't run into aliens along the way and start a war with them).

It's really not such a far-fetched idea. We're just not likely to see it in our lifetimes.
Re:This is pretty neat! by Anonymous Coward · 2004-01-20 03:05 · Score: 0

"It's really not such a far-fetched idea..."

Or maybe we can ride a wormhole through a black hole! Or maybe we'll invent teleporters! Or maybe we'll invent warp drives and send a group of intrepid explorers out to see the universe (along with an alien babysitter)!

Oh wait - that won't happen. They cancelled that Star Trek show because it was a DUMB IDEA!

j/k!
Re:This is pretty neat! by stevelinton · 2004-01-20 19:43 · Score: 1

Getting close to light-speed is also a problem. All rockets essentially work by converting some of the initial vehicle (the fuel) into energy and using it to accelerate another part of the vehicle backwards (the reactin mass), thereby forcing the remaining part of the vehicle forwards. This covers chemical rockets, ion drives, mass drivers, fission rockets of various kinds, project Orion and so on.

There is a simple equation relating the speed at which you can throw the exhasut backwards (in the ships rest frame), the proportion of the ship made up of fuel
and reaction mass at launch time and the total delta-V which can be achieved. A slightly more complicated equation deals correctly with what happens when the exhaust velocity or the ships velocity approach light-speed and relativity plays a role.

Using this and imposing a ceiling of say .9999999 on the proportion of the launch mass made up of fueld and reaction mass (ie at least 1 part in 1 million must be payload) you can easily find that no chemical or fission based system can get you even close to light-speed because it simply doesn't convert enough of the mass of the fuel into energy. This basically leaves fusion (and you need a pretty efficient fusion plant, and you still don't do go very fast) or antimatter, which works just fine (in principle), or you need to cheat.

Cheating is a matter of not carrying all your fuel with you. You either leave it at home and get the folks there to ship you momentum in the form of a beam of something (photons, charged particles, smart bullets,.....) or you pick it up as you go along, which is the Bussard ramjet idea. Both have their problems. Antimatter and beam riders seem like the best ideas so far.

An ommision of their current projects... by kommakazi · 2004-01-19 17:34 · Score: 5, Informative

The ESA also has a probe named Huygens headed for Titan, the largest moon of Saturn that will land on the surface in 2005 and send back photos. Titan is the only moon in our solar system with a thick atmosphere. It is believed it may be similar to that of Earth's millions of years ago.

Re:An ommision of their current projects... by obey13 · 2004-01-19 17:41 · Score: 2, Interesting

Nasa also has a probe headed to Saturn. Its called Cassini, and should be seven months, though its only an orbiter.

http://saturn.jpl.nasa.gov/news/press-releases-0 3/ 20031205-pr-a.cfm

--
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Re:An ommision of their current projects... by MarkLR · 2004-01-19 17:47 · Score: 2, Interesting

They should get together ...

The Huygens is being carried on the Cassini orbiter until it will be released in the same manner as the probe from the Galileo.
Re:An ommision of their current projects... by gr0ngb0t · 2004-01-19 17:55 · Score: 4, Informative

They are together

"Launched in October 1997, Huygens is currently in space, hitching a ride on NASA's Cassini spacecraft." (2nd last paragraph)
Re:An ommision of their current projects... by Anonymous Coward · 2004-01-19 18:40 · Score: 0

Learn to read.
Re:An ommision of their current projects... by Fr33z0r · 2004-01-19 20:56 · Score: 1

It's also practically *covered* in biological matter.

Not a very hospitable place for life, I'll grant you, but all it would take is a nuke :D
Re:An ommision of their current projects... by fucksl4shd0t · 2004-01-19 23:06 · Score: 1

Titan is the only moon in our solar system with a thick atmosphere. It is believed it may be similar to that of Earth's millions of years ago.
Not to mention the little guys with the Masters on their backs... Luckily, though, they don't breathe oxygen, so we're safe from them if we go to Titan.
Now, if they come here, that's a different story.

--
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Re:An ommision of their current projects... by Vintermann · 2004-01-20 00:13 · Score: 1

"that will land on the surface in 2005 ... "

I think we'll say TRY to land. Beagle 2 didn't go to well, although the orbiter is still useful.

--
xkcd is not in the sudoers file. This incident will be reported.
Re:An ommision of their current projects... by MalachiConstant · 2004-01-20 02:06 · Score: 1

Hey, I don't need any company out here! All the statues Salo made are more than enough for me. Haven't you bastards done enough? Leave me alone! And they better stay away from my son Chrono, he can be a bit violent at times.
(If you don't recognize my handle this joke will make no sense. Carry on.)

Ion Drive Mass? by ciroknight · 2004-01-19 17:34 · Score: 3, Interesting

I've only read that Xenon is used in current Ion drives... kinda wondering why more common gasses *read, nitrogen, probably the cheapest* can't be used. Anyone know?

--
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush

Re:Ion Drive Mass? by ak_hepcat · 2004-01-19 17:53 · Score: 5, Informative

Probably has to do with the number of available electrons to strip away.

Xenon is pretty plentiful (8 valence electrons), and compared to nitrogen (5 valence electrons), seems to have just a few more electrons available with little increase in mass, while still remaining a noble, inert gas.

IANAC

--
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Re:Ion Drive Mass? by stevelinton · 2004-01-19 17:54 · Score: 5, Insightful

You need an element which is easily ionized. you also want the individual ions to be pretty massive. A bonus is if the ionized version of the element is not too reactive. Early drives used mercury or cesium, but they had a habit of sticking to things and clogging them up, and had to be heated before they were ionized.

i'm pretty sure the cost of the xenon is negligible compared to almost any other cost around.
Re:Ion Drive Mass? by Anonymous Coward · 2004-01-19 17:54 · Score: 1, Informative

Xenon has an atomic mass of 131.30 (element 54 on the periodic table). More mass per atom than nitrogen (atomic mass 14 and change, element 7) means more thrust for the same number of atoms that are carried. And as a noble gas it doesn't react with anything.
Re:Ion Drive Mass? by McSporrran · 2004-01-19 18:03 · Score: 1

Simple, it's the most massive "noble" gas. Atomic weight of 131. As mass x velocity = mass x velocity an ion of Xenon gives the greatest thrust, compared to Nitrogen with an AW of 14, So Xenon would provide 131/14 ( 9 ) times more thrust.

--
gis-itna
Re:Ion Drive Mass? by Ancil · 2004-01-19 18:05 · Score: 3, Informative

1. Xenon is pretty heavy per atom. Because of how the ideal gas law works, that means a given mass of Xenon takes less volume than lighter gases at equal pressure / temp.
2. As a noble gas, Xenon is mostly inert -- important for a long mission where you don't want, for example, vaporized mercury corroding parts in your ion drive.
3. The cost of Xenon is non-existant compared to overall mission cost ($500 million or more? No idea, but moon shots ain't cheap).
Re:Ion Drive Mass? by that+_evil+_gleek · 2004-01-19 18:19 · Score: 1

Anyway--- I'm up late at night just to reply to a random note ;-]
And I say how would we know how to know whether or not a bacteria that did in fact die from acid rain may or may not have created something that resembled an art form somewhere on the surface of mars? And if first life did that then what ;-]?

And if we found what looked like a random tear drop later? then what?
Or perhaps a large form of a colony of one-celled etc, etc, & et al.

HMM... anyone one care if it turned out both sides of that argument were wrong?

Anyway, still.. somewhere in my possesion I have in a frame of something that looks like a pie-plate art from 1st grade going on second, and you have you seen that picture
from mars?
Well if you haven't then the jokes on heisenberg and your electron too
BAH-BUMP-BUMP

P.S. Or perhaps as well... yours truly etc etc
Re:Ion Drive Mass? by bfree · 2004-01-19 18:42 · Score: 1

Radon seems to be the most massive noble gas, but I guess it is useless here "because of its short half life (the longest life isotope has a half life of less than 4 days)".

--
Never underestimate the dark side of the Source
Re:Ion Drive Mass? by Beryllium+Sphere(tm) · 2004-01-19 19:43 · Score: 1

Xenon atoms are more massive than most. The other thing that comes in handy is that it's relatively easy to ionize. It's a big atom with the outer electrons far away from the nucleus and loosely bound.
Re:Ion Drive Mass? by kramer2718 · 2004-01-19 20:10 · Score: 1

Why not Radon? It also has 8 valence electrons, but more mass.

--
http://yetanotherpoliticalrant.blogspot.com
Re:Ion Drive Mass? by Anonymous Coward · 2004-01-19 21:54 · Score: 0

It's radioactive.
Re:Ion Drive Mass? by fucksl4shd0t · 2004-01-19 23:08 · Score: 1

Xenon? I love that game!

--
Like what I said? You might like my music
Re:Ion Drive Mass? by jandersen · 2004-01-20 00:11 · Score: 1

You said: "2. As a noble gas, Xenon is mostly inert..."

This of course only applies to the not yet ionised atoms. The reason Xenon is an inert element is that it's electron configuration makes less chemically reactive.

SMART-2 by Aardpig · 2004-01-19 17:36 · Score: 5, Informative

SMART-1 is part of the Small Missions for Advanced Research in Technology; these missions are specifically designed to develop new space-based technologies. A sister mission, due for launch in June 2007 is SMART-2 , which will be a testbed for laser ranging. The technology will eventually be put to use by LISA (Laser Interferometry Space Antenna), a proposed ESA mission intended to look for the gravitational waves predicted by Einstein's General Theory of Relativity.

The knowhow obtained from SMART-2 will also prove instrumental in developing ESA's Infra-Red Space Interferometer, known informally as Darwin. Darwin, part of ESA's Horizons 2000 programme, will consist of 6 infra-red telescopes flying in precise formation, with the aim of performing nulling interferometry of nearby solar-type stars. Darwin will be sensitive enough to detect the infra-red absorption-line signatures of water, ozone and carbon dioxide in the atmospheres terrestrial-sized planets orbiting one of these stars; these signatures, if detected together, would amount to strong evidence for extraterrestrial life.

--
Tubal-Cain smokes the white owl.

IIRC by anzha · 2004-01-19 17:37 · Score: 4, Interesting

The Italians had to fight tooth and nail to get the Vega launch system to be accepted by ESA for development. Part of it was, again, iirc, because it was would be separate from Arianespace. The whole point was to have an European developed follow-on for the Scout rockets that the Italians were building under license from the US.

The ATV is an excellent idea. I find it a little sad at this point that ESA hasn't successfully gone down the path of an independant manned space flight capability. Sure, they can use the Russians or the US or even the Chinese, I suppose, but it'd be interesting to see ESA come up with their own. I know they tried the Hermes space plane, but that turned out to be something of a boondoggle, didn't it?

--
Do you know why the road less traveled by is littered with the bones of the unwary?

Re:IIRC by GonzoDave · 2004-01-19 17:45 · Score: 1

but it'd be interesting to see ESA come up with their own Yeah, but you'd have to see an end to European bureaucracy first. Which isn't going to happen to a scale necessary for developing manned space flight. Concorde was a miracle, and probably the limit of English/French co operation
Re:IIRC by houghi · 2004-01-19 19:41 · Score: 3, Funny

Concorde was a miracle, and probably the limit of English/French co operation

Other things DO work. CERN is ione, wich brought us HTTP. Airbus is another example. The question remains if Europe wants it at this moment. It will naturaly be good footage on newsprograms. OTOH it will draw away money that could have been used better. I am not saying it would not be a good idea. I just wonder if the money spend can't be used better.

I also wonder if we already know all there is to know about the moon, because we send things to mars and not the moon, or is that just imagebuilding?

Also let us not forget the last time Europe send somebody into the unknown. He stumbled upon a new continent. Look what mess that brought us in. Europe does not want to make that same mistake again. ;-)

--
Don't fight for your country, if your country does not fight for you.
Re:IIRC by johannesg · 2004-01-19 21:12 · Score: 3, Informative

Although Hermes is gone, ESA is quietly working on capsules, such as this.
And I agree ATV is an excellent idea, but then I'd say that - I'm working on it ;-)
Re:IIRC by Ami+Ganguli · 2004-01-19 21:49 · Score: 1

I think the ESA is on the right track - there's no point in spending money duplicating other people's technology. Spend it doing something useful and different. SMART is an example of this.

--
It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail. - Abraham Maslow
Re:IIRC by fucksl4shd0t · 2004-01-19 23:15 · Score: 2, Insightful

Also let us not forget the last time Europe send somebody into the unknown. He stumbled upon a new continent. Look what mess that brought us in. Europe does not want to make that same mistake again. ;-)
Yeah, Europe doesn't want to have some upstart criminals on some new continent to bail them out of two world wars that they couldn't solve themselves, do they? ;)
Other things DO work. CERN is ione, wich brought us HTTP. Airbus is another example. The question remains if Europe wants it at this moment. It will naturaly be good footage on newsprograms. OTOH it will draw away money that could have been used better. I am not saying it would not be a good idea. I just wonder if the money spend can't be used better.
My guess is that Europe is putting to the test an unmanned space program. Here in the US a LOT of people criticize NASA for spending too much time and money putting men into space when they could be pursuing other things, and it looks like Europe is putting that to the test.
One thing's certain, from what I can see. :) It sure is nice to see different space exploration models cropping up besides NASA's. NASA may have gotten us to the moon, but they seem to have burned out sometime around SDI.

--
Like what I said? You might like my music
Re:IIRC by Anonymous Coward · 2004-01-19 23:28 · Score: 0

Yeah, Europe doesn't want to have some upstart criminals on some new continent to bail them out of two world wars that they couldn't solve themselves, do they? ;)

Hey, a European nation was going to win those wars either way. Besides, three of them bailed you Yanks out in the 18th century, or you'd still be singing God Save the Queen.
Re:IIRC by Anonymous Coward · 2004-01-20 00:41 · Score: 0

Why should we send people out of the gravity well? Other than to find out how to send people out of the gravity well ofcourse. There's really no destination yet. You can't really send people much further than mars with current tech, and as is being shown by the mars rovers, robots can do the job cheaper.

Maybe when we develop tech to fly spacecraft to another solar system in a reasonable timeframe. The comms delay would make robots pretty much a no-go there. So at that point I would agree manned space flight would be a good idea. But right now it seems to be not more than a PR stunt to me.
Re:IIRC by meadowsp · 2004-01-20 01:54 · Score: 1

Eurotunnel anyone?
Re:IIRC by Anonymous Coward · 2004-01-20 04:17 · Score: 0

the Soviets may have been upstart criminals but they were hardly on a 'new continent'

20 million dead
Re:IIRC by VanillaCoke420 · 2004-01-20 04:24 · Score: 1

I am sure we could manage to reach that goal. The ATV is comparable in size tothe Apollo craft. If ESA could get Ariane 5 approved for manned launches, then the step wouldn't be terribly big to launch manned capsules. The Hermes could have been something, but as usual the budget was blown to pieces. The Hermes was another similar project.
Re:IIRC by cheesybagel · 2004-01-20 10:35 · Score: 2, Informative

Actually, ESA had some concepts for a Crew Transfer Vehicle capsule, after the Hermes mini shuttle proved to be a failure. However it was decided not to fund development besides the ARD reentry demonstrator. They decided to help the USA in the "more advanced" X-38 CRV instead. But then NASA pulled the plug and the rest is history.
There are currently moves to design the next generation launch system after Ariane 5. It is supposed to come online sometime after 2020. The Germans made a study called FESTIP. They studied several alternatives. SSTO and TSTO, winged, ballistic, etc. They identified two concepts as having the highest payoff and highest chance of success: a TSTO winged launch system and a suborbital so-called HOPPER space vehicle. They settled on HOPPER as the lower cost and risk approach and are currently doing a prototype.
In the meantime the French recently awoke to the necessity of an Ariane 5 replacement and have signed a deal with the Russians to develop two new reusable high performance engines. One using LOX/Hydrocarbon and another using LOX/LH2. They also started their own study, called FLPP. FLPP will build a test vehicle called Socrates using the Russian engines and the thermal protection systems pioneered in the yet to be launched EXPERT test vehicle. Talk about NIH syndrome. In their defense, the French are responsible for the Ariane 5, 4, 3, 2, 1 designs, so they probably think they have more experience to be able to pull this one off. That has some merit, but then again CNES was also responsible for the Hermes boondoggle... Not that the Germans are any better, with plans for expensive vapourware like this in the past.

Re:4n 0m1510n 0f 73h curr3n7 pr093c75 by Deraj+DeZine · 2004-01-19 17:39 · Score: 0

It is believed it may be similar to that of Earth's millions of years ago.

Correct me if I'm wrong, but wasn't there quite a bit of life on Earth "millions of years ago?"

--
True story.

Moon by skydude_20 · 2004-01-19 17:42 · Score: 3, Insightful

Looking at the ESA site, if we're thinking of going back to the moon soon and possibly bringing back a bunch of old Apollo systems, why don't we buy some of the ESA's ATV's and slap on a larger booster? seems like it'd be a nicer ride (once modified) than the old Apollo craft. With the added bonus of being a spacecraft that is actually in production (no need to try and re-invient the wheel).

--
Jesus saves souls and redeems them for valuable cash prizes

Re:Moon by WegianWarrior · 2004-01-19 19:01 · Score: 3, Interesting

Apart from the fact that you will have to modify the ATV pretty heavily to make it work... for starter, even I can see that you must:
- Provide a larger engine for orbital manuvers. The old Apollo system had a trust of 97860 N (roughtly ren (metric) tons), while the ATV has an enginetrust of a paltry 1960N (or about 1/50 of the Apollo).
- Provide some form of manrated capability. The ATV is launced unmanned, and as far as I can see from the article carries no life support system on it's own.
- Some form of reentry capability must be provided, unless you plan to dock at the ISS on the way home. If you do plan to dock at the ISS, you need to carry enought fuel to brake down and enter earth orbit.
I fear that modefying a ATV can turn out to cost more and provide a less optimum vessel for going to the moon than a new design based on the Apollo. Despite the fact that the design of the Apollo is close to 40 years, they got a lot of things right, and a few wrong. Possible (cheap) ways to optimise the Apollo design might include:
- Use of a Soyuz-shaped return vehicle (better volume-weight ratio than the coneshaped Apollo).
- Modern electrics (lighter, less bulky, uses less power).
- Solar panels instead of fuelcells (solar panels have come a long way since the early sixties, and you don't have to carry along oxygen and hydrogen to make them work).
- An ion engine for long duration, low trust burns to optimise trajectory (?).

I am not a rocketscientist, but I don't see how the ATV cam be a good choice to go to the moon. It's designed to be a cargotruck, not a manned vessel for going far into space.

--
Everything in the world is controlled by a small, evil group to which, unfortunately, no one you know belongs.
Re:Moon by Polkyb · 2004-01-19 22:50 · Score: 1

It would probably be cheaper if they were to take the apollo blueprints and build the same moon ship using today's technologies.

They would probably be able to shave 5-10 tons from the launch mass just by using modern materials alone, not to mention the miniturisation that has occured in most of the equipment they would need to carry.

--
I've never shoed a horse, but I once told a donkey to piss off!
Re:Moon by WindBourne · 2004-01-20 00:25 · Score: 1

No sense sending a same size ship to there. It would be much better to design one that can carry a large amount of cargo and ppl (6-8) to their and then have a small return craft.

Unfortunatly, it will require a new launcher, but that has been needed for 20 years.

--
I prefer the "u" in honour as it seems to be missing these days.

ATV by Aglassis · 2004-01-19 17:44 · Score: 5, Interesting

The ATV design strikes me as particularly interesting because it brings up a point that I've been wondering for awhile: Why don't we have more automated exploration and maintenance vehicles in Earth orbit. It seems to me that a spacecraft that could launch, orbit earth, and return to earth (not that the ATV can do that) without humans onboard and built in a mass manufactured way would be extraordinarily effective for Earth orbit science experiments. It might also be useful for maintenance of high value satellites (like HST). Since Earth orbit is almost real-time transmission there is no reason to think that putting a mechanical arm on a spacecraft to do maintenance would be any different that a surgeon doing a remote operation via a mechanical hand. The most complicated part would be the approach of the satellite to be maintained, but since the Space Shuttle obviously had no problem doing this there is no reason to believe that an automated spacecraft (with real-time human backup in a controlling station) couldn't do the same (a little more complicated than the ATV's purpose of docking with the ISS, but I don't think its inanely so).

--
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.

Re:ATV by Anonymous Coward · 2004-01-20 00:45 · Score: 1, Interesting

If you've seen space repairs on nasa tv before you'd know something ALWAYS goes wrong. What do you do if your robotic arm loses a necessary screw? Saying "whoops" doesn't really help you all that much.

When you're doing robotic surgery, the stuff you're manipulating has nowhere to go. When you're doing space-based repair, you have to hang on to EVERYTHING, or it floats away. Much more complicated.

Having said that, I agree there should be more research done towards this. Even if robots aren't capable of it today, they might be one day, and it would be in humanity's interest to have robot handymen roving around in earth orbit.
Re:ATV by *SpOoNdRiFt* · 2004-01-20 03:44 · Score: 1

Speaking of the ATV design, Darpa is sponsoring a race http://www.darpa.mil . This technology will be used by the military and maybe NASA.
Re:ATV by uradu · 2004-01-20 05:50 · Score: 1

> What do you do if your robotic arm loses a necessary screw?

And what do you do if your orbiter loses a necessary patch of insulation? Sure, humans in orbit give you added flexibility, at much added cost. Overall the loss of flexibility with purely robotic maintenance could be offset with extra backup mechanisms and some more up-front design thought, plus the cheaper cost of not having humans there.

you sir, are an asshat by Anonymous Coward · 2004-01-19 17:47 · Score: 0

from the link:

Astronomers think this atmosphere might closely match the one Earth possessed millions of years ago, before life began.

That's just fine by ktanmay · 2004-01-19 17:47 · Score: 3, Insightful

Just because Bush unveiled grandiose plans for NASA, and they took note of it and adjusted a few of their plans (which in retrospect were due for a change anyway) does not mean other space agencies will follow suit.

The reaction given to Bush's plans by other nations have been circumspect, lets see where this all goes after the elections are over.

New roles for ESA? by wrmrxxx · 2004-01-19 17:51 · Score: 4, Insightful

Bush's moon and mars plan seem like such a comprehensive change for NASA that they might also have a serious impact on the ESA. With NASA's budget redirected into the new plan, will the ESA pick up the slack with greater involvement in the ISS beyond the ATV? Or will they have a significant involvement in the moon and mars plan - maybe using the ATV to supply a moon base? It would be a shame for them to spend a fortune developing the ATV, only to be told that it was no longer needed because the ISS was no longer maintainable due to a lack of US funds.

Re:New roles for ESA? by HarveyTheWonderBug · 2004-01-20 01:16 · Score: 1

will the ESA pick up the slack with greater involvement in the ISS beyond the ATV?
I doubt it, and I sincerely hope not. Most ESA members country were reluctant to put more money in the ISS a few years back, and I do not see why this would change: the ISS is pretty useless. Look on the scientifc return for example. I can count the scientific publications published from data obtained with the ISS on my hands. Compare it with the thousands the HST has generated.

longer not worse by NightLamp · 2004-01-19 17:51 · Score: 0

If the project costs are sufficiently reduced from a regular launch then I am all for it.

Personally I want a mars rover launched every day for less than $1000, it would be the ultimate saviour of Radio Shack, just think, 4-wheeling on the red planet, all from the comfort of your living room!

Yeehaw!

ESA and NASA covering each other? by sailracer6 · 2004-01-19 17:55 · Score: 3, Insightful

So it seems that ESA is working on a next-gen cargo craft, and NASA is working on a next-gen human transporter. Could it be that Europe and the United States are actually splitting the design costs necessary to replace the Space Shuttle?

These two separate systems can do what the Shuttle could do by itself -- haul cargo and move people -- and I'm betting it's cheaper, too, to do things with two separate devices.

Re:ESA and NASA covering each other? by Hittite+Creosote · 2004-01-19 23:31 · Score: 1

Well, the ESA one will be a hell of a lot cheaper, getting the cargo into space without wasting all that weight having to haul humans up into orbit and get them down again safely.
Re:ESA and NASA covering each other? by shotfeel · 2004-01-20 06:20 · Score: 1

And its not just the weight of the humans -its everything needed to support them. Much cheaper if you don't have to worry about food, air, temperature, waste disposal...

Additional picture of Vega launcher by nacturation · 2004-01-19 18:17 · Score: 2, Funny

available here

--
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.

Re:Additional picture of Vega launcher by Anonymous Coward · 2004-01-19 18:25 · Score: 0

I saw that moive

Depends on mission Re:Ion drives... by StefanJ · 2004-01-19 18:20 · Score: 3, Interesting

OTOH, a fairly fast trip to Mars requires about 20 kps in velocity changes. Which makes a 30 kps ion drive just about right.

But there's complexities there, too. Most of these velocity changes come at the beginning and end of the journey (getting into an elliptical orbit, then getting out of it once you reach Mars).

Re:Depends on mission Re:Ion drives... by tho+1234 · 2004-01-19 20:15 · Score: 1

Huh?

The 30 km/s mentioned by the parent poster is a VELOCITY, while you're referring to a rate of change of velocity, ie ACCELERATION. The poster was referring to the velocity of the gas leaving the thruster, which is totally different from either the velocity or acceleration of the craft.

From that information alone, you can not figure out the acceleration of the ship, as you also need to know the mass/mass flow rate of the particles leaving the thruster. Actually, ion thrusters have extremely low acceleration because of the incredibly small quantities of mass involved. The key advantage is that they don't need to carry much fuel, and over long periods of time, the acceleration adds up. However, there's no way you could use it for a manned mission to mars, or ANY "fast trip" period.
Re:Depends on mission Re:Ion drives... by Anonymous Coward · 2004-01-20 02:30 · Score: 0

Uhmmm, I think your a bit confused. The velocity changes he is referring to are not acceleration. He was stating that 20 km/s the delta V for mars from earth. And that the 30 km's velocity output from the ion drives would be closer to the ideal efficiency stated by his parent. (I don't understand what he's basing that figure on though, is it mass/energy ratio's or so?)

Infact he even realised I believe low ion drive acceleration there he noted that usually most of the speed for switching orbit is given early in the journey and at the end. Not that that really matters, you can achieve a slower trip just by spiraling outwards until you get there.

Quickshot

1500 hours of thrust time? by Qinopio · 2004-01-19 18:21 · Score: 0, Offtopic

I don't know about the other Slashdot readers (male or female), but I could get there about 15000 times in 1500 hours of thrust time :)

--
__________
[Big Brick Wall]

Re:1500 hours of thrust time? by Anonymous Coward · 2004-01-19 18:32 · Score: 0

which is why you have callouses the size of small cars on your hand

Please learn how to use links. by Anonymous Coward · 2004-01-19 18:23 · Score: 0

Please learn how to use links.

<a href="http://www.physics.montana.edu/faculty/corni sh/lagrange.html">Here's how</a>

yields: Here's how

Re:Please learn how to use links. by kfg · 2004-01-19 19:38 · Score: 2, Informative

I promise I'll give the matter some consideration.

Please bear in mind that it was only fairly recently that I started doing this instead of *this* and I'm used to cut and pasting urls by taking a wax impression of the cuneiform tablet and impressing that into fresh clay.

It's not that I don't know how to make a link, it's simply that I don't think about it, having plain text relexes.

I shall strive to cure my errant ways.

KFG
Re:Please learn how to use links. by Anonymous Coward · 2004-01-19 20:06 · Score: 0

It wouldn't be a big deal if slashdcode didn't throw spaces in long strings of plaintext.
As an avid reader of your posts (I'm the one that called myeslf "your personal stalker" a while back), I can say that I'm very certain you know how to make a link, and the other AC here should feel a bit silly trying to educate the nearly all-knowing KFG.
I always assumed that having 3000+ posts meant you simply didn't waste time typing a href blah blah and then previewing just to make sure the whole post doesn't turn into a link, heh.
Re:Please learn how to use links. by kfg · 2004-01-19 20:59 · Score: 1

The "all-knowing" KFG wouldn't know as much as he does if he weren't willing to be educated. I make mistakes. I get my ass handed to me. I try not to make that mistake again.

Sometimes I'm a bit slow and I need my ass handed to me a few times before I get it.

I was once accused of being a "know it all" in meatspace by someone who didn't know me very well. A friend of 20 years responded with "But you have to understand that in his case he really does know it all.

My friend was very kind, but he lied. I know a lot. One of the things I know is that I'm ignorant, so I strive to become less so.

You have a point though. I type fast. My typing lags far behind my thoughts (which are often ill considered at the time)leaving my fingers on complete autopilot, leading to mistakes I never notice and I don't do a lot of previewing. I've any number of posts that turned into a giant block of italics through failure to close a tag properly (and a few where I've just come from a vB forum and use square brackets instead of angle brackets. What the hell was Jelsoft thinking?)

I shall have to consider that as well.

KFG
Re:Please learn how to use links. by Anonymous Coward · 2004-01-19 21:35 · Score: 0

Heh. I said nearly all-knowing, and I'm pretty sure that's accurate. Let's see... You know all about how to survive "off the grid" and what-not, yet you're certainly not a "back to nature" person and know more about science and technology than most people that post here. You've had insightful comments (many of which are not modded up as such) on topics from power generation to space exploration, and to advice about living "no more employed than a sparrow" as you might say.
And all that while suffering from two fatal diseases? Just incredible. Really. So why not just admit that you're nearly all-knowing and to hell with the "ignorant" shtick, especially here on Slashdot.
Some of your posts have been life altering (at least for mine anyway) so when someone bitches about you not making HTML links and implies that it is due to ignorance, I guess my kneejerk reaction is that said person should be flogged.
Re:Please learn how to use links. by kfg · 2004-01-19 23:14 · Score: 1

Heh. I said nearly all-knowing. . .

See? I make mistakes. Just drop the ass in the bag and I'll deal with it later.

And all that while suffering from two fatal diseases?

Ok, I got a bit "lucky" there. They were both death sentences at the time I was born.

Being genetic neither can be cured, but one is now survivable with strict attention to diet (one of the reasons I grow my own food. It isn't fun knowing that anything you consume could, at least theoretically, kill you if it doesn't come from a trusted source) and the other has a rare genetic variation in people of eastern European descent ( my mother's family is Russian/Polish/Romanian) that gives an off chance at survival of you make it through childhood, but even then something as simple as a cold could conceivably do me in. Last I checked there were 14 of us known.

Sooner or later one of these is going get me, but if I take care of myself I might well make it to an advanced age in spite of them. Death is not imminent so I perhaps stretched the truth a bit by calling them fatal, at least in my case.

In any case while they impose limitations on me I don't let them limit me.

As for the ignorant "shtick," well, I'm afraid that's one of my defining characteristics. If I didn't actually feel that way I wouldn't know as much as I know. Things interest me. All things. There's just too many things. On a day to day basis I'm far more concious of what I don't know than what I do. I have little compunction these days about admiting that I know far more than most, that I'm smarter than most, or even that I'm wiser than most. I'm even begining to accept that I've done more than most ( although this still surprises me since I consider my life fairly slow moving compared to most. On any given day I'm likely to do little more than read, write, go for a bike ride, dick around in my "lab" a bit and maybe do some street performing or something. Unless I have a contract. Then I have to work just like anybody else).

But that leaves me, in my own estimation, ignorant. It's not my fault if some others are simply a bit more so. It's all just a matter of degree.

And there are certainly people far less ignorant than I on any given subject. I try spend some time around them now and again to become less ignorant.

My thought processes, on the other hand, are weird in the technical sense. Growing up truly aware of my mortality may have something to do with that, at least in a contributory capacity. I have never had the luxury of that particular bit of common ignorance and the bliss it seems to confer on some. In some ways I was thus old even as a child.

But then that carries its own peculiar form of bliss.

KFG
Re:Please learn how to use links. by mraymer · 2004-01-20 00:54 · Score: 1

If you die, please make a post letting everyone here know. Err... Heh.
I guess if you just stop posting someday we'll know what happened?
Anyway, it kind of makes sense that if you didn't admit your own ignorance you wouldn't be you. It reminds me how Conan O'Brian always tells Oscar winners things like "If I had one, I'd have it strung up from the ceiling so I could just lower it down during dinner and say OH, what's this!" Heh. Which is probably one of the reasons he is in no danger of getting an Oscar.
But you are in danger if becoming even less ignorant with that mindset, I guess.
A scary thought. I wonder if perhaps one day your head will just explode. Then, in the end, it won't be your "genetic lottery" that has the last laugh, after all.

--
"To confine our attention to terrestrial matters would be to limit the human spirit." -Stephen Hawking

Re:i know by Anonymous Coward · 2004-01-19 18:24 · Score: 1, Troll

Well considering that ESA's budget is about $5 billion (vs NASA's $17 billion), that the ESA has yet to land a spacecraft on any planetary body, that ESA has yet to build a rover, that there are intense political struggles within the organization, and that there are likely to be more budget cuts, its not suprising that ESA is slow as hell to do *anything*. NASA got where it is today (where most people think NASA might be the only competent government agency in the US) by being extraordinarily sucessful in its early programs. Contrast this with the Russians and look where they're at. ESA hasn't had much sucess lately (due to the Arianne and Beagle 2 fiascos), and really needs to rebuild public confidence in them. Smart people want to work for NASA because they feel they can make a difference. At the ESA they won't feel that way because there is so far little pride in the agency and too much political infighting.

Re:4n 0m1510n 0f 73h curr3n7 pr093c75 by Anonymous Coward · 2004-01-19 18:35 · Score: 0

As another poster pointed out - it may be similar to conditions way back before there was life on Earth.

The atmosphere contains hydrocarbons - the basic building blocks for life. Energy from the sun converts simple molecules into more complex ones through fairly well known chemical reactions. The atmospheric pressure is 150% of Earth's at sea level. The only problem is that the "sea" may very well be liquid ethane - it is bitterly cold.

Current planetary theory says that when the sun heats up just before it's death, it may be enough to unfreeze Titan - and life could very well begin on it's own. Uh.. then the sun explodes and whatever microbes that form all die before they have time to evolve.

Current active spacecraft by Anonymous Coward · 2004-01-19 18:38 · Score: 3, Informative

Nine Planets has a big list of all spacecraft - past, current and future (although it is a little out of date).

Re:Current active spacecraft by catfry · 2004-01-19 20:59 · Score: 4, Informative

I would say that is the smallest "big list of all spacecraft" I have ever seen. A more comprehensive resource on spacecraft, be it manned, planetary or ordinary telcomms, is the ever-useful www.astronautix.com. Go here for a full list sorted by type of mission. (scroll down to 'planetary' for the interesting stuff).
Re:Current active spacecraft by catfry · 2004-01-19 21:07 · Score: 1

I am an asshole. The page haven't even stopped loading before I started spouting crap.

France? by graveyardduckx · 2004-01-19 18:44 · Score: 1, Funny

With the Control Center for the transport to the ISS being in France, would this be the "French Transport to ISS" or the "Freedom Transport to ISS"? I still call them French Fries....

Re:France? by Anonymous Coward · 2004-01-20 02:48 · Score: 0

Offtopic but well, I always thought the freedom part was rather ironic considering the french are all with the liberte thing.

Long term big planning by Iron+Sun · 2004-01-19 18:52 · Score: 4, Informative

ESA has a long term exploration program called Aurora that aims to take humans to the Moon by 2020 and Mars by 2030. This was announced some time ago, well ahead of Bush's proclamation. The nearer term goals include ExoMars, a long-duration rover, and a Mars sample return mission with the ambitious launch date of 2011.

Hey, I've got an idea... by HotNeedleOfInquiry · 2004-01-19 18:59 · Score: 1

Go to the moon and bring back our flag!!!

--
"Eve of Destruction", it's not just for old hippies anymore...

Re:Hey, I've got an idea... by Anonymous Coward · 2004-01-19 19:54 · Score: 0

Nah, I'm sure the ESA will get there first and burn the American flag (after building a transparent air cage around it). Then they'll throw the charred pole down to earth and skewer the whitehouse.
Re:Hey, I've got an idea... by 4ntifa · 2004-01-20 02:13 · Score: 1

Howzabout the EU go capture the US flag? Ha ha, that'd be the ultimate Capture The Flag game!

--
-=- 4ntifa -=-
Re:Hey, I've got an idea... by Anonymous Coward · 2004-01-20 03:39 · Score: 0

Just have the Beagle do it... oh wait.. ummmm..errr

why are they still useing rockets by you_think_I'm_dumb! · 2004-01-19 19:02 · Score: 0, Troll

I just don't understand why the old method of reaction mass rockets is still being used. There are several ways of giving an object velocity without reaction mass, as some term "inertia drives". They DO exist so why are they ignored by mainstream science? Google for yourself. The simplist method is a tube, bouncing a mass off a spring and letting it go clunk at the other end. Energy is applied to accelerate the mass for both directions. The difference in directional energy is obtained from the fact that when the mass goes klunk energy is lost through deformation etc. You don't have to take my word for it, use your brain, analyse the forces. Then you can wonder why we still use reaction mass rockets.

Re:why are they still useing rockets by The+Cookie+Monster · 2004-01-19 20:14 · Score: 1

You are confusing momentum and kinetic energy.
The momentum of a system is always conserved,

Momentum is mass x velocity, but kinetic energy is 1/2 mass x (velocity squared).

This inertia drive you describe puts energy into accelerating the mass, which is lost when the mass deforms, however the momentum of the system is conserved - that means the system starts moving in the opposite direction to the mass as the mass moves, and then stops moving when the mass stops.

The center of mass of this 'inertia drive' system will not change, so for the drive part to keep moving yet maintain the same center of mass, the acellereted mass would have to keep moving further away from it, ala a rocket.
Re:why are they still useing rockets by kfg · 2004-01-19 20:36 · Score: 5, Informative

They are not ignored by "mainstream" science. Mainstream science has already determined that they don't work.

So mainstream science "ignores" them only in the sense that they also ignore reading chicken entrails to fortell the future.

For starters, this is not a drive without a reaction mass. That's what the ball is.

When the ball hits the spring the spring compresses,i.e. deforms, otherwise it wouldn't be a spring, now would it? But only some of the energy of the ball goes into compressing the spring. Some of that energy goes into driving the entire tube "backwards." When the spring expands, again, some of that energy goes into driving the ball forwards, but some into driving the tube backwards again. In the process, as you note some energy is lost as heat.

When the ball "klunks" it drives the tube forward and the ball backward and some energy is lost as heat.

There is no essential difference between the spring and the klunk with regards to energy transfer other than the difference between the energy losses, as you note, which are very small (the klunk heats the ball more than the spring does).

What you have described is an oscillator that winds down after a relatively few klunks because energy is lost at each exchange. Use your brain. Analyze what "energy is lost" means.

It means the thingy goes back and forth a few times and then stops.

Unless you add energy.

By driving a reaction mass.

i.e. the ball.

And you still need a rocket to get it "up there" 'cause it ain't gonna do squat but fall over if you set it up on end and start it going here on earth. And that rocket has to carry the fuel to get the ball going in the first place, and all the fuel to keep it going, so that it can sit there in space and wobble until the fuel runs out. A quantity of fuel that still has to equal the energy value you intend to get out of the device.

This is nothing more than an obfuscated version of the drop hammer that lifts veeeeeeeeery slowly and thenswings down against a stop suddenly.

When the hammer lifts slowly the machine moves backwards slowly. When it swings down and hits the stop it moves forwards quickly but an equal distance less the heat loss in the impact versus the heat loss in the bearings as it rises and it needs fuel to drive it. Fuel which must be lifted into space and carried by the device. About the same amount of fuel that a conventional rocket uses.

And all it does is wobble.

KFG
Re:why are they still useing rockets by krysith · 2004-01-20 01:55 · Score: 1

I ought to point out that there ~are~ some effects which could result in a 'reactionless engine', such as the one mentioned in the paper by Dr. Jack Wisdom of MIT in Science, "Swimming in Spacetime: Motion by Cyclic Changes in Body Shape", Science 2003 299: 1865-1869. This is very different from the naive suggestion above. However, this effect is far to small for practical use (on the order of femtometers per cyclic modulation). Also, such an effect isn't really 'reactionless', rather it pushes back on the object producing the gravitational field.
Re:why are they still useing rockets by uradu · 2004-01-20 06:14 · Score: 1

These are probably the same people that notice that you can turn in a swivel chair by swinging your outstreched arms quickly in one direction and slowly in the other. Sadly not all of them experience the aha-moment of learning about bearing friction.
Re:why are they still useing rockets by kfg · 2004-01-20 09:00 · Score: 1

They aren't the worst of the bunch either. That prize goes to the people who suddenly discover magnetism and think "Ahhhhhhhhh, deep Juju!" and spend the rest of their lives trying to find just the right sort of clever combination of magnets to make an infinate repulsion loop.

Those people drive me nuts.

KFG
Re:why are they still useing rockets by uradu · 2004-01-20 09:17 · Score: 1

> "Ahhhhhhhhh, deep Juju!"

More like "Ahhh, free energy!" At my previous job there was this guy with a BS in physics who was the most technically gullible person I ever met. He firmly believed that perpetuum mobili don't exist only because of government conspiracies. When reminded of the concept of preservation of energy, he scoffed at it as just the opinion of "one guy" or "the establishment".

Anyway, he found some plans on the internet for some pure magnetism motor that employed just the right complexity of gear arrangements and planetary motion to trick a set of rotating magnets into providing perpetual motion. He even brought the contraption to work one day--it consistend of some weird circular plywood sandwich with rotating metal bits inside, held together by some rusty bolts. His only concern was that the plywood wouldn't be strong enough to contain the vibrations and sheer energy released by the device, so he only considered it a "prototype". I agreed with his assessment and left the room fighting hysterical laughter.
Re:why are they still useing rockets by cheesybagel · 2004-01-20 09:47 · Score: 1

If your problem is carrying heavy fuel, just use a lightbulb or a cathode ray gun for your engine. Of course, the thrust will be nothing special...
Re:why are they still useing rockets by you_think_I'm_dumb! · 2004-01-20 10:18 · Score: 0

The other example I can think of is based on light pressure. The same principal as a radiometer. There seems to be a popular misconception as to what causes the radiometer to spin, expasion due to heating. If a light source has a mirror at one side and a black absorber at the other this will cause a movement. The mirror reflects the light with almost no acceleration and the black absorber does experiance an acceleration. Lots of power to get any useful effect. No thowing away of reaction mass.
Re:why are they still useing rockets by meringuoid · 2004-01-20 10:37 · Score: 1

Does that work? My guess would be that it would actually move towards the mirror. You're throwing photons both forward and backward from the source, and each photon carries momentum (+-) 'p'. Absorbing a photon on the black surface, the device's momentum changes by -p, while on reflecting one from the mirror the momentum changes by +2p. Assuming that all the photons striking the mirror entirely miss the absorber, that's a net change of +p. You can double that by just removing the absorber, and having _both_ photons escape. Then you get rid of the -p retardation and get double the acceleration. Of course, what you have then is a light rocket - a beam of light is shot out the back, and the spacecraft is pushed forward. No reaction _mass_ is thrown away, but the principle's the same :-)

--
Real Daleks don't climb stairs - they level the building.
Re:why are they still useing rockets by you_think_I'm_dumb! · 2004-01-21 09:49 · Score: 0

The mirror reflects and no (minimum, not perfect ) it is the absorbtion of the photon that reacts. Yes it is counterintuative.

creators, planet/population, all on the same page by Anonymous Coward · 2004-01-19 19:20 · Score: 0

that's right. there's only won way out from here. see you there?

building a vessel that floats on any suBStance by Anonymous Coward · 2004-01-19 19:26 · Score: 0

better than sinking amongst the execrable.

Re:Ion Drive Mass? - Cheap! by Anonymous Coward · 2004-01-19 20:05 · Score: 0

Actually ESA reports that SMART-1 mission's budget is really cheap one: only 150 (185 US).

Beagle by Anonymous Coward · 2004-01-19 20:06 · Score: 5, Funny

Beagle is alive! I just got a message from it in my inbox! Lemme double-click it and see what it says..

Oh.. wait...

BBC: Europe's stunning Red Planet view by Anonymous Coward · 2004-01-19 22:19 · Score: 2, Informative

Stunning view of Mars from ESA

Beage 2 was 20% of Mars Express by Anonymous Coward · 2004-01-19 23:09 · Score: 0

You know, Beagle 2 was a cheap add-on to Mars Express. It was not even part of the original plan.
The problem is that most of the publicity was directed to Beagle 2. That's why its loss overshadowed the much more important orbiter.

Re:i know by SenseiLeNoir · 2004-01-19 23:09 · Score: 4, Informative

> hasn't had much sucess lately (due to the
> Arianne and Beagle 2 fiascos)

Beagle 2 was a late "add on" to the Mars Express Mission... Beagle 2 was developed by the British. Attributing the failure of Beagle 2 to ESA is tantamount to saying there is UNIX code in Linux.

The Mars Express is SUCCESFULL, and is already returning clear stereo pictures of the Martian surface.

I am still sorry Beagle 2 failed.. but dont catogorise the whole mission a failure for ESA, just because of one part. rememebr the original mission did NOT include a lander....

--
Have a nice day!

Re:i know by Anonymous Coward · 2004-01-19 23:30 · Score: 0

The margin for failure is the space program is 0.000000%. Anything higher than that and the public begins to lose confidence at an exponential rate, and then politicians can cut budgets (because the space programs can't defend themselves with "We have a special group of people who can do anything, except fail"). Politics typically runs in 2, 4, or 6 year cycles. This is too small to see any political gain from any space action a politician can support, so there is no reason to support any.

The truth of the matter (and the ESA should have known better--they didn't learn from NASA's mistakes) is that the ESA shouldn't have allowed the Beagle 2 to be attached *because* it was rushed. Scientists will call the mission a sucess but the public will remember the Beagle 2 and think "What's the ESA going to screw up next time?".

Re:i know by gnalre · 2004-01-19 23:47 · Score: 2, Informative

Hey Trollboy,
Firstly how much of the 17bn is purely military funding. Secondly Ariane has been a great success taking a large percentage of the global launch market and of course you forget to mention the NASA failures including the early space program, Apollo 1, 2 shuttles,2 mars probes and other commercial launch failures.

The ESA program is primarily targeted at commercial launch vehicles(ESA can't depend on a military budget), saying that they have some highly successful scientific missions

--
Choose your allies carefully, it is highly unlikely you will be held accountable for the actions of your enemies

Earth observation by d-Orb · 2004-01-20 00:09 · Score: 3, Interesting

It's interesting that one of ESA's greatest achievement areas, namely Earth Observation (things like ERS 1/2, Envisat) are not mentioned. This is an important area, with all the exciting stuff about oceans rising and engulfing towns and the Seychelles (serves them right for living in a bloody paradise :D). There are a large number of unknowns regarding the Earth's environment that could be alleviated by a (relatively) cheap fleet of EO microsatellites. I don't know whether ESA wants do commit more budget to these areas (after all, a lot of the stuff on Envisat is only of very limited commercial interest, and they seem to be pushing for commercial use), but it certainly would help. On the other hand, looking at the deforestation rate over Siberia might not be as cool as putting some gimp on the Moon...

Don't forget VENUS Express and Rosetta by zoney_ie · 2004-01-20 00:53 · Score: 2, Interesting

As has been done in the past with Soviet missions, both Mars and Venus will get probes, using some spares and the design from the first launch for the second probe.

In this case, the second probe will be launched as Venus Express. This will be launched in Nov 2005, also by Soyuz from Baikonur Cosmodrome in Kazachstan.

Soyuz is working out so well, that ESA is building Soyuz launch facilities in French Guiana - which is of course MUCH nearer the equator and is E.U. territory. (It's a problem for Russia that Baikonur is no longer in their territory).

Then there's Rosetta, this flagship mission will be launched in a month or so. It's a mission to chase a comet, taking TEN years to catch it! It will also flyby at least one asteroid.

--
-- *~()____) This message will self-destruct in 5 seconds...

NASA's success...? by jamdognut · 2004-01-20 01:27 · Score: 0, Flamebait

"ESA hasn't had much sucess lately "...
Hmmm, does loosing 2 space shuttles + crew count as a "Success" ?
NASA got where it is today by being bankrolled by the US gov for military aims. Bush's push for the Moon/Mars are veiled methods for pumping money into space for military purposes.

Carl Sagan (slightly off topic) by Myopic · 2004-01-20 01:30 · Score: 1

I'm reading Cosmos right now (published in 1980), and Sagan includes a little daydream about the future of Mars exploration (the Viking was the first, non-roving Mars lander):

For all the tantalizing and provocative character of the Viking results, I know a hundred places on Mars which are far more interesting than our landing sites. The ideal tool is a roving vehicle carrying on advanced experiments, particularly in imaging, chemistry and biology. Prototypes of such rovers are under development by NASA. They know on their own how to go over rocks, how not to fall down ravines, how to get out of tight spots. It is within our capability to land a rover on Mars that could scan its surroundings, see the most interesting place in its field of view and, by the same time tomorrow, be there. Every day a new place, a complex, winding traverse over the varied topography of this appealing planet.

Such a mission would reap enormous scientific benefits, even if there is no life on Mars. We could wander down the ancient river valleys, up the slopes of one of the great volcanic mountains, along the strange stepped terrain of the icy polar terraces, or muster a close approach to the beckoning pyramids of Mars. Public interest in such a mission would be sizable. Every day a new set of vistas would arrive on our home television screens. We could trace the route, ponder the findings, suggest new destinations. The journey would be long, the rover obedient to radio commands from Earth. There would be plenty of time for good new ideas to be incorporated into the mission plan. A billion people could participate in the exploration of another world.

The only thing he got wrong was the medium by which many people would participate in the mission, since there was no internet/web in 1980.

Galileo by K3lvin · 2004-01-20 02:28 · Score: 1

Galileo is not mentioned yet?

Re:i know by Anonymous Coward · 2004-01-20 03:02 · Score: 0

Your rather cynical, fact remains you can't have big success without taking risks. And those big successes are also remembered. ESA isn't quite as high profile as NASA, but it does lauch some interesting missions now and then, the next high profile one will likely be the huygens lander on titan. So if that succeeds it will more then balance the cheap british lander failure.

Monkies! by turgid · 2004-01-20 03:06 · Score: 1

Yes, but when are they going to put monkies in orbit? Because after that, people will not be too far behind. I like monkies.

--
Stick Men

Re:Monkies! by turgid · 2004-01-20 03:15 · Score: 1

....and I can't spell monkeys.

--
Stick Men

Here is another good data source about ION Drives by ahbrown41 · 2004-01-20 04:47 · Score: 1

Pretty cool :-) http://nmp.jpl.nasa.gov/ds1/tech/ionpropfaq.html

we'reking IT's weigh towards you by Anonymous Coward · 2004-01-20 05:23 · Score: 0

mynuts won unintellibuybull?

maine pond analcysts a couple of piNTs behind by Anonymous Coward · 2004-01-20 05:33 · Score: 0

the ate bawl. that's all? see yo there?

New role of ESA & European Union Space Policy by Petrush · 2004-01-20 09:59 · Score: 1

It seems likely that ESA or at least parts of ESA will be quite involved with the implementation of a "Space Policy" from the European Union. A white paper was recently released, http://europa.eu.int/comm/space/whitepaper/whitepa per/whitepaper_en.html It points out some areas where space is considered as an important, vital or necessary part. Although science is highly valued in the paper, and stated that no more cuts should be done, it points out directions to space applications - areas where society can benefit from space. The areas include navigation (through Gallilleo), Global monitoring, Digital Divide (communications to remote areas), for emergency & rescue. Also strategic areas are mentioned, as well as the importance of international partnership. The white paper suggests a two phase approach for implementing this, first as a cooperation between EU and ESA with ESA as the implementing agency for space matters. In a second stage, the ESA should be organised within the EU (in some way), 2007->. This is quite a different agenda, that was presented this autuumn. The Bush approach for NASA might surely influence the schedule, and maybe approach?

Fast rides: Orion by Anonymous Coward · 2004-01-20 11:02 · Score: 0

This has been gone through so many times here that I'm not going to explain what it is.

20,000-30,000 TONS of payload.

We just need something to get off the planet efficiently. Orion isn't practical for inhabited areas and rockets are just plain inefficient when it comes to dealing with gravity wells.

Would someone be insane enough and rich enough to make RAH's giant conveyor belt? One of these could be the freight elevator, while Clark's elevator would be the biological stuff lifter.

178 comments