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Solar Super-Sail Could Reach Mars in a Month
ti-coune sent us a story running on newscientist describing
solar super sails and how they could one day get us to Mars in a month. The key is a special new paint. The cast of Trading Spaces is unavailable for comment.
I don't see any cast.
BTW. The sail emits carbon monoxide to get its speed boost. You know, the stuff the kills humans almost as fast as dihydrogen monoxide.
You really want to be behind that thing for a whole month?
Karma: Chameleon (mostly due to the fact that you come and go).
The invention of a warp drive or time machine could get us there immediately. Weather at 10.
The cast of Trading Spaces is unavailable for comment. TSIA.
....cast of Trading Spaces unvailable for comment.
You're being sued by the entire readership of Fark.Com for violation of our intellectual property. Have a nice day.
--Farkers everywhere
Yea, I imagine carbon monoxide poisoning is probably the biggest issue facing unprotected free-floating humans in space.
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It is very cost benefitial to not have to take fuel with you... or at least not as much.
My question is, what kind of payload is practical with this kind of thing? I've always read that to get any kind of larger payload, you cannot use solar sails. Do they get around this by using the microwave beam they talked about (ie higher energy per square meter)? I wish there were more numbers in the article...
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
So you're going faster than any interplanetary craft to date, and your only propulsion system requires you to be moving away from the sun (or the Earth, if they're using a laser to push you).
How do you slow down? Orbital insertion at that speed would be seriously difficult, if not impossible.
"The Benfords calculate a one-hour burst of microwaves could accelerate the craft to 60 kilometres per second" That's quite fast... :) With the trip only taking a month, I'd imagine it would make it much more manageable for whoever made the journey.
Although it may not be the most practical thing in the world, having people visit Mars gets me excited. It's just like something out of TV shows
I store my recipes online (the way nature intended)
Mars in a month is great but when are we going to reach warp 9 :)
i want to know how to stop that sail ????? or maybe it wil became a mars impactor ?
a quebecer certainly :)
Or get back to earth for that matter? Nice idea as long as you don't mind a one way trip into deep space.
I thought this was an advertisement for my local tanning salon at first. Jeez what a disappointment.
News Reporters Make Tasty Polar Bear Treats!
The cast of Trading Spaces is unavailable for comment.
Did you even bother to ask them?
All employees must wash hands before seeking equitable relief.
You're in front of it - you'd be pushed along so it would make sense to put the sail at the back. I'd be more worried though about the effects if the craft turned unexpectedly and dropped your capsule into the microwave beam.
--- Users are like bacteria -> Each one causing a thousand tiny crises until the host finally gives up and dies.
Why does this seem incredibly wasteful of energy?
Wouldn't it be far wiser to build solar panels in orbit, use them to power Microwaves, and avoid the attenuation in the atmosphere? This would have the added advantage of not draining power from the Earth to power the spacecraft: we would get our power from the Sun and pipe it directly to the spacecraft as Microwaves, without involving the planet at all (except, of course, as controlling entity).
The Future of Human Evolution: Autonomy
You do realize this will be used in space right?! The CO will not be a big problem out there!
powered by a solar sail get from Earth to Mars in just one month
Then what....!?
The best result comes from everyone in the group doing what's best for himself and for the group
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If they could find a way to reflect or refract microwave radiation from the sun they could use a space based "microwave lens" to get the 60MW microwave beam. Probably would have to be a pretty big lense.
"Emergency channel, zero-one-three-zero, Code Red. It has been three hours since our contact with the alien probe. All attempts at regaining power have failed. All non-essential fuel has been given...to slow our consumption of life-support reserves. Our chief engineer is trying to deploy a makeshift solar sail. We have high hopes that this will, if successful, generate power to keep us alive."
The coolest voice ever.
The grandparent was meant as a joke (almost as fast as dihydrogen monoxide is the tip off).
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
BTW. The sail emits carbon monoxide to get its speed boost. You know, the stuff the kills humans almost as fast as dihydrogen monoxide.
You really want to be behind that thing for a whole month?
Right, like they're going to be flying along to Mars with the windows open.
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BTW. The sail emits carbon monoxide to get its speed boost. You know, the stuff the kills humans almost as fast as dihydrogen monoxide. You really want to be behind that thing for a whole month?
Do you really think that they haven't thought about that? First of all, the astronauts would be in some sort of pressurized cabin that will take care of all their air-breathing needs. I'm pretty sure they wouldn't let the CO from outside get in. Furthermore, the pressure inside will be much greater than the pressure outside. Hence air will have a tendency to flow out, rather than the CO flowing in.
Vivin Suresh Paliath
http://vivin.net
I like
I think it would be kind of neat to go back to the "sail" days. Sort of like that one star trek movie - where there was the big sail device that would suck up the energy of the planet - except this one is used for something beneficial :D
I mod down so you can mod up. Your welcome.
BTW. The sail emits carbon monoxide to get its speed boost. You know, the stuff the kills humans almost as fast as dihydrogen monoxide.
I'll take that risk. I was never that good at breathing in outerspace anyways....
TWO JOKES!
:P
:P
I should be modded funny. Not interesting, and not troll.
That was supposed to be funny. You're in a vaccuum. I almost mentioned something about Paige Davis and sex tapes, and STAYED ON TOPIC!!!!
Come on mods, live a little.
Karma: Chameleon (mostly due to the fact that you come and go).
"The feat would require a 60-megawatt microwave beam with a similar diameter to the sail. It would also have to be capable of tracking the craft as it accelerated away. But this power level could not be delivered by any existing microwave transmission system. The deep-space communications network that NASA uses to communicate with Mars rovers and the Cassini probe now orbiting Saturn can only manage half a megawatt. The Benfords say the power could be ramped up in future and hope to persuade NASA to consider doing this as part of a future upgrade to the network.
So basically NASA's currently-used equipment is 1/120th of the power needed to get this sail to Mars. I would say this idea is not in our near future for sure.
Naturally, the development of solar sails would lead to the production of interplanetary sailing ships, which would give us something like this.
...the rest of the equipment?
Is that what Landis means by "some details to be worked out"?
Scientist 1: Well, I've got some good news and some bad news about our new solar-sail microwave-powered craft.
Scientist 2: Okay, what's the good news?
Scientist 1: Our craft reached acceleration at unprecedented rates!
Scientist 2: That is good news! What's the bad?
Scientist 1: We also nuked its millions of dollars in research equipment.
Scientist 2: Oh well, it's not like we've wasted money before on ambitious space projects. *cough*
It's such a fine line between stupid and clever.
leaving a micrometre-thin sail to continue the voyage to Mars.
I wonder how susceptible this sail would be to space dust, meteorites and space junk? Also, in response to an earlier comment made by someone about CO, I believe this technology would be used to send PROBES mostly and not people to Mars. Think about it... if they sent a person out there, how would they get back? They would need to use conventional means, which would defeat the whole purpose. Unless of course, they had another sail, AND a microwave transmitter on Mars.
This technology will be good for sending probes, but not for sending people, just yet.
Vivin Suresh Paliath
http://vivin.net
I like
come on mods, mod parent up. this was a joke god damn it. not a troll!!
I don't expect to see it in reality anytime, though, due to the basic problems with a one-way propulsion system. How do they decelerate when they arrive? There won't be anybody waiting for them at Mars with a laser pointed the other way, after all.
Have you read my blog lately?
at least it's not 1.21 Gigawatts...
Your mother says it's okay to start now.
this isn't off topic?! hes asking when its all going to be built!
granted he should RTFA but hes still on topic.
are the mods on crack or something?
Not an astronomer or space engineer, but does this one month timeframe take the required slowing down into account? You can't just point a spaceship at something, shoot it away at 60 km/s and expect it to both stop at its destination and survive arrival.
And while we're at it: how does one slow down a craft like this? Without destroying it or tugging along a rediculous amount of fuel, that is.
Storm
dihydrogen monoxide. http://www.dhmo.org/
Worst. Sig. Ever.
I was a little groggy this morning and did think I was reading Fark. Needless to say I didn't RTFA so STFU.
Stupidest Post Ever!
Tholar Thuper-Thail? Thounds like an excthelent job for Thylvethter Phthe Catht!
Does that go something like this:
Or did you need a redirect in there somewhere?
Mod parent up as accurate. ;)
This is where a craft uses the planets atmosphere to dramatically reduce speed using friction. Its actually been used for decade but never on this large a scale..!! Later on
2. Slowing down sufficiently with a Mars based system similar to the one on earth.
OR
3. A series of mirors which are swung into position at the right time to begin deceleration which reflect the light onto a surface pointing the opposite direction from source of beams..
Look up the term, dihydrogen monoxide. Let the enlightenment hit you.
[
Ah yes playing with nomenclature. I missed that the first time. Kind of like the second Austin Powers movie and the space suit which has p^2 labeled near the crotch zipper.
Those environmental terrorists will start kicking in if you try to use warp 9. Gotta be careful and such.
Karma: Chameleon (mostly due to the fact that you come and go).
We could use a buttered cat array! Infinite power at your disposal.
just line up 30 million old microwave ovens (that still work) with the doors ripped off and the safetys disabled. :-)
-nB
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Last I heard the entire concept behind solar sails (electrons providing momentum) had yet to be demonstrated. There is a possibility the friction from the small amount of matter in space (a few molecules per cubic meter) would be enough to nullify the acceleration from electrons. The coating could be an effective way to counteract though, as the gas release would provide considerably more force than mere electrons.
That's like saying since your cell phone can only put out 1/2 a watt it's impossible to heat things in your microwave.
A couple of points of reference, the radar mounted on US Aegis cruisers can put out 4 MWs and the stationary Cobra Dane early warning radar that went online in 1977 puts out 15.4 MW.
I don't think we are that far away from building a 60 MW transmitter now that we have a reason to.
Can we seriously get a muzzle for the /. editors?
Jesus H Cristof! A solar cell with "special paint" can reach Mars in a month? Uhm... yeah. And the fucking Scientologists are right - we're all aliens and the mothership(TM) is coming, but George Clinton ain't driving.
Slow news day?
space based 60 megawatt microwave projectors? Wouldn't that have some really ugly military applications?
Reject Fear - Embrace Hope
Actually, if you RTFA you'll see that they discovered the effect as a result of inadvertently boiling off carbon monoxide, but the paint that the article is about would actually use something like hydrogen (or perhaps methane).
You know, the stuff that burns much faster than dihydrogen monoxide ;)
We can generate 60-megawatts is space. It would just involve putting a nuclear reactor in space.
Fly me to the moon Let me sing among those stars Let me see what spring is like On jupiter and mars
... Putting a sail at the back of a ship is like pushing on a rope, since the sail won't be rigid.
Less is more.
The article states that the Carbon Monoxide is being bubbled off because it is pretty much being boiled off. Now here is my question. What happens when all the carbon monoxide in the paint has dissapated? Do you have to put another coat of painting outside? This makes no sense.
But it just might work.
our written thoughts are gifts to our future selves
In case you didn't notice it, it would appear that the Gregory Benford cited in the article is the same Gregory Benford who writes some very good hard sci-fi.
People like Benford who do many things well are inspiring.
Now, go check out the Galactic Center series. (Someone else can find the link to Amazon, Barnes and Noble, or your local book seller.)
-Peter
. Penguins Surely Ca
Well apparently more people die drowning in shallow puddles and shallow washbasins than die from Carbon Monoxide poisioning .
I for one, welcome our new Martian overlords.
Or is this the work of (over)enthousiastic mods?
One of their minor obstacles is going to be finding some way of heating up their reaction mass to fantastic temperatures while not simultaneously heating whatever is containing it. And forget about nano-tech. The basic laws of scale are working really hard against them. The volume being heated is miniscule, while the surface area is much larger in proportion, so it's effectively impossible to heat anything very small. Think of the smallest flame you've ever seen. You just can't make them any smaller.
how else are they going to stick their elbows out of the windows?
One can use sails to accellerate away from the sun, but coming back may be a problem. Maybe Titan was constructed by aliens as a pitstop on an intergalactic bypass? Guess we just need to find another gasball with some oxydizer.
I think the term "solar sail" is a bit of a misnomer here. If I understood correctly, almost all the thrust comes from the recoil of particles boiling off the surface, because the surface is heated by a microwave beam. This thrust is therefore perpendicular to the surface of the "sail", which is (largely) independent of the direction towards the microwave source. The exception is that, if the sail is parallel to the beam, then the microwaves don't hit the sail at all, and the system doesn't work.
But it would work perfectly well for travelling towards the microwave source (i.e. Earth), or, equivalently, for slowing down on the way to Mars: just have the paint on the other side of the sail, which gets heated from behind.
So one can imagine a craft which has two sails. The first is unfurled in Earth's orbit, with paint facing the Earth, which is used to kick it in a suitable direction to get it to Mars. After the microwave beam is turned off, the sail is discarded. Once the craft gets close to Mars, it unfurls a second sail, this time with paint on the other side, pointing towards Mars. Again a (extremely well focussed!) microwave beam from the Earth heats this sail from behind and the craft can slow down to safe speeds to land on Mars.
Of course, if your beam is so well focussed that you can use the sail near Mars, then you can use a much weaker beam for much longer to get up to the same (or greater) speed. This means you don't need a 60 megawatt beam at all - just use a 1 megawatt beam for 60 hours or whatever.
"...Look on my works, ye mighty, and despair!"
Nobody seems to think about the giant cooking beam going up through the atmosphere that "cooks/heats" anything with water vapor in it (the atmosphere, birds, people in small/large aircraft, satelites that scroll by as they orbit the earth).
While feasible from a technical standpoint - from a political "real world" standpoint its just not realistic.
Just like any other rocket, the thrust comes from the thermal expansion of gasses pressing against the sail-shaped surface. The major difference in this design is that the energy to heat the gasses comes not from chemical, nuclear or solar power onboard the craft but from on off-board source on the ground. It is functionally identical to the Laser Launch concept.
This system would work like a cannon, accelerating the craft within the span of hour or so to the orbital velocity of its target. Then the craft would coast up to that orbit like a cork bobbing to the surface of the water. It would arrive at that orbit with zero velocity relative to its target. In order to make an orbital insertion, it would require only relatively small, onboard maneuvering thrusters .
Of course, since the energy source is back on Earth, the same system could not be used for a return flight without building a microwave generator at the target.
Long term, you could set up a type of railway system, with generators around all the planets which could cheaply shoot packages back and forth.
It could be done with solar power. Of course, full spectrum vacuum solar in earth orbit is about 1.3 kW/m^2; so, for 60000 kW, you need a minimum of 45000 m^2 of solar collection area. Since conversion efficiency tends to be about 30% at best, 135000 m^2 is more realistic-- ballpark a dozen football fields worth.
Using that area for reflectors to concentrate down to smaller power cell areas might reduce cost. On the other hand, the expense of lifting the mass to orbit without a beanstalk is still hardly economical. On the gripping hand, it's cheaper, lighter, and safer than putting a 60MW reactor topside.
//Information does not want to be free; it wants to breed.
it's called tacking
What about putting the microwave transmitter on the moon? You could cover the whole light side with solar panels to charge the system up. Maybe even put up a nuclear reactor or something...
Just a thought...
No they've thought of that. They will use 3 or 4 coats of paint at the start and maybe more for longer journeys.
Pity they couldn't have got those rifle stocks in production for Uzis or Kalashnikovs though.
Panurge has posted for the last time. Thanks for the positive moderations.
LOL.... you plan to leave the window cracked or something?
...because Plutonians are teh suck
Wow. Count Dukoo can really make a fast getaway in that.
"We shall party like the Greeks of old! You know the ones I mean." - HedonismBot
Toasted Astronaut.
This brings up old cartoon imagery but I was wondering... since the propulsion comes from the emission of gas from the surface of the sail, couldn't you bring your energy source *with* you?
I mean, you could have a nuclear reactor and a microwave emitter along with the payload. I know this would add to the mass, but it seems you could then have the energy to decelerate when you reach your destination.
Anyway, I was just wondering...
lorem ipsum, dolor sit amet
I can't picture this ever being effective. I mean, seriously - what sort of ISP are they expecting to get from paint outgassing? With no nozzle or mechanism designed for ion acceleration, I can't picture it being very high at all.
We also have a halon fire extinguisher. Its always nice to have a fire extinguisher that kills people around.
Hard science fiction has never inspired anything practical.
Now leave me alone so I can watch my satelite TV.
The key is a special new paint...
The "ricers" were right!
And all this time, I thought that inane changes to your vehicle to make it *look* faster wouldn't actually do anything for the performance.
Boy, was I wrong.
wouldn't that be the first reply?
I'd say the original article is the first actual post.
Why can't you drag the beam-producing sattelite with you?
Its heating, not applying force.
------ The best brain training is now totally free : )
Remeber, both Mars and Earth are going around the sun. You aren't sending it in a straight line. You are actually pushing it out to a "higher" orbit to intercept with Mars. To bring it back, simply change the angle (vector of force) and push it to a "lower" orbit. Plain 'ol high school physics here.
- higher means further from the sun and lower means closer.
----- If communism is a system where the government owns business, what do you call a system where business owns govern
Are the moderators now trolling by auto-modding the first post as off topic no matter what it's about?
Hare are his:
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
For some reason I thought that solar sails captured photon pressure to accelerate an object by very very teeny tiny amounts over a long period of time.
As I read the article, they're still using the idea of a sail, but the acceleration comes from the release of gas. So isn't this a "gas sail"?
If it is a gas sail, then don't you have to worry about holes in the sail fabric/material? You're back to fluid pressure on a sail surface, aren't you?
It seems (admittedly, in my own uneducated, poorly-informed estimation) like the "gas sail" material would have to be more robust than with a solar sail.
Can someone clarify for me?
.. pa-ra-bo-la, pa-ra-bo-la, 2 pi R, 2 pi R, where's your latus rectum, where's your latus rectum, 2 pi R
Ohh great, forget global warming we'll have solar system warming due to the green house gass effect.
Paying taxes to buy civilization is like paying a hooker to buy love.
And the Type-R decal.
nice post - it cracks me up that this long after your post, noone's commented on the funniest part of your post - the offhand reference to dihydrogen monoxide poisoning. Well - it cracked me up :)
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
So you sail to Mars in a month, you solve the landing issue.... then how the #(*%^# do you get BACK?
Traditional sailboats can tack into the wind.... but that relies on friction between the boat and the water. There's not enough friction in space. Bringing enough rocket fuel along for the launch from the Martian surface would be tricky, and the many year voyage home isn't a welcome prospect.
Forward suggests that research needs to be carried out into materials that release gases when heated so they can be used to drive the sail. If he read the issue of New Scientist that contains this story he'd find another story that deals with precisely this issue. It turns out that The Terrorists have been doing this research for him.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
I'm pretty sure they wouldn't let the CO from outside get in
You mean they wouldn't leave a door open to the Vacuum of space? Well maybe not a complete vacuum with the CO emmisions. There might be an atom or two of gas per cubic meter.
----- If communism is a system where the government owns business, what do you call a system where business owns govern
If my aunt was a bicycle, I could ride her into town. (On-topic, you just have the think about it a little bit.)
"None are more hopelessly enslaved than those who falsely believe they are free." -- Goethe
How do you stop? the only option I really see is having spacecraft carry 2 sails (one to start, one to stop), and have a microwave on earth, and another on mars.
All misspellings and grammatical errors in the above post are intentional and part of my artistic expression.
Let me guess - a flame job on the hood to make it go faster.
Slap a whale tail on the trunk and a chrome tailpipe out the back and you could get to Mars in a week!
how would they get back
As your high school physics class should have taught you (basic Newtonian physics) and other posts have mentioned, getting back will not require a remote generator and microwave beam. It would help to have a sufficient coating of paint though.
----- If communism is a system where the government owns business, what do you call a system where business owns govern
And a lot less complicated, less expensive, more robust and you have a plasma rocket to maneuver with, and enter orbit with. One that you can refuel with Martian CO2 or water.
It also happens to be a matter of scale and efficiency to develop from the VASMiR plasma rocket to a fusion torch.
If I'm not entirely off my mark, the idea of solar sails has been around for a long time, and I actually had a friend in highschool who did a nationally recognoized science fair project concerning materials for and propulsion from solar sails. A few microns thick is all it needs to be, and it's still quite tough, think super-thin garbage bags, the sail material has similar tensile properties. A 60MW microwave beam seems like it would make an awful nice weapon, but I imagine if it were space based, it could be somewhat less powerful to achieve a similar effect on the spacecraft. That and the fact that the power is spread over the area of a 100m diameter circle... 50*50*Pi comes out to around 7850 square meters, which means you get 7.643kW per meter squared... about 710W per square foot for those of us who don't like metric. I'm not an expert, but 710W/sqft sounds like less power than the microwave in my kitchen can put out.
And this is different from a conventional chemical rocket in what way?
Think about it - you still would need the coating on the sail (fuel) that would then be externally "ignited" by the microwave energy. So you still run into the problem of carrying your fuel source with you. The whole concept of solar sails is supposed to eliminate that need.
Now, whether this may be a more efficient chemical rocket is different topic...
An ounce of perception is worth a pound of obscure
Actually, it would be trivial. All you need is a heat shield.
If you go into a direct entry, i.e. you don't go into orbit around Mars first, you just hide behind your heat shield and let friction with Mars' atmosphere slow you down.
This is the method that the Space Shuttle uses to slow down to land back on Earth -- its moving at 5 miles per second, and slows down using atmospheric friction. This is how the Apollo astronauts returning from the Moon slowed down from 7 miles/second. It is how the Mars Rovers slowed down when they arrived at Mars (not sure of the closure rate), and how the Huygens probe that just landed on Titan slowed down when it got to Titan 2 weeks ago.
What's HARD is to slow down at a place WITHOUT air, like the Moon. However, since objects without air usually have lower gravities than those that do, its not as hard as trying to land on a place like Earth without air. That would be TRULY difficult.
I can see it now...another quality Benford Tools product...where's Al to give us a witty statement about Tim's inability to fly it correctly after he "rewires" it?
Warning: Not for terrestrial escape. Solar sail for outdoor use only. Do not deploy in poorly ventilated regions of space. Emissions sticker must be displayed on windshield of personnel module at all times. Solar System law prohibits tampering with or disabling of solar sail emission control systems. (Additional requirements apply above Earth's California.) It is illegal to use 60 MW microwave source in any manner inconsistent with labeling (e.g. popcorn, "phone home", mind control of homeless.) Not safe for children under 6 (toxic if eaten, asphyxiation hazard). May be fatal if used as shelter in bright sunlight or under lightning conditions. Improper disposal threatens wildlife and environment - ask local authorities about stellar propulsion system recycling programs.
"Yeah, they found the poor bastard in his space garage with the door closed and the solar sail running. Damn shame."
Is this Greg Benford the same as the science fiction author Greg Benford? Putting sf authors to work seems like a good way to get "out of the box" thinking.
Read a good book lately?
These guys are definitely on an interesting track, though. The problem with rocket engines in general is that they have a tradeoff between mass efficiency (you want to put as much momentum on each piece your propellant as possible, so that you get as much push from it as possible) and energy efficiency (it costs energy to push propellant, and you have to supply the energy).
Chemical rockets can't get much more efficient than the Space Shuttle Main Engines, because the amount of energy available for each molecule of exhaust gas is whatever you can get by chemically reacting your fuel to make the propellant molecule. The SSMEs use one of the most energetic-per-unit-mass chemical reactions around: hydrogen and oxygen (fuels) combining to make water (propellant).
Electric ion rockets do better because each molecule of propellant gets much more energy than would be available from chemical reactions. The problem there is that you still have to produce the energy. Nuclear electric propulsion uses plutonium to generate heat, which is converted to electricity and then used to run the ion rocket. Solar electric propulsion uses solar panels to generate electricity that runs the ion rocket. The problem is that both of those schemes are limited by the power available: it's hard to make energy rapidly with either a conventional radiothermal (noncritical) generator or solar panels, so while the rocket is extremely fuel efficient it is also quite slow.
Pure solar sails use the best/worst propellant in the Universe: photons. Best, because photons are disposable -- "use all you want, we'll make more!". Worst, because photons use the most energy per unit delivered momentum of any propellant in the universe. So a sail transduces huge amounts of power (at least in the inner solar system) but uses a very inefficient process to convert that energy to momentum.
Making the sail into a hybrid rocket is a Good thing, but using this paint scheme doesn't help, because the ejected molecules don't ever get much more energy than their own chemical binding energy into the paint -- that means they're being more or less wasted as propellant, because you want to put as much kinetic energy on the propellant as possible.
A better scheme is to use a curved solar sail as a concentrator to heat up a high power electrical generator, and then use the electricity to drive an ion rocket. In 2000 or 2001 I and a colleague worked up the numbers for such a scheme (there are technical problems with making high-power ion rockets; but we considered just energy flow). A smallish curved solar sail (say, 120m in diameter) can concentrate 10 megawatts of heat onto a heat collector. At 10% conversion efficiency to propellant power (15% for conversion to electricity, times 67% efficiency in the rocket engine) that would still be a megawatt of power, enough to provide hundreds or thousands of Newtons of thrust. In several scenarios we considered, the acceleration of the whole craft is higher than the unloaded self-acceleration of the sail, so it would be necessary to repel the sail electrostatically or something like that to keep its shape correct.
Ion rockets can be 100 to 1000 times more propellant-efficient than chemical rockets, provided that there is enough energy available.
Nope. I believe they said that it would require ONE hour of focused microwave energy on the sail while still in low earth orbit to achieve Ludicrous Speed.
Then it coasts.
So, basically you build 20 2 MW transmitters and focus their output on a point a few hundred or thousand miles away -- I assume after an hour the craft will be moving away pretty damned quick, so a few thousand miles then.
How does this thing STOP? You make Mars, but what's slowing it down from 150 miles per second so that it'll achieve orbit? Atmospheric braking? Um, no, let that go - no airbraking, it'd vaporize. Even if it could withstand a 150 mps entry without puffing out, it'd punch out of the atmosphere in seconds, with no time to kill much speed. No rockets either -- can't carry enough fuel to kill 150 mps.
You'd need another microwave array in a high Martian orbit to fire at the solar sail as it came streaking in from Earth, if you want it to downspeed to make orbit. I'd assume the sail reverses somehow, so the craft comes in tail first.
Now. If you want a FAST vehicle, build a solar powered multi-megawatt laser at an LaGrange point, and use the nicely focused red laser on a solar sail. The craft'll be at Mars in, what, two weeks?
There's a couple of points that occur to me: the mass of the object being towed by the sail is irrelevant, mostly; you could tow the Sears Tower if you want. You'd just have to fire the lasers/microwaves for a longer time. A laser/purely reflective sail would be used for really heavy objects, and the gas-outing microwave system for smaller payloads, because the amount of paint on the sail is limited and will be exhausted, while a pure mirror-sail is static and can be used indefinitely.
and 5 hundred years later once again man used sails to explore a new world...
funny how history reapeats itself
replace that "150 mps" with "60 kps". I'd pulled the 150 out of me butt, just for argument's sake.
It looks like this is the first entry here on Mars (topic #226). Are our editers expecting many new articles now, or have they just put off naming a new topic until we already had put a ton in the Space section?
I found it a little weird that a post on solar sailing appears on slashdot and no one mentions arthur c. clarke in the entire discussion. (although i am not sure about whether he originally proposed the solar sailing idea.. perhaps twas Kepler)
I remember first reading about this in school in this book. One of the short stories is about some this space sailing race in which sailing boats have to complete a round around the moon and then return to earth.
I also heard that he just managed to survive the tsunami.
Cheers to a great mind.
[all generalizations are untrue except this one]
is this now /fark?
"It's not like your minds are as open as the source you love..." - Me to the majority of Slashdot.
How is this particularly better than carrying the mass as fuel and oxidizer and expelling it backwards by burning it in a rocket engine? As far as I can see, the main difference is the mass of the rocket engine itself, and I suspect that even a light sail spacecraft is still going to have rockets on board for those occasional moments when you'd like more than 0.001 g's acceleration (to avoid collisions or do docking maneuvers, for example).
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
Look up the term, dihydrogen monoxide. Let the enlightenment hit you.
Thanks, but I've already called my senators urging them to ban its use in our governmental facilities.
$8.95/mo web hosting
fnah
I don't know the meaning of the word 'don't' - J
What I want to know is...
What happens to anything that gets in front of this microwave beam? I remember reading about the early days of radar where birds would fall from the sky when flying too near the towers.
MMMMMMM, pigeon....
Ok, so I have come to the basic conclusion that this is not really a sail with an external force pushing it. Instead it is a large surface covered in paint (basicly the fuel) that when heated to a boiling point will emit gasses that produce thrust.
Now I'm no mathmatician, but I guess it comes down to which is more efficient, a large surface, or a small (relatively) rocket nozzle, providing thrust?
Also since it is the paint (fuel) of the "sail" providing the trust, can't you attach the power supply and microwave emiter to the craft? I mean it's not pushing the craft, its just heating the "sail" that produces the thrust....
Do not meddle in the affairs of sysadmins, for the are subtle and quick to anger.
will you? You don't carry your "fuel source" with you, because fuel is energy and you don't carry energy, you carry only working body.
Doing some rough calculations, Vf = Vi + a*t, the acceleration of 0 to 60,000m/s is 16.67m/s^2, or not quite 2G's. I know fighter pilots in special g-suits are supposed to be able to sustain brief periods of upto 9G's, but what about 2G's sustained for an hour? Any ideas?
Learn ... and FEAR!
:D
I didn't think the house band in Hell would play this badly.
I admit I didn't RTFA. 60 km/s is too fast for slowing down at Mars using atmosphere alone, you're right.
Would work at Titan, though, with its huge, puffed up atmosphere. You'd need an old-school ablative shield instead of the sissy ceramic tiles that the Shuttle uses.
You're not a physicist either. Or a speller, for that matter.
can't you attach the power supply and microwave emiter to the craft?
Sure, just give me a power supply of zero mass. Pure genius.
German scientist Heim developed a strange theory in the 50ies of the 20th century. It would make it possible to manipulate gravity and reducing the objects mass to zero, allowing FTL travel. it does seem to be sincere, and not yet another magical star trek-science. anyone got more information about this one? is there real hope this one takes off?
This sig does not contain any SCO code.
I'm no rocket scientist, but I don't agree. In a rocket engine, the energy pushing your particles out the exhaust has to come from that chemical reaction, and so be stored in the molecules somehow. But here, the energy is coming from some external source, like a solar powered orbital maser. You only need enough bond strength in the paint to hold the mass there while you heat it, and chemical energy stored in the paint doesn't matter at all.
The laws of reaction still apply to the emiiter, but at these levels it should be negligable (most of the thrust on the other end is coming from the boiling gas).
...
Okay, I am not a physiscist, and its been 13 years or more since my last physics course, but
The thrust which isn't is due to electromagetic radiation, i.e. photons, which have no mass. The microwave transmitter won't have any back thrust, any more than a flashlight hanging in a perfect vacuum is going to produce "thrust" opposite the direction of the flashlight's beam.
The photons hit the sail, experience redshift as they reverse direction (thereby imparting some energy on the sail, which pushes it forward). They aren't particles with mass hitting the sail the way ions would be, or molecules of air in the wind against a sailboat. The exchange of energy is reletavistic (red shifting) IIRC, not Newtonian.
I don't believe a space based microwave transmitter will experience any thrust due to the emission of electromagnetic radiation, any more than a laser would if we were using Dr. Forward's solar sail design.
The Future of Human Evolution: Autonomy
something called "stored energy density". For rocket fuel it's X J/kg (look up a suitable value for X, I'm lazy). For microwaves it's exactly infinity J/kg because microwaves are not stored on board. There's some difference, eh?
The thrust which isn't is due to electromagetic radiation, i.e. photons, which have no mass.
should read:
The thrust which isn't is due to material boiling off the sail is due to electromagetic radiation, i.e. photons, which have no mass.
The Future of Human Evolution: Autonomy
I wonder if a high-altitude skim could be constructed that could use the solar sail itself for aerobraking. It would be touchy, at best. Too high, and it would do nothing. Too deep, and it would rip itself to pieces, as well as breaking the shroud lines.
Science Fiction reference:
"Flight of the Dragonfly" by Robert L Forward
***** minor spoiler *****
The solar sail was designed to be partitioned en-route. At the appropriate time, the outer (forget the fraction) of the sail was disconnected from the inner fraction and the spacecraft. But since it was in space, and presumably had at least a little spin, it stayed reasonably unfurled.
Then the launch laser beam arrived from Earth, and hit the separated outer sail. It popped inside out from the light force, and focused the light back on the inner sail that was still attached to the spacecraft. This accelerated the outer sail harder, but supplied decelerating force to the inner sail and spacecraft. The inner sail also received some of the beam from Earth on the wrong side, but that was much less than the focused beam from the outer sail.
The living have better things to do than to continue hating the dead.
*could*
Being "behind that thing for a month" would not make it more dangerous to travel in space. Actually, it would make it safer to travel than conventional solid fuel rockets that causes explosions that could send your granny to the moon.
Carbon monoxide is toxic to us when we breath it. We would be breathing the air within the spacecraft...not it's exhaust.
Well yes, but do you really want a 60 megawatt microwave beam shooting at you, I'd find some way to put the sail behind you. Maybe like this...
ship---sail--anchor
with a bar running between the anchor and the ship through the middle of the sail, and the sail attached to the anchor.
Though you'd still melt the anchor in no time with the microwaves. So no, I have no idea.
Ion rockets do this by putting an electrical potential on the propellant mass. Then when a freshly ionized propellant molecule leaves the engine, it is electrostatically repulsed from the back of the engine (and perhaps attracted by the exit grid). That repulsion is what imparts the final "kick" to it. It's the same technology that makes old-style television sets and other particle accelerators work.
But this paint scheme has no such macroscopic design -- from the article, it sounds like they're just trying to heat it fast with microwaves.
At 60 kps, you ain't slingshotting, you're getting a minor course deviation. The craft has solar escape velocity, and its going, going, gone....
Oh shit..turns out we forgot to install a laser on mars Plus we only have one can of this paint to repaint the sails....man...it's going to be a long ride back.
Yes, but you could anchor the corners, like we do here with a mast. Does a sailboat sail only provide momentum to the portion of the boat that is behind it? A mast erected at the stern of a sailboat still pushes the whole of the boat forward.
So long and thanks for all the fish . . . !!!
So what about an orbital microwave complex (like it was proposed above) to accelerate the craft and another one in martian orbit to slow it down?
Such stations could be computer controlled, making the craft a kind of train in an interplanetary subway. This scenario would allow less expensive interplanetary travel.
Science, philosophy and wine, could there be eanything more human?
But if it takes you that long to slow down, seems like you could get there faster using conventional means.
The old idea was to heat a mass of frozen carbon dioxide with a ground based laser and eject the gas through a nozzle. Don't remember who invented this but Jerry Pournelle used it in one of his novels.
A second related old idea is the idea of propelling aircraft with microwaves from space based power stations.
The more serious problem is it won't work.
Isp is Isp. That's what controls your fuel to payload ratio. Note that this system is primarily NOT working as a solar sail - the reaction mass is coming off the sail itself, not incident upon it. You only win if you can increase the Isp.
Lets assume you can't heat the sale to several thousand degrees. Carbon fibre won't stand up to that and you have the additional interesting diffculty of keeping one side of the sail very hot and the other side cool - so the sail is not going to be thin and light.
So we are knocking off molecules as a quantum process. The energy of each ejected molecule is one microwave photon's energy. So its not very hot. If we work at the top of the microwave range (300Ghz) each photon is 2E-22J. If we are ejecting atomic hydrogen (best case), and if my calculations are correct (hah!) the hydrogen comes off at 550 metres/second. So the Isp is roughly 60, which is lousy.
Now using a sail to focus ground based microwaves on an ion engine - that could be worth doing. You heat the engine and then inject hydrogen into it.
Squirrel!
another question is, arent there microwaves in space? and wont that interfere with the operation of the sail?
Two ways to do it:
1) Swoop past Mars to Jupiter, sling shot around while turning, and return to Mars tail first while firing the laser at the backside to slow down:
Earth Mars sail
O --beam---o---<=)
2) Have the sail be a two part sucker, with an inner area and a detatchable donut-shaped portion, with some streamers attached to it. Once past halfway, detatch the donut while keeping the beam on, and having lower mass than the inner area+capsule portion, it will accelerate past the capsule/inner sail. After a reasonable amount of time, change the beam projector to project a donut-shaped beam that will only hit the donut-shaped sail, reflect off, and hit the back side of the inner sail, slowing it (have the capsule swing through the center, so it'll decellerate properly):
start:
View from Earth:
------
|.._..|
|.|_|.|
|_____|
View from side:
../|
..\|
<==|
After (from side):
......-|
......-|
|==>...... (Mars this way -> )
Ignore the periods - they're there 'cause I can't figure out how to make slashdot give me monospaced-spaces.
-T
Solar Super-Sail Could Reach Mars in a Month Mars
from the check-out-that-stylish-new-icon dept. ti-coune sent us a story running on newscientist describing solar super sails and how they could one day get us to Mars in a month. The key is a special new paint. The cast of Trading Spaces is unavailable for comment.
My other sig is a Porsche.
Sure, but any rigid truss arrangement that can transfer the thrust generated by the sail in compression or bending loads will still be far heavier than a set of cables that can handle the same load in tension.
The microwave radiation thing wouldn't be an issue to the occupants of the ship - they're going to be sitting inside a metal enclosure, and will be shielded from the radiation the same way you are if you're standing in front of your countertop microwave waiting for the water to boil. Similarly, the metal enclosure can be designed as a deflector for the microwaves, so that it won't melt.
Less is more.
Yeah, I did not RTFA 'cause I am at work.
I highly doubt that is 4 and 15.4MW in CW. Only doppler radars use CW, and those are hardly used for air and surface search.
Why not create a large shuttle with its own 60MW Microwave and a big arse sail and replacements. Jetisen to orbit, deploy the sail and propel your own self through space. Then we could be talking about a whole mars station making its way to orbit around mars, or wherever, and being able to get its self back or further into space. It could be manned or otherwise and it wouldn't require us aiming around the object to get at the sail.
WHADDYA MEAN WE'RE OUT?!?
"Things are different now, Bob. Just give em a couple DVDs, a case of Evian, some TV dinners and they'll be fine."
to the velocity of outgoing paint molecules. That's momentum conservation:v_craft*m_craft = v_paint*m_paint. To increase velocity, you just pump more energy (and maybe use paint that boils at higher temperature).
I'm assuming the sail isn't to be used for a round-trip, anyway, considering you're boiling the special paint away on your outward boost phase. So why not aerobrake? Sure, the sail won't survive, but your payload capsule can with no problem... same way the MER rovers got there.
But how do the supplies stop?
Most spacecrafts are almost entirely cargo and fuel. This craft won't require much fuel so virtually all of the mass is going to be cargo.
We are stuck with the same problem.
I don't read or respond to AC posts
OK so I'm sure you've read about the [possiblity] that mobile phones (cell phones for you americans :p) can cause a whole load of different health problems for heavy users. Whats it gonna do if you have that much high energy EM radiation pointed at you? Cooked in their own juices?
If you need more speed, you don't take more reaction mass with you, you just pump more energy. There's no limit as to how much external energy you can apply (within reason :)
Simple energy calculation:
1/2*m*v^2=P*t.
P=60MW, t=3600s, v=60km/s.
At an efficiency of 100%(!), the maximum mass you can give this speed is 120kg.
The sail will be 100m across, this is 10,000 m2.
The maximum mass per square meter, including structural integrity (there will be quite a bit of force on the sail to make it accelerate to 60 km/s in just one hour, about 2000N!) is 12g/m2.
Then, I think, you will want to have some payload to reach Mars to do the actual experiments with... This needs to be subtracted from the mass of the sail.
OK, some of the mass of the sail will evaporate to enhance propulsion, so acceleration at the end (when the construction is lighter) will be higher than in the beginning, but a lage part of the energy will be taken away by the evaporating gas as well, so efficiency will be quite abit lower than 100%.
All in all, how do they think to make this construction?
There's supposed to be a metal enclosure for my countertop microwave?
Oh shit.
Great job!
But, in this modified solar-sail plan, the beam isn't interplanetary. The microwave emitters are on earth, and are only in play for the first hour after the craft starts the journey. I don't think they can focus the microwaves across interplantary distances -- you'd need a laser for that kind of tight focus. I don't think masers can do the distance.
One would think that a picture of mars would be better...
Begging to differ, but the first test coating, when microwaved inside our atmosphere, emitted CO. A carbon coating in space would not. And those who read to the end know that they are investigating other coatings.
"But all your emitter and collector are belong to me!"
Quick! Someone with skillz work out what the per-square-meter power of a 100 meter diameter beam that originated with 60 MW emitter and traveled 300 km would be. And I apologize for the poor construction of that sentance.
The Spoon
Updated 6/28/2011
That's a lot of burnt popcorn!
"I worked hard for it. I deserve it. And I have it," Campbell said. "It's all mine."
So does coherent radiation, bunky. Diffraction and/or Heisenberg, take your pick of explanations.
"But all your emitter and collector are belong to me!"
...until a Zeta Reticulan pilot and and the FBI are standing on your doorstep for shining one into a UFO cockpit...
Blacker than my baby girl's stare. Black like the veil that the muslimina wear. Black like the planet that they fear...
If the sail was mounted in a circular frame which was attached to the ship (rather like a shuttle cock with the sail in the open end) then you could rear-mount it...
--- Users are like bacteria -> Each one causing a thousand tiny crises until the host finally gives up and dies.
being in a metal can with other ppl, you may wish to be concerned about methane instead. Now, that will kill.
An argument I've long made: if you want to colonize and explore Mars, stop thinking in terms of "returning" people like some gigantic Apollo program. One-way tickets ONLY, until the new martians build their own ships. I'd go in a shot. So would thousands of others. After all, it's not necessarily forever, and secondly, with a whole world to see for the very first time, why would you want to go back?
It explains exactly what you want to know...
It even gives you some nice little pictures...
Sure, but any rigid truss arrangement that can transfer the thrust generated by the sail in compression or bending loads will still be far heavier than a set of cables that can handle the same load in tension.
I disagree. Since the objects are in space, virtually any connection between two objects will be of virtually identical thickness/mass. Put the solar sail as the whole stern of the ship and you have a most efficient arrangement. Having the ship behind the sail will mean that the ship's profile will be interrupting and dispersing a portion of the beamed microwaves. Naturally, this can be minimized, like a reflector telescope. I still wouldn't want to ride in a ship being hit by industrial strength microwave radiation. You could be shielded, but why add risk to already risky space travel?
So long and thanks for all the fish . . . !!!
First let's get a working solar sail. Just one measley working
prototype. THEN regale us with how bright the future is. The fact is, this is not a proven technology. And at least one scientist has had the balls to stand up and say that maybe it won't work. This March we'll know for sure.
"Consensus" in science is _always_ a political construct.
I'll bite. 100m diameter gives 7850 square meters area, so the power density is 7600 watts per square meter - toasty warm. I'd say that's between five and ten times what the inside of your microwave sees. You'd definitely want anything that's exposed to that intensity to reflect or deflect, rather than absorb, the radiation.
Since the beam was intended to be parallel, the distance doesn't matter. You could do this I suppose if you built a 100m diameter maser, although it's not immediately apparent to me how exactly that would be done.
Less is more.
Totally off-topic ( and yet, actually, mentioned in the story, so is it? ) and yet fantastic Paige from Trading Spaces dirt !
I don't know if I should be happy that everyone is so geeky here that they're not talking about Paige's sex tapes, or if I should be as bewildered as I am... hel-looo, people, SEX TAPES!?!! And they all pile on the carbon monoxide comment. What dorks. I guess nobody can be bothered to click on links to get the joke.
Eh. Same ol' slashdot.
But how is it that I, with a reality-TV-addicted wife ( she's been hooked since the _first_ frickin' "Real World" for cryin' out loud ) don't know about this www.realityblurred.com website!? That guy needs some publicity for his site, a reality TV gossip site the most obvious brilliant website idea I've seen in a while.
His voodoo is also pretty impressive, because he has just helped me create a perpetual motion machine.
I could point two near perfect reflectors at each other in a vaccuum, bounce a beam of microwaves between them and rake in nearly double power I put into the system every time the wave was reflected!
Energy is gained from the absorption of photons and not their reflection. Otherwise you are violating the ever so important laws of thermodynamics. It makes me angry when people describe a solar sail as a "giant mirror in space".
*Splort*
this same solution could be positioned at mars to stop it. While it would not have 60MW of power, it would not need it. It would simply run longer, say 5 hours.
But to be honest, I would want at least several of these at Mars. There is a lot of metrioites between mars and jupiter.
The other advantage of this, would be a kicker for an interstaller craft. As the craft passes Mars, simply hit it again. Cheap way to get to the outer planets.
I prefer the "u" in honour as it seems to be missing these days.
it would be cool to latch one of these things onto a small asteroid, and use it as a source of ionizable material.
love is just extroverted narcissism
this would really be called vaporware.
True, though you could cheat - use some more of your solar sail material, except less reflective and more refractive, to build a big ol' Fresnel lens. Hang it at an Earth LaGrange point (maybe the Earth-Sun L2 so that the sun wouldn't push it out of position), have your maser orbit the lens a thousand miles around the L2 point at a focal point, and use the fresnel to sharpen the beam into a much tighter maser.
-T
Hate to go offtopic but...
You've forgotton that the same effect is happening to the emmiter. Say we place a flashlight in vacuum, and it emits a beam in one direction. The light bulb is actually emmiting light in all directions simultaniously, but the light is only escaping in the forward arc. The rest is reflected, or absorbed, by the backing in the flashlight, pushing it backwards via the same effect as the light impacting a solar sail pushed forwards. If no reaction effects apply to the light bulb filament, then the net thrust is opposite the amount of thrust provided by the beam were it applied to a light sail. If reaction effects apply to the filament, then it's still thrusting away from the beam opening, since the light is only leaving via that arc. So the laws of reaction still apply, regardless.
A laser is subject to the same effect, since lasers have mirrored backing (the light beam is parralel, but projects equally in both directions unless reflected).
Erotic is when you use a feather. Exotic is when you use the whole chicken.
don't think the distance is all that important, as they were estimating it using 60MW spread over the 100 meter diameter. So that means the surface area (assuming flat circle, which this is not) is 7853.75 square meters. That is 7.6 Watts per square inch. Enough to definatly cause some heat, but I guess with some shielding could be dealt with. But ultimatly you'd be blocking those precious rays from the sail, so in front with a small anchor would be preferable.
Arghhh!! Those damned Zorgs be blastin' the sail again! Fire the port cannons!
Let me guess, speed stripes?
Chemical rockets can't get much more efficient than the Space Shuttle Main Engines, because the amount of energy available for each molecule of exhaust gas is whatever you can get by chemically reacting your fuel to make the propellant molecule.
The problem with standard rocket design is that they expend much of their energy accelerating most of the fuel in the wrong direction. Using an "explosive solar sail" system can burn more of the fuel simultaneously than pumping it from a tank to a nozzle, making it, in theory, far more efficient.
The other factor is that we can generate power far more easily than we can store energy, but the equipment to do so is generally very heavy. Keeping that heavy equipment on earth and "beaming" the power to the spacecraft can be more efficient than toting the weight of the energy storage system, even if the power transfer is very inefficient.
Would accelerate in the opposite direction. Of-course by so very little that noone would notice, but if this tech is used for hundreds of years, many times a year, our orbit would change for sure. As if the global warming is not enough...
You can't handle the truth.
Psst, did ya read the article? They are talking about the thing moving 7 times faster than the rovers vehicle. Something that survives areobraking at one speed, might become a crispy piece of toast at 7 times that speed.
While I can not speak about the chinese, NASA is not a 100% civilian effort. Much of their tech. is shared (and sometimes forced over) to the hands of the DOD (which BTW, the DOD has also had its hands force open to NASA from time to time). For starters, other the saturn V, all the early rockets were missle launchers.
Likewise, the shuttle does (did) a large number of military work. This was hidden from civilians. As it is now, where is the X-33? and soon another X project will be turned over to the DOD (hypersonic flight).
I prefer the "u" in honour as it seems to be missing these days.
Would you really need to fire the lasers/microwaves for a longer time? No friction/gravity in space thus nothing stopping you from throwing the Sears Tower out toward Alpha Centauri so long as you can get a footing on something and the Sears Tower cannot. Same principles apply to the sail, only its pulling instead of throwing and we've got control of the footing.
Please correct me if i'm wrong.
eric http://www.ericdfields.com/
Yes, point taken. One has to wonder why the Mars icon appears to be casting a shadow as if it were resting on a flat surface. Somebody at Slashdot likes that drop shadow effect way too much.
One way to slow down or stop relative to Mars would be to carry weights with you on your way there. That darned law of physics that says that for every action there is an equal and opposite reaction would come in handy. Say your Shuttle weighs 1 ton, then carry along 1 ton of dead weight. When you get to Mars, fire some actuators or boosters to throw the dead weight off into space and the shuttle stops or slows. You could have the whole contraption spinning and use centrifical(sp?) force to throw off the shuttle, stopping it, and send your weight off into space.
Where is a good patent lawyer when you need one?
I surrounded my whole countertop with 6 inch lead, just ot be sure.
You could also put the sail between a rod and the spacecraft if its not rigid like so:
/
\
)
----|--SC
}
such that the sail will be wired to the tip of the rod.
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
"Since the objects are in space, virtually any connection between two objects will be of virtually identical thickness/mass." Structural behaviour is much the same in space. You still can't push with ropes... Why would all elements be the same?
Okay I'm not a huge microwave energy buff. But looking at size and weight constraints, is it possible to make a small enough microwave emitter to power the sail from right behind the sail? Basically to have the emitter drug through space so that it is never more than maybe 100 yards behind the sail?
If I recall from Niven and Pournelle's The Mote in God's Eye, the Moties' ship used light-sails boosted by a laser from their home planet.
Yeah, I kept waiting and waiting and waiting for someone to ask for a torrent, and it never came.
:P
Go fig.
Now the readers will never...ah nevermind.
Karma: Chameleon (mostly due to the fact that you come and go).
Wouldn't it be easier to just have paint in a bucket with a venturi at one end and burn it with a laser? (Hmmm a standard rocket)? A vehicle that loses mass as it accelerates is essentially a rocket.
I think if they can increase the efficiency of solar sails would be a better idea to pursue.
I can hear the complaints now: threats of galactic warming!
The sail might pickup Tachyon particles and propel the solar ship to warp speed. Hell, it would probably warp all the way to Cardassia.
Make it less than 6 hours or sun will push you backward in the afternoon. :(
[self dealloc];
Microwaves - gotta love em.
:) "Roger Moonbase -
Seriously though, how the heck do I stop my ham
sandwiches from blowing to pieces in the microwave.
Sometimes it takes only 12 seconds! Yiches - I
grok the technique, it's a serious problem when
snack time comes around!
So why not use just water for the momentus
occasion? Just a thought. Or build a whole
bunch of smaller "beaming" stations and
FOCUS them on one target at a time. Hmm,
is that a scallable solution to solar system
transport?
"Moonbase beam station #1 to Earth - We are
go at 1.2 Terrawatts"
AlphaProxima Probe #1 is go for transstellar
manuever. Let her rock!"
Now, how the heck to I get the mustard of the
top side of my microwave!!!
Worse than that: you'd want the paint to be very opaque to microwave for efficiency, yet the microwave beam has to penetrate the cloud of paint you leave behind.
Using ground-based power to heat reaction mass carried in the space ship (either painted on the sail, or something more realistic) just doesn't seem like that big of a payoff to me. Hydrogen/oxygen engines produce remarkably high exhaust velocities already.
It's possible, of course, to throw enough microwave power at the problem to make the spaceship design worthwhile, but that just moves the engineering challenges to the design of the microwave cannon. Not to mention that you're going have problems with losing both energy and focus as the microwave beam penetrates the atmosphere.
Socialism: a lie told by totalitarians and believed by fools.
I think it's just a matter of speed...
It'd still be moving, but much much slower.
What if an airliner or anything else flying through the beam - Instant toast.... Naaa!!! Nice idea though.... but a lot of issues to be resolved for sure... like where and how to get an 80 Megawatt beam that narrow.
BTW. The sail emits carbon monoxide to get its speed boost. You know, the stuff the kills humans almost as fast as dihydrogen monoxide.
You really want to be behind that thing for a whole month?
You know, it's really sad that no one gets this parody anymore. Here's the link. Oh yes, DHMO is dangerous! /sarcasm
Anyways, for those who still don't get it, think about the chemical symbol for DHMO (Hint: it isn't DHMO!)
"There are 10 types of people in this world--Those that understand binary, and those that do not..."
Like in the Road Runner cartoons where Wile E. Coyote has a skateboard with a sail on front and an electric fan on the back?
Cthulhu loves you.
Funny, I just read the story to which you are referring; I would post the name but I just returned the book and already forgot the title. It may have been "The Wind From The Sun".
The very first thing I thought of when I saw this story was "Hey, just like that story I just read" :-)
Yet Another Contentless PostKlingon programs don't timeshare, they battle for supremacy.
Unless it works in 48 hours, the trading spaces crew doesn't want it.
Correct me if I'm wrong..but if what you're saying about this technique is true, then it does have the oppourtunity to generate thrust in excess of chemical rockets. Since chemical rockets are powered by the reaction itself, the reaction must be thermodynamically favored, and the thrust you receive comes from the reaction. in this technique the reation is being driven by the maser- thus it could be thermodynaically unfavored. In fact, as you pointed out, the thrust would be proportionally only to activation energy. Thus you would want a reaction with a high activation energy, as it would be able to absorb more of the incoming radiation.
I assume they'll pull in the solar sail as they get closer to Mars, so they can use aerobraking (or ares-braking, ahahaha).
It's getting back that I'm worried about.
when suddenly the plane bursts into flames from getting hit by a 60 megawat beam.
There's a couple of points that occur to me: the mass of the object being towed by the sail is irrelevant, mostly; you could tow the Sears Tower if you want.
...mainly) and kill two birds at once: get rid of "excess" water on Earth (you know... all of these enviromentalists complaining about global warming melting the Poles and flooding most of us... STFU) and on the other hand .... let the terraformin' begin!!!
If that reasoning isn't flawed... what about towing HUGE icebergs instead???
Stop complaining about not finding water anywhere else but on Earth (well,
makes our cars faster.
in 2041, maybe it really will.
SIGERR: laziness exceeds quota
If the 60 megawatt microwave they are talking about becomes a reality, hydrogen or methane propellents can take a back seat to this
Depending on the frequency of interest, do many of these lenses and reflectors already exist as interstellar gas and dust clouds? One would only need a map of them and a way to make a sail opaque or transparent or reflective at the appropriate frequency. This would seem to be easiest with a very large sail that is mostly "not there". Just give me a supernova and a sufficient lens and sail array and I'll move the earth as easily as you please.
Starship Trooper, go sailing on by.
Catch my soul, catch the very night.
Hide the moment from my eager eyes.
Though you've seen them, please don't tell a soul.
What you can't see, can't be very whole.
-Yes
Obviously not. "For every action...", after all.
After all, I am strangely colored.
It was in Mote in God's Eye IIRC... you simply charge the craft up to a couple million volts, then since the sun's magnetic field is perpendicular to the plane of the solar system you get a hefty torque at right angles to the direction of travel. (Left Hand Rule.)
Use that to shed velocity in a spiral round the destination planet and insert into a low altitude orbit. Simple As.
Your not using hemp ropes, your using pieces of metal. To make a rigid piece of metal, in space, requires no more mass than to make a wire. The resistance to compression and resistance to stretching are virtually identical for metallic solids in space.
So long and thanks for all the fish . . . !!!
how many miles per gallon is that? maybe i'll rtfa...
Get your torrents...
your idea of an ion engine is a bit distorted. ion engines have no chemical bonds to break. the use ionized gas to accelerate the particles toward the grid, which in turn accelerates the ship in the opposite direction. the only reason they spew electrons out the back is so that the particles don't try to go backwards through the grid and slow the ship down.
it's true that in chemical rockets you are constrained by the bonds. but the reactive paint doesn't have to rely on the bonds. remember that heat equals velocity on the microscopic scale. so you want the paint to get as hot as posible before vaporizing. also the mass the heated particle has the more push it will have.
of course, whatever system you use you would have to make sure the underlying sail was still undamaged.
I think everyone here keeps thinking of microwaves as electromagnetic waves, when it's quite obvious what the plan is. A GE microwave runs up 1,100 watts, which means the solar sail is going to be made up of over 54,500 microwaves. Think about the benefits. GE gets rich off the order, there's no neded for a 60 MW space station, and best of all, the astronauts get a thrill because they don't have to have a cold meal in space ever again. And who wants their liquid beef cold? This plan is perfect. (Except for the extension cords..better start wiring those now)
Ion engines do have chemical bonds to break: they work using a stream of lone ions, which are generally delivered at the launch pad as part of a bulk material. But the bond energy is a tiny fraction of the total energy. Er, I think we're saying the same thing about the ions, just slightly differently.
"The resistance to compression and resistance to stretching are virtually identical for metallic solids in space"
Sorry, but that is wrong. The capacity of a tension member is limited by the net area of the cross section. On the other hand, compression member capacity is typically governed by the shape of the cross section, not the cross sectional area.
As such, tension capacity and compression capacity are usually different for any given member (whether hemp, steel, magnesium or whatever). This applies whether you are in space or not...
This kind of thing has been put forward before, where a ground-based laser is used to boil atoms off a base-plate. Using a sail just allows for greater beam dissipation.
Specialisation is for insects
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Opps that should be 7.6 K watts damn that is hot.
dude, if you _have_ a torrent, why are you keeping it to yourself ?
har har...
Nobody asked because we all know you'd have posted it in your first comment if you did...
Is the "solar wind" similar in it's effect on a solar sail as wnd is to a wind driven sail? In other words does Bernoulli's principal apply to the solar wind allowing upwind solar sailing, ie tacking back towards the sun?
Nope, the solar wind actually doesn't carry nearly as much momentum as the light itself. But you can tack a solar sail by tilting the mirror so that the exit beam shines in different directions. The thrust from the sail is the vector difference between the incoming and outgoing beam directions, times the total amount of sunlight power you're reflecting.
But, like the GP said, I don't think there would be a red-shift in that case. It's the red-shift that causes energy transfer, not a reflection of light. Since the back of the flashlight isn't moving away from the original source of light there wouldn't be a red-shift in the reflected light. Therefore, no energy change.
Of course, that would assume the GP knows what he's talking about. And that I know what I'm talking about, which I don't.
Hi...Is there any transfer of energy (kinetic) from the light that is being reflected to the mirror itself causing the mirror to move away from the desired vector?
1. Build rocket, 100m solar sail and 60 megawatt microwave ...
2.
3. Profit!
The paint is made just from carbon and it emit carbon monoxide. This will not work in space - there is no oxigen there...
". . . The capacity of a tension member is limited by the net area of the cross section. On the other hand, compression member capacity is typically governed by the shape of the cross section, not the cross sectional area . .
I agree but since the members are in space (and thus their within structure mass is irrelevant) the building up of a cross section area requires as much additional mass as adding to to the shape of the cross section. Thus this just confirms my original point . .
" . . . virtually any connection between two objects will be of virtually identical thickness/mass. . . "
Rigid construction beams in space can be made structurally sound from a width of metal much more typical for a width of foil on Earth. But tethers in space have to maintain the cross section (and thus mass) of those on Earth. That is, ropes or wires which suffer tension in space have to be of the same size as on Earth. Rigid beams holding things apart in space, as long as they are appropriately constructed, can be as thin as that which wraps your stick of JuicyFruit.
So long and thanks for all the fish . . . !!!
http://www.sjgames.com/carwars/cardgame/ So, nifty new idea has been subjected to open source peer review and consensus has been formed as to .. what exactly?
Not a hoax, but not very useful?
A slight improvement over other lightsail models?
A new task for nasa?
Will it do the kessel run in 3 parsecs?
Some things I'm not clear about - this version uses microwaves instead of lasers. Is that a significant advantage?
How much does the atmosphere interfere with microwave transmission? What kind of distance can you have and still focus the beam on a target?
What's it cost to run a 60 MW microwave for an hour, at nights and weekend rates? One Meelion dollars?
Apparently there's a stopping problem for the earth to mars run. Has that been fixed yet?
I see several aspects of that - if there is a speed at which it is too fast once it gets to mars, don't run it that fast.
The stopping problem is easily solved if you use this thing for the Mars to Earth trip.
Also, stopping is less of a problem at Jupiter than Mars.
Slender members buckle under compression regardless of whether they are space or not. Gravity has little to do with a members compression buckling load.
Members which 'hold things apart' as you put it, cannot be thin, because thin members buckle. Have you never pushed on the ends of a ruler and seen what happens? This buckling behavior happens in space too. Based on what you are saying, astronauts could not push on the ends of a ruler and make it buckle. The simply fact is that thin elements, or more specifically members with a very low section modulus, are not rigid in bending, and are thus not suitable as compression members.
Not if the ruler was a tube. I happen to have seen the prototype for the machine which 'builds' the space station's booms. Three sheets of metal are arranged in a triangular tube, with two bracing streams rotating about on the inside between the three faces. None of the sheets or streams are wider than a human hair and a linear foot of it is lighter than a linear foot of #6 guage copper wire.
READ this line carefully:
If it is constructed properly, slender members can be lighter than equivalent lengths of binding wires.
Ever try to crush a triangular beam? Use your head next time!!
So long and thanks for all the fish . . . !!!
I heard asbesthos is better. (How do you spell asbesthos?)
Yeah. Would you choose a neurosurgeon who pokes around people's brains in his spare time? I wouldn't.
NO, You said the beams can be thin, you did not say the beam can be comprised of thin elements. There is a major difference. I am fully aware than thin-gauge cross sections can be efficient. But you specified a thin beam, not a beam made of thin elements. (I don't even know why we are referring to them as beams, beams are bending members) I have compression tested many hundreds of thin gauge specimens and I know how they behave. First you say that members are the same in tension and compression in space, and now you decide to sneak in the requirement that the compression members must be tubular after all!! Of course they must be tubular (or some other efficient shape)!, thats what I've been saying all along.
In frames where the light is doing work on the mirror (the light is speeding it up), the exiting beam appears redshifted compared to the solar beam, and in frames where the mirror is doing work on the light (the light is slowing it down) the exiting beam appears blueshifted compared to the solar beam. Strange stuff, but it all works out so that energy appears to be conserved from every point of view.
Congratulations, you are now officially off my Christmas card list. I send them only to people who can read with comprehension and don't alter my statements when summarizing.
So long and thanks for all the fish . . . !!!
You like lying way too much. What is the difference?
Hope no holes are punched on the sail near the windows for the craft. Boiled-without-fire humans would be more like it.