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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.
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...
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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.
Or get back to earth for that matter? Nice idea as long as you don't mind a one way trip into deep space.
The cast of Trading Spaces is unavailable for comment.
Did you even bother to ask them?
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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.
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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).
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powered by a solar sail get from Earth to Mars in just one month
Then what....!?
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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).
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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?
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
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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.
I'll take that risk. I was never that good at breathing in outerspace anyways....
"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.
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
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...
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.
Yeah, I thought of that after I'd posted. How's about sending a conventional rocket to mars with the microwave emitter as payload first, robots could deploy it and it could be activated by remote. Not sure what commercial benefits this would have though...
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..
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.
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.
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 ;)
... 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.
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I see even classic Slashdot is now pretty much unusable on dial up anymore.
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.
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.
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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.
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.
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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?
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Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
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!
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."
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.
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
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....
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.
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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?
*could*
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.
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.
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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.
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?
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.
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?
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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.