Slashdot Log In
NASA to Launch Solar Sail
Posted by
timothy
on Sat Jun 28, 2008 12:31 PM
from the cue-bad-brains dept.
from the cue-bad-brains dept.
arbitraryaardvark writes "Physorg reports that NASA will launch a solar sail around the end of July. It'll be the first of its kind; a previous attempt blew up. It's a small proof-of-concept gizmo, not a full-on spaceyacht.
Solar sails operate on photon pressure from sunlight. They are well known to science fiction readers, otherwise not so much." C-net has coverage, too.
Related Stories
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Ah, sigh (Score:5, Funny)
Re:Ah, sigh (Score:5, Insightful)
Parent
Re:Ah, sigh (Score:5, Insightful)
"Yeah well, Hollywood and {science, art, engineering, law, philosophy, history, fantasy, ...} haven't ever mixed well, for the most part."
There. Fixed it for you.
I'll give you a hint. Hollywood is like a marketing department at an engineering firm. They have learned very well that they don't need to understand the product to sell it. Package a movie with a couple of hunks and babes as well as some explosions and dramatic music, and nobody is going to care about its accuracy.
Parent
Re:Ah, sigh (Score:5, Funny)
Package a movie with a couple of hunks and babes as well as some explosions and dramatic music, and nobody is going to care about its accuracy.
Well, except sad bastards like us.
Parent
my parents (Score:4, Funny)
Parent
Re: (Score:2, Insightful)
Stupid disney and their stupid wooden ships in outer space.
And stupid children too dumb to even think about questioning any of it.
Re:Ah, sigh (Score:4, Insightful)
Joke, right? Because know a lot of science fiction movies that contain some very rotten science, doesn't mean they're bad films only that you shouldn't take it as a science class. I'd rather have entertaining entertainment than accurate yet extremely boring movies. Yes, I know that in space noone can hear you scream but I don't care when the star destroyer comes "whooshing" by. And that most things don't blow up like they were packed with dynamite. If you didn't learn that outside the movies, maybe the problem is that you take all your learning from movies rather than the movie...
Parent
Re:Ah, sigh (Score:5, Interesting)
Parent
Re:Ah, sigh (Score:4, Informative)
Almost right. The revised version of 3 pages of technobabble became "Reverse Course!", not "Turn around!'
Parent
Re:Ah, sigh (Score:4, Informative)
At the risk of replying to myself, I believe that story was first related in Whitfield's "The Making of Star Trek".
Parent
Re: (Score:3, Interesting)
Re: (Score:2, Funny)
Funny, that's how you get from Bajor to Cardassia as well.
Re:Ah, sigh (Score:5, Informative)
Is there anything wrong with the idea of combining solar sails WITH Ion thrusters? Both should be light weight, not require a large energy source, and theoretical light speed acceleration.
Ion engines still need fuel. Ions, to be precise. Just because they use electricity to accelerate them (instead of some kind of combustion process) doesn't mean that the energy doesn't have to come from somewhere, so now you need an energy source. Which is either solar (cutting into your available area for a sail and becoming increasingly infeasible when you get away from the sun) or nuclear (which means enormously heavy: RTGs are many kg per Watt and a full-blown reactor weighs tons before you've generated the first Watt).
Parent
Re: (Score:2)
Which is either solar (cutting into your available area for a sail and becoming increasingly infeasible when you get away from the sun) or nuclear (which means enormously heavy: RTGs are many kg per Watt and a full-blown reactor weighs tons before you've generated the first Watt).
Or you can make the solar sail out of a flexible solar panel and kill two birds with one stone.
Re:Ah, sigh (Score:5, Interesting)
Every time I read something like this ("but that's impossible!"), I think about 1900. Amazing the number of things that were "impossible" in 1900 that we do routinely now....
Parent
Re: (Score:2)
First time I've had mod points and a story accepted at the same time. But I might want to comment, so I'll just say mod parent up.
What other type of vehicle could a solar sail and Ion thruster be used for?
Robot ninja asteroid pirates?
The 2024 Honda hybrid?
Adding an ion thruster adds some weight, and solar sails tend to work better with low payload vehicles, but yeah, that seems to work.
Maybe the ion drive could be jettisoned once it runs out of fuel, if it's still close enough to the sun/a star that the sa
What a stupid generalisation! (Score:4, Funny)
They are well known to science fiction readers, otherwise not so much
Excuse ME, I'm MORE than aware of what they are and I DON'T read science fiction.
.
.
.
.
.
Star trek ftw!
Re: (Score:3, Insightful)
Let me guess... (Score:4, Funny)
And in 50 years, the US Post Office will still be using said technology, while FedEx is traversing through worm holes.
Re:Let me guess... (Score:5, Funny)
while FedEx is traversing through worm holes
Oh great! So FedEx will now tell me that my package was delivered. The bad news: it was delivered to me in an alternate reality. With my signature to prove it no doubt. Never mind the fact that "I" didn't get the damn package.
Parent
Re:Let me guess... (Score:5, Funny)
Parent
Re: (Score:3, Funny)
while FedEx is traversing through worm holes
Oh great! So FedEx will now tell me that my package was delivered. The bad news: it was delivered to me in an alternate reality. With my signature to prove it no doubt. Never mind the fact that "I" didn't get the damn package.
No, it will deliver the package back in the future. Why does everything have to be Trek?
Re:Let me guess... (Score:4, Funny)
Yes, walk outside tomorrow, and get a crapload of packages from yourself from the future, with a note "store these for me, k?" Maybe some UPS discount if they can deliver the package "anytime", cutting down on the number of stops they have to make. You know, saving money and all. Meanwhile, you're getting all these random packages for yourself 20 years from now.
Parent
Re:Let me guess... (Score:4, Funny)
Parent
Its the first of its kind. (Score:5, Funny)
You use this phrase Its the first of its kind. I do not think you know what it means.
And yes .. welcome to /. etc etc
Re: (Score:2)
Re: (Score:2, Insightful)
Name suggestion (Score:2)
Bajoran-One (ST:DS9 reference).
Interesting (Score:2, Interesting)
Still, the idea of a science-fiction object being realized in the real world is mighty interesting.
Maybe tomorrow they will think about warp drives.
Re: (Score:2, Informative)
The hard part is creating the antimatter. By the way, for warp drives we need something more exotic than antimatter. Matter with negative mass or something.
Re: (Score:3, Insightful)
Even if we could make antimatter cheaply and on a large scale it still isn't very practical for interstellar travel. The distances are just so unimaginably immense. There isn't yet even a theoretical substance that could propel us to the stars within a human lifetime and then have enough "fuel" to slow down again. Surely everyone has read that NASA "warp drive when" link by now. I'm getting tired of posting it. The idea is that we really need a true "space drive" for practical interstellar travel. Rocket te
Beating against the solar wind? (Score:5, Interesting)
Re:Beating against the solar wind? (Score:4, Informative)
Or am i missing something?
Gravity.
Disclaimer: Won't work if you accelerate beyond escape velocity.
Parent
Re:Beating against the solar wind? (Score:5, Informative)
No, that's incorrect. In space travel, the vehicle is in some orbit, and in the absence of a force other than gravity, it's just going to continue in that (typically elliptical) orbit forever. Say you're going to Mars, for instance. You needed to match orbits with Mars, which means you're in the same nearly circualr orbit around the sun that Mars is in. (Of course you also have to insert yourself into orbit around Mars, and get yourself out of that orbit as well, but let's not worry about that for now.) Once you're ready to leave, you don't just wait for the sun's gravity to pull you downhill back to Earth. You're in a circular orbit whose radius is greater than that of the Earth's orbit, so you're not coming back toward the sun unless you can reduce your velocity.
To understand how you'd really use a solar sail, let's start with the case where you just want to increase your distance from the sun. Intuitively, you'd think that you'd just orient the sail perpendicular to the sun's rays, and let it thrust you outward. However, that doesn't work, because the thrust from the sunlight is orders of magnitude less than the sun's gravitational force. Doing that would be sort of like dialing down the strength of the sun's gravity by some tiny percentage, which would alter your orbit for a given velocity vector, but only by a tiny amount.
What you actually do is to point your sail at an angle. The sunlight's thrust then has both a radial component and a tangential component. The tangential component does mechanical work [lightandmatter.com], because it operates in the same direction as the motion of the vehicle. That means it increases the vehicle's kinetic energy. The higher-energy orbit takes you farther out away from the sun.
When you want to come back, you do something similar, but you tilt the sail the opposite way. The tangential component is now in the opposite direction compared to your motion, so it does negative work, reducing your kinetic energy.
This web page [lightandmatter.com] has an example that calculates the optimal angle to tilt the sail at.
Parent
Re: (Score:2)
So the sailing analogy breaks down pretty fast. Too bad we can't just stick some kind of fin into the aether.
Re: (Score:2)
Re: (Score:2)
Re:Beating against the solar wind? (Score:4, Interesting)
Parent
Re: (Score:3, Informative)
Tilt the sail. In one direction, it will increase your tangential velocity, and raise your orbit. In another direction, it will decrease your tangential velocity, and lower your orbit.
Rail Sail (Score:5, Interesting)
I'd like to see a maglev train on an Andean mountain firing a ship into Earth orbit, which then deploys solar sails to catch the much more plentiful direct solar radiation to accelerate it away from the Earth. That seems like a better way to use the infrastructure we have on Earth, where at least 25-30% of the solar power is lost in the atmosphere and the air creates drag on the accelerated ship, and to use the microgravity and vacuum of space where it's easier to deploy light, flimsy solar collectors in the full sunlight.
Skip it (Score:2)
Planetary Society's solar sail (Score:4, Informative)
Boost laser time (Score:2, Funny)
Yep, we'd best start working on the boost lasers, they'd be handy for the 1st Kzin war too.
Where's the keel on a solar sail-powered ship? (Score:2, Insightful)
Cue Light Sailor by Wendy Carlos (Score:2)
And now you'll have two renegade programs running all over the system in a stolen simulation.
End of line.
Sure. Next article (Score:4, Insightful)
> It will travel to space onboard a SpaceX Falcon 1 rocket
Good luck with that one. They can't even get any time on the island because they have to beg & steal for government launch facilities.
A bit disappointing that the space station isn't being used for breathrough research like this. Instead it's busy enough keeping itself alive & selling Buzz lightyear promos.
Re: (Score:3, Interesting)
Re:I wonder... (Score:4, Interesting)
Parent
Re:cool cool (Score:5, Insightful)
Probably interesting to watch, but something of a waste. The moon's close enough we could study an area carefully (for minerals and features and other details), then when we know it's composition well, we put a nuke up there, and we'll get much more helpful information about it, as well as be able to select the damage threshold more exactly. Less variation in the results is better, correct?
Roughly speaking, a 220lb spacecraft at a million miles an hour would be 6-1/2 kilotons, about 1/2 the energy of Hiroshima, except of course, it would distribute that energy directly into the ground, not in an air burst. It wouldn't even make the news, from an earthquake point of view, they're measured in thousands of megatons. To eyeball it, take a look at "Minor Scale", it's a little smaller, 4.8 ktons, but wikipedias got a decent picture of the detonation. http://en.wikipedia.org/wiki/Minor_Scale [wikipedia.org]
My guess is the moon probably still gets impacts like this on occasion, so wasting a spacecraft might be redundant.
Parent
Re:cool cool (Score:4, Informative)
Only problem with that being that a million miles a second is roughly five times the speed of light. Last time I heard, it's not possible go that fast.
Parent