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Solar Sails And Space Propulsion
Doomie writes "The Economist has an interesting article about solar sails. It talks about the Russian ICBM that will launch Cosmos 1 (mentioned previously on /.) 'The first craft powered by solar-sail technology to orbit the Earth', and the link between this technology and interplanetary travel. Cosmos 1 will orbit Earth starting on June 21st and could, in theory, reach '200,000kph after three years of acceleration' due to the fact that 'particles of light, or photons, that strike a surface give it a tiny push'. The official homepage of the project has more details." Update: 06/18 18:57 GMT by Z : While space trains would be cool, that wasn't the intent of the story. Changed rails to sails.
Isn't this supposed to be a professional website? I'm not the first poster, I realise, which means I'm certainly not the first person to notice the spelling error. But... hasn't this gone past an editor? I mean... what is going on here. Every post has an error of some kind... spelling, grammar... anything...
I'd offer my services as a proofreader but I don't think I want to be associated with something so consistently shoddy...
Union Pacific is to build the ship?
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
Sail of the century
Jun 16th 2005
From The Economist print edition
One small step into orbit may be one giant leap for interplanetary travel
Rick Sternbach, The Planetary Society
ON JUNE 21st, a Russian nuclear submarine is due to launch an intercontinental ballistic missile (ICBM) from beneath the surface of the Barents Sea in the Arctic Ocean. Fortunately, this will not be the opening volley in a global thermonuclear war. Rather, it is intended to open up a new age of space exploration.
The ICBM's payload is Cosmos 1, an experimental spacecraft being launched by the Planetary Society (a space-advocacy group founded in 1980), in conjunction with NPO Lavochkin (a Russian firm which built the craft) and the Makeev Rocket Design Bureau (which modified the ICBM). If the mission, which will cost $4m and has been paid for entirely by private subscription, is successful, Cosmos 1 will become the first craft powered by solar-sail technology to orbit the Earth.
Solar sails rely on the fact that particles of light, or photons, that strike a surface give it a tiny push. Ideally, such sails should be as big as possible, to maximise the amount of sunlight collected, and as reflective as possible, because a photon bouncing off a perfectly reflective sail produces twice as much thrust as one absorbed by a non-reflective sail. Even so, the thrust generated is tiny: a sail with an area of one square kilometre would feel the same force that a kilogram weight exerts on a table on Earth. But there is no air resistance in the vacuum of space, and the sun shines continuously. Slowly but surely, the light-propelled tortoise outruns the rocket-driven hare, reaching 200,000kph after three years of acceleration.
The Planetary Society has details of the forthcoming launch of Cosmos 1. The Makeev Rocket Design Bureau modified the ICBM which will carry the craft.
Solar sails would thus be especially useful for journeys to distant planets or vastly more distant stars, as they do not need to carry any fuel with them. But while they have lived in the imaginations of scientists and science-fiction writers for over a century, their track record in real life has been limited. The Japanese Aerospace Exploration Agency has tested the unfurling of solar sails on sub-orbital rockets, but no one has put solar sails into orbit. Cosmos 1 should change that and, if it works, it will prove the feasibility of the technology for future missions.
Eight triangular sails arranged like the petals of a flower will propel the craft. Each of the sails is 15 metres long, and in total they span 600 square metres--roughly the size of the penalty area on a football pitch. During launch, the sails will be rolled up like so many sleeping bags. Once the ground crew has decided that the craft is in a stable orbit, though, a series of tubular "masts" will be inflated that will unfurl the sails as they expand.
Solar sails require special materials if they are to reflect sunlight efficiently while weighing as little as possible. They must also be able to fold up easily into a small space. Cosmos 1's sails are made from plastic sheets just five microns (millionths of a metre) thick. That is about a quarter of the thickness of a plastic dustbin liner. The plastic in question, Mylar, is coated with aluminium to make it reflective. Mylar is perhaps more familiar from its use in helium-filled party balloons.
If all goes as planned, the spacecraft will go into an orbit that flies over the Earth's poles. Four days later, the sails will be deployed. Once this has happened, the team will monitor Cosmos 1's altitude. The sails are able to swivel slightly, and the ground crew can tilt them individually in order to catch the most sunlight. The resulting increase in the altitude of the orbit will indicate that the sails are indeed feeling the sun's push.
Provided all this works well, the team will then try one last experiment. In order to use solar sails to travel to the outer planets, where the sun's l
200,000kph = 200,000 km/h
Looks like the spelling was derailed.
Yeah, I noticed that, too. Also incorrectly stated:
Cosmos 1 will orbit Earth starting on June 21st and could, in theory, reach '200,000kph after three years of acceleration' due to the fact that 'particles of light, or photons,
Actually, "in theory", the thing will fall apart in months because the mylar is not designed to withstand long-term solar exposure. A spacecraft designed for lasting longer could, in theory, reach those speeds.
Did he just go crazy and fall asleep?
Now all they need to do is hit a tachyon eddy and we can reach Cardasia
The only things certain in war are Propaganda and Death. You can never be sure which is which though
These solar sails really blow!
And you know what? when the sail decelerates, they really suck.
Sorry...
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
You tried to read the article?? You must be new here.
Untrue. By changing the angle of the surfaces reflecting the sunlight, one can change direction. Admittedly, this is like turning the Titantic with a spatula. But given enough time, you can change direction.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
I don't think Union Pacific builds their own equipment anymore. But maybe General Electric or Electro-Motive / GM EMD could provide build the ship.
Hmm, I can't seem to find the "Add To Shopping Cart" button on either of those websites. Internet shopping revolution my foot!
Darn, I was in the middle of preparing a submission on Cosmos 1 when I saw this. Anyways, I have a little more info which people might find interesting, so I'll go ahead and paste it below:
Countdown to First Solar Sail Spacecraft
The Planetary Society's Cosmos 1, the first spacecraft to be propelled by a solar sail, has just been loaded onto a converted ICBM in preparation for its launch from a Russian submarine this Tuesday, June 21. This is the first mission by a non-profit space advocacy group and is being funded by private donations. Project Operations Assistant Emily Lakdawalla is posting a running description of events on the official blog. Videos and animations describing the mission are available, including commentary from the Planetary Society's Vice President, Bill Nye the Science Guy. Downloadable print-out model kits are also available.
One of the many neat things about this project is that if the first phase of regular solar sailing is successful, they'll run a later experiment with focusing a microwave beam on the sail to see how well it propels the craft. I wish the Planetary Society the best in this high-risk endeavour.
Check out this week's Quirks and Quarks podcast, which covers the same topic. They interview the Planitary Society project manager about the upcoming solar sail launch.
While I'm at it, they've also got a segment on quantum cryptography this week which is kind of interesting.
ENDUT! HOCH HECH!
Two things: the sails are maneuverable, so you can get different thrust vectors within a certain rangle of angle.
More importantly, you have solar gravity pulling you in the exact opposite direction of the photon pressure. So, to go towards the sun, just use the solar sail to kill some of your orbital momentum. This also works around smaller bodies such as the earth, assuming you already are in orbit (which is a given for the Cosmos I satellite).
Remain calm! All is well!
Its about a training voyage with six cadets and a instructor who thorougly trains his cadets by making the voyage a living nightmare of failures, as well as making sure they make it on their own ( as he's already seen to it the radio does not work, and he's let it be known very clear to the cadets he expects to die in space - the ship is theirs to navigate using the forces of nature at their command, and he's not lifitng a finger to help.).
Jack seems to have his physics pretty accurate -
I have re-read that story often. It would make a helluva movie.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
Am I the only one who thought of Interstella 999?
I think it's important to note that this spacecraft will never reach these speeds because it's only designed to last a month or so, as can be read here:
http://www.planetary.org/solarsail/timeline.html
The flight of Cosmos 1 will not last long. Within a month the mylar sails will begin to degrade in the harsh sunlight, and the tubes supporting the blades will be losing pressure. It is possible that by this time the spacecraft will have risen to a high enough orbit that it will remain there, forever orbiting the Earth. It is more likely, however, that the orbit will slowly decay, and Cosmos 1 will end its days as a fireball in the Earth's atmosphere.
The idea of rail-guns for launching vehicles came about because on other planets there wasn't enough atmosphere for aerodynamics to work or for jet engines to work. The relative vacuum and low gravity was an advantage for anything that didn't need to carry its own fuel. The rail gun would use electromagnetic fields to accelerate the vehicle to beyond escape velocity.
However, for Earth, you need a take off velocity of at least 7 miles/second (or 25,000 miles/hour). And that doesn't take into air friction. Assuming you could build such an aerodynamic capsule, you would need a considerable acceleration for a period of the launch phase.
To minimize the amount of energy you need to use, you'd want to travel straight up, and to generate enough energy you would probably have to burn gallons of hydrocarbons or run a whole chain of nuclear reactors. Since energy is most efficient when you use the least number of conversion stages, you really end up with a vertical rocket launch with solid or liquid fuel.
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If this is to "orbit" the earth it faces alot of challenges. Out atmosphere extends quite a distance to the moon. Sure it is atoms per cubic meter but it's appreceable . I suspect there will some frictional losses that will constrain the top end velocity. If it orbits that means that it has to go back around the other side, while the front surface is facing to the sun. Sure you can play tricks where maybe one side is reflective and the other approaches an ideal black body object and just absorbs. Or maybe when it is on it's orbit facing to the sun and while it is "tacking the wind" you retract the solar sail to reduce drag. Lots of challenges there to consider. You probably could get better performance if it had a highly elliptical orbit, in other words, more acceleration as it has the "wind in it's sails" and then when it reaches apogee you close the sails and let it accelerate back to earth using gravitational attraction. As this thing accelerates the orbit would become even more elliptical and as it does a swing by the earth (to go back into space) it faces frictional heating, geomagnetic forces where the electric charges on the instrumentation packages begin to wear on the electronics packages. Remember what happens when you move a piece of metal rapidly through a magnetic field, it induces voltages into the object being moved. It would be cooler, probably easier and more impressive if you sent it into deep space. Then when in mid course to another star, once it senses decelleration caused by the star it's heading to it would either close or eject the sail. Think of a solar sail built like a umbrella. Put the instrumentation package in the "handle" and also a microwave transmitter and feed horn. Face the feed horn right at the surface of the solar sail and this thing can do double duty as a giant microwave antenna (50-100 meters across). This would have a greater communication range than any deep space probe out there that are limited by the gain that their antennas can produce because of their relatively small size (a few meters across). Let's say you want to decellerate at the other end. Use a small thruster to turn the thing around mid-course and re-deploy the sail. The probe would slow down the closer it gets to the distant star. Possibilities, possibilities, my mind is awash.
Tisha Hayes
3. Lawsuite Would this be a collection of lawsuits, all joined together with some common bond?