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Cosmos Solar Sail Getting Close To Launch

Posted by simoniker on from the shimmering dept.

digitalcaffeine writes "The Guardian is reporting that US and Russian scientists are planning to launch a spacecraft that will use solar sails to move about in space. This venture, called Cosmos 1, is backed by the Planetary Society and Cosmos Studios. The spacecraft, finally due for launch in late 2004 or early 2005, will use a converted SS-N-18 submarine launched ballistic missile fired from beneath the Barents Sea to get it into a 800 x 1000 km elliptical orbit. It will then unfurl its 15m sails and start moving about. So, for all the governments that have been working on a similar project, the first solar-sailed spacecraft is going to be from a private venture." An update on the official site notes that "The world's first solar sail craft is nearing completion. All electronic systems are now flight qualified and were delivered to the spacecraft for final assembly and testing" - we previously reported on the Cosmos Project and the efficacy of solar sails.

182 comments

  1. Wind gusts by Supp0rtLinux · · Score: 1, Interesting

    Well, at least this privately funded space endeavour can't, or at least isn't as likely to, explode as the recent Canadian mishap, but then again... what happens when the sails get a gust? Last time I checked... there're no brakes in space... if you accelerate, you continue at that speed until something stops you. Personally, I think I'd rather take my changes with a potentially exploding spacecraft than one that might start and never be able to stop... ;)

    1. Re:Wind gusts by jZnat · · Score: 1

      But if you do that, you might end up becoming God, then meeting God later on and learning something deep! Don't forget that God looks like a few stars that light up when he talks. ;)

      --
      'Yes, firefox is indeed greater than women. Can women block pops up for you? No. Can Firefox show you naked women? Yes.'
    2. Re:Wind gusts by cephyn · · Score: 5, Informative

      They can be hard to stop its true, except when approaching another star, which is the ultimate goal for the technology. The wind from Star B pushes back, slowing it down. When it achieves proper orbit speed, it furls the sails.

      Within the solar system, the idea is you get the solar wind to push hard enough to achieve a certain speed, then you furl the sails and it coasts into the new orbit.

      --
      Moo.
    3. Re:Wind gusts by tarquin_fim_bim · · Score: 1

      a potentially exploding spacecraft

      That's similar to potentially cold block of ice or a potentially vulnerable Server 2003 box, right?

    4. Re:Wind gusts by jcr · · Score: 2, Informative

      Within the solar system, the idea is you get the solar wind to push hard enough to achieve a certain speed, then you furl the sails and it coasts into the new orbit.

      Umm, no.

      What you want to do is find the optimal use of the available thrust, which is to accellerate continously. The first half of the trip is increasing your velocity relative to your target, and the second half is decreasing velocity to match the target. If you have some other means of slowing down at the end, such as aerobraking or a chemical rocket for orbit insertion, you can spend more of the time speeding up.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    5. Re:Wind gusts by DonGar · · Score: 0, Redundant

      There are no breaks, but you CAN use it to manuver in any direction that is not 'up wind'.

      However it's not as flexible as standard sailboat because there is no sideways resistance to push against (normally proviced by the hull and keel pushing against water). Otherwise it would be able to sail 'up wind' the same way that sail boats can.

      I have seen some strange schemes proposed that would allow solar sails to be used to accelerate towards their light source, by dropping a larger sail that reflected light back (as it was accelerating away). See Robert Forward's book 'Dragonfly' for details.

      --
      plus-good, double-plus-good
    6. Re:Wind gusts by NotQuiteReal · · Score: 2, Funny

      Just toss out the space anchor.

      --
      This issue is a bit more complicated than you think.
    7. Re:Wind gusts by Supp0rtLinux · · Score: 1

      Depends... I'd be more inclined to trust a space craft won't blow up them to trust that Windows 2003 Server can ever be secure. In recent history we've had two space shuttles and one Canadian test space craft blow up compared to millions of Windows machines being vulnerable and/or compromised. You do the math. ;)

      Self-moderation:
      -2 (Flamebait for anti-M$ statements)
      -2 Troll
      +5 Insightful since I just got done watching the World Poker Championships and now know something about odds

    8. Re:Wind gusts by cephyn · · Score: 1

      well the real world is not full of optimal situations. if you want to get to pluto, you're gonna have to carry a chemical rocket (heavy) or be happy with creating an orbit with your sail and then furling them up.

      --
      Moo.
    9. Re:Wind gusts by Supp0rtLinux · · Score: 1

      And what happens when space debris hits the sails??? Reminds me of that story of the guy with chair and balloons that *planned* to shoot the balloons with his beebee gun, but chickened out when he got too high...

    10. Re:Wind gusts by jcr · · Score: 2, Informative

      well the real world is not full of optimal situations.

      Every interplanetary mission to date has been pretty damn close to optimal from an orbital-mechanics standpoint. It's too expensive to go, otherwise.

      be happy with creating an orbit with your sail and then furling them up.

      You furl them up when you get to your target.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    11. Re:Wind gusts by cephyn · · Score: 1

      IF your target is pluto and you wait til you get there to furl them up, you'll go flying right by with no way to stop. Unless you've worked out the engineering to tack against the force of the sun, in which case you've been altering the plane of the sails the whole way, and wouldn't furl.

      As for optimal missions, I'd disagree with that. Optimal would be a direct shot out to whatever planet you wanted to. But that would be VERY energy expensive -- but it would be optimal. Instead, we give a little nudge here and there and steal energy by gravity-assisting from venus and multiple passes by earth. It all takes much longer, and I don't consider that optimal. Maybe you do, and that's fine. But to me, optimal is not "as little energy as possible, sacrificing time" but "as little time as possible".

      --
      Moo.
    12. Re:Wind gusts by Anonymous+Writer · · Score: 3, Funny

      Don't forget that God looks like a few stars that light up when he talks.

      You really should stop sitting in front of Christmas trees while on acid.

    13. Re:Wind gusts by barawn · · Score: 2, Informative


      There are no breaks, but you CAN use it to manuver in any direction that is not 'up wind'.

      No.

      http://www.ugcs.caltech.edu/~diedrich/solarsails/i ntro/tacking.html

      Solar sails can tack, because slowing your orbital velocity moves you closer to the Sun. If you put the sail at an angle such that majority of the light pressure opposes your direction of motion, you will move inward.

      So to slow down, you just alter the angle of the sail. Easy enough.

    14. Re:Wind gusts by jcr · · Score: 1

      IF your target is pluto and you wait til you get there to furl them up, you'll go flying right by with no way to stop.

      Incorrect. For the latter part of the journey, you use the thrust of the sails to slow you down. You furl them up when you get there.

      Unless you've worked out the engineering to tack against the force of the sun, in which case you've been altering the plane of the sails the whole way, and wouldn't furl.

      The way that you've phrased this tells me that you're not getting the picture. You use the force of the solar wind all the time, whether speeding up or slowing down. You'd have to be able to change the orientation of the sail already, or you'd have no hope of steering the spacecraft.

      Optimal would be a direct shot out to whatever planet you wanted to. But that would be VERY energy expensive -- but it would be optimal.

      Nope, impossible != optimal. An optimal flight is a least-time trajectory, given the energy available.

      With a chemical rocket, that's a burn at the beginning and the end of the flight, with perfect steering initially, so that midcourse corrections aren't needed. With a sail, the optimal flight is using the pressure to speed up until a crossover point, and using the pressure to slow down all the rest of the way.

      The point at which you switch from speeding up to slowing down is affected by such factors as whether you're going nearer or farther from the sun (nearer means more thrust, farther means less), and whether your spacecraft is losing mass along the way (such as by venting consumables).

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    15. Re:Wind gusts by jcr · · Score: 1

      There are no breaks, but you CAN use it to manuver in any direction that is not 'up wind'.

      You're not taking gravitation into account. You can use the force to speed you up or slow you down in your solar orbit. If the latter, you're moving closer to the sun, which is "up wind" by definition.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    16. Re:Wind gusts by DonGar · · Score: 1

      Clever! It does impose some restrictions, but they don't seem like a problem.

      For example, if you have reached solar escape velocity, it doesn't seem like there would be anything you could do to prevent escape.

      --
      plus-good, double-plus-good
    17. Re:Wind gusts by Anonymous Coward · · Score: 0

      Solar wind pummels you with atoms which stick to you, and are always an outward force. Solar radiation (light) can be reflected, and is useful for navigation. It's also significantly stronger on average. Solar radiation is what solar sails use.

      You should both read up a bit more before pontificating.

    18. Re:Wind gusts by recharged95 · · Score: 1
      If a solar sail wants to use pressure from another star, it will need to be reflective on both sides. Usually most sails that I have researched have the composite "dark on one side, reflective on the other"--they must furl/unfurl the sail to reorient it in the opposite direction which will likely take a good amount of power (AND leads to more weight somewhere).

      As from the previous poster, you have the 3 forces (and heat generated from the sail itself, as we can't make something with 100% reflectivity [yet]), so you need to use them accordingly. I remember proposing a trajectory pattern such that a solar sail, if have reached it's critical velocity (need to look up poynting vectors which some of sail theory is based on) could use a curved trajectory, such that gravity from the destination can "capture" the sail--just like a comet trajectory to an extent. Energy from the vehicle slowing is recycled as heat and used/expelled accordingly. This of course would take a longer travel time since it's not the least distance between 2 points. Since sails can accelerate for longer periods of time, higher terminal velocity can make up for the extra distance as long as you choose a velocity that can still be "captured" by the gravity of the destination (of course!).

      Anyway, computers have made be stupid, that science was really neat stuff. Though only issue I have with the Cosmos and Japanese teams is no one has yet to mention to confirm what the pressure of light is!!! I was able to measure the pressure and simulate it, I was off by 10^-4 (i.e. 16 bit cpu). One would think that's a "huge" difference, but it was decent (I got scholarship $$ from that) given it was in a man-made vacuum at sea level using gravity as a reference. Sure miss those days (sorry had to reminisce)

      Anyway an immediate use of solar sails is to keep satellites in orbit cheaply, I think Hughes Space (now Boeing) had a prototype that works (they also have xenon ion drives too :) )

    19. Re:Wind gusts by Anonymous Coward · · Score: 0

      The sail doesn't HAVE to be reflective on both sides, it would merely have to be able to rotate so it is facing the other direction.

    20. Re:Wind gusts by jcr · · Score: 1

      Solar wind pummels you with atoms which stick to you,

      To be precise: ions, and they don't all stick to you. Once you acquire enough charge, many of them bounce off.

      and are always an outward force. ..as is the force of the light. It's all about vector addition.

      Solar wind pummels you with atoms which stick to you, and are always an outward force. Solar radiation (light) can be reflected, and is useful for navigation. It's also significantly stronger on average. Solar radiation is what solar sails use.

      You should both read up a bit more before pontificating.

      That's advice which you would do well to heed!

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    21. Re:Wind gusts by Captain+Segfault · · Score: 1

      For example, if you have reached solar escape velocity, it doesn't seem like there would be anything you could do to prevent escape.

      I don't think that's correct. One could easily imagine a parabolic path on which some solar sailboat is on, and reducing that velocity to below escape.

      It wouldn't work if the boat is far away, but if you couldn't prevent escape if you are above escape velocity then you would have a problem entering any stellar orbit with a sailboat. :-)

      In other words, it's not that simple. (unless I'm mistaken!)

    22. Re:Wind gusts by GodEater · · Score: 1

      Incorrect. For the latter part of the journey, you use the thrust of the sails to slow you down. You furl them up when you get there.

      I'm not sure I understand how slowing down using the sail is possible. Isn't the solar wind always blowing outward from the sun ? How do you use this to slow down once you've reached the halfway point to Pluto ?

      --

      Gentlemen, start your penguins

    23. Re:Wind gusts by smooth+wombat · · Score: 2, Informative
      The guy didn't chicken out when he got too high. His gun fell out of his lap. He actually did shoot some of his balloons. For reference:

      Snopes
      Link
      Wikipedia

      --
      We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
    24. Re:Wind gusts by FictionPimp · · Score: 1

      That's not god, its god who colided with a robot in space.

      And who cares about god, he doesn't even know where earth is.

    25. Re:Wind gusts by anno1602 · · Score: 1

      As has been answered in the comments to this article and the last one about solar sails, you don'z go there in a straight line. Rather, you use the sail to accelerate your orbit around the sun, later, you can sue the force to decrease it. The gravitational pull from the sun will do the rest.

    26. Re:Wind gusts by barawn · · Score: 1


      I don't think that's correct. One could easily imagine a parabolic path on which some solar sailboat is on, and reducing that velocity to below escape.

      Depends which direction you're heading when you're at escape velocity. You can't slow radial velocity no matter what: if your radial component (outward) exceeds escape velocity, no solar sail could ever stop you: you're heading out of the system.

      Any other direction, it's possible, however, it is actually harder: you can't reduce your tangential speed without increasing your radial speed slightly (because if the sail is edge on, there's no surface area) so there's actually a range of directions, centered on radially outward, where if you exceed solar escape velocity along any of those directions, you're leaving the neighborhood.

    27. Re:Wind gusts by cephyn · · Score: 1

      If you think about it, the accelerate/decelerate model doesn't apply well to solar sails. With a more conventional, internal power source, you would accelerate (for "optimal") halfway at x force, then turn the emitter around and decelerate at x force. with the solar sail, the force applied to the sail decreases (the density of photons hitting the sail) as you further from the power source (sun) -- that makes it real hard to accelerate/decelerate as "optimally" as self contained source. I don't know the math involved, but youre not going to be able to accelerate much past what you need to push to the new orbit -- there's just not enough energy further out to slow down enough, comparitively.

      --
      Moo.
    28. Re:Wind gusts by jcr · · Score: 1

      I'm not sure I understand how slowing down using the sail is possible. Isn't the solar wind always blowing outward from the sun ?

      Regrettably, slashdot doesn't offer any means of embedding a diagram.

      Let me put it this way: suppose you're holding a kite, and a fan. The breeze from the fan tends to push the kite out from you, while the string pulls it back towards you. The pressure from the sunlight is like the breeze from the fan, and the pull of the string is like the sun's gravity.

      Now, picture tilting the kite to the right or the left. It will move sideways. In space, if that sideways movement is along its orbital track, it will gain angular momentum, and move into a more distant orbit. If you tilt the kite the other way, it will lose momentum, and fall into a closer orbit.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    29. Re:Wind gusts by GodEater · · Score: 1

      That was a superb explanation - I get it now - thanks very much!

      --

      Gentlemen, start your penguins

  2. Finally, some progress. by Anonymous Coward · · Score: 0

    Well, now we'll just have to see if it sinks or swims... Here's to hoping.

  3. Who retasked the Guidance System? by aelbric · · Score: 2, Interesting

    I hope they were reliable. Somehow I don't think NORAD will care for excuses if an SS-N-18 starts dropping towards Chicago.

    --
    nos laetus epulor qui would domito nos
    1. Re:Who retasked the Guidance System? by Anonymous Coward · · Score: 0

      Interesting?? Don't you guys mean funny? Come on, I doubt missiles have targets hard coded into them, expect maybe in a spy vs. spy comic.

    2. Re:Who retasked the Guidance System? by aelbric · · Score: 1

      No kidding. Maybe my dry humor is a little too dry. Besides, if it's a Russian missile I'm sure it would accidentally hit Berlin first

      (P.S. ^^ Joke)

      --
      nos laetus epulor qui would domito nos
    3. Re:Who retasked the Guidance System? by TheGavster · · Score: 1

      Well, certain models of first-gen ICBM had a region 'hard coded' into them by virtue of their silos being tilted towards intended targets. For a modern-ish submarine-launched missle, there is no problem, however.

      --
      "Because Science" is one step from "Because old book". Try "Because of my experiment testing my falsifiable assertion".
  4. But... by fiannaFailMan · · Score: 5, Funny

    will it be ready in time to get Count Dooku back to Coruscant?

    --
    Drill baby drill - on Mars
    1. Re:But... by Anonymous Coward · · Score: 0

      No.
      that was in a galaxy a long time ago, and far far away....

  5. SS-N-18? by Anonymous Coward · · Score: 2, Interesting

    A private venture has had access to an intercontinental missile??

    1. Re:SS-N-18? by Marxist+Hacker+42 · · Score: 2, Funny

      Minus the warhead, but yeah- it's amazing what you can find these days on ebay. Just enter "Russia" and "Surplus".

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    2. Re:SS-N-18? by Anonymous Coward · · Score: 0

      You probably have to agree to some anal probing by the Russian government before you get to do this. I don't think you can say: 'Yo, I'm OBL and I want to launch this nuke-like object'.

    3. Re:SS-N-18? by hcdejong · · Score: 1

      It seems the SS-N-18/Volna is being offered by the government (warning: link contains badly-translated English), not a private venture.

      Oh, and the missile is launched from a submarine.

  6. Just like with Columbus... by k4_pacific · · Score: 4, Funny

    ... most people expect it sail off the edge of the world.

    --
    Unknown host pong.
    1. Re:Just like with Columbus... by Anonymous Coward · · Score: 0

      who modded this funny? it deserves to be insightful imvho

    2. Re:Just like with Columbus... by Anonymous Coward · · Score: 0

      it deserves to be insightful

      Perhaps if the problem with Columbus was that he thought the world was round and everyone else thought it was flat - but that's just a myth. Any educated person of the time was well aware that the earth was a globe. Columbus proposed that they were incorrect about the size and that because of this he would be able to reach india. He was wrong and was just lucky that there was a continent in the way to supply him with food.

  7. IANARS by SatanicPuppy · · Score: 1

    But I thought the idea of solar sails had been scrapped due to the relaitve scarcity of interstellar hydrogen?

    Even in a relatively rich environment like a solar system, you're going to lose thrust the farther away from the sun you travel.

    --
    ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
    1. Re:IANARS by Gothmolly · · Score: 2, Informative

      You're thinking of the Bussard Ramjet. Solar sails use the momentum of light as thrust, as opposed to sucking up interstellar gas. This has all been covered before, recently even, in a Slashdot article about the Japanese solar sail project.

      --
      I want to delete my account but Slashdot doesn't allow it.
    2. Re:IANARS by Sheetrock · · Score: 2
      It's space, so it'll never lose velocity as a result of drag. There's lots of other suns out there too, so it can pick up more speed if it passes through other solar systems.

      Besides, it should see lots of stuff on its way out.

      --

      Try not. Do or do not, there is no try.
      -- Dr. Spock, stardate 2822-3.




    3. Re:IANARS by AKAImBatman · · Score: 4, Interesting

      But I thought the idea of solar sails had been scrapped due to the relaitve scarcity of interstellar hydrogen?

      Actually, light alone is sufficient to produce thrust. The problem is that at 1.3kw/m^2 (the power that reaches Earth), you're not going to go very fast with the mass of the solar sails added on.

      I've been keeping an eye on Mini-Magnetospheric Plasma Propulsion (M2P2) technology, myself. Basically, it uses an EM field to increase the surface area of the ship without the added weight of solar sails. As a bonus, the ship is protected from the most common forms of radiation and cosmic rays. The concept is particularly interesting when one digs the Orion concept out of memory.

      The biggest problems with Orion were plate ablation and scalability concerns (scaling DOWN, not up). With an M2P2 shield, you could use larger pulsed units, and there's no plate to erode. As a bonus, radiation protection comes as a nice side-effect. (Although some steel would still be needed to block neutron radiation.)

      --
      Javascript + Nintendo DSi = DSiCade
    4. Re:IANARS by AmonRa1979 · · Score: 1

      You're right in that the sail wouldn't help much as you increase the distance from the sun. However, if you were able to build up enough speed while still close to the sun you could escape the solar system and have plenty of speed left over. As for the force the particles coming off the sun will exert on the sail, I suppose that depends on the size and material of the sail.

      The thing I'm curious about, and will read up on, is if they think they can tack to manuver within our own solar system. I don't think you can use tacking manuvers in space. You would need a fluid for your vessel to travel in and also need a preferred direction of travel due to the shape of the vessel. Without it I believe the only direction to travel (neglecting gravity wells) would be directly away from the sun. Just thinking about this now, though, it might be a useful means of adjusting an orbit by unfurling the sail at an appropriate time.

    5. Re:IANARS by Anonymous Coward · · Score: 0

      wow. those things sound like star-trek shields. cool

    6. Re:IANARS by Chuck1318 · · Score: 4, Informative
      The problem is that at 1.3kw/m^2 (the power that reaches Earth), you're not going to go very fast

      It's much worse than that. Solar sails don't convert the energy of the light, they just receive momentum from the light as it bounces off. The momentum is equal to the energy of the light divided by the speed of light.

    7. Re:IANARS by Rorschach1 · · Score: 1

      How's that going to work with Orion? I can't imagine an M2P2 setup withstanding the force of a nuclear blast. Seems to me you've got to be pretty close to the propulsion unit to capture any decent fraction of its energy. It'd be like subjecting a soap bubble to a firecracker.

      Supposedly plate ablation can be avoided by spraying a thin coat of oil on the plate between pulses.

      Of course, it's never going to be a popular idea for ground-launched vehicles. Can't beat it for raw power, though. I say we build one and let all of Greenpeace protest to their hearts' content right at the launch site.

    8. Re:IANARS by kaschei · · Score: 1

      If you can get into orbit around the star, you can orient your sail in such a fashion as to decelerate, slowing you down and thus decreasing the radius of your orbit, bringing you closer to the star

      --
      I should not talk so much about myself if there were anybody else whom I knew as well. -Henry David Thoreau
    9. Re:IANARS by Chuck1318 · · Score: 1
      The thing I'm curious about, and will read up on, is if they think they can tack to manuver within our own solar system. I don't think you can use tacking manuvers in space. You would need a fluid for your vessel to travel in and also need a preferred direction of travel due to the shape of the vessel. Without it I believe the only direction to travel (neglecting gravity wells) would be directly away from the sun.

      Tacking with a solar sail is possible, but the physics is different. First of all, you can't neglect gravity wells, because the acceleration due to gravity will be greater than the acceleration from the solar sail. So the solar sail craft will essentially be in orbit, with the sail making changes to the orbit. By tilting the sail to reflect the light toward the forward direction of the orbit, the solar sail slows the craft down, and it drops into a lower orbit.

    10. Re:IANARS by AmonRa1979 · · Score: 1

      By neglecting gravity wells, I was avoiding orbits. This means that for a traditional sail (i.e. a canvas of some sort) it would be hard to orient the sail so that you could try to go in another direction (without the drag of a fluid keeping you going in the direction the shape of your craft prefers). However, the sails I saw depicted onboard one of the artists renderings were hard flat surfaces that could be tilted. The resulting thrust direction would then be perpendicular to the surface of the sail.

      With a flexible sail that simulated a canvas type sail, pretty much the only direction you would go is directly away from the sun. This means if you were in orbit, you could increase or decrease your speed appropriately to gain or lower your orbit's altitude. However, if you are not in orbit you would not be able to adjust your free trajectory very well with such a sail. Again, this is avoided with the hard flat surfaces as I saw in one of the depictions.

      So, in essence I was talking about using this between planets where you would not have gravity to help you change direction... hence why I initialy said I was neglecting gravity wells, but then said how it would help when you are in orbit.

    11. Re:IANARS by AKAImBatman · · Score: 2, Interesting

      How's that going to work with Orion? I can't imagine an M2P2 setup withstanding the force of a nuclear blast. Seems to me you've got to be pretty close to the propulsion unit to capture any decent fraction of its energy. It'd be like subjecting a soap bubble to a firecracker.

      1. You have to calculate the effective range. i.e. The pulse units must be exploded far enough back so that the pulse doesn't damage the craft.

      2. Orions aren't actually propelled by the explosion. The pulse units are sort of "shaped nuclear charges" where all the force is applied to a plate of propellant (tungsten, IIRC). The vaporized propellent collides with the pusher plate, resulting in thrust. The actual nuclear explosion itself would be far enough back not to impart much force on the craft.

      In an M2P2 Orion design, you simply choose a propellant that interacts positively with the shield, and adjust the charge to spread it evenly across the surface of said shield.

      --
      Javascript + Nintendo DSi = DSiCade
    12. Re:IANARS by Chuck1318 · · Score: 1

      When I was talking about being in orbit, I was including being in orbit around the sun, not just around planets. A solar sail vehicle does not have nearly the thrust to move directly away from the sun. Without having orbital velocity around the sun, it would just fall into the sun regardless of the solar sail. However, the solar sail can shape its orbit, either accelerating it to a higher orbit, or, by pointing the reflection in the direction of the forward motion in its orbit, drop it down into a lower orbit. To escape entirely from the sun's gravity, it gradually shapes its orbit into a narrower ellipse, until it can cross over from an elliptical orbit to a hyperbolic escape orbit.

    13. Re:IANARS by AmonRa1979 · · Score: 1

      I believe I stated that... Not so precisely, but adjusting orbits certainly includes what you are talking about...

    14. Re:IANARS by AmonRa1979 · · Score: 1

      That pretty much answers my question... I wasn't sure if it could get enough 'thrust' to counteract gravity and just assumed it could for what I was considering tacking. I also understand what you were saying about orbits, but again, was trying to avoid orbits for the time being due to what I was considering for a free non-orbit motion. Afterall, the acceleration due to the sun's gravity (at Earth) is only .006m/s^2... I figured this might be able to be overcome with a solar sail on a lite enough object, but haven't read what range of acceleration is possible. I would assume very little since the light offers only small momentum transfer and the particles coming off the sun, while offering more momentum transfer per particle, are very sparse. Some sites I've Googled show it to be around 10^-4 m/s^2 but that sounds too good to be true, especially this far away from the sun.

  8. just been done by Anonymous Coward · · Score: 1, Informative

    weren't these things in the news last week? yup

  9. Fud:Who retasked the Guidance System? by Anonymous Coward · · Score: 0

    iF yoU Do this what happens again?

  10. Cold War Rockets Better? by cephyn · · Score: 5, Insightful

    I think its great that former weapons are being used for constructive science. Continues a long tradition. Plus, I bet those missiles are the most reliable chemical launch vehicles around -- the military does not mess around when trying to kill people, and frowns heavily on equipment failure. (as a rule)

    And was all that talk (Sagan's wife) about it being visible to the world true? Or was it metaphorical? I can't imagine it being THAT big at this point...

    --
    Moo.
    1. Re:Cold War Rockets Better? by Anonymous Coward · · Score: 0
      Plus, I bet those missiles are the most reliable chemical launch vehicles around -- the military does not mess around when trying to kill people, and frowns heavily on equipment failure. (as a rule)

      Not necessarily. If 8-10% or 5-30% of cluster-bomblets lie unexploded in schoolyards in the mid east, it doesn't matter that much to the military so long as the 60% that exploded killed whomever they were trying to drop them on.

      Same probably goes for ICBMs. It doesn't as much how many fail, as much as how many happen to work.

    2. Re:Cold War Rockets Better? by cephyn · · Score: 1

      cluster bomblets to ICBMs are a poor analogy methinks. If youre firing nukes off, its the end of the world, and youd better hope your nukes blow up more than the enemies -- otherwise they might be left around to repopulate and you won't.

      --
      Moo.
    3. Re:Cold War Rockets Better? by Anonymous Coward · · Score: 0
      Ok... would 50-82% with an average of 79% success rate of the 364 Atlas-Centaur & Atlas SLV-3 [ICBM launcher] test launches be a better comparison? (Or 86.46 by other studies.)

      Seems they do about the same or even worse than cluster bomblets.

    4. Re:Cold War Rockets Better? by gloth · · Score: 1

      Sorry, but I can't resist. This is just a very funny example of how bad spelling shoots yourself in the foot sometimes. It's enemies', not just enemies. The way you wrote it turns the whole meaning upside down.

    5. Re:Cold War Rockets Better? by cephyn · · Score: 1

      you're absolutely right. sometimes i type too fast for my own good. i swear, it's because my boss was nearby... ;)

      --
      Moo.
    6. Re:Cold War Rockets Better? by Rich0 · · Score: 1

      Yeah, it's the end of the world and wouldn't it be a shame if anybody was left alive due to a missle malfunction. That would be a total disaster, or maybe that is a less than total disaster...

  11. Space debris by tao_of_biology · · Score: 4, Insightful

    That sail makes a nice big, easy to penetrate target (no BBW jokes, please).

    The article describes the sail as thinner than a garbage back. Even the tiniest speck of space junk would would easily blow a hole in this. And, if that happens enough times, and especially with bigger pieces of space junk, won't it be filled with thousands of various sized holes?

    It doesn't seem like it's being put into orbit high enough to avoid this kind of damage. Obviously they thought of this... are the holes inconsequential?

    --

    -- "A chicken is an egg's way of making another egg."

    1. Re:Space debris by Carnildo · · Score: 4, Informative

      It doesn't seem like it's being put into orbit high enough to avoid this kind of damage. Obviously they thought of this... are the holes inconsequential?

      Pretty much. The material is so thin, holes made by space debris won't be larger than the debris itself, and most of the stuff up there is sandgrain size or smaller. Given the size of the sail, a bajillion pinholes won't reduce the effective area much.

      --
      "They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
  12. Japanese solar sail by Anonymous Coward · · Score: 5, Informative

    Earlier this month the Japanesesuccessfully deployed two solar sails.

    1. Re:Japanese solar sail by mfearby · · Score: 0, Offtopic

      I wonder how come they call Cosmos 1 the first craft to use solar sails, then?

    2. Re:Japanese solar sail by PaulBu · · Score: 3, Insightful

      From the official site:

      The mission goal - to fly the first controlled solar sail flight - remains the same.

      I guess the "controlled" part is important. The sail itself is actually a set of blades which can be tilted to steer the craft.

      Paul B.

    3. Re:Japanese solar sail by Celt · · Score: 2, Insightful

      America had nothing to do with it so it did'ent happen :)
      Actually has anyone been to the space museum beside the meteor crater in Arizona? It lists everything about space except in leaves out one minor detail Russia never went to space apparently

      --
      "WebTV: bringing the Internet into the shallow end of the gene pool since 1995" - Martin Bishop
    4. Re:Japanese solar sail by Anonymous Coward · · Score: 0

      Russia? Is that the state next to North Dakota?

    5. Re:Japanese solar sail by sjames · · Score: 1

      Because the Japanese flight was simply a test of the deployment system. They deployed a sail, then jettisoned it, and deployed another and the mission was over. They never actually used the sails for propulsion.

  13. Fire missile tube one! by Anonymous Coward · · Score: 0, Funny

    Oh wait I mean two .. umm what was in one?

    1. Re:Fire missile tube one! by Anonymous Coward · · Score: 0

      FWIW, I laughed. Not sure why you got Offtopic...

    2. Re:Fire missile tube one! by Patrik_AKA_RedX · · Score: 1
      what was in one?
      The captains laundry. Think he's going to be pissed.
  14. Re:Mars? by Erwos · · Score: 0

    I got the impression from the article that this thing was relatively light. Any manned expedition, hell, unmanned expedition, to Mars is going to be a LOT heavier. It's unlikely that the Sun would give you a noticable speed boost for about a million years in that situation.

    -Erwos

    --
    Plausible conjecture should not be misrepresented as proof positive.
  15. Solar Sails... by Icarus1919 · · Score: 5, Funny

    Now that we have solar sails, it's only a matter of time before we need to start worrying about space pirates.

    Where's Samus when you need her?

    1. Re:Solar Sails... by red+floyd · · Score: 1

      Great. Now you'll have the MPAA, RIAA, and the BSA opposing this research! "It could lead to piracy in space!"

      --
      The only reason we have the rights we have is that people just like us died to gain those rights. -- Cheerio Boy
  16. Re:Mars? by cephyn · · Score: 2, Interesting

    you just build a bigger sail. It's light, and that's the point. HUGE sails are possible in a weightless environment, and a bigger sail harnesses more energy.

    --
    Moo.
  17. Why use the sub? by Anonymous Coward · · Score: 2, Interesting
    Geez, talk about adding needless complexity and risk. Too many Russian subs submerge more times than they surface.

    So why the sub? Extra publicity?

    1. Re:Why use the sub? by Kesha · · Score: 2, Interesting

      I agree, but I think it's because it's the cheapest rocket they can ride on. A commercial launch of SS-N-18 from a submarine is a double win for the Russian NAVY - they essentially get paid for a "live" battle drill. It helps them evaluate their battle readiness and get paid in the process. It would make sense for them to make this launch affordable, but with a few strings attached, such as launching from a submerged sub.

      Of course, this is what I think is happening, I can't be sure exactly...

      Paul.

    2. Re:Why use the sub? by gl4ss · · Score: 1

      CHEAP!

      that's right. CHEAP. of course it's not cheap if you would first build the sub from scratch for it.

      but when you can buy services from a sub or the whole damn sub for el cheapo then why not, especially if you get a ballistic missile to use as the rocket base thrown into the deal as well?

      --
      world was created 5 seconds before this post as it is.
    3. Re:Why use the sub? by Ernesto+Alvarez · · Score: 1

      I guess they had some extra rockets that they wanted to use. Check this project. It's been there for a couple of years. They must have seen a way of getting rid of them and getting some cash in the process.

      Look like they've got something else to do with those SS-N-18.

      --
      GPG 0x1B479C78
    4. Re:Why use the sub? by harborpirate · · Score: 4, Informative

      For the sub launch, another poster helpfully posted the following information:

      Near Earth, Solar Sails are particularly suited for high orbital inclination satellite missions. Weather forecasting and global positioning systems would directly benefit from satellites orbiting the poles. Most satellites take advantage of the natural speed of Earth's rotation to boost them into an orbit relatively close to the equatorial plane. Changing the plane requires a large fuel burn for a conventional rocket and greatly increases launch costs. With its small but continuous thrust, a solar sail can reach polar orbits without a massive fuel payload, making them more accessible to scientific research.
      It would appear that the scientists want to insert the satellite into a polar orbit, which is confirmed by the fact that the launch point will be the Barents Sea, part of the Arctic Ocean. Since this location is a rather inhospitable region for a conventional launch, the scientists have rather ingeniously selected a submarine launch. The Russian military is highly likely to be the provider making this available for a "reasonable" price, since the mission is scientific in nature. Thus it poses no threat to them, while providing profit where it is much needed.

      The reason for using a ballistic missle is that Russia is brimming with extra ballistic missles. They've been decommisioning hundreds, if not thousands of former nuclear missles over the last couple decades. This does not mean they've destroyed the entire missle, merely that the nuclear warheads have been removed, and they're no longer housed in silos or subs for launch against other countries. Since the rockets were designed to carry nuclear payloads, they are both powerful and highly reliable. This obviously makes them an ideal platform for carrying anything into orbit which they can be fitted to carry.

      This situation is really a win-win propostion. The scientists get a powerful, highly reliable launch platform and rocket in an inhospitable launch location for likely a rather sweet price. The Russian military gets rid of a decommisoned rocket they just had laying around anyway, and gets to run one of their subs through a launch test complete with the actual launching of a rocket, plus they make a profit on the deal.

      --
      // harborpirate
      // Slashbots off the starboard bow!
    5. Re:Why use the sub? by mpthompson · · Score: 1

      with a few strings attached, such as launching from a submerged sub.

      Actually, IIRC modern missiles are designed to be cold-launched from a submerged submarine. Compressed air forces the missiles from the silo and the engine is not ignited until the missile breaks the surface of the water. The earliest generation missiles were hot-launched with the engine ignited within the silo, but tended to cause a lot of damage making for expensive repairs. I'm assuming the same goes for Russian submarines.

    6. Re:Why use the sub? by CXI · · Score: 1

      Geez, talk about adding needless complexity and risk. Too many Russian subs submerge more times than they surface.

      So why the sub? Extra publicity?

      You're kidding, right? Why use the sub? How about because it was specifically designed to launch the SS-N-18 they are using?? How would it be less complex and error prone to redesign the entire system on land when they have a working mobile version that's already built, tested and comes with a support staff? *sigh*

  18. World's First? by greypilgrim · · Score: 1, Redundant

    Wait, how is this the world's first solar sail powered craft? So I guess http://science.slashdot.org/article.pl?sid=04/08/0 9/2259214 never happened? Maybe what the article meant to say was that it is the first solar sail powered craft to orbit the earth?

    1. Re:World's First? by cmacb · · Score: 1

      No, what you are referring to was the zeroth solar sail launch. Remember your audience.

    2. Re:World's First? by Anonymous Coward · · Score: 0

      So, what did the Japanese solar sail carry? Nothing? Okay, so did it navigate anywhere? Nope? Not a "craft," sorry.

    3. Re:World's First? by snake_dad · · Score: 2, Informative

      This was not a solar powered craft, it was just a test launch using a less than impressive rocket, to test how the sail(s) would unfold in a space environment. A good test, a great project, but not a solar powered craft in any sense of the imagination.

      --
      karma capped .sig seeking available Slashdot poster for long-term relationship.
  19. 15m Solar Sails a bit small? by Kotukunui · · Score: 3, Interesting

    IANASSE (Solar Sail Expert), but 15m sounds a little small. I mean we are talking about pushing a satellite around with *photons*. I guess the amount of energy required to move a spacecraft in orbit is miniscule. I remember reading an article about early space efforts that said something like "the smallest rocket motors are little more than cap-gun ammunition but, they are sufficient to nudge a spacecraft in orbit"

    1. Re:15m Solar Sails a bit small? by back_pages · · Score: 1

      I've also heard it said that contemplated solar sail designs will have roughly the same force of acceleration as dropping a piece of notebook paper from one inch here on Earth. That's nothing by itself, but you have free fuel and time to kill.

    2. Re:15m Solar Sails a bit small? by cephyn · · Score: 1

      15m may be small for human+support payloads. But its still pretty big -- imagine you're standing in a slight, steady breeze. Run into the wind. Not too hard. Now open a "small" umbrella, maybe 1-2m across. Put it behind you. Now try running into the wind. That breeze, caught by the umbrella, is now a pretty formidible Force.

      --
      Moo.
    3. Re:15m Solar Sails a bit small? by dykofone · · Score: 1

      9.8m/sec^2?

    4. Re:15m Solar Sails a bit small? by frizzbit · · Score: 2, Informative
      Yes it is a small area but remember that in space there's no air resistance and friction of any kind to sap your speed so even a small acceleration can build up to an enormous speed over time.

      The key question is the weight of the craft. On the Planetary Society website they state that the mass of their craft is 100kg. Sunlight in Earth orbit is able to exert about 9.12 microNewtons of force per square metre. So a sail 15m^2 will be pushed by up to 137 microNewtons. This tiny force applied to the weight of the craft would be able to achieve an acceleration about 1.4microns per second^2. This is a tiny acceleration so it will take a long time to get anywhere but eventually the change in speed will add up. For example, it would take a year to accelerate to 155km/h (approx. 100miles per hour)

      They also state some example accelerations but they seem to imply the weight of the craft of only 275 grams so they must be talking about a sail accelerating alone without a payload. The much lower mass makes a huge difference. Such a light craft could achieve 16km/s in a year and make a journey to any planet in the solar system within 5 years.

    5. Re:15m Solar Sails a bit small? by CodeSniper · · Score: 1

      A piece of notebook paper has enough air resistance compared to its weight to have a much smaller rate of acceleration

    6. Re:15m Solar Sails a bit small? by amalcon · · Score: 1

      That's acceleration. He said force...

      9.80n/kg.

      Notebook paper doesn't have a lot of kg's...

      --
      -Amalcon
    7. Re:15m Solar Sails a bit small? by Chuck1318 · · Score: 3, Informative

      The 15m figure is the length of one of eight triangular vanes that make up the sail. According to the FAQ the total area is 600 square meters.

  20. Using this technology by thephotoman · · Score: 3, Interesting

    What would this technology be used for in the short-term, though? It seems to me that without an immediate way to utilize this solar sail, there cannot be a profitable business application. It belongs more in the realm of the government at this time, as the government doesn't need to turn a profit.

    --
    Haec merda tauri est. Ceterum censeo Carthaginem esse delendam.
    1. Re:Using this technology by Ra5pu7in · · Score: 1

      Not all privately funded research is focussed on immediate short-term profits. Some people / businesses do look much further. First of all, it would validate the feasibility of the process. Second, it would help show up any issues that could be serious problems in a "real" application. Third, in the longer term it is clear that travel outside our solar system would require some energy source beside packing that much more fuel (which adds weight increasing the amount of fuel needed ...)

      --
      I was taking one day at a time, but then several days got together and ambushed me. (from a Rhymes with Orange comic)
    2. Re:Using this technology by sjames · · Score: 1

      That's why the Planetary Society is involved. Not only does it not need to turn a profit, it isn't allowed to :-)

    3. Re:Using this technology by Dr.+Smeegee · · Score: 1

      "The Long Range Foundation found itself making an embarassing amount of profit for a non-profit organization, so it began happily wasting money on ideas that wouldn't even begin show promise for at least a generation." --Paraphrasing Robert A. Heinlein, "Time for the Stars"

    4. Re:Using this technology by Anonymous Coward · · Score: 0

      "What would this technology be used for in the short-term, though? It seems to me that without an immediate way to utilize this solar sail, there cannot be a profitable business application"

      How is the weather in Wall Street today?

  21. Solar sail mechanics? by delibes · · Score: 3, Interesting
    Can anyone shed light (sorry, bad pun) on the following:

    1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto? Actually, is it really 5 years constant thrust or does the solar sail's thrust decrease as an inverse square law as you get more distant from the sun?

    2) Can you sail "upstream" into the solar wind? Is it possible to tack and jibe in a solar sail propelled craft?!

    --
    This is not a sig
    1. Re:Solar sail mechanics? by cephyn · · Score: 1

      2) if Yes, it answers 1) -- you could tack around into a matching orbit. Is 2) possible? I don't know for sure, but I bet with sophisticated enough engineering and dynamic shaping of the sail, yes.

      --
      Moo.
    2. Re:Solar sail mechanics? by jcr · · Score: 1

      is there a way to decelerate as you reach Pluto?

      Yes. You just tilt the sail so that the net thrust is against your flight path.

      Keep in mind that there are two main forces at work here: the solar wind, and the sun's gravity. Think of it as if you were flying a kite with a fan pointed from you to the kite. Tilt the kite to the left, it will move left. Tilt it to the right, it will slow down and then move right.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    3. Re:Solar sail mechanics? by MyHair · · Score: 3, Informative

      1: Rocket propelled probes so far don't decelerate (much?); they just enter orbit with careful aiming.

      2: Tacking in a water-based sailboat uses the water to prevent lateral motion. Try sailing without any sort of keel/centerboard or asymmetric hulls or rudder--you can't go towards the wind this way. Hmmm...I wonder if chemical or ion propulsion could be used as lateral resistance with solar sails in an analog to hybrid gas/electric cars...would there be any economy or advantage to that?

    4. Re:Solar sail mechanics? by Frostalicious · · Score: 1

      1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto?

      Well you could arrange to arrive with enough velocity to enter orbit around Pluto. That's not slowing down, you just start going in circles.

      As for coming back, I don't know how. I don't think you can tack back, as doing so in a boat relies upon the force of the water against your boat. There's no water in space so I don't think that will work.

    5. Re:Solar sail mechanics? by Anonymous Coward · · Score: 0

      1) bollucks. Simple physics shows you need to lose speed. Thrusters, or (more risky) atmosphere.

      2) correct!

    6. Re:Solar sail mechanics? by Anonymous Coward · · Score: 0

      1) no.
      2) no.

    7. Re:Solar sail mechanics? by Anonymous Coward · · Score: 0

      How? The flight path is always away from the Sun when you're on your way to pluto.

    8. Re:Solar sail mechanics? by mindviews · · Score: 1, Informative

      1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto? Actually, is it really 5 years constant thrust or does the solar sail's thrust decrease as an inverse square law as you get more distant from the sun?

      2) Can you sail "upstream" into the solar wind? Is it possible to tack and jibe in a solar sail propelled craft?!

      The answer to 2 is no. On the water, you use a rudder to redirect the force on the sail in a different direction. In space, there is no "water" for a rudder to work in, so you can't make any headway against the wind. As a result, the answer to 1 is that you can't slow down using the wind. You could always cut the sail and let the Sun's gravity slow you...

      And for those of you wanting a quick description on how sailing "into the wind" works, here it is: If you turn your flat sail at an angle (a1) to the wind (a1 < 90 degrees), it will be pushed in the direction of a1. Now, if you have a rudder starting at a right angle to the sail, you can turn it an angle (a2) toward the wind - this will redirect the force on the sail to push the boat in the direction of a2 (where a2 < 90 degrees). So, if a1+a2 > 90 degrees, you can sail "into the wind".

    9. Re:Solar sail mechanics? by jcr · · Score: 1

      As for coming back, I don't know how.

      1) To escape pluto orbit: use the sail to increase your velocity. This will involve rotating the sail in phase with the period of your orbit.

      2) To return to the inner solar system: use the sail to decrease your angular momentum relative to the sun. Slower orbit means closer orbit.

      3) Profit!

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    10. Re:Solar sail mechanics? by barawn · · Score: 1

      The answer to 2 is no.

      Actually, it's yes: http://www.ugcs.caltech.edu/~diedrich/solarsails/i ntro/tacking.html

      In space, there is no "water" for a rudder to work in

      Actually, there kindof is : because all motion around the Sun is necessarily rotational (especially if you launch from Earth!), your tangential velocity is essentially your "water" - to fall inward, you angle the sail so that it slows you down, rotationally.

      You could always cut the sail and let the Sun's gravity slow you...

      Things going around the Sun are in orbit. There's no possible way that a solar sail could fully oppose gravity unless it were gigantic. Actually, that's not such a bad undergrad physics problem... anyway. The Sun's gravity wouldn't slow you down - it keeps you in orbit. You actually use the sail to slow you down, and then your slower orbital speed lets you fall in.

    11. Re:Solar sail mechanics? by barawn · · Score: 2, Informative


      How? The flight path is always away from the Sun when you're on your way to pluto.

      No solar sail could ever fully oppose the Sun's gravity unless it was, I dunno, half the size of Jupiter's orbit or something. OK, maybe not that large. But it'd be huge.

      All you're doing is adding to your orbital speed by tilting the sail to accelerate along that direction. So you slowly spiral outwards.

      To return, you just do the opposite: slow your rotation, and you spiral inward. You'll have to be careful to alter orbit at several points to circularize it (so you're not going at an insane speed when you hit the inner solar system), but it can be done.

    12. Re:Solar sail mechanics? by bandy · · Score: 1

      Just like an ion drive, you're counting on a small constant accelleration to eventually bring you to escape velocity. Whether that's earth orbit escape velocity or solar escape velocity. To do it quickly, you'd need a large sail, but probes are patient beasts and can afford to wait.

      --
      "You might as well get your son a ticket to hell as give him a five string banjo." -unknown minister
    13. Re:Solar sail mechanics? by sjames · · Score: 1

      1) bollucks. Simple physics shows you need to lose speed. Thrusters, or (more risky) atmosphere.

      Actually, no. The objective is to spiral out towards Pluto. With the right timing as the probe is approaching Pluto's orbit, Pluto overtakes and captures the probe in it's gravity.

      It's a good thing since with Pluto, atmospheric braking is not an option.

    14. Re:Solar sail mechanics? by Sgt+York · · Score: 1
      I know only basic physics, so I am probably just talking out of my ass here, but...

      I have heard it commented elsewhere that it may be possible to use gravity as the countering force for tacking with a solar sail. Does anyone know if this is possible, or is it just a bad sci-fi element?

      --

      There is a reason for everything. Sometimes that reason just sucks.

    15. Re:Solar sail mechanics? by MyHair · · Score: 1

      I have heard it commented elsewhere that it may be possible to use gravity as the countering force for tacking with a solar sail. Does anyone know if this is possible, or is it just a bad sci-fi element?

      Sounds reasonable to me, but I'm too tired to imagine all the vectors. However with water this is lateral resistance for any direction when the keel/centerboard is deployed or if an asymmetrical hull is under way, but with a solar sail gravity won't be as convenient as water.

      By the way, in another thread here I learned that you can still use a solar sail to approach the sun by slowing down your solar orbit and "falling" towards the sun, if you will. So it's not tacking, but from a layman's point of view you can move towards the sun which at first glance sounds like into the "wind".

    16. Re:Solar sail mechanics? by wisdom_brewing · · Score: 1

      no... theres no chance of "sailing upstream" unless you build a lot of momentum then turn into the decelerating path... the idea of a solar sail is to build momentum over a long(ish) period of time, the 45 degree into the wind motion would just be counterproductive (it would require fuel counteracting the point of a solar sail) and at the speeds solar sails hope to achieve, there would be the need for a *lot* of fuel...

      sorry if im making little sense, more than a little hungover...

      --
      I am very sucseptible to "let's have another drink"
    17. Re:Solar sail mechanics? by Saluton_Mondo · · Score: 1


      No, ion drives do not have enough thrust to achieve escape velocity (25'000 mph for Earth).

      --

      Batman: "Slake your thirst. You'll have worse than a parched sensation when we're through with you!"
    18. Re:Solar sail mechanics? by PhuCknuT · · Score: 1

      No, you CAN go 'upstream' with a solar sail. You have to remember, the sail isn't flying straight away from the sun, it's starting in a solar orbit (the same as earth) and sprialing out into a larger orbit (pluto or whereever it's going). To go 'downwind' you put the sail at 45 degrees, between the orbital direction adn the sunlight direction, with the read side closer to the sun. The light bounces at a right angle and increases the orbital speed and makes the orbit sprial outwards. You put the sail 45 degrees in the other direction, with the front towards the sun, and the push is in the opposite direction of the orbit, and slows the ship, making the orbit spiral towards the sun.

      The key is to not think of it as going straight downwind, with the sail pushing away from the sun, but always being on a reach (sailing term for perpendicular to the wind) and using the 'wind' to increase or decrease orbital speed. 0 fuel required, just a couple solar cells to get power to move the sail, and you can go anywhere in the solar system.

    19. Re:Solar sail mechanics? by mark2003 · · Score: 1

      You do not gybe to sail upwind - a gybe is where you change tack with the wind crossing over the stern of the vessel - i.e. pointing directly away from the wind.

      A solar sail would definately be able to do that.

    20. Re:Solar sail mechanics? by bandy · · Score: 1

      Then explain to me how Deep Space 1 managed to break Earth orbit.

      Sure, chemical rockets were used to put it into orbit. But once it's in orbit, it's there to stay. The minimal accelleration provided by the ion drive gave it a higher and higher orbit, eventually accellerating it to breakaway speed.

      --
      "You might as well get your son a ticket to hell as give him a five string banjo." -unknown minister
    21. Re:Solar sail mechanics? by barawn · · Score: 1

      No, ion drives do not have enough thrust to achieve escape velocity (25'000 mph for Earth).

      They don't have enough thrust to reach escape velocity for Earth, and that's because there's this nasty blanket of stuff around us called the atmosphere.

      There are mechanisms which generate far less thrust than an ion drive (the Yarkovsky effect: the differential light pressure between radiated photons and incoming photons due to rotation) and still push something to escape velocity. It won't work on Earth because static friction and air resistance reduce the net thrust to zero.

    22. Re:Solar sail mechanics? by jcr · · Score: 1

      It won't work on Earth because static friction and air resistance reduce the net thrust to zero.

      More like, you can't get an ion beam thruster to work in an atmosphere. They need a near-vacuum to strike a plasma.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    23. Re:Solar sail mechanics? by mindviews · · Score: 1

      Good point - I was neglecting orbital motion and only thinking along radial paths. But then, you can't really equate the problem with a sailboat on water. It'd be more like a sail-hovercraft sliding frictionlessly in a bowl-shaped valley, but whatever...

    24. Re:Solar sail mechanics? by wisdom_brewing · · Score: 1

      my point was you cant increase your speed going 'upwind' like you can in a sail boat...

      --
      I am very sucseptible to "let's have another drink"
  22. Interesting Uses for Solar Sails by Zentakz · · Score: 5, Interesting

    Posted before under the Japanese Solar Sail Deployment:
    Though Solar Sails are often associated with interstellar travel they have many extremely useful applications in Earth orbit and local solar system exploration. Most potential applications take advantage of the continuous thrust and zero fuel payload of a solar sail.

    Near Earth, Solar Sails are particularly suited for high orbital inclination satellite missions. Weather forecasting and global positioning systems would directly benefit from satellites orbiting the poles. Most satellites take advantage of the natural speed of Earth's rotation to boost them into an orbit relatively close to the equatorial plane. Changing the plane requires a large fuel burn for a conventional rocket and greatly increases launch costs. With its small but continuous thrust, a solar sail can reach polar orbits without a massive fuel payload, making them more accessible to scientific research.

    Away from Earth, Solar Sails offer a number of other interesting options. Missions have been proposed for asteroid rendezvous, travel to the inner planets (yes, solar sails can travel toward the sun), and an interesting idea using Lagrange points. More advanced solar sails could use their continuous thrust to enlarge the regions where they are able to "hover" well away from Earth. This allows much better observation of solar activity. Solar sails not only have an appealing sci-fi flair, but appear to be quite practical as well. I hope to see the technology develop rapidly.

    1. Re:Interesting Uses for Solar Sails by MyHair · · Score: 2, Interesting

      (yes, solar sails can travel toward the sun)

      Um, how? I just got done posting that you couldn't sail into the "wind" without some form of lateral resistance. Inquiring minds want to know...

      Or is it just a matter of using solar energy to slow down solar orbiting speed to 'fall' towards the sun?

    2. Re:Interesting Uses for Solar Sails by cephyn · · Score: 2, Interesting

      using the sail to slow down is one way. the other way would be the same way a sailboat sails into the wind, no?

      --
      Moo.
    3. Re:Interesting Uses for Solar Sails by Moofie · · Score: 4, Informative

      Tacking into the wind requires a keel, and there's no corollary with a solar sail. You can use the sail to slow down, though, decreasing your orbital energy and bringing you towards the sun.

      --
      Why yes, I AM a rocket scientist!
    4. Re:Interesting Uses for Solar Sails by Bob+The+Cowboy · · Score: 1

      Flashlights!

    5. Re:Interesting Uses for Solar Sails by argent · · Score: 1

      There are three forces on a solar sail: gravity, pulling it towards the sun, the solar wind (protons) pushing it away from the sun, and light, which can be vectored by tilting the sail. To move away from the sun, you turn the sail in the direction of orbit to accelerate it into a higher orbit. To move towards the sun you turn the sail to decelerate into a lower orbit.

      It's just like rockets, really. They don't accelerate directly towards the sun either, they just adjust their orbit.

    6. Re:Interesting Uses for Solar Sails by Zentakz · · Score: 1

      The analogy to sailboats is "tacking," but a solar sail is really a very different device than a conventional sail.

      First of all solar sails do not use solar wind. Instead, they rely on the pressure generated by photons striking (and reflecting off) the solar sail. "Solar Radiation Pressure" is 1,000 to 10,000 times the strength of the solar wind. (See this site for more on the principles of solar sailing.)

      In terms of maneuvering, sailboats use the differential pressure caused by wind flowing over their sails to create lift and direct it using a keel into forward motion. To sail in to the wind a sailboat zigzags at angles to the wind in order to keep its sails full and still make progress.

      A solar sail utilizes its thrust in a rather different way to sail towards the source. If you are familiar with orbital mechanics you will know that if you increase your velocity in the same direction as your current orbit (prograde), you will "climb" to an orbit of a larger radius. Likewise if you decrease your velocity along your orbital path (retrograde), you will descend into an orbit of smaller radius. Though a solar sail cannot position itself for prograde or retrograde thrust because it is perpendicular to the Sun, it is equally easy for it to orient its thrust to increase or decrease its orbital velocity. Thus, not only can a solar sail travel towards the sun, but it can do so as easily as it can go away. In fact, since the intensity of solar radiation varies inversely with the square of distance, getting closer to the sun will actually provide more thrust.

    7. Re:Interesting Uses for Solar Sails by TheSync · · Score: 1

      Yes, the lateral resistance is called "gravity".

  23. Imagine a Beowulf Cluster of Those! by ackthpt · · Score: 1
    Seriously, I didn't even run across these things in Sci-Fi until reading some of the old BattleTech novels (in many cases these 'sails' were actually for capturing solar energy and recharging some fusion hyper space thingamajig.

    For my lacking education I blame my main educators.

    --

    A feeling of having made the same mistake before: Deja Foobar
    1. Re:Imagine a Beowulf Cluster of Those! by Fred_A · · Score: 1

      Planet of the apes by Pierre Boulle (Frenc author, sorry) is a fairly famous SciFi novel...

      --

      May contain traces of nut.
      Made from the freshest electrons.
    2. Re:Imagine a Beowulf Cluster of Those! by ackthpt · · Score: 1
      Planet of the apes by Pierre Boulle (Frenc author, sorry) is a fairly famous SciFi novel...

      Bugger! All I ever saw were the movies (not the recent one, though) where the astronauts came back in Apollo era vehicles (IIRC).

      Too much of the Heinlein stuff, I guess, not enough of the type of reads which got into technological exploration.

      --

      A feeling of having made the same mistake before: Deja Foobar
  24. Re:Mars? by Fred_A · · Score: 1

    Bigger sails are desirable, because 15m sails are definitely not going to cut it...
    Wherever they want to go.

    --

    May contain traces of nut.
    Made from the freshest electrons.
  25. Theme song by Anonymous Coward · · Score: 2, Funny
    all together now...

    come sail away
    come sail away
    Come sail away with me

  26. Private company? by Anonymous Coward · · Score: 4, Funny

    How does a private company get ahold of a submarine-launched ballistic missle? We could sure use one of these for our current... uh... project. Where can I get one?

    Osama Bin Laden

  27. Re:Mars? by Anonymous Coward · · Score: 0

    Getting to Mars might be great, but it's the getting back part that would be the problem.

    On the Earth, winds go in many directions. In space, there's no competing force to bring you
    back home.

  28. So soon? by Anonymous+Writer · · Score: 0, Troll

    Every time I hear about something being developed that they are going to launch into space, the timeframe is always in a decade or something. This is great to actually hear an announcement that will be followed by a launch in the same year. I wonder if they'll get it out before Windows XP SP2? Wait a minute- I hope it's not going to be running Windows XP SP2!

    1. Re:So soon? by Anonymous Coward · · Score: 0

      I'm pretty dense, so I might not be getting the joke...

      but you know SP2's out of beta and is available for download now, right?

  29. A subroc? by Anonymous Coward · · Score: 0

    The spacecraft, finally due for launch in late 2004 or early 2005, will use a converted SS-N-18 submarine launched ballistic missile fired from beneath the Barents Sea to get it into a 800 x 1000 km elliptical orbit.


    1. Using a ballistic missile.
    2. Firing the damn thing from underneath the sea.


    What in the HELL good does that do you? Firing the thing from underneath the ocean doesn't give you any extra boost; they are engineered to provide enough force to lift the entire missile 30 or 40 feet above the surface, which is all it needs to get an attitude stable enough to stay pointed toward the sky and fire it's solid propellant. It uses a gas-jet out of the tube and a void-section in the shell casing to provide the clearing thrust.

  30. Helpful by dg41 · · Score: 4, Funny

    Helpful if we ever have a whale-seeking probe come to our planet and we need to generate some quick power.

  31. Power by xant · · Score: 1

    What about simply tethering one to the earth and using its continuous, fuel-less thrust to generate the force needed to turn a turbine? Sounds like free energy to me.

    --
    It's rare that you're presented with a knob whose only two positions are Make History and Flee Your Glorious Destiny.
  32. Re:Mars? by Fearless+Freep · · Score: 2, Funny

    Just attach a bungi chord to the earth on the way out...and snap back home

  33. must be cheap by bandy · · Score: 1

    This has got to be a way of recycling soon-to-be-retired SLBMs. The only advantage over a regular ground launch is you can position the submarine anywhere you want.

    --
    "You might as well get your son a ticket to hell as give him a five string banjo." -unknown minister
  34. Always under way. by argent · · Score: 2, Informative

    A solar sail has three forces acting on it. Gravity, pulling it towards the primary (planet or the sun), light, pushing it in the direction it aims the sail, and solar wind, pushing it away from the sun. How much you can balance these to "brake" (say, by tacking against solar orbit and moving back towards the sun) is still a matter of speculation.

    But the solar sail is *always* accelerating under these forces. If you get a "gust" you simply reduce sail for a while and adjust trim until you're back on the original course. Unlike a rocket, which has a fixed amount of acceleration and if it needs to change its course it can end up lost in space with no fuel, so long as the sail's intact making corrections is merely a matter of time.

  35. Netcraft... by Fuzzums · · Score: 1

    I only believe it if Netcraft confirms it's launch...

    --
    Privacy is terrorism.
  36. Japan and NASA by argent · · Score: 1

    Meanwhile, Japan has deployed two sails from a rocket, and NAS has deployed two sails... in vacuum chambers on earth.

  37. well. yes, no.. by Fuzzums · · Score: 2, Informative

    My first thought was the same.

    My second thought said 'no'. This had something to do with the way the sails work.
    The wind blows against the sail and behind the sail a lower air-pressure (wing effect) pulls the boat forward. But there is also a pushing effect against the sail... So this was BS.

    But why does a sailboat sail into the wind? Resistance of the water. It's the shape of the boat, combined with the rudder combined with the resistance of the water that resolves in a forward force. This only works is the bost has enough speed or else it will drift away with the wind.

    Well, probably this isn't the whole story, but since the 'water' element lacks in space there is nothing to give the needed friction to sail against the solarwind.

    Or at least that's what I think.

    --
    Privacy is terrorism.
    1. Re:well. yes, no.. by cephyn · · Score: 2, Informative

      right, but with a solar sail you can change the angle the sun hits, thereby changing the angle of direction of force. That means you can use it to turn, maybe even up to 90 degrees from the source. So you can do lateral movement.

      Now, you can also use a solar sail to slow down your orbital speed, meaning you will fall into the sun. So with combined left-right movement, alternately slowing down and speeding up orbital momentum, falling and then accelerating out, you could conceivably traverse the whole spectrum. And you could do it in three dimensions, moving into polar orbits etc.

      At least, I think.

      --
      Moo.
    2. Re:well. yes, no.. by Fuzzums · · Score: 1

      It might just be possible, but it isn't simple. If you use the sail o break, you need to turn then whole thing 180 degrees or otherwise the satellite would crach into the sail.

      An other question is how to ajust the position of the sail. but thide things can be worked out ;)

      --
      Privacy is terrorism.
    3. Re:well. yes, no.. by PhuCknuT · · Score: 1

      The satellite is attached to the sail, how would it crash into it?

      It really is simple. You put the sail at a 45 degree angle to the sun, with the rear side towards the sun, and you increase your orbital speed and move away from the sun. 45 degrees with the front towards the sun and you lose orbital speed and move closer to the sun.

      Moving the sail is simple, if the satellite can rotate freely in the center of the sail, you just turn the satellite one way (by pushing against the sail, not thrusters) and the sail will turn the other way.

    4. Re:well. yes, no.. by Fuzzums · · Score: 1

      I was thinking of a parachute-like construction like http://images.usatoday.com/news/science/wonderques t/xml-images/2003-09-05-solar-sail.JPG but http://solarsails.jpl.nasa.gov/introduction/images /sail-design-types.gif is a different way to do it.

      I think I'll read http://solarsails.jpl.nasa.gov/introduction/how-sa ils-work.html now. it seems to cover sailing aspects :)

      --
      Privacy is terrorism.
  38. Re:Mars? by Moofie · · Score: 2

    Dubya's "plan" is about as efficient as waiting for warp engines to be developed before going to Mars.

    There are better faster cheaper safer solutions than building Battlestar Galactica in orbit. Unfortunately, defense contractors don't get gigabucks for fielding practical solutions...they get gigabucks for fielding solutions that have subcontractors in every single congresscritter's district.

    Hell of a way to run a railroad.

    --
    Why yes, I AM a rocket scientist!
  39. Perfect solution for this case by harborpirate · · Score: 1

    I think both of these questions can easily be addressed.

    The reason for using a ballistic missle is that Russia is brimming with extra ballistic missles. They've been decommisioning hundreds, if not thousands of former nuclear missles over the last couple decades. This does not mean they've destroyed the entire missle, merely that the nuclear warheads have been removed, and they're no longer housed in silos or subs for launch against other countries. Since the rockets were designed to carry nuclear payloads, they are both powerful and highly reliable. This obviously makes them an ideal platform for carrying anything into orbit which they can be fitted to carry.

    As for the sub launch, another poster helpfully posted the following information:

    Near Earth, Solar Sails are particularly suited for high orbital inclination satellite missions. Weather forecasting and global positioning systems would directly benefit from satellites orbiting the poles. Most satellites take advantage of the natural speed of Earth's rotation to boost them into an orbit relatively close to the equatorial plane. Changing the plane requires a large fuel burn for a conventional rocket and greatly increases launch costs. With its small but continuous thrust, a solar sail can reach polar orbits without a massive fuel payload, making them more accessible to scientific research.
    It would appear that the scientists want to insert the satellite into a polar orbit, which is confirmed by the fact that the launch point will be the Barents Sea, part of the Arctic Ocean. Since this location is a rather inhospitable region for a conventional launch, the scientists have rather ingeniously selected a submarine launch. Again, the Russian military is highly likely to be the provider making this available for a "reasonable" price, since the mission is scientific in nature. Thus it poses no threat to them, while providing profit where it is much needed.

    This situation is really a win-win propostion. The scientists get a powerful, highly reliable launch platform and rocket in an inhospitable launch location for likely a rather sweet price. The Russian military gets rid of a decommisoned rocket they just had laying around anyway, and gets to run one of their subs through a launch test complete with the actual launching of a rocket, plus they make a profit on the deal.

    --
    // harborpirate
    // Slashbots off the starboard bow!
    1. Re:Perfect solution for this case by Anonymous Coward · · Score: 0

      It's just that one hopes that the company, or the russian military and preferably both are screaming their heads off at NORAD and NATO and all the other relevant defence agencies the fact that this launch will be for scientific purposes.

      Even given that sort of effort, I can only imagine the nightmare that would be trying to communicate the fact that this is a non-threatening launch to all of the relevant interested parties--from POTUS on down to the captain of a non-russian submarine shadowing the russian ballistic missile submarines.

      IIRC, the Barents is where all the old wargames gameplanned that the Soviets/Russians would launch their SLBMs from. Given that (again, IIRC) the missiles only take 30 minutes to get to the lower 48 from there, what's the liklihood that someone over-reacts?

      If you were a U.S. sub commander and you heard a Russian sub preparing to fire its missiles, what would you do without other information? What would your rules of engagement be in that situation?

      And, on a separate but related note, isn't there something to be said for not launching scientific missions from a sub in general? Assuming that the submarine is submerged at launch, how can observers be sure that the missile launched out of the Barents is from the correct sub, or is the correct missile from that sub?

      Seems to me that, although there are probably some good scientific reasons for launching close to the pole as a previous commenter noted, and potentially some good business reasons for choosing the russian military as a launch contractor (reliable launch platform, reasonable price, low levels of red tape???) the negative externalities involved are very significant.

      Also, solar sail. Way cool.

    2. Re:Perfect solution for this case by Anonymous Coward · · Score: 0

      Don't be daft, they'll tell NORAD and NATO they're doing it and nothing bad will happen. It's a decomissioned missle which means since it has no payload, it's just a rocket. Nobody will care, they'll more than likely casually watch the launch since this would be prudent, and they really dont have much else to do with all the nuke watching equipment. Hell it even gives the Americans a chance to test any early warning systems they want. They'll be told where and when the launch is happening!

      Also they don't really have to tell anyone but the American ambasador and that's just to be polite. That's why militaries have chains of command. One missle would never kick off a nuclear war, pretty much no matter where it landed. You might like to think "Nuke us and we'll nuke you right back with everything before your missle even lands!", I on the otherhand, like to hope that the person with his finger on the button has a little more sense when it comes to destroying the whole fucking planet and everyone and everything on it.

      Have you seen Dr Strangelove, that's more or less what I would expect to happen in the case of a wacko or accident... except the doomsday part...

      The reason they're going for a sub is that the barents sea is a pretty bleak place, not really worth building a whole launch site there for one test. Russia also has a whole bunch of subs, remember the cold war? They're just sitting around doing nothing now. The reason they're using a missle designed to toss a nuke is probably a) its reliable b) it fits in the sub (this is important when you dont want to build a launch site). The reason they're launching up north in the first place is they'll want to get the thing up, and also want it to prove that it is cheaper and more effecient and now practical to actually use solar sails for something today. It's all well and good to have theories about solar sails and how to use them in 10 year to get from plannet to planet, but they like any other technology need to provide somehting useful now to get adopted. That someing is saving the extra burn usually needed to insert a satallite into a polar orbit.

      If they launch up north, insert into a polar orbit and prove that it was efficent and can be done reliably, I think we'll see an awful lot more interest in solar sails than we've seen so far. Two unfurled , and a few in some vaccum chambers.. isn't really that exicting.. but now a practical use with deployment and operation in space.

      Nothing to see here. Remove the tinfoil hat.

  40. Timing by coyotedata · · Score: 0

    Here Stephen Hawkings renounced his Blackhole and we are still set to sail into it even thogh it is not there as it once was.

  41. Not necessarily by Anonymous Coward · · Score: 0

    this assumes big things are penetrated often. Just because something is big and easy to penetrate doesn't mean it will be penetrated at all, or if it is, often.

    If you don't believe me just ask a fat chick. Bet you she hasn't been penetrated.

  42. Good layman's discussion... by Anonymous Coward · · Score: 2, Informative

    ...on the feasibility of solar sails can be found in one of Robert A. Heinlein's collections: "Expanded Universe."

    Solar sails delivering a 0.001G acceleration are feasible - and yes, you *want* constant acceleration, not kick and coast. At that lousy 1/1000G you get a round trip to Pluto in about 3.5 years. Of course that puts the asteroid belt much, much closer...

    3 1/2 years is the same time scale wind-powered ships were on in the 1600-1800's. It made the whole Earth accessible then. The solar sails can make the whole Solar system accessible. Moreover, those sails could be modified in place to - oh, let's say - boil off a bit of front end of a convenient asteroid, for convenient insertion into high-Earth orbit for refining and manafacturing.

    And it's a damn good way to use up those old boosters! Recycling rules!

    Best,
    Mal the Elder

  43. Previous failure, visibility by XNormal · · Score: 4, Informative

    These launchers do fail occasionally, just like any other launcher in the business. In fact, this specific type of launcher has failed on the previous attempt to launch a solar sail by the same group!

    ...it did fail us on July 20 when the 3rd stage motors failed to provide the necessary velocity change and the rocket computer shut overrode the command to separate the spacecraft from the booster...

    Yes, it will most likely be visible. You can see satellites every evening. The sail is bigger than the solar panels of most satellites.

    --
    Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
  44. Hope they gave NORAD notice first by payndz · · Score: 1

    "Holy shit! We have a launch, repeat, we have a launch! Looks like an SS-N-18 coming out of the Barents Sea!"
    "Take us to Defcon 1! Alert the President! Get Major Kong airborne! Bring the WOPR online! Activate the Stargate!"

    --
    You must think in Russian.
  45. sailing solar without the "sail" by Anonymous Coward · · Score: 0

    some links:
    http://science.nasa.gov/newhome/headlines/ prop19au g99_1.htm
    http://www.abc.net.au/science/news/spac e/SpaceRepu blish_44491.htm
    http://www.ess.washington.edu/Spa ce/propulsion.htm l

    basically a plasma on-board the spaceship replaces
    the real solar sail.

    "Mini-Magnetospheric Plasma Propulsion (M2P2)"
    sounds and looks very promising ...

  46. Why the Polar Orbit/Barents Sea? by hughk · · Score: 1

    I thought the test was about orbital progression from equatorial to polar? Why aren't they launching from closer to the equator and using less fuel?

    --
    See my journal, I write things there
    1. Re:Why the Polar Orbit/Barents Sea? by Anonymous Coward · · Score: 0

      Because they have a big fuck off missle and don't have to care about the fuel.

      It's a missle designed for a sub, and it's designed with one goal, which is to get the paylod into space where the PBV (Post Boost Vehicle) takes over to deliver the payload to the target. Chances are the missle was never designed to that if you use a 3/4 tank you can launch from the equator. It was designed to hit the US from the Barents Sea with a nuke. Fill it up, shoot and away it goes to orbit, it's the PBV that does all the real targeting work the missle is nothing more than a big dumb rocket designed to get it to where it can do it's job.

      So as I said, they don't have to worry about fuel, they've got a big fuck off missle! :)

  47. automatic response????? by Anonymous Coward · · Score: 0

    excuse me???

    Ballistic missile launch from the Russians naval Sea area?

    wont this automatically activate a couple of response missiles from USA bases in Alaska and UK ??

    8-|

  48. Space mirrors by kippy · · Score: 1

    Not a whole lot in the short term but it's very important in the long term.

    Thin film reflective objects in space aren't only potentially useful as a means of propulsion but also as just plain old mirrors.

    The Russians tried to deploy a mirror back in 1999. It didn't work but part of the intention was to put a bright "star" in the sky for Siberia so they would have more daylight. Not too bad of an idea if you ask me.

    Don't forget the idea of space based solar power generation. You can buy a lot more Mylar for the dollar than solar panel. If you can collect and focus square kilometers of sunlight on a collector, you've just boosted your productivity on the cheap.

    Consider the usefulness of being able to redirect large amounts of sunlight in space. With a large enough film at the Earth/Sun L1 point, you could block some of the incoming heat and mitigate global warming if it ever becomes an urgent problem.

    A large shade in front of Venus is pretty well agreed upon as a starting measure for terraforming that planet.

    You know how Mars is all distant from the sun which makes it so damn cold? Put a reflector in orbit and you can add terawatts of power to the surface to heat things up.

    In the much more distant future, large (very large) sheets of reflective material can be used to influence the life of a star by reflecting energy back into it.

    Another far out idea is the Dyson Sphere. One of the models for that is just a bunch of thin film reflectors/collectors that enclose the sun to harness all the power it's producing.

    Robert Zubrin speculated that thin film reflectors are probably going to be the most important technology for a space-faring civilization.

    --
    Blaze a trail to the New World
  49. How solar sails work by Fuzzums · · Score: 1

    The http://solarsails.jpl.nasa.gov/introduction/how-sa ils-work.html article nicely explains the concept of solar sails to "dummies".

    --
    Privacy is terrorism.
  50. Gaurniad by vuo · · Score: 0
    But under this lighter-than-featherweight touch, the spacecraft will begin to move. The 100kg object will accelerate at a barely measurable fraction of a millimetre per second, but will gain speed with every second in the sun. By the end of the first day it will have increased its velocity by 100mph. In 100 days, it could reach 10,000mph.

    Gaurdain. 100-kg object or 100 kg object, not "100kg object". Acceleration isn't measured in velocity units (mm/s). What does it mean if something has "increased its velocity by hundredemphhh"?

  51. This author claimed they would be first to do so. by Anonymous Coward · · Score: 0

    They claimed to be first to launch a solar sail? Umm... What about the Japanese attempt. http://www.universetoday.com/am/publish/japanese_s olar_sail_launched.html