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The Flight of the Solar Sail
N3wsByt3 writes "After months of uncertainty, the final verdict has fallen: The Planetary Society has reveiled that it will launch its Cosmos 1 on June 21. Cosmos 1 will be the first non-governmental spaceship that makes use of solar sails as main propulsion mechanism - it is pushed along by light particles from the Sun, instead of bringing its fuel along for the ride - which makes this a unique experiment in more then one way." This was supposed to have happened already, so here's hoping things get off the ground this time.
whoops i foobard the link, here it is again
w ind
http://en.wikipedia.org/wiki/Sailing#Running_Down
This particular sail is not expected to escape from earth. From the article: " 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."
That's because the material of the sails is not very resistant and will break after about a month. I suppose that a stronger sail could eventually reach the edge of the solar system, but someone else will have to fill us in on how long that would take.
The problem with the parent's post is the sail itself. Our solar system is a rocky and dangerous space, and so far, we have no idea what the area outside of it is like either.
The sail would quickly break apart as it gets struck by all kinds of space debris, some left by us, others by more natural occurances. Thus, for an effective craft, multiple sails would be kept on board, being deployed stratigically when the previous sails are no longer providing maximal thrust, and when the coast is clear.
Next, between those times when the sails are not up, the ship will probably want to keep thrust, so it will have to carry onboard some propellant to keep its thrust up during the times it is without sails. Thus, the ship will lose a significant portion of weight during its travel.
Lastly, unless we align everything like we did with the Voyager launches, gravity will not be so forth coming for this space craft. This will probably mean multiple near-sun passes to build up the speed nessicary to exit the solar system and continue on to the next star. This means some clever routing by computer simulations, along with a computer figuring when to discard and open new sails along the way.
Not only will all of this cost a lot, it will likely make it take much longer to get out of the solar system. Lucky for us, as we can pile on the goodies like cameras, radio antenna, and do some exploration as it passes through the planets building up gravitational accelleration.
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
I don't think this approach would work with space sails for one single reason: you are neglecting the effect of a sailboat's keel or daggerboard in the mechanics of upwind sailing. Without a keel, you will slide sideways because there is nothing in the stationary medium of water to resist the pressure differential produced by the sails acting as airfoils.
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