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The Flight of the Solar Sail
Posted by
CowboyNeal
on Sat Jun 04, 2005 12:42 PM
from the kon-tiki-in-space dept.
from the kon-tiki-in-space dept.
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.
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Uhm (Score:5, Funny)
So confused.
As opposed to... (Score:2, Insightful)
Re:As opposed to... (Score:2)
http://www.jpl.nasa.gov/missions/past/m [nasa.gov]
Re:As opposed to... (Score:4, Informative)
This is the first spacecraft propelled completely by solar wind.
Parent
This seems silly (Score:3, Insightful)
The idea of using the suns energy is good, but maybe they should find a way to harness that energy so one could move the direction one pleases.
Re:This seems silly (Score:5, Informative)
As the sail would approach another star, the sail would slow if both sides of the sail were mirrored. This would merely mean that were we traveling to another star, we could actually stop rather than keep on going. Doesn't that kinda sound handy at all?
Parent
Re:This seems silly (Score:3, Insightful)
But yes, its not that easy. And yeah, at least in earth orbit, solar wind dominates over photon pressure. Also, the interstellar medium would be a muc
Re:This seems silly (Score:4, Insightful)
Parent
Re:This seems silly (Score:3, Insightful)
Tacking (Score:5, Informative)
Angle it so that thrust is opposite the orbital motion of the earth. You slow down relative to the sun. You fall to a lower orbit. Nifty, huh?
If you're really in a hurry to slow down you detach a reflector, let it fly in front of you, and have a planet-based launching laser fire at the reflector, bounce back to you and slow you down.
Parent
Re:This seems silly (Score:3, Informative)
It may seem counterintuitive, but sailboats here on Earth can actually sail against the wind. Not directly -- most sailboats can point about 45 degrees into the wind (i.e., if the wind i
Re:This seems silly (Score:3, Interesting)
Re:This seems silly (Score:4, Informative)
From the Planetary.org solar sail FAQ [planetary.org]
9 . Can a solar sail only provide thrust away from the sun?
No, thrust can be generated inward or outward with respect to the sun. By turning the sail at different angles, we can add or subtract velocity to the spacecraft. When we add velocity, the sail flies away from the Sun. When we subtract velocity, its orbit spirals inward.
Parent
Re:This seems silly (Score:3, Informative)
Also from the Planetary.org Solar Sail FAQ [planetary.org]
5. Does a solar sail fly on the solar wind?
No! The solar wind is made up of ionized part
Re:This seems silly (Score:4, Interesting)
http://en.wikipedia.org/wiki/Sailing#Running_Down
Parent
Solar Sails (Score:2, Insightful)
Re:spelling police! (Score:2)
Re:The Google Slashdot effect (and solar sails) (Score:3, Informative)
Re:So umm.. (Score:2, Informative)
Re:Are we there yet... (Score:3, Interesting)
Short answer: a few days (Score:5, Informative)
A solar sail could, theoretically, pass the Voyagers in less than a week. That's the advantage of having continuous thrust along the way, rather than one impulse at the start and then coasting as the Voyagers did.
The Voyagers are now at a distance of about 13 light-hours from the sun. A thin and lightweight solar sail would quickly accelerate to almost the speed of light, so it's possible to cover that distance in a few days at most.
Parent
Re:Short answer: a few days (Score:3, Informative)
Relativistic effects means that once you start t
Re:Short answer: a few days (Score:4, Informative)
Alas, ramjets don't work in Sol's part of the galaxy --- the interstellar medium's not right. (I don't know the details, but I believe that you can't get enough thrust from a certain collector area to overcome the drag needed by your collector.)
And you're quite right, it takes about a year's worth of 1g acceleration to reach relativistic velocities. Which is why Starwisp [wikipedia.org], the closest thing we've got to a decent design for an interstellar probe, will accelerate at 115g.
The entire probe only weighs 16 grams. It is, in effect, a microwave-frequency light sail, a kilometre across, powered by a 10 gigawatt maser based in Earth orbit; the maser provides both propulsion and power for the probe to return data once it reaches its target.
Starwisps should be mass producable, and only require a few days of thrust to launch, so you could use one maser to power practically any number of them. Since they cruise at 0.2c, we might also end up getting data back within our lifetimes...
Parent
Long answer: a few years. (Score:4, Interesting)
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.
Parent
Re:Need explanation (Score:3, Informative)
second, unless you have