Skip to comments.NASA tests solar sail technology
Posted on 05/16/2005 5:56:33 PM PDT by KevinDavis
CNN) -- A solar sail that scientists believe could power missions into deep space has passed its first major test.
(Excerpt) Read more at edition.cnn.com ...
Robert L. Forward would have been proud.
I wonder if you can sail upwind like a sailboat ;)
Wonder why this makes me slightly uncomfortable...?
Short answer: Yes.
Who knows.. I wish the best of luck to them.....
[Solar sail propulsion uses energy from the sun in the same way that a sailing boat is powered by the wind.]
There may be a similarity, but it's hardly "the same way"
I think it would be pushed by solar winds..
"Dragon's Egg" was my favorite story of his.
Short answer: Yes.
Long answer: No. A sailboat can tack upwind because it uses a keel, daggerboard, or centerboard as leverage against the water. Raise the centerboard on a sailboat, and it will only go directly down wind.
Since there is nothing for an analogous keel to work against in space, you cannot tack upwind.
If said spacecraft had another means of propulsion, such as a solar powered ion engine, or some such, that could be used for upwind or cross wind maneuvering, but that wasn't the question.
I want to know what the centerboard is going to bite into!
This thing is 400 sq.m. and tares 23kg? That's about 66' square and 50 lbs. Doesn't seem very light to me. The article talks about spans of 80-160 m. (6400-25600 sq.m.) "depending on [sic] the mass of the craft" (OB-viously).
Has anybody seen anything anywhere concerning the pressure of raw sunlight at 1 AU? Can't be much. No matter what the velocity boost from a rocket, the acceleration can't amount to a lot.
[Sunlight exerts a very gentle force. The power of sunlight in space at Earth's distance from the sun is between 1.3-1.4 kilowatts per square meter. When you divide 1.4 kilowatts by the speed of light, about 300 million meters per second, the result is very small. A square mirror 1 kilometer on a side would only feel about 9 Newtons or 2 pounds of force.
Fortunately, space is very empty and clean compared to Earth, so there is plenty of room for a 1 kilometer wide sail to maneuver, and there is no noticeable friction to interfere with your 9 Newtons of thrust. A sailboat on Earth wouldn't be going anywhere with that little force because of drag from the water and air. Some rockets can push millions of times harder, but the sail keeps pulling so long as light shines on it. Months or years after the rocket runs out of fuel, the sail is still pulling.]
That was from this site:
I much prefer the m2ps (mini-magnetosphere plasma propulsion, which is studied by a Dr. Winglee. It uses plasma to make a huge "virtual solar sail". Charged particles from the solar wind push against it. A tiny helicon can make a "sail" 15km in diameter.
The analogy to the force applied to the keel of a boat is gravity. Angle the sail to increase the vector sum in the direction of the orbit, the mean distance from the Sun increases. Reverse the angle to decrease the vector sum in the direction of orbit, the mean distance to the Sun decreases. Remember that the light is reflected off of the sail, so the sum of the impulse is the sum of the incoming and outgoing vectors. As I recall, the optimum angle between the sail and a line to the Sun would be 35.3 degrees.
Not much. At first.
But there's nothing to slow that 'not much' down, so every second you have your 'sail' unfolded, you add that much more.
Second after second after second. Minute after minute. Hour after hour.
I read a dissertation on it, literally decades ago. It's not the initial velocity thrust that works for you in this case, it's the longevity and the consistancy of the thrust, weak though it may be. Literally days, weeks, months of low but constant thrust, constantly compounding.
Still like Project: ORION better, though. It goes 'boom', big time.
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