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Space Spiders to Assemble Satellites in Orbit
Grubby Games writes "New Scientist reports that a JAXA mission to determine whether spider-like robots could construct complex structures in space is set to launch in January 2006. The spider bots could build large structures by crawling over a 'web' released from a larger spacecraft. The engineers behind the project hope the robots will eventually be used to construct colossal solar panels for satellites that will transmit solar energy back to Earth."
I don't know if anyone's done the calculations. Better fix that!
Photon pressure force:
F = PA/c
At 1 AU from the sun, P=1400 watts/m^2. For a 1km^2 collector we have A = 1*(1000*1000) = 1 million m^2.
So F = (1400)*1x10^6/3.00x10^8
F = 4.7N
4.7N is almost enough to hold half a kilogram up on the surface of Earth. Divert a bit of the power to some ion thrusters, and you should be fine. You might have to shuttle up some reaction mass every few years, but that mass would be REALLY insignificant compared to the mass of the array itself.
The mass of the array is irrelevant for countering the solar sail effect. You're not trying to accelerate it, you're trying to STOP it from accelerating, so you just have to counter the force being applied to it, which is the same regardless of the mass of the array.
Rigidity shouldn't be a problem -- any sort of solid structure shouldn't have a problem withstanding tiny forces like that.