Something has always bugged me about the design of Cosmos 1 design, and I just put my finger on it. Hopefully I'm wrong, but the more I think about it, the more questionable the design seems.

Traditional solar sail designs look much like kite or a parachute: a large sail of mylar (or something) with cables anchored between the perimeter of the sail and the spacecraft, which is being towed behind. Intuitively, this makes a great deal of sense.

However, the Cosmos 1 design is more like a helicopter: eight variable-pitch solar-sail "blades" radiating out from the spacecraft. According to the FAQ, the blades will work much like a helicopter's, angling broadside to catch the light and solar wind when desired. However, here's the problem: unlike a helicopter, these blades are entirely flexible. Therefore, the torque produced by the blades will push the blades -- but not the spacecraft -- forward, until they are coaxial with the spacecraft, and no longer producing any thrust.

I suppose that this problem could be solved by tying the corner of each blade back to the spacecraft with another cable, but I haven't seen anything like that in any of the illustrations. Hopefully they were just left out of the drawings... it would be really awful to lose a mission like this on account of failing to consider torque.

Cheers,

Nathan.