Graphene to the rescue (was A different kind of SBSP)

> > > > Mass of ISS 450 MT (metric tonnes), area of panels (0.0015 km2), mass of mirror satellite 1600 MT, area of mirror (78 km2), so the ISS is 300,000 MT/km2 and the mirror sat is 20.5 MT/km2
>
> --- In spacesettlers@yahoogroups.com 13331, "brooksn" wrote:
> > the gravity exerted on the satellite is estimated at 3 million lbs, the pressure on the surface from the sun of the 78 km2 is 36,620 lbs. So you would need to increase the altitude dramatically or surface area without increasing weight or reducing weight with the same surface area.
>
> Graphene to the rescue:
> http://www.graphenea.com/pages/graphene-properties
>
> "Not only is graphene extraordinarily strong, it is also very light at 0.77 milligrams per square metre"
>
> At 0.77 milligrams per square meter, a sheet of graphene would weigh
> 770 grams per square kilometer, or 60 kilograms per 78 square kilometers. Structural support tubes could be made of rolled-up graphene. Even if the addition of these support tubes, and a thin layer of aluminum to make the graphene sheet reflective, caused the solar sail-mirror to increase in weight to 1 metric ton, it should still easily be able to fly in light pressure of 16.61 tonnes (36,620 lbs).

130 lbs for a 78 sq km mirror? That is fantastically light, according to the wikipedia page it is not quite ready for industrial uses but it doesn't seem too far away. And as I'm not a mechanical engineer I'm not sure what other issues might arise.

Either way carbon could be used to reduce the weight of the mirrors/structure. It would be interesting to see if the whole thing could get down to the roughly 16 tonnes from the current 1600 in order to match the light pressure, without blowing up costs too much.

A nice advantage of the statite mirror would be you wouldn't be wasting as much time over the poles shooting light at the caps, and you should be able to use the mirror itself to adjust altitude, eliminating fuel costs.
Brooks