Solar Power Satellites.

Bill wrote:

>
> Does anyone know what the present efficiency of solar cells are? A
> typical rankin cycle power plant gets about 30-40% thermodynamic
> efficiency. Is solar cells up there? If not are they substantially
> cheaper to make.

I think the best solar cells are somewhere near 20% efficient (this is vague
memory working here). Prices have come down A LOT.

>
> I'm asking this, because I watched rerun of the space station being
> deployed with solar power satellites. My gut feeling is that NASA
> didn't try to look at alternative designs for power system and they
> picked the most expensive method. If this is true for power it is
> probably true for much of the space station.

NASA did a bunch of work on space power using concentrators and turbines for
the space station. They almost decided to fly them. A one point there were
plans to put turbines up as supplemental power, but I haven't heard anything
along these lines for a while.

Al Globus
aglobus@..., (650) 604-4404
http://www.nas.nasa.gov/~globus/home.html

The dinosaurs weren't spacefaring. We are. I don't think that's an accident.

Maybe we are life's taxi to the stars.

I think we should:

1. Devote half of NASA's budget ($7 billion) to reaching NASA's 2020 goal of

reducing launch costs to Low-Earth-Orbit to $220/kg with a 0.01% failure
rate.
This should enable space tourism. The resulting orbital hotels will need to
develop efficient orbital life support and other necessary technologies.

2. Build orbital space colonies. The materials in the largest asteroid are
sufficient for orbital colonies with a combined surface area about 500 times

greater than Earth's. Eros alone could make over ten thousand space
colonies,
each with about about 10 square kilometers of 1g living area.

3. After a few generations of orbital living, people won't need their colony

to be near Sol. Then small groups of colonies with populations in the
tens-of-thousands can set out on multi-decade journeys to nearby stars.

Except the launch goals, none of this is even a little bit official.