Solar power sats without colonies...

> From: Dan Wylie-Sears
> Panels costing $500/kg after the economies of scale kick in?

It's hard to get any idea of what high performance solar panels will cost.
Remember though, that earth bound solar panels are made very thick or given
hard backing material to make them durable. This would not be required in
space, and would significantly reduce cost/area or cost/wattage - which is a
more accurate measure of cost than weight.

> Either one takes care of the nighttime issue by
> just having some thermal mass to store the heat.

I'm pretty sure the laws of thermodynamics would stop you from being able to
store, say, a few million gallons of high temperature steam without loosing
significant amounts of energy. Ground based thermal power plants make more
sense from that point of view.

> If a bit of space junk hits the wrong wire, what do you do?

That's a silly question. If we're building these things on a commercial
basis then we have a crew of hundreds/thousands in geo orbit putting the
things together. A space taxi with a deltaV of 2kmps can get from one side
of GSO to the other in about 1.5 days and back again in the same period.
Besides which, where ever possible SPSs would be built so that a single wire
couldn't knock them out.

> And how much did you budget for maintenance, in order to get
> higher reliability than can be achieved with maintenance and repair
> workers commuting on wheels?

Let's see:
Cost of fixing global warming caused by those 'wheels'.
Cost of environmental erosion on the array
Cost of cleaning up localised environmental contamination.
Cost of not setting up misc space industries by not developing low cost
launch capacity.

> But if you go to a higher
> delta V orbit, you need to pay the rocket equation.

There are no commercial figures for nuclear or solar ion propulsion.
Especially on a large scale. Since this is the method most SPS builders
advocate they do naturally ignore the wasteful and small scale costs of
chemical rockets.

John