[ExI] Power satellites (was: Is Global Warming Junk Science?)

[Keith Henson]

On Tue, Apr 21, 2009 at 12:59 PM, John K Clark <jonkc at bellsouth.net> wrote:
> Me:
>>>
>>> The reason putting something into geosynchronous orbit is so
>>> astronomically expensive is not because of the high cost of rocket fuel.
>
> "Keith Henson" <hkeithhenson at gmail.com>
>
>> Of course I agree with you.How would you go about reducing the cost?
>
> Use lunar materials, but you don't like that idea.

The idea is fine.  The problem is what it takes in time and cost.  I
have not worked the numbers, but Dr. Peter J. Schubert and a bunch of
his grad students did.

 "A cummulative investment of $1200B results in an annual factory output
equivalent to 330 GW, which is sufficient to match EIA-projected growth
rates (worldwide) for the first half of this century."

I can send you the power point presentation about this if you want it,
but this is 12 times the cost Jordin Kare estimates for the lasers and
rockets for the pop up and push transport system, and at least 4 times
the total investment we estimate to build power sats at this rate from
the ground.

>A space elevator would be
> nice but I don't expect to see one anytime soon.

Even if moving cable space elevators are *never* built, they are still
useful as the gold standard for space transport.  $0.15 for the energy
and a share of the capital to put one up.

At 5kg/kW, an elevator pays back the lift energy in about 3 days,
rockets in about 100 days.

Pop up and push takes ~1/5 the energy (fuel) for doing it with pure
rockets, and ~5 times the power for an elevator.  I.e., the rocket
parts of the lift takes 20 days and the laser about 15 for energy
payback.

So if rockets cost ~$300/kg to GEO, it's within reason to expect pop
up and push to cost ~$100/kg to GEO.

If the structural part of power sats are made from Invar (35% nickel)
they will exhaust the mines on earth in less than a decade at this
production rate.

Can you think of another source for nickel?

Keith