[ExI] Could Thorium solve our energy problem?

[Keith Henson]

On Thu, Jul 8, 2010 at 6:02 PM,  samantha <sjatkins at mac.com> wrote:

[sorry for not fixing the subject on the previous reply]

> I agree that this is a much more immediate energy solution than space
> based solar, at least SBSP of any design I am familiar with.  The first
> problem with SBSP is the huge mass all the mirrors and collectors
> represent and the high cost of launch.

To put numbers on it, for two cent power and a ten year payback, the
cost limit is around $1600/kW  (80,000 hr at 2 cents per kWh).

Though people have been more optimistic, the general consensus is that
5kg/kWh is reasonable.  so if parts and ground rectenna cost $1100/kW,
then the transport cost can't be more than $100/kg.  That's a 200 to
one reduction from current cost.  It's doable (I think) with something
like a Skylon to the point you run out of atmosphere and laser heated
hydrogen from there on up to LEO and a second stage also using laser
heated hydrogen from LEO to GEO.  It does take some $60 B of lasers.

> The second is that you have no
> way to do all the assembly and maintenance required at GEO.  Doing it
> with astronauts is a non-starter.  We would need a lot better space
> robotics than we have.

Not actually.  Supporting 1000 people at GEO to do assembly takes
around 1% of the mass flow to build power satellites.  But it doesn't
matter.

Keith