Crosspost: SPS and $87 billion

--- In spacesettlers@yahoogroups.com, Andy Goddard
> Hi Bill and all!
>
> 87 Billion dollars, huh?
>
> Here's the back of my envelope: what needs to be done first?
>
> 1/ Big dumb booster development to get access to orbit down to
$1000 per kg.

Build a space elevator instead.

> 2/ PV research to get flight-quality solar cells at a realistic 3
$/W,
> 150W/m2 and 2kg/m2.

Much of the SPS may be covered with a reflective material rather
than a solar cell. The amount of light incident on each panel can
be increased for a fraction of the mass: a 10m x 10m aluminized
Mylar reflector aimed at a 1m^2 solar panel would mass much less
than 100m^2 of solar panels (assuming that solar panel can handle
130kW of incident light).

> 3/ Some form of microwave beam-back infrastructure.
> 4/ Presumably build a hydrogen net to distribute the energy for
> non-electric use.

How about plug the rectennae directly into existing power grids?

Ed