On the PBS show "Nova" tonight...

> From: Ed Minchau
> That is something that cannot be set aside, whatever
> one thinks of space-based solar power.

Not entirely sure I agree. People who think that's a sumbling block tend to
vastly underestimate the gross profits of such a satellite over it's
lifetime. Usually because they have some blinkered belief that the
electricity must be sold to America. Sell it to Europe (where we pay 2x as
much for power) and suddenly you have $160B to cover construction costs.

> That's a huge mistake. Photovoltaic cells require
> more energy to manufacture than they ever themselves
> produce.

How do you figure? A 1W panel will over a 20 year lifetime on an SSPS will
produce 630MJ of energy. In reality there will be some loses of course, but
that's still a lot of energy to counter manufacturing energy use.

> Which brings us back the question of economics,
> arguably the biggest objection to the whole thing.
> Delivering that much material to orbit from the
> earth's surface would be very expensive. However, the
> moon has a high aluminum content, so perhaps a
> mining/processing/launch facility on the moon would
> make economic sense.
>
> Even so, at 100 metric tonnes per gigawatt, the price
> of launch to orbit from the earth's surface is still
> less per gigawatt than the cost of building a nuclear
> reactor.

I really don't understand why people obsess over the cost per power output
figures. It's largely meaningless. Surely what matters more is cost per
energy output. As in $$/kWh. SSPS win over nukes because they come with
massive fringe benifits, because they don't produce waste, and because they
can be easily recycled on an on going basis (the material doesn't have to be
launched a *second* time) and hence can last effectively forever. It's a
case of $100B in, $300B+ out.

John