Seth Potter says SBSP is $240/watt (was Why Sustainable Power is Uns

>> Seth Potter of Boeing recently made a case for 5-gigawatt GEO
>> power sats in the range of $240,000/kW:
>> http://www.sspi.gatech.edu
>> http://www.sspi.gatech.edu/aiaa-2009-0462_ssp_alternatives_potter.pdf
>
> From the same chart on page 33, the 5GW satellite would weigh about 23kt.

That's not an unreasonable number, 4.6 kg/kW.

> $240/W * 5GW = $1.2 trillion
> $1.2 trillion / 23kt = $52,173 per kilogram delivered to GSO.

Considering current costs with expendable rockets are about $20,000/kg
that is unreasonable.

> That an 'I can prove Bumblebees can't fly' figure. It assumes no reduction
> in launch costs. Quite the oposite in fact. Eeven if you include
> construction, it appears to assume massive increases in GSO cost. No
> advances in space technology. It doesn't even assume usage and deployment of
> *existing* technology; or even five year old technology. Solar electric
> propulsion of any kind makes a ccomplete mockery of this figure. With that
> GSO would be a small percentage increase on LEO cost. If we assume LEO is
> $10k/kg then GSO would be $15k/kg. The other $37k/kg is spent on ... what?

Power sat parts? Construction worker box lunches?

> Consider spending a whole $100B developing a launch system that cut costs to
> 1/10th their current value. (You'll find few reputable individuals in the
> aerospace industry who would dispute such a claim.)

The typical number is $300/kg down from the current $20,000/kg to GEO.
You should be able to get a lot done with $100B.

My thoughts (really largely Jordin Kare's thoughts) are that a $40
billion laser and $60 billion for the focusing bounce mirrors at GEO
and a fleet of reusable first stage booster rockets will get the cost
per kg to GEO down to less than $100/kg.

>The total cost of this
> trillion dollar satellite is now 'only' $220B. By investing $100B, you have
> saved $800B.

Exactly. The cost savings is so high that it is not worth building a
full scale test power sat using existing rockets. Even to build *one*
it's cheaper to spend the money for a decent transport system and then
build a test power sat.

Good analysis.

Keith Henson