> > 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/aiaa-2009-0462_ssp_alternatives_potter.pdf
> From the same chart on page 33, the 5GW satellite would
> weigh about 23kt.
> $240/W * 5GW = $1.2 trillion
> $1.2 trillion / 23kt = $52,173 per kilogram delivered to GSO.
> That [...] figure [...] assumes no reduction in launch costs.

There is not enough information to conclude what that figure assumes. However, we might assume that only about one half of the cost estimate represents launch costs, since the previous page (32) says:

++++++++++
Notional Mass of the SSPS System for Forward Military Base (LEO, 5-30 MW)

First unit cost is for a 10 MW satellite is about $145 per installed watt (including launch but not non-recurring engineering), which is about 2 orders of magnitude higher than that of conventional power plants

Additional units will be somewhat less expensive

$100/watt, excluding launch
++++++++++

In that LEO SPS case, adding the launch cost only increases the overall cost by 45%.

> It doesn't even assume usage and deployment of *existing*
> technology; or even five year old technology.

Have you talked to Seth Potter about it? Two of the people from SSPI, the organization hosting the documents (Seth Potter's, and other's, SPS presentations), are right here in the present discussion group: Darel Preble and Mark Wallach. Have you asked them?

> Solar electric propulsion of any kind makes a ccomplete
> mockery of this figure.

Seth Potter discusses solar electric propulsion on pp13-14 of his June 2008 presentation:
http://www.sspi.gatech.edu/wpt_options_for_ssp_potter.pdf

++++++++++++
Wireless Power Transfer Options for SSP - Seth Potter, Boeing

Presented at the International Space Development Conference, Washington D.C., June 1, 2008
[...]
Autonomous Segment Ops:
1) Solar Electric Propulsion from Low Earth Orbit
[...]
8 Ion Thrusters
++++++++++++

> There is not enough information to conclude what that figure
> assumes. However, we might assume that only about one half of
> the cost estimate represents launch costs, since the previous
> page (32) says:

True, which is why I reject it.

> In that LEO SPS case, adding the launch cost only increases
> the overall cost by 45%.

And I'd say that a $145M price tag for an experimental satellite (plus
launch cost) sounds reasonable.

> > It doesn't even assume usage and deployment of *existing*
> > technology; or even five year old technology.
>
> Have you talked to Seth Potter about it?

Okay... At this point I might have been exaggerating. But I should not have
to talk to him. It's his report and his job to justify any claims he makes
within it; especially extraordinary ones. The trillion dollar figure is
pretty much pulled from nowhere. Since Seth fails to say one way or another
whether the price tag assumed the use of existing electric propulssion, I'm
going to assume it doesn't, based upon the extremely high cost estimate.

If he wants to say SSPS is practical if X, or not practical because of some
fundimental Y, then fine. But just producing a figure that 'proves' it's too
expensive is essentially a Bees Can't Fly claim.

> Seth Potter discusses solar electric propulsion on pp13-14 of
> his June 2008 presentation:
> http://www.sspi.gatech.edu/wpt_options_for_ssp_potter.pdf

Only for very small scale satellites. The report doesn't really mention
strictures in the 23,000 ton except in passing. I remain skeptical of the
conclusions; no matter where it has been presented. :)