What's your own analysis of SPS economics? Also, what are the technological
and market assumptions behind it?

Forgive me if this is not the case: I'm assuming that any serious SPS
advocates in this group have at least as good an understanding of existing
and competing large scale ground powerplant types as I do. To make amends,
I can get you caught up on that qualitative understanding.

IIRC the "break-even" point of an SPS powerplant requires a 2400fold
reduction in launch costs, which is unlikely even with a beanstalk elevator
or high tech factories on the moon with magnetic launchers.
Electrogravitics is the only family of technologies that can achieve this
sort of a reduction in launch costs; but electrogravitics would render every
current type of powerplant quaint and the SPS would become moot. My
estimates for cost/kg for runway operated two stage fully reusables (After
Columbia Project's Bluestar) is $200/kg to LEO, with estimates to GEO
(complete delivery) at $2500/kg (both are 8000kg payloads.) That is three
generations of booster technology away. Current costs are about $10,000/kg
to LEO (6000kg payload) and $40,000/kg to GTO (1500m/s short of GEO; 4000kg
payload.) So ACP concepts can get launch costs down about 50fold, another
100fold is needed before the SPS can make money vs. solar powerplants on
earth.

One of the nettlesome pains is the rectenna power density vs. safety and
environmental impact. By the time a rectenna's power density is down where
is no longer a safety/environmental problem, the rectenna area is about a
quarter to a third the size of an equivalent direct solar fired
thermodynamic powerplant. (The SPS rectenna modelled in SimCity 2000 is
obviously using a dangerously high power density, as an SPS transmitter
misalignment is one of the disasters it can model...come to think of it as a
high power density SPS transmitter can be easily ordered to aim as a weapon,
so deploying one would require new international treaties.)

Currently, the costs of a 100MWe gas turbine/heat recovery powerplant (ref:
I visited the 2006 Global Petroleum Show) is about the same as that of a
fully loaded (18kWe; about 1/6000 the power) HS 601 satellite (ref: ibid;
SES Americom had a booth at the 2006 GPS, much to my surprise.) About $400
million. I expect the cost of a 100MWe solar thermodynamic/steam turbine
powerplant would be about three times as much (1000 - 1500 million.) The
costs would not be in the hardware (concentrator mirrors do no need to be
optical instrument quality, and steam turbines are old-fashioned, but still
the most complicated part of a solar TD powerplant) but in the land; A solar
TD plant would need to have a lot of land to place its concentrator mirrors,
along with attendant zoning problems and such. A solar TD plant is
literally an eyesore in addition to being nearly as unpretty as a gas
turbine/heat recovery plant: the boiler would reflect enough of the
concentrated sunlight that it would be hard to look at without sunglasses
on. It would also radiate heat and feel warm; a normal boiler has this
property too, but normal boilers are locked away in engineering compartments
and boiler rooms...a Solar TD boiler has to be visible to its concentrator
array for obvious reasons. An unfortunate side effect is that it would also
be visible to the public roads just outside its concentrator array. (To
address solar TD weather related power instabilities, a concentrator array
could have wind turbines interspersed with it; and at night and on cloudy
days, boiler heat could be provided by an alternative heat source such as a
waste incinerator, coal firebox, nuclear reactor, or my personal favorite: a
gas turbine exhaust heat recovery system.)

On 7/5/06, john s wolter <johnswolter@...> wrote:
>
> It is good to see discussions about finding a way for SPS's to fit into a
> market structure. That is where the action is. Zubrin has been great at
> finding ways to make Mars exploration closer in time but not
> profitable. I
> don't think he's a credible source on financial analysis for an SPS
> business. Now that I know about his comments I'll get his book from the
> library and see if he is even the ballpark. The exploration of Mars does
> not yet have to consider what markets are being served or how a profit is
> going to be made. All the funding for that is government money.
>


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