What would you like to be our major goals in space

On Wed, 6 Dec 2006 12:26:36 -0600, in a place far, far away, "Mike
Combs" made the phosphor on my
monitor glow in such a way as to indicate that:

"Paul F. Dietz" wrote in message
.. .
Joe Strout wrote:

No, global warming will be halted by not pouring carbon into the
atmosphere anymore, because we're using cheap space solar power instead.

No it won't, Joe. SPS is a terrible substitute for many
uses of fossil fuels, even if by some miracle it does become
competitive with other sources of electricity.

This all turns on our assumptions concerning the economics of using SPS
power to synthesize liquid fuels, or on our assumptions about the future of
fuel-cell automobiles.

Still, in any case I can certainly see SPS replacing coal-fired power
plants. That's got to count for something wrt CO2 emissions.

But if SPS power can make any inroads at all against fossil fuels, Joe's
point that using orbital construction to create SPS would have much greater
leverage than using orbital construction to prevent some sunlight from
making it to the Earth is valid. A percentage or two difference in CO2
content of our atmosphere can make a big difference in terms of global
warming; a percentage or two difference in insolation, not nearly so much.

But it's not obvious that the same expenditure of funds will result in
the same percentage of CO2 reduction or solar insolation reduction.

"Rand Simberg" wrote in message
...

But it's not obvious that the same expenditure of funds will result in
the same percentage of CO2 reduction or solar insolation reduction.

Yeah, I think I see your point here. On the one hand, the leverage from
reducing CO2 is greater than the leverage in reducing insolation. But on
the other hand, a sunshade would be much cheaper on a square meter basis
than a SPS. I'm forced to agree that we can't really say which will win out
in a comparison.

And thanks for reminding me that the bottom line is always the bottom line.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

But it's not obvious that the same expenditure of funds will result in
the same percentage of CO2 reduction or solar insolation reduction.

Yeah, I think I see your point here. On the one hand, the leverage from
reducing CO2 is greater than the leverage in reducing insolation. But on
the other hand, a sunshade would be much cheaper on a square meter basis
than a SPS. I'm forced to agree that we can't really say which will win out
in a comparison.

Reducing insolation does nothing to stop the acidification of the upper
ocean. We really do need to stop dumping fossil CO2 into the air.


And thanks for reminding me that the bottom line is always the bottom line.

The bottom line changes significantly when all external costs are
accounted for.

richard schumacher wrote:

Reducing insolation does nothing to stop the acidification of the upper
ocean. We really do need to stop dumping fossil CO2 into the air.

The big advantage of the shade is that it will work even without
global cooperation.

Acidification could be addressed by adding finely ground calcium
carbonate to the oceans. This might even suffice as a geoengineering
solution, since it will near-permanently take CO2 out of the atmosphere
by converting it to bicarbonate ions.

Paul

"Mike Combs" wrote in message
...
Yeah, I think I see your point here. On the one hand, the leverage from
reducing CO2 is greater than the leverage in reducing insolation. But on
the other hand, a sunshade would be much cheaper on a square meter basis
than a SPS. I'm forced to agree that we can't really say which will win
out in a comparison.

Of course, a SPS system would be far smaller than a sunshade and be direct
(rather than an indirect) source of revenue.

20TW of production from a SPS system would ...
Require about 40,000 km^2 of collecting area (assuming 50% efficiency) or
a square about 200km on a side.
Generate about $1.7 trillion/year (assuming a net-profit of $0.01/kW-h).

An opaque sunshade that reduced insolation by 1% would ...
Require a surface area of about 1.3 million km^2 (30x the side of the SPS
system).

"David Pugh" wrote in message
...

Of course, a SPS system would be far smaller than a sunshade and be direct
(rather than an indirect) source of revenue.

And that latter part might be the real kicker. I'm perfectly open to the
idea that the economic disruption which might result from some of the
affects of global warming would probably cost us a lot more than the cost of
erecting the sunshade. But on the other hand, we're asking some people to
pony up billions when the climatic changes

a. Are open to dispute
b. Might affect somebody else worse than they might affect them

Might be hard to raise the money under those circumstances. On the other
hand, the payback for SPS is more direct and obvious.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Mike Combs wrote:
"Paul F. Dietz" wrote in message
...
Joe Strout wrote:

No, global warming will be halted by not pouring carbon into the
atmosphere anymore, because we're using cheap space solar power instead.

No it won't, Joe. SPS is a terrible substitute for many
uses of fossil fuels, even if by some miracle it does become
competitive with other sources of electricity.

This all turns on our assumptions concerning the economics of using SPS
power to synthesize liquid fuels, or on our assumptions about the future of
fuel-cell automobiles.

Or perhaps more optimistically, the future of batteries. Even if
batteries don't progress significantly from current status, they're
still good enough (if not yet cheap enough) to make Plug in Hybrids a
winner. With 100km range, that would pretty much halve fossil fuel
consumption in the USA. More than halve it in Europe.

Paul F. Dietz wrote:
Joe Strout wrote:

No, global warming will be halted by not pouring carbon into the
atmosphere anymore, because we're using cheap space solar power instead.

No it won't, Joe. SPS is a terrible substitute for many
uses of fossil fuels, even if by some miracle it does become
competitive with other sources of electricity.

IF it becomes competitive with other sources of electricity, becoming
cheap enough to displace fossil fuels could for heat and locomotion
would be quite feasible. I would expect SSP to have very low marginal
costs.

Alex Terrell wrote:

IF it becomes competitive with other sources of electricity, becoming
cheap enough to displace fossil fuels could for heat and locomotion
would be quite feasible. I would expect SSP to have very low marginal
costs.

It would have to be much cheaper than current electricty in order
to compete for many heating applications.

And why do you expect SSP to have a low marginal cost? The cost
of adding another powersat will not be cheap. Do you mean low
*operating* cost? That may be true, but it's not at all important
in the context of the issue being discussed. Nuclear also has
very low operating costs. It's a shame the people lending
the money to build the things expect to be repaid, with interest.

But back to global warming: the big advantage of sunshades is that
they work even in the face of defection. In contrast, if there's
substantial resistance to the prohibition to exploit fossil fuels
(and in the long term, emission rates will have to be reduced 90% or more
to halt CO2 buildup). then global warming will happen, just more
slowly than otherwise.

Paul

On Fri, 08 Dec 2006 21:44:46 -0600, in a place far, far away, "Paul F.
Dietz" made the phosphor on my monitor glow in such a
way as to indicate that:

Alex Terrell wrote:

IF it becomes competitive with other sources of electricity, becoming
cheap enough to displace fossil fuels could for heat and locomotion
would be quite feasible. I would expect SSP to have very low marginal
costs.

It would have to be much cheaper than current electricty in order
to compete for many heating applications.

And why do you expect SSP to have a low marginal cost? The cost
of adding another powersat will not be cheap.

Unless we do it in the stupidest way possible (quite conceivable, if
it's a government, and particularly a NASA project) it will certainly
be much cheaper than the first one...