Lunar Solar Power Stations vs. The O'Neill Proposal
For those of you who may have read my article about planetary chauvinism "Somewhere Else Entirely" at http://members.aol.com/howiecombs/somewhere_else.htm, I just wanted to let you know that I did have to back away from one of my assertions, and I wrote a bit more to clarify some issues. Dr. David Criswell noted some critical things I'd said about his LSP proposal, and we resumed our previous debate on the merits of LSP vs. lunar-resources-derived SPS in GEO. In my article I had asserted Criswell had not made sufficient comparisons between his proposal and the O'Neill one. After some discussion, I followed that paragraph with a parenthetical "(But I may now need to retract at least this point.)" which was a hyperlink to the following: Lunar Solar Power Stations vs. The O'Neill Proposal
In May of 2006, Dr. David Criswell became aware of this article and contacted me to resume our debate about the relative merits of Lunar Solar Power (LSP) stations vs. lunar-resources-derived GEO SPS.
Dr. Criswell said that all of his comparisons were toward the GD-Convair study, which included SPS where 90% of the construction materials were lunar-derived (SSI later calculated this number could be boosted to 99% for SPS designs optimized for use of lunar materials). I'm sure my previous comment in this article would have been based on me going through the Criswell papers looking specifically for references to O'Neill or to manufacturing in HEO. Dr. Criswell went on to say he had calculated LSP could provide power at a cost 1/50 that of power delivered from SPS built as O'Neill had recommended.
Interestingly, Criswell said the GD-Convair study judged the lunar-material-derived SPS option less risky than the Earth-launched one for several issues, among them the environmental damage which would doubtless be done to the upper atmosphere of Earth by all of those thousands of mega-rockets thundering upward.
One very good point Dr. Criswell raised was that GEO SPS might suffer from an orbital debris problem absent from the lunar surface. My take on this is that hopefully a significant manned operational capability in GEO might mean a better ability to manage and combat the debris problem. But Criswell relates the severity of this hazard with the surface area of the satellites in GEO. To say that SPS would lead to a significant increase in this area is putting it mildly, to say the least.
He says that my emphasis on the day/night cycle of the moon and my assumption of a 2-to-1 advantage for GEO is wrong, making the point that GEO SPS, being a baseload (flat) source of power, must be similarly oversized around 2x in order to meet peak power demands. But I'm not convinced this is the best argument, since an oversized GEO SPS can obviously be selling excess power to secondary markets during off-peak hours.
Despite the fact Dr. Criswell brought up much new and helpful information and helped me appreciate certain aspects of LSP a bit better, I still can't entirely rid myself of the conviction a planetary bias may be involved here. When he says, "The Moon exists. You do not have to build it, and you can use its materials," I think we're veering from the point. The O'Neill proposal agrees the moon is the right source for the materials, and I don't think our choice is between building an orbital ore refinery or not, it's between building a refinery in orbit or on the lunar surface. Ditto manufacturing facilities.
It can't be denied lunar materials take a much longer path in the O'Neill scenario vs. LSP, and Criswell rightly points out that the more steps, the greater the expense. But lunar lift costs are a one-time expense. The 50% duty cycle resulting from the moon's day/night cycle is an operational disadvantage which lasts the lifetime of the power plant.
On the other hand, there are some at SSI who tell me there are too many unknowns to conclude that Criswell isn't right, and that power beaming from the moon should not present major problems.
I'll say that if Dr. David Criswell has come up with an alternative to SPS which can undersell it by a factor of 50, then he's done more to advance us toward space settlement in recent decades than anyone. There could be no doubt his LSP scenario would lead to the High Frontier. For example, any universe in which many thousands of square kilometers of the moon's surface is being coated in photovoltaic arrays, the manufacture of a lunar mass driver (the most massive part of which would be its PV array) would certainly be done on the lunar surface from local materials instead of it being sent up as a kit from Earth. Thus, in a future Criswell presents us, an important component of the O'Neill vision becomes trivially easy to manufacture.
Mike Combs
[mailto:spacesettlers@... On Behalf Of Ian Woollard
> and from what I've seen payback is about 3 years or so.
>
> Startup costs for lunar power is about $100+ billion.
Do you happen to have on hand the startup costs for GEO SPS derived from
lunar resources? I remember that O'Neill compared it to the costs for
the Alaska Oil pipeline, and I would think that would put it closer to
the lower numbers than to the higher one.
One of the things Criswell quoted back from the GD-Convair study (and
apparently what he uses for his comparisons) which didn't quite sound
right to me is that in a comparison of Earth-launched SPS vs.
lunar-derived SPS, costs were pretty much the same for the first 30
satellites, and that beyond that there was a slight price advantage for
the lunar resources option. I would rather have expected that use of
lunar resources would have made the first 30 satellites more expensive,
but beyond that point would achieve major cost reductions.
Regards,
Mike Combs
One thing that bugs me about the lunar scenario is
that the power transmitted from Luna to Earth is
required to be retransmitted eleswhere over the
planet, by cable or otherwise, since the moon can at
most transmit to only 1/2 the Earth at a time. SPS
would have a multiplicity of transmitters covering the
entire planet, so less need to distribute from one
half the planet to the other.
> For those of you who may have read my article about
> planetary chauvinism
> "Somewhere Else Entirely" at
>
http://members.aol.com/howiecombs/somewhere_else.htm,
that the power transmitted from Luna to Earth is
required to be retransmitted eleswhere over the
planet, by cable or otherwise, since the moon can at
most transmit to only 1/2 the Earth at a time. SPS
would have a multiplicity of transmitters covering the
entire planet, so less need to distribute from one
half the planet to the other. Criswell proposes orbital microwave reflectors, and points out that these can be much less complicated and massive than a SPS. My take on it it that it's just one morecomponent that LPS needs which SPS doesn't.
Mike Combs
Seems like an awful lot of ad hoc reasoning in the LPS
scenario. I suppose we won't know what's what until we
actually go out and BUILD a real power sat, either in
GSO or on Luna. That should give us the experience we
need to make fruitful choices.
[mailto:spacesettlers@... On Behalf Of Ian Woollard
> Early studies by NASA were trying to find a use for the Shuttle, which
> should be clear is a fairly expensive launch system. The numbers came
> out pretty high with the Shuttle. (Gee, do you think?) I'm not sure
> whether that's what the GD-Convair study did too.
I'd be real surprised if the study hadn't assumed the kind of massive
HLLV Boeing had touted for SPS launch.
> I think in the long run that O'Neill's idea is good, and Criswell's
> option is even cheaper,
So do you see the avoidance of lunar lift costs as outweighing the
operational disadvantage of power stations which only operate half the
time? But then I see you're saying people place greater emphasis on
startup costs than ongoing costs, so maybe you're only saying the
startup costs are less, which I might even agree with (though I think it
would be much closer than if the comparison were with Earth-launch).
> I think the lunar resource options are higher risk, because you
> have to be able to process the lunar material, and that's very
> researchy thing right now.
That was my take on it too. In fact, when Criswell told me that the
GD-Convair study had considered the lunar materials option to be lower
risk, I initially thought he had just said the opposite of what he had
meant. I would have accepted that the O'Neill proposal was higher risk
(but ultimately produces the cheapest SPS).
> From earth launch perspective the numbers I've worked suggest
> that expendable Falcon I's launched a *lot* (and I *really*
> mean a lot) would bring the wallplug costs down to about $0.05/kWh,
> but I'm not very happy with that option (Falcon I is too small to
> launch people on, so a dirt cheap Falcon I wouldn't do much for
> space access, is cheap, reliable electricity enough of a goal on
> it's own if it doesn't lead to space colonisation????)
I think a world in which SPS starts out with Earth-launch for the first
few might still lead down the High Frontier road provided that we became
seriously committed to SPS as a solution to global energy needs. That
kind of commitment might not happen prior to the era that at least a few
SPS are up there and functioning productively.
Regards,
Mike Combs