[ExI] Thoughts on Space based solar power (risks)

hkhenson hkhenson at rogers.com
Sat Nov 22 15:56:11 UTC 2008

At 06:32 AM 11/22/2008, you wrote:
>hkhenson wrote:
> > I don't see any reason some hundreds to a thousand power sats and
> > rectennas would be any more brittle than the current situation.
> > Rectenna goes out, there are several feeding that section of the grid.
> > Power sat dies, there are spares.  Should be more robust.  The only
> > common mode would be a big solar flare wiping out the PV cells.  For
> > other reasons I doubt PV cells will be used anyway.
>There is the risk of failure of capital concentration. Put all our 
>eggs in the SPS basket (and launched from Earth, not built in space) 
>and we may have to stop investing in renewables on Earth. That is a big risk.

If people stop investing in enewable energy sources on earth because 
space based solar power is less expensive, that's only logical.  I 
fail to see any virtue to solar power collected on earth compared to GEO.

>Then there is common mode failure. They may all be subject to the 
>same attack via their control signals.

Why would they be using the same control signals?  Anyway, that's an 
argument for people in GEO.

>Or they may be all easily targeted by a military strike or terrorists.

It would be easier to get inside a nuclear plant on earth and blow it 
up than to get to GEO.  A nation state could take out a few with 
large nukes, or KE weapons, but *why*?

>Or they may all be shattered in a chain reaction from orbital debris 
>(there is a lot of junk up there already ready to go).
>   http://en.wikipedia.org/wiki/Space_debris
>   http://en.wikipedia.org/wiki/Kessler_Syndrome
>"The Kessler Syndrome is a scenario, proposed by NASA consultant 
>Donald J. Kessler, in which the volume of space debris in Low Earth 
>Orbit is so high that objects in orbit are frequently struck by 
>debris, creating even more debris and a greater risk of further 
>impacts. The implication of this scenario is that the escalating 
>amount of debris in orbit could eventually render space exploration, 
>and even the use of satellites, too prone to loss to be feasible for 
>many generations."

This is LEO, not GEO.  Very little is out there and it has very low 
delta V compared to the GEO orbit.  Besides, no matter how you get 
the millions of tons of parts up there, at least one ablation 
propulsion laser is needed to clear away the space junk.

>Then there are unknown physical effects of long term space 
>operations and material degradation in space, which are much bigger 
>unknowns that ground based operations.

That's grasping at straws.  Not only to we have many decades of 
experience with how things age in space, we have nickel-iron 
asteroids that we know have not degraded for a billion years.

>But the bigger point is even with thousands of rectennas, you still 
>need a grid to distribute the power. If people can soon generate 
>their own power at a lower price than maintaining the grid, then who 
>are your customers?

How are they going to do this?  Basement nukes?  If you have a big 
chunk of land in Arizona and a ton of money yeah, but how about 
apartment dwellers stacked 15 stories high in NYC?  How do you 
propose to get them off the grid?

>Even if you get big industrial customers, home use will drive 
>falling renewable costs. Then competing will be hard on a price 
>basis. So there is a fundamental economic business model risk.

So you would not invest (if you had the opportunity) in power 
satellites because you think earth based renewable energy will solve 
the energy crisis.  Speaking as an engineer, it's going to take some 
really disruptive technology to do that.  I am reluctant to count on 
disruptive technology even when I think it is inevitable in the long 
term.  If we don't build power sats I sure hope you are right, 
because if you are not, many billions are going to die in famines and 
resource wars.

Of course the power sat model I am proposing is a design to cost 
effort with a target of penny a kWh.  Sort of "dams in space".

There is a business risk to building power sats, like there was for 
Iridium only much larger.  That's what Charles Miller's idea is about.


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