[ExI] Obama Transition Team Examining Space Solar Power

hkhenson hkhenson at rogers.com
Wed Dec 24 04:00:37 UTC 2008

At 10:33 AM 12/22/2008, you wrote:
>On Sun, Dec 21, 2008 at 5:53 PM, Keith Henson 
><<mailto:hkeithhenson at gmail.com>hkeithhenson at gmail.com> wrote:
>it largely depends on the cost to lift power sat parts to GEO.
>It's probably the most realistic near-term method, unless we're 
>looking to NASA, ESA, etc.  Looking at the numbers, if we can 
>somehow do this from a lower orbit it would be much cheaper.  I know 
>a low earth orbit would have some of the same disadvantages as on 
>earth: only twelve hours of sunshine a day.

You should look into the physics.  With high exhaust velocities it 
isn't significantly harder to get to GEO than to LEO.  In fact, the 
most interesting proposals don't bother with LEO at all.

>  Someone mentioned a sun-synchronized orbit, but I don't see how 
> that is possible.

Google.  410 for sun-synchronized orbit.  It's not useful for power though.

>The satellite would have to orbit the earth once every year, which 
>would be way to slow and, to my knowledge, much higher than 
>GEO.  But it seems that full GEO isn't necessary, we could tolerate 
>a couple hours of night every day, and the costs savings would 
>probably add up when you're doing this on a large scale.

The advantages of being in GEO far outweigh the problems of getting 
stuff there.

>  The
>advantages are not just in the power multiple, but in the fact that
>the energy is steady, no clouds, no wind stopping, i.e. no storage.
>The other advantage is that you don't have to build massive and very
>expensive lines from the southwest to the mid west and east.  You just
>plunk a rectenna down close to the load.
>I guess I just don't have a rubric to compare costs here.  But yeah, 
>storage is a big problem here on earth.  The other issue, I think, 
>is how *light* they can make the SPS's.  Some of the proposals I've 
>seen (sorry, I can't find the links right now) don't use solar 
>powers at all, but mirrors to some device that directly turns 
>visible light radiation into microwaves.

I don't think that is possible.

>But the solar constant is on average 1366 W/square meter.  There's 
>just no more energy out there from the sun than that at the distance 
>of the Earth (1 AU).  That's our upper bound of what we could 
>expect.  That's 732 square m of panels/reflectors to transmit 1GW.

1,000,000,000/1366 is 72300 square meters.  That's the collection 
surface at 100%.  For current PV cells it's more like 5 square km to get a GW.

>If you can haul the parts up on a space elevator, there is no question
>that power sats are the less expensive approach.  If you have to haul
>the parts up on rockets, it's marginal.
>I think that's the show-shopper here.  Rocket technology is here and now.

And too expensive to even consider.  Not to mention that the low 
payload mass fraction leads to ridiculous flight rates.  If you try 
to do a 100t/hr materials pipeline to GEO with conventional rockets, 
you have to launch something twice the size of a Saturn V ever 
hour!  If you just put that amount in LEO, it's still 7 or 8 launches a day.

>I think even if we could build a space elevator, even a partial one, 
>it would take too long to build the technology.

That's silly.  The "technology" is ROPE.  And motors to move the 
rope.  This really isn't rocket science.

>   Honestly, to save us from the energy crisis, I think at least 
> part of the system needs to be up and transmitting power within 
> twenty years, and even that might be stretching it.  Some experts 
> believe that we've already reached peak oil.

Twenty years is *way* too long.  To deal with the energy crisis we 
need to build a GW/day, perhaps twice that.  The proposal I have been 
working on envisions the materials pipeline and the dry dock for 
building power sats operational by 2015.

>  The hybrid methods of using
>rockets to suborbital and lasers to kick the payload into GEO meets
>the penny a kWh requirement.
>Except, you know NASA, it would take twenty years to research laser 
>propulsion before they can approve writing a report on it.

I don't expect this to be done by any US government agency.

>  Of course the old method of developing
>extraterrestrial materials works best of all, but there is not enough
>time to develop space industry.
>Has anyone considered pumping hydrocarbons, methane and ethane, from 
>Titan?  We know the lakes are there, the trouble is it would take a 
>long time for us to get anything back from it.  The advantages are 
>that Titan has a smaller gravity well than the Moon, and the 
>interplanetary transport network could cause it to cost nearly 
>nothing to transport fuel ships there and back.  Of course, we 
>haven't solved the problem of cost to orbit....

If you work out the energy to get from Titan to the earth, I believe 
you will find that hydrocarbons don't have the energy needed to move 
them that far.

>  It's not entirely obvious that any
>long term energy solution is needed.  If I were confident the
>singularly would get here before famines and resource wars I wouldn't
>worry about it.  But I can't put a firm date on either.  The
>consequences of running out of energy are really dire.  Some models
>show the population dropping a hundred million a year, bottoming out
>at 1-2 billion.
>I know.  This is stuff we should have been working on since the 
>70's, but instead forward their problems into the future.

In late 1975 a team from the just formed L-5 Society went to the 
limits to growth conference held that year near Houston.  Dr. Peter 
Vajk (physics) was with us so we had the credentials to present power 
satellites as long term solution to the energy (resource) limits and 
to be taken seriously.  We were nearly kicked out.  It isn't that 
people disbelieve that there is a solution to such problems, the 
_DON'T WANT A SOLUTION_.  A substantial fraction, perhaps even a 
majority of the elite, want a collapse.  Exactly why isn't easy for 
me to pick out of their rationalizations.  Guilt perhaps, I just 
don't know.  I had another of these experiences last week.

>BTW, I'm not confident that a singularity will ever happen.

I don't see any way we can avoid it.  Eventually we are going to make 
intelligence 2.0.  At that point, it isn't our problem any more.  If 
things work out well, humans will have the relation to our 
"offspring" that cats do to us.

If you can make a case this won't happen, please do.


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