[FoRK] Are you Malthusiastic? Re: Concrete results

Eugen Leitl eugen at leitl.org
Wed Jun 19 01:57:10 PDT 2013


On Wed, Jun 19, 2013 at 12:50:12AM -0700, Stephen Williams wrote:

> Probably a good idea.  In any case, that analysis only considered PV
> panels in space with LEO or GEOSync orbits, transmitting with safe
> beams all the way to the ground.  That leaves many permutations not
> considered.  High elliptical or Lagrange point orbits are
> interesting possibilities.  Multiple satellites to provide
> continuous coverage.  Using solar wind and ion engines to actively
> position extremely lightweight reflectors.  Concentrating power
> manifold over sunlight, beaming to high-altitude platforms, such as
> lighter than air factories / transports / cities / energy packagers
> / relays for instance, as I previously suggested here.

The core of the problem is low EROEI and high energy input to
get these things high up at Mach 25. The ultimate high ground
doesn't buy you that much to warrant that expediture.

If you can do ISRU fabbing and launch from an annular linear
motor around Shackleton the sky's definitely not the limit.

But, this is best tackled by 2050. There's plenty of work
to do before that.
 
> Solve concentrated energy storage or concentrated beamed

We're getting very good MWh scale batteries from cheap
ubiquitous materials. That's enough for night baseline.

> transmission and this is probably feasible.  Even relatively
> simplistic solutions, like simply heating something dense and bulky
> to lava-levels and then gliding it down to an energy plant would

Heat=Carnot. Electrochemical energy sources are non-Carnot.
We have lightweit 95%+ rare earthless motors now, no need
to stick in 18th century, and go right for large scale
batteries. I see no reason why we can't double PV effiency 
in 20 years, too.

BTW, InP PV on kapton has 2 kW/kg energy density, at 1 AU.

> probably work.  The station wagon speeding down the highway with
> tapes transfer model.  How many tons at 3000-5000F does it take to
> run a good sized power plant for a significant period of time?
> 
> To be clear, when I said "heliostats", I was referring to space
> solar heliostat concentration and relay more than ground base.
> There's no reason for the latter to take 20 years to deploy.

For illumination (and fucking it up for night active animals)
orbital mirrors will do, but not for power production. You'd
do much better with thin-film PV and target terra-side
rectenna arrays by phased arrays during flyby (you'd need 
to have several stations within LoS for smooth handover,
so there needs to be considerable density of them in LEO
and MEO).
 
> Is this a no-ideas-after-30 pity party or something?
> 
> >>>Anyway, hopefully you are wrong, but we should act like you are close
> >>>enough to right and start doing something.
> >>Thaaat's the spirit!
> >>
> >>It pleases me that most folks appear to be at the point of discussing what
> >>to do and how much money to spend, rather than arguing over whether there's
> >>a problem and/or standing in the room shouting, "what elephant?"
> >Most population is very unlike FoRK. The Nile is a comfortable river to stand in.
> 
> We're trying to earn the Musky money to do Elonesque public works.

Multiple TUSD/year is distinctly out of scope of such investors.
They can do initial R&D, but that's not what we need right now.
We need to deploy, deploy, deploy.

> The solution to mankind's biggest problems are (probably) in stealth
> mode.


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