[extropy-chat] [Bulk] Re: [Bulk] Re: Forbes Magazine on Robotics

Eugen Leitl eugen at leitl.org
Tue Aug 22 12:58:39 UTC 2006

On Tue, Aug 22, 2006 at 08:31:22AM -0400, Keith Henson wrote:

> >Current PV arrays are already warranted for 20-25 years weathering,
> >and they don't require to be launched, and produce power where it's
> >consumed. PV is already economic off the grid, and will probably
> >break-even with fossil within a decade, depending on how robust
> >nonrenewable energy price development is.
> Do you go to bed when the sun goes down?

Actually, the bulk of my energy use is during daytime. There's a
massive overcapacity during nocturnal time, because large power plants
take days to power up/down. That would not be a problem with
terrestrial PV.

And of course there's the grid, or if you're off-grid, you store
your energy. You knew I knew that, so why did you ask? (I actually
kinda anticipated people would bring up storage, but I don't have
time to write treatises -- in fact, I've just dropped about 99%
of my list traffic over the last two days, which should free up 
a couple hours for the day minimum).

My point is that all the technology is already there, requires
no huge R&D expenditures in large chunks (unlike solar sat fleet)
and is already happening (with subsidized power buyback by the
grid, which doesn't have to be subsidized after fossil break-even).
> >I agree that a launch cost drop to LEO by an order of magnitude would
> >make solar satellite power cost-effective.
> Not at all.  Even two orders of magnitude is no where near 

It depends on how much mass you have to use, solar panels can be in
few um range. You just have to be sufficiently high so drag doesn't
bring you down faster than you can push.

> enough.  Besides, you don't want to reduce cost to LEO, you want to reduce 
> it to GEO.

Most of the expensive mass lifting is for LEO, once you're there, you can
unfold part of the panel and go up anywhere with very little reaction mass
by ion drive, or even pure photonic pressure.

I'd personally prefer coverage from LEO, using phased-array realtime
beamforming by the uninsolated backside. There's not much space left
in GEO, and it is really high up (both for beaming power, and ascending
up there).
> >But launch costs are far more
> >unyielding
> That's the point of a mechanical (moving cable) space elevator.  Once built 

You are rather fond of megascale engineering, aren't you. I have problems
with terrestrial space elevators (much less so with lunar elevators), largely
because of need of actively moving the ribbon to avoid perforation by debris,
because the tensile strenth required is borderline to what physics gives you,
with not much safety margin, and if you fail only once
you've wrapped all your infrastructure around the equator. That's not so
forgiving. I prefer linear-motor driven launch ramps, which are more or less
unobtainium, too, but slightly less so (allright, would take more mass).
As a realist, I prefer grassroot solutions. A self-inflatable photovoltaic-polymer
dome with solid-state air conditioning and water condensation/desalination system
for a family which fits in the back of an F250 truck and costs about as much
would be a far larger progress in my book. It would empower people to be able
to set up shop self-reliantly anywhere they want to, with minimal environment
footprint (add a hydroponics unit, and you've partly covered caloric intake, too). 

> up to a mature size, it is lifting 2000 metric tons per day and using a Gw 
> of power.  In 5 days it puts up 10,000 tons, which is enough for a 5 Gw (at 
> the ground) power sat.  So a power sat pays back the energy used to lift it 
> to orbit in *one day*.  To put it in monetary terms, a Gw hour lifts about 
> a hundred tons.   At ten cent/kwh that's a million dollars to lift 200,000 
> pounds or $5 a pound.  Once you get the first few on line, I can't see 
> power being rated at more than a cent/kwh, which means 50 cents a pound to 
> GEO . . . . and falling.

I agree that we don't have an energy crisis, we have a mental crisis. There's
a lot of energy to tap, what we need is bringing down the tap costs. Right
now the smallest PV unit would set me back some 25 kEUR, which is an order
of magnitude too much (I'm ignoring subsidy for the moment). 
> At some point you start building stuff our of asteroid materials just to 
> avoid shipping on earth's surface!

Yes, once Earth ceases to be important, it becomes really insignificant
really fast. But I'm already 40, and it may well take more than my residual
lifetime to see the beginnings of it. I once would have thought different,
but things have turned out much slower than I anticipated.
> >The economics of it doesn't work even now, and it would have looked
> >even worse 30 years ago.
> The economics were fine.  See the article in Science written by O'Neill and 
> vetted by half a dozen economists.  The problem was that the overall chain 
> of complexity of mining the moon for materials, launching them off the 
> moon, refining them in orbit to what you needed and then building the power 
> sats was more than investors could cope with.  The payback time was a bit 
> long, and the business went through a fair amount of money (some small 
> fraction of what the Iraq war has cost) before it made money hand over fist.

The economics of megascale projects doesn't work because they *are* megascale
projects, and they require megascale funding. Because the state is no longer
concerned with our visions (unlike the Moon race), and the private enterprise
is only beginning to enter the space sector. Fortunately, our control of
very small packages is getting lots better, so the size of the bootstrap
material will become less and less, ultimatively being in reach for smaller
players, which have the motivation.
> > > We didn't.  We are not likely to do anything useful about the energy
> > > problems unless someone can see huge profits to be made.
> >
> >Efficient burners (recently, pellet burners), house insulation,
> >efficient light ICEs, thermal and PV solar and wind is doing very
> >well here. If you remove the fossil volatility by a tax ratchet the
> >market will do the rest quite efficiently, starting with the
> >small end, but eventually arriving at the top end (solar power
> >satellites).
> So we are seeing a year to year drop in energy use and cost?  I think you 

No, I'm seeing lost higher productivity for the unit of energy consumed
in EU than in NA. As to to energy use, it doesn't matter, if you're 
producing all the energy you can consume locally, sustainably. The energy
you save you don't have to buy, which buys you time to implement
more long-term plans. Such as orbital PV, for instance.

> have a bit of misunderstanding on this topic unless you have a pellet stove 
> and are off the grid.  Most people currently live where such things are 
> outright impossible.  If you do live such a place, you may have some idea 

I live on the outskirts of a >10^6 city.

> of how much of your time is eaten by maintaining the stuff you need to live.

Pellet burners, to make an example, require as much maintenance as your
oil or gas burners.
> All these things help, but not enough in the long run, not if you have any 
> desire to live in style.

The heat from a pellet burner is not measurably different from the
heat of a gas burner. Insulation doesn't result in higher noxious
emission, if you're putting a heat exchanger in the ventilation.
A light, efficient electric/hybrid vehicle can give you the same
amount of space and same or superior performance on the road as the
equivalent old-style SUV.

Living in style doesn't mean your environmental footprint needs
to be large. With nanotechnology, the footprint can become about zero.

Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
ICBM: 48.07100, 11.36820            http://www.ativel.com
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE
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