[ExI] Solar power satellite logistics

Keith Henson hkeithhenson at gmail.com
Tue Jul 14 05:53:35 UTC 2020

Adrian Tymes <atymes at gmail.com> wrote:


> I assume that "ratio of" means the infrastructure is rated to provide
80,000 hours - just over 9 years - of output.  That
seems possibly reasonable, but where does that figure come from?

Levelized cost of electricity.  It is exactly the same way you get ~11
cents per kWh for nuclear plants.  It is not complicated, look it up
or ask me to send you the spreadsheet I used.

> If the lift cost is $100/kg, does that mean the solar power satellite
designs you are aware of produce 13 kW/kg?

No.  The power satellites have to be moved to GEO and that about
doubles the transport cost to LEO, thus the 6.5 kg/kW number.  This
takes electric propulsion and considerable development work, but looks

Space junk complicates building power satellites.  It looks like the
parts have to go up to a 2000 km orbit to get above the junk.
Otherwise, the power sats get hit too many times on the way out to
GEO.  2000 km is in the lower Van Allen belt, and the radiation level
there precedes human workers.

> Parts is one thing (though at 13 kW/kg, that's about $100/kg, which seems a
bit high given the parts in question), but what sort of "labor in space"
are you thinking of (that can't be done for less cost by automation, or
bypassed entirely)?  Could this be driven down to closer to $130/kW, or

I don't know.  If you want to work out a less expensive design, be my
guest.  Getting the cost down to $900/kW took years.  One of the hard
problems was collecting 10 GW and getting it to the transmitter.
Don't forget you have to generate 2kW in space to get one kW on the
ground due to transmission loss.

I don't work on power satellite design much any more because I don't
know enough about robotics and teleoperation to put a price tag on it.
Without such cost and development numbers, the financial model is
incomplete and of no use.   I have asked the foremost robotics
engineer of our time what it would cost and no answer was forthcoming.

> And do you have a source for the rectenna cost?

It was one of the early things I did.  Ten years ago or more by now.
Nobody has ever challenged my work on rectenna cost or proposed a
different cost.  This is probably due to lack of interest.

Some changes happened over the years.  For example, the original idea
of underground wiring to collect the power has been replaced by lower
cost overhead wires.  It is not easy to get 5 GW of electric power out
of a rectenna.

Some of this has been discussed on the Google Group power satellite
economics.  If you ask I can add you to the group so you can post.
(You can read it without being a member.)


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