[ExI] Air-powered cars

Keith Henson hkeithhenson at gmail.com
Fri Jun 6 02:22:46 UTC 2008

On 6/5/08, spike <spike66 at att.net> wrote:

> Whenever one looks at the alternative means of hauling apes, one always
> comes away with a new respect for good old gasoline.


So what do we need for carbon neutral synthetic gasoline?

At a recent conference a guy had worked out the numbers to suck carbon
dioxide out of the air and combine it with hydrogen in a reverse
combustion industrial operation.

He got 79kWh/gallon.  I have confidence in that number because the
energy in a gallon of gasoline is about 38 kWh and this number is
close to twice that.

So if you want gasoline for about a dollar a gallon, you can do it on
a megascale if you can get massive power in the penny or sub penny per

If you assume 2kg/kW power sats and work the numbers backwards from
penny a kWh, you can afford about $75/kg for the lift cost to GEO.
That's easy with a space elevator, which takes about 15 cents of
electricity and (if it cost $100 billion) a capital charge of
$12.50/kg for an 800,000 ton per year delivery model.

Reuseable heavy lift launch vehicles will do that for an incremental
cost of about $300 a kg split between $1.5 billion for the rocket and
$1.5 billion for operations.  In 100 flights, a single rocket
delievers 10,000 tons to GEO.  ($3 billion/0.01 B kg)

I have a proposal out to reduce this cost to at least 1/3 and perhaps
1/6.  I don't want to make it public just yet, but if you feel up to
checking assumptions and my math, ask and I will send you a copy.

Keith Henson

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