Zubrin

Zubrins estimate of lunar material launch costs (1/10,000th current price)
is probably about right, for the first ten years of operations. When you
consider the cost associated with setting up the moon base and all of the
necessary hardware in HEO, $4/kg is about right for the first 5-10 years,
assuming that the mass driver is on-line 100% of the time. The main points
that he missed are as follows:

1) Space habitats need not weigh 1 billion tonnes. Island-1 weighs 3
million tonnes, 300-400 times lower than Zubrins mass estimate. A fully
shielded space manufacturing facility, capable of producing several SPS
satellites per year, would be in the few 100,000's of tonnes range,
shielding included. Even if all of Zubrins pessimistic assumptions were
true, the SMF would still produce enormous returns within a few years.

2) 1/10,000th current launch costs ($4/Kg) is easily cheap enough to
allow economic production of SPS satellites.

3) Plants are relatively hardy to radiation. Solar flares of the
variety that kill crops, do not occur frequently. We would expect to lose
only one harvest every 10 years or so, even assuming that the crop modules
are poorly shielded.

4) Mirrors in space can be as thin as foil, and support structures,
would weigh very little. The mirrors can be not rotating and would never
experience forces exceeding 1/1000th of a gravity.

Tony

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