SPACE: Economic Benefit of Manned Space Stations (fwd)

Robert J. Bradbury (
Wed, 28 Jul 1999 21:38:05 -0700 (PDT)

> Eugene Leitl wrote:

> 11 day for Mercury, that's awfully swift. How's that supposed to
> happen, by building beanstalks? Mercury surface is already pretty hot
> for machines to operate, it won't take too much additional insolation
> to make the environment intolerably harsh.

Ah shucks, I never get to make any outrageous claims in this group without somebody sticking a pin in the balloon.

The basic strategy is to construct an exponentially growing array of solar collectors that beam the power back down onto Mercury. You could vaporize the planet completely, but I favor a strategy of using mass drivers to hurl selected materials into space over the entire surface of the planet. It requires nanotechnology mass doubling times to be done in 11 days. The surface temperature on the sun-facing side of Mercury is below the operating temperature of diamondoid materials. How harsh the environment gets depends entirely on how efficiently you can convert the incoming energy from its "beamed" form (e.g. light, microwaves, etc.) into the form(s) you need for mining/mass-drivers activities. I believe that Eric has pointed out in Nanosystems that some of these conversions can be quite efficient.

There are two constraints on the speed:
(a) How thin you can make the solar collectors in space. (b) How long it takes you to position the solar collectors on the

far side of the sun.

There may be an additional constraint when you get to the point where the amount of power being delivered to the planet exceeds any possible cooling technologies. At that point you either have to go the vaporization route, or perhaps expand the planetary surface area [as you point out, perhaps unintentionally, via diamondoid beanstalks :-)].

> Once the stuff is in space, and more or less dispersed, anything is
> cheap. The hard part is getting a massive planetary body dispersed
> without rendering it unusable. How do you do that?
Mass drivers or condensation of a gas at various distances from the source. You never render material unusable unless you let it "escape". Most of the techniques for moving materials around in space were worked out in detail in the late '70's for Space Manufacturing, Lunar Colonization & O'Neill's colonies. The self-replicating factories were worked out in NASA's Advanced Automation for Space Missions study (and then forgotten...).

Last year I asked Robert Freitas (one of the authors on the NASA study), what the advantages were for nanotech based self-replicating factories vs. the macro-scale versions envisioned in the NASA study? He gave a rather succinct answer that summed up the basic reason nanoscale manufacture trumps macroscale -- "The parts count is lower". You only need ~10-15 part-types (i.e. elements) for most nanoscale manufacturing. What needs to be done is the updating of all of old designs for macro-scale self-replicating factories and mass-drivers to nanotech based designs. There *might* be difficulties if some essiential element happens to be in short supply on Mercury (though I expect substitutions could occur).

> I would like to see an easy way of translating power into such a
> coordinated activity as planet dismantlement.
The easiest approach is to vaporize the planet and condense it. I suspect however, that this approach wastes energy (and therefore takes longer). Much better is to dismantle the planet bit-by-bit and only launch into space those materials you absolutely need there. I believe that if you do this cleverly, you may be able to recapture some of the energy used to get the material out of the gravity well either to "recast" the materials into useful forms or provide the deltaV required to move the materials into more useful orbits.

The basic approach I've developed works with the asteroids too but I think it takes longer because the solar insolation is lower at most asteroid orbital distances.

If you are really interested in the nuts & bolts, I've got rough draft paper at: Constructive comments would be welcomed.

I've also got a C program that does a "brute force" simulation of a planetary disassembly using exponentially growing energy availability if anyone wants to tinker with it. If anyone is good with graphics adding "visual" output would make this a great toy. It takes apart the small planets quite quickly, while Jupiter takes many CPU hours. Of course, IMHO, simulating taking apart Jupiter *has* to be a better use of excess CPU cycles compared to certain *other* recently discussed uses of such resources...