Clearly, the Earth/Moon assymetry in the hypothetical conflict will force
the Earthlings to use thermonuclear charges. Nukes work differently in
spece: there is no atmosphere to transform the shortwave EM radiation
into IR range, also there is no attenuation. If the fireball does not
touch the ground, the EM flash will slag a thin surface layer, which
then can cool off by radiating heat into space. However, localized
surface infrastructure can still be destroyed, especially sensorics and
photovoltaics arrays (moonies can't live in permanent mole mode). If we use
depth-penetrating nukes the result would be a shockwave, which might
cause near-surface habitats to breach and thus to decompress. Of course
this is not a problem for deeply buried habitats, but they must come out
from there, sometime. If the nukes are dirty/high flux ones, surface
activation might become a problem, but not for machines and very well
protected humans.
So the idea would be to intercept incoming warheads on their ballistic (if
they are smart, their sensorics is susceptible to damage, and the exhaust
is visible) course. The sensible thing to use would be a particle weapon,
or a laser. Laser is difficult, since warhead reflexive coating will make it
difficult to absorb energy (which will be diluted by focusing/tracking
trouble), but particle beams are different. Trouble is, a focused
charged beam will expand in space, so a neutral high-speed beam
would be much more efficient (basically, this is just a gigantic
groundbased ion/plasma drive, which is currently used to propel some probes
and to keep satellites in their orbits, counteracting deccelerating
effect by atmospheric drag, which is a function of solar activity, btw).
Even better would be an antiparticle/antimatter beam, since energy
released upon impact won't come from kinetic energy invested by the
accelerator. (Another thing would be Moon rings made from brilliant
pebbles (check out Stanislaw Lem's "Fiasko", also "Peace upon Earth").
Whatever happened to them (apart from the TWA desaster, that is), btw?)
Tipler speaks about antihydrogen production for the Forward rocket, but I
found his cost discussion far from being convincing. Current production
processes seem to be of very small yield (he speculates about developing
better ones, which SSC might have done), and current storage is possible in
particle traps solely. If we are talking of g or kg of antimatter for
energy conserve than these issues will much more relevant. I've thought
about storing a microscoping needle of, say, antiiron magnetically
suspended in a cryogenic chamber with very hard vacuum, but it seems very
problematic due to the secondary-electron-multiplier kind of effect (boom).
ciao,
'gene
P.S. the machine is molasses slow, I'd better stop. One thing: in "Flying
Buttresses, Entropy, and O-Rings" James L. Adams speaks about a 3 sec
delay for the autofeedback coordination loop for Moon telepresence, which
is a strong no-no for teleperating Moon factories. So it better be
von-Neumann probe, after all.