Responding to Mike Comb's Space Settlement FAQ
http://members.aol.com/oscarcombs/spacsetl.htm>
bias against nuclear development in space which
was not explained. To me, it's as simple as this. If the environmentalists shriek and come perilously close to blocking the launch of a Saturn probe over a small, thermionic generator, what are they going to do when you proposed launching a full-blown nuclear power plant on a rocket? The imagery of Challenger is still very vivid in everyone's mind. I hear it argued that the nuclear fuel rods would not be hot prior to first power-up, but could we convince environmentalists of that? If nuclear material were mined from ET resources, and the nuclear engines built in space, I can't see a legitimate cause for objection. But by the time we could do that, we'd already be well intoa High Frontier era. I'm more interested in figuring out how we can get there from here. I saw discussion concerning
the benefits of solar power out to a great distance
from the sun but much of the construction materials
for large space based habitats past Mars and the
asteroid belt would likely have to be imported
from the inner solar system. Not at all. There are many asteroids which orbit well outside of the belt. There are Jupiter's Trojans and Apollos. There are Kuiper objects. Given the desiccation of bodies in the inner solar system, and our dependence on hydrogen and other volatiles, there may sooner be a market for importing materials from the outer solar system to the inner than vice-versa. The vast majority of
mass in low gravity wells is in the form of cometary
material well past Pluto. In this region nuclear
rockets and nuclear fission/fusion hybrid reactors
could turn this vast desert of ice into a garden. I don't see much point in struggling with the problem of how to build habitats beyond Pluto before we've even built our first one in HEO. The problems concerning populations doubling
every forty years are acknowledged to only be delayed
by moving into the nearby solar system. In reality
it does not directly benefit Earth population pressures
at all [the indirect benefits may be large however]. Agreed. There has never been any serious talk of large masses
of people moving to space in order to relieve the Earth
of population pressures. The numbers of people you
would need to move are simply staggering. If by "serious talk" you mean informed scientific speculation, you're certainly correct. But many laymen continue to talk in those kind of terms. (There's a guy on one of the space newsgroups who wants to depopulate Earth and turn it into a big park.) Talk about reducing Earth's population via space settlement may have been more prevalent in the 1970s than today. Maybe I'm beating a dead horse. But since people still ask questions about this topic, it seemed appropriate to include it in a FAQ. Moon, Mars, and/or asteroid infrastructure will
need to be erected before large space based
habitats can be erected from materials originating
from space. Certainly either lunar development or asteroid development (and possibly even both), would precede large space habitats. But I could see space habitats coming about prior to any serious kind of economic development of Mars. Although the Moon and Mars have low
gravity, a sleeper car on a circular track can
perform artificial gravity the same as a spinning
platform, at a greatly reduced cost. Perhaps, but why compare this with orbital habitats? Do you plan to built 10,000 person permanent settlements on sleeper cars on circular tracks?
Regards,
Mike Combs
I assume a Stanford Torus is small and intended to
be pre-built on Earth with the Moon resources
providing only shielding. Fine, but that's contrary to the recommendations of the NASA-Ames/Stanford Summer Study Group. They assumed the metal and glass structure of the habitat as well must come from space-derived resources to be economical. For myself, I'd have to say that building such a torus at even 1/2 or 1/3 of the scale but entirely from Earth-boosted components doesn't sound very likely to me, even if the shielding did come from space resources (but granted, that's the lion's share of the total mass). How you get from where we are to where you want
to be is very much the point. The huge infrastructure
required for such building projects will mean dealing
with human health issues on a large scale before the
even larger scale becomes possible. The NASA studies assumed that we could get to the Stanford Torus stage of operations with just a few people on the moon who would presumably get rotated back to Earth at regular intervals. Orbital workers were assumed to have small, shielded, rotating habitats available to them well before completion of the first Stanford Torus. A very small shielded habitat can only house
a very small work crew. The kind of habitats
some have envisioned will require work crews
in the hundreds or thousands working for many
years. You would not want this structure
rotating while being constructed. Agreed, but again, the NASA experts seemed to feel that small, shielded, rotating habitats could be built with sufficient capacity to house all of the workers needed to build the firstlarge, Earthlike habitat. Until you have produced a large habitat with
sufficient mass for protection from radiation a
rotating habit is only fixing one of two health
problems. There was a "construction shack" design published in one of the SSI Conference Reports that was based on clusters of Space Shuttle ETs. They were surrounded by radiation shields derived from the very first lunar materials retrieved to HEO. They rotated to provide a full 1-G. This can be done on a scale much smaller than Island One. A circular track on the moon sheltered
from radiation fixes both problems. Again, you seem to proceed from the idea that this circular track and large, high-speed vehicle is going to be easier to construct than a small, rotating, shielded habitat in orbit. Both construction programs would take place in vacuum, and well away from the Earth. I don't see the lunar track being all that much cheaper. Once a small habitat is set rotating in orbit, it basically will rotate forever. Those working
on the habitat during construction will need to go
somewhere to regain health, the infrastructure on
the moon or asteroids will need workers also, so
rotating crews would solve both problems. Perhaps, but I havea very difficult time seeing regularly rotating orbital workers to the moon and back as ever being economical. Less expensive than rotating to Earth and back, granted, but the cheapest solution of all is to provide them with spin and radiation shielding at the construction site, and letting them stay put. Mass drivers or light gas guns can push out projectiles
with ablation noses and steering rockets to put them
into whatever corrected orbits they later require. Certainly true, but we're now discussing projectiles (and launchers) of much greater complexity and size than what O'Neill proposed for his lunar operation. To me, getting needed water from the lunar poles or NEOs is many times easier and more economical. I can't see Martians ever makinga profit from the export of water when they reside at the bottom of such a steep gravity well, are so distant from the initial markets, and must compete with both lunar ice and water-bearing NEOs. Mars has the raw materials, the deep gravity well is
not much of a consideration once a nuclear/electric
infrastructure is built up. I'm of the opinion that deep gravity wells will continue to be a significant economic issue for a good time to come. The small amount of ice
or water available from the moon means finding the
resources elsewhere shortly after the Moon has an
industrial infrastructure. And if there were no such thing as CC type NEOs, I'd agree that Mars would be next.
Mike Combs