Writing at his blog Centauri Dreams, Paul Gilster in the previous days has made three posts about the audacious possibility of colonizing the Oort cloud, drawing on earlier writers referenced in the posts. The Kuiper belt and the scattered disc, zones of the solar system stretching far beyond the orbit of Neptune, are remote enough: frigid, distant, icy. The Oort cloud, the cloud of innumerable comets orbiting our sun at a distance of sizable fractions of a light-year, are more remote yet.
The first post was “Into the Oort Cloud: A Cometary Civilization?”. Resources are available.
Embedded with rock, dust and organic molecules, comets are composed of water ice as well as frozen gases like methane, carbon dioxide, carbon monoxide, ammonia and an assortment of compounds containing nitrogen, oxygen and sulfur. Porous and undifferentiated, these bodies are malleable enough to make them interesting from the standpoint of resource extraction.
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Put a human infrastructure out in the realm of the comets, in other words, and resource extraction should be a workable proposition. Terra talks about colonies operating in the Oort Cloud but we can also consider it, as he does, a proving ground for even deeper space technologies aimed at crossing the gulf between the stars. Either way, as permanent settlements or as way stations offering resources on millennial journeys, comets should be plentiful given that the Oort Cloud may extend half the distance to Alpha Centauri.
The second was “Life Among the Comets”. This one imagined sources of energy for these deep-space colonies, including nuclear energy but also mirror farms.
[M]irror farms are themselves components of even larger arrays, spread out perhaps 200,000 kilometers from the cometary nucleus. Growing the community would mean creating comet clusters by moving new comets into range, which would allow populations up to 100,000 or so to exist, though spread out widely through the cluster. With perhaps a light-day of separation between communities living in such clusters, the colonists would be in constant electromagnetic communication with other settlements scattered throughout the inner and outer Oort.
As wondrous a science fictional setting as this provides (and vast mirrors inevitably call to mind the continent-sized sails of Cordwainer Smith’s “The Lady Who Sailed the Soul”), I’d like to think there are more practical ways to produce the needed energy. But what? Fission doesn’t fly out here because the heavy elements are found in only minute amounts. Remember, we’re not talking about a colony world that is sustained by regular supplies from the inner system. We have to exploit local resources, and that takes us to the deuterium available in comets.
The third, “Into the Orion Arm”.
A small but growing human population in the Oort Cloud will master cometary motion, taking advantage of the fact that at 10,000 AU, the speed needed to orbit the Sun is just 300 meters per second. Compare this to the Earth’s 30,000 meters per second and it should be obvious that it takes only a small change in velocity to alter a comet’s orbit. We’ll have learned this in theory if not in practice because it factors into the engineering needed to divert a potentially dangerous comet from striking our planet decades in the future. Learn how to bump comets to change their orbits and you start thinking about what else you might do with such an object.
Interstellar space must be littered with comets that have been ejected from our system through the 4.6 billion years of its existence. Some estimates run as high as 1000 Earth masses in cometary material, so the resource base between us and the nearby stars should be plentiful. If Oort Cloud comets are separated by about 20 AU, these interstellar comets may be hundreds of thousands of AU from each other. The Oort Cloud should be in perpetual flux as some interstellar comets enter and move through it while other comets are pushed back out.
The whole idea strikes me as very implausible, given the vast distances and scarcity of resources needed to support life. Even if there are–quite plausibly–rogue worlds, dwarf planets like Pluto and even larger worlds, in the area of the Oort cloud, that still leaves vast spaces without resources. The whole area of the Oort cloud is likely to be lacking in the metals–conventional metals such as iron and copper, not just elements heavier than hydrogen–that play critical roles in industry, even if other materials are present. As for the sociology of scattered groups of dozens of people separated from realistic likelihoods of physical context, I’m confident in fearing the worst.