It’s hard to imagine a sane human being who would choose to live in the Oort Cloud, on a colony world where the outside temperature is in the single digits Kelvin and small bands of maybe 25 each would tend to the problems of energy production and resource extraction. Human contact beyond this would be sporadic, though Richard Terra makes the case (in “Islands in the Sky,” an Analog article I referenced yesterday) that a larger community dispersed through nearby settlements would meet regularly to ensure genetic diversity and relieve isolation.

History tells us that people do all kinds of inexplicable things, and perhaps a small number of adventurers, outcasts, zealots and other dissidents would find a home here. But given the abundant resources closer to the inner system, I’m more inclined to look at the Oort Cloud as a source of raw materials for colonies on the move between stars. These would be generation ships moving perhaps no faster than Voyager 1 moves now, about 17 kilometers per second. The main point is that the space between the stars is hardly empty, and future generations with the tools of advanced propulsion may take not one giant leap but many small steps in the direction of Alpha Centauri.


Image: The Oort Cloud in relation to the Solar System. Credit: UC-Berkeley/Comet’s Tale Development Team.

Whether we’re settlers or voyagers (and I suspect we’ll be both), we’ll learn all along the way from the experience of adapting to space. Ben Finney and Eric Jones put it this way in their paper “Fastships and Nomads” (reference at the end of yesterday’s post):

If interstellar settlement happens at all, it will come after our descendants have learned to maintain self-sufficient communities detached from Earth’s nurturing biosphere, learned to tap the knowledge and skill potential of advanced computers, learned to efficiently harness the energy that flows out of the Sun, and even learned to extract useful energy from the fusion of atoms. We are on the verge of achieving all these things. With sufficient skill and patience we will attain the stars.

Of course, we have been on the ‘verge’ for a long time when it comes to fusion. But taking the long view of human expansion and looking not just decades but centuries ahead, these words resonate.

Finding the Energy

Whichever scenario strikes your fancy, the energy conundrum is still huge. Yesterday I talked about Finney and Jones’ ideas of concentrating starlight through vast mirrors the size of the continental United States. Terra picks up on this to describe colonists living in O’Neill cylinders, each housing a band of outer system stalwarts who would tend a mirror farm stretching across 30,000 kilometers of space. Maybe ‘tending’ is the wrong word, though — robotic systems would surely do the heavy lifting with substantial human oversight. From Terra’s paper:

The primary sector of the economy — the exploitation of natural resources — is likely to be small and almost completely automated. Human involvement will be minimal. The primary sector will consist of two basic activities: energy production and the harvesting of cometary resources. Once the appropriate systems are established, both will be relatively simple activities.

The secondary sector — the transformation of the natural resources — will include refining and processing the raw cometary feedstock, manufacturing, construction and assembly operations, agriculture and food production, and recycling. Again, many of these activities will be highly automated, but closer human supervision will be necessary to tailor these activities to the current needs of the community.

Terra goes on to cite a third sector where most of the human skill set will go to work. Here he’s talking about support services that maintain the life support systems and needed repairs to the colony world. Information processing, education, administration, and eventually business and commerce between settlements will command the attention. The latter, keeping colonists in contact with other colonies, has also been proposed in various starship scenarios over the course of long voyages, with multiple ships accompanying each other on the journey.

Both Terra and Finney and Jones, of course, are talking about full time colonies rather than crews in transit. Their mirror 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.

The Fusion Alternative

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.

If fusion can be mastered, we have changed the game. In his book Entering Space: Creating a Spacefaring Civilization (Tarcher, 1999), Robert Zubrin points to the progress in both robotics and artificial intelligence that will be needed to sustain widely scattered colonies, adding that previous experience settling the asteroid belt may teach us many lessons. But he doesn’t like the starlight mirror idea one bit:

While some have suggested concentrating starlight, it doesn’t really make sense. To get a single megawatt of power, the mirror would have to be the size of the continental United States. The only viable alternative based on currently known physics is fusion. In the Kuiper Belt, it might be possible to get helium-3 shipped out from mining operations around Neptune. Oort Cloud settlements would be too far out to obtain much from the solar system, though deuterium should be available in all iceteroids, so perhaps the colonists might choose to build reactors based on that fuel alone. However, helium can exist in the liquid phase below 5 K (-268 degrees C), which is the environmental temperature at about 3000 AU. It is therefore not impossible that liquid helium could exist within Oort Cloud objects beyond that distance.

But even if we can make fusion work — and I’m assuming that a civilization that can move large payloads to the Oort Cloud is one that probably has — our isolated communities still have an energy conundrum. They’ve got a couple of centuries worth of fusion fuel in the comet cluster they’ve cultivated, but it’s still a non-renewable resource. That’s going to mean tight rationing of fusion fuels even if the technology is available, unless somehow proton fusion can be mastered. Maybe an Oort Cloud settlement of any size would have to have Finney and Jones’ mirrors after all, constructing them as the only renewable solution for succeeding generations.

Zubrin thinks wanderlust and the pioneer spirit will drive some humans outward to test out such scenarios. After all, the great bulk of human society will remain in the inner system where the warmth is, and its possible that the growing centralization and homogeneity of culture here over the course of centuries would incline the more independent-minded to emigrate. O’Neill cylinders, asteroids and comets may be the ideal home for dissident groups trying social experiments and pushing the envelope on what a human society can become. “Why live on a planet whose social laws and possibilities were defined by generations long dead, when you can be a pioneer and help to shape a new world according to reason as you see it?” Zubrin asks.

But there may be other scenarios that would force us into the Oort Cloud. Tomorrow I’ll look at a couple of possibilities that could make the outer system our stepping stone to the nearest stars.