Into the Oort Cloud: A Cometary Civilization?

by Paul Gilster on March 26, 2013

Jules Verne once had the notion of a comet grazing the Earth and carrying off a number of astounded people, whose adventures comprise the plot of the 1877 novel Off on a Comet. It’s a great yarn that was chosen by Hugo Gernsback to be reprinted as a serial in the first issues of his new magazine Amazing Stories back in 1926, but with a diameter of 2300 kilometers, Verne’s comet was much larger than anything we’ve actually observed. Comets tend to be small but they make up for it in volume, with an estimated 100 billion to several trillion thought to exist in the Oort Cloud. All that adds up to a total mass of several times the Earth’s.

Of course, coming up with mass estimates is, as with so much else about the Oort Cloud, a tricky business. Paul R. Weissman noted a probable error of about one order of magnitude when he produced the above estimate in 1983. What we are safe in saying is something that has caught Freeman Dyson’s attention: While most of the mass and volume in the galaxy is comprised of stars and planets, most of the area actually belongs to asteroids and comets. There’s a lot of real estate out there, and we’ll want to take advantage of it as we move into the outer Solar System and beyond.

Comets and Resources

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. Richard P. Terra wrote about the possibilities in a 1991 article published in Analog:

This light fragile structure means that the resources present in the comet nuclei will be readily accessible to any human settlers. The porous mixture of dust and ice would offer little mechanical resistance, and the two components could easily be separated by the application of heat. Volatiles could be further refined through fractional distillation while the dust, which has a high content of iron and other ferrous metals, could easily be manipulated with magnetic fields.

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. Terra goes on:

Little additional crushing or other mechanical processing of the dust would be necessary, and its fine, loose-grained structure would make it ideal for subsequent chemical processing and refining. Comet nuclei thus represent a vast reservoir of easily accessible materials: water, carbon dioxide, ammonia, methane, and a variety of metals and complex organics.

Energy by Starlight

Given that comets probably formed on the outer edges of the solar nebula, their early orbits would have been more or less in the same plane as the rest of the young system, but gravitational interactions with passing stars would have randomized their orbital inclinations, eventually producing a sphere of the kind Jan Oort first postulated back in 1950. Much of this is speculative, because we have little observational evidence to go on, but the major part of the cometary shell probably extends from 40,000 to 60,000 AU, while a projected inner Oort population extending from just beyond the Kuiper Belt out to 10,000 AU may have cometary orbits more or less in the plane of the ecliptic. Out past 10,000 AU the separation between comets is wide, perhaps about 20 AU, meaning that any communities that form out here will be incredibly isolated.

Kuiper_oort

Image: An artist’s rendering of the Kuiper Belt and Oort Cloud. Credit: NASA/Donald K. Yeomans.

Whether humans can exploit cometary resources this far from home will depend on whether or not they can find sources of energy. In a paper called “Fastships and Nomads,” presented at the Conference on Interstellar Migration held at Los Alamos in 1983, Eric Jones and Ben Finney give a nod to non-renewable energy sources like deuterium, given that heavy elements like uranium will be hard to come by. Indeed, a typical comet, in Richard Terra’s figures, holds between 50,000 and 100,000 metric tons of deuterium, enough to power early settlement and mining.

But over the long haul, Jones and Finney are interested in keeping colonies alive through renewable resources, and that means starlight. The researchers talk about building vast mirrors using aluminum from comets, with each 1 MW mirror about the size of the continental United States. Now here’s a science fiction setting with punch, as the two describe it:

Although the mirrors would be tended by autonomous maintenance robots, the nomads would have to live nearby in case something went wrong… Although we could imagine that the several hundred people who could be supported by the resources of a single comet might live in a single habitat, the mirrors supporting that community would be spread across about 150,000 km. Trouble with a mirror or robot on the periphery of the mirror array would mean a long trip, several hours at least. It would make more sense if the community were dispersed in smaller groups so that trouble could be reached in a shorter time. There are also social reasons for expecting the nomad communities to be divided into smaller co-living groups.

Jones and Finney go on to point out that humans tend to work best in groups of about a dozen adults, whether in the form of hunter/gatherer bands, army platoons, bridge clubs or political cells. This observation of behavior leads them to speculate that bands of about 25 men, women and children would live together in a large habitat — think again of an O’Neill cylinder — built out of cometary materials, from which they would tend a mirror farm with the help of robots and computers. Each small group would tend a mirror farm perhaps 30,000 kilometers across.

The picture widens beyond this to include the need for larger communities that would occasionally come together, helping to avoid the genetic dangers of inbreeding and providing a larger social environment. Thus we might have about 500 individuals in clusters of 20 cometary bands which would stay in contact and periodically meet. Jones and Finney consider the band-tribe structure to be the smallest grouping that seems practical for any human community. Who would such a community attract — outcasts, dissidents, adventurers? And how would Oort Cloud settlers react to the possibility of going further still, to another star?

More on this tomorrow. For now, the Terra article is “Islands in the Sky: Human Exploration and Settlement of the Oort Cloud,” Analog June, 1991, pp. 68-85. The Jones and Finney paper is “Fastships and Nomads,” in Finney and Jones (eds)., Interstellar Migration and the Human Experience, University of California Press (1985), pp. 88-103.

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{ 42 comments }

Bret Moore March 26, 2013 at 9:22

If you have a mirror that big, how do you keep the sunlight/solar wind from pushing it out further, like a solar sail?

Tdaly March 26, 2013 at 10:10

I read your blog every day and greatly enjoy your writing. While I am an avid proponent of migration out into the solar system and beyond, I have a concern with whether people can really adapt to living in space. No human society exists where it’s members spend their entire lives inside a structure or in tunnels underground, as would be required in order to colonize the solar system. I suppose that a second or third generation would be capable of living under those conditions, since that is all they know. But would a first generation colonizer be able to adapt to such conditions?

Reverend Richard Prichard March 26, 2013 at 10:44

To get to the Ort Cloud, we would need to pass through the Kuiper-Belt, where significant unexplained heat signatures have been discovered. Maybe our next door neighbors will invite us to a barbecue:

“We might have alien colonizers in our own backyard. The fact that we have detected several Kuiper-Belt objects with unexpected and substantial red excess (infrared heat signature) should be disturbing for two reasons: First, that there is substantial red excess; two, the alien colonizers are not bothering to hide their heat signatures. “

stephen March 26, 2013 at 11:39

Since the nearest stars aren’t all in the same direction…the Oort Cloud wouldn’t resemble a sphere, would it? Could it extend halfway to Sirius, halfway to Procyon, halfway to Tau Ceti, etc.? As the stars move around, their Oort Clouds might start to mingle and trade bodies.

GaryChurch March 26, 2013 at 11:53

I would say the energy source of choice would be fission. The Moon has thorium to start with. I am not a big fan of fission on Earth- but deep space was made for the nuclear industry. There are really only two energy resources in space and solar is going to work really well close to the sun- but I doubt it will be practical in the Oort cloud.
There is the possibility of fusion bombs being used to generate energy :
http://en.wikipedia.org/wiki/Project_PACER

And though I dismiss fusion reactors I accept the possibility of future technologies such as anti-matter catalyzed fusion bombs (yes I know it is not really a catalyst) that would remove the need for fissionables in the fusion process.

David Cummings March 26, 2013 at 12:53

The cosmic radiation out there has to be intense and deadly. I bet that for many decades (at least) comet-mining in the Outer Reaches will be a strictly robotic affair.

Alex Tolley March 26, 2013 at 13:17

Unless you really want to live a life in isolation (and force your offspring to do so as well), I don’t see teh logic of this at all.
Firstly, if it is is resource extraction for a space colony that you want, why not mine the comet robotically and send the resources back down teh gravity well? Maybe just wrap the comet in that aluminum foil to slow its losses?

Secondly, If you want solar energy for colonies in deep space, wouldn’t it be better to focus/collect the energy near the sun and then send it on its way to the target colony? The energy could be sent as a beam or a mass of chemical/nuclear fuel.

Thirdly, I do not see the advantage in living light days and months from everyone else. You are cut off from other human interaction, receiving culture only via one way transmission. “Civilization” is just going to evolve and leave the colony behind, a relic of the past.

Fourthly. If you want living space, you need to build 3D structures. Whether multi-kilometer high cities on earth (easiest), or spinning, inflated space structures.

Living in the Oort seems like the space age equivalent of wanting to live in the desert, or setting up a small, isolated commune in the country. A romance. Why assume because you seem to be alone, you will be left alone?

Rob Flores March 26, 2013 at 13:24

Staying positive, Like to the idea to try develop infrastructure to mine
ice bodies in the KBO and beyond. I think it’s a question of efficiency,
how much energy does it take to sift through cometary material, and what
is the yield per ton. I am not sure if surface harversters would be cost effective, with nanotech who knows?

An alternative: if you have efficient heating sources.
It might be possible to make it easier to harvest volatiles from Ice balls.
in the following manner. Taking your 1km dirty ice ball and drilling to the
core. If you create a heat source at the core and liquefy say 15% of the
mass. Then spin up the ice ball. Won’t that create a centrifuge effect?
accumulating in a concentric shells of various materials accoding to their
mass? If the heat source is turned off and the spin remains, then wont
you have VEINS, concentric veins of valuable materials when the core
cools off and spin removed.? As a bonus you could use the
Tuneled out veins near the core as a base, if you spint it again.

JoeP March 26, 2013 at 15:18

I agree with some of the posts here that are a bit critical of solar energy being the energy source that far out in the solar system.

It doesn’t make much sense to collect such something with such poor energy density.

That leave us with fission and fusion. Both are optimal for deep space. Aneutronic fusion would be the best choice, if we ever develop a powerplant, such as Polywell.

Also, if I recall correctly, our theory about the relative rarity of uranium in the outer solar system is pretty much based on meteor and cosmic dust analysis. That said, we do not know for sure until we start sampling some outer solar system bodies. Maybe there are some dwarf planets out there that have enough heavy elements to make mining for fission fuel worth while.

Adam March 26, 2013 at 16:33

Of course there’s the rather more exotic lure of Pluto-sized objects that might out-number the stars 100,000-to-1. A million cometoids per Plutid (since “pluton” and “plutoid” have different meanings now) might allow the Comet-Riders to have their own centres of civilization. Also there should be a substantial population of interstellar cometoids on all sorts of trajectories which might appeal to those wanting a slow escape from the Oort Cloud.

If we can pipe light from the Sun, then there’s plenty to go round – but that’s a challenge for future engineers…

GaryChurch March 26, 2013 at 17:28

“Aneutronic fusion would be the best choice, if we ever develop a powerplant”

I am a critic of fusion reactors- not fusion. It takes the gravity of a star or the power of a fission bomb to efficiently light off a fusion reaction. I doubt it will ever work as a continuous power supply. Basic physics. Then why have we been trying all these years?
Weapons research on the sly.

“-why not mine the comet robotically-”

Because nothing with so many moving parts will last very long without a human technician keeping the gears turning.

“I do not see the advantage in living light days and months from everyone else.”

Survival colony. Several separate populations in case the world ends.

Danangel March 26, 2013 at 22:44

Reverend Richard Prichard talks about “significant unexplained heat signatures” in the Kuiper Belt. Can someone explain what this is about? It would be very interesting, if true. Thanks.

Andrew W March 27, 2013 at 0:38

I can’t see how EROEI can be positive for mirrors focusing light from such a distant sun.

Andrew W March 27, 2013 at 0:40

… Though I see no problems in using solar concentrators at a mere 40AU from the Sun.

ljk March 27, 2013 at 0:44

Reverend Richard Prichard said on March 26, 2013 at 10:44:

“We might have alien colonizers in our own backyard. The fact that we have detected several Kuiper-Belt objects with unexpected and substantial red excess (infrared heat signature) should be disturbing for two reasons: First, that there is substantial red excess; two, the alien colonizers are not bothering to hide their heat signatures.”

Where did this quote come from? And what is the evidence?

Could certain KBOs have natural internal activity such as Neptune’s moon Triton? Going along for a moment with the above quote that if we can detect heat signatures in the KB due to ETI activity: Suppose they are like Rama in Arthur C. Clarke’s famous SF novel, Rendezvous with Rama. They have no awareness or no interest in humanity but are in the KB for other reasons. Besides, what could we possibly do to an ETI so far out at the edge of the Sol system even if we wanted to threaten or attack them out of paranoia?

As for those other comments wondering how a group of humans could handle the confined spaces and other factors of being among those distant, ancient iceballs, these are the very issues I brought up in the recent discussions on Worldships. The humans who do venture at the edges and beyond the confines of our Sol system probably will not be like the humans of today, in part due to cultural changes by the time such missions happen and also because of the recognized need to modify people to handle the rigors of living in deep space.

In the event that unmodified humans do head out first into the KB and eventually the galaxy, I am willing to bet they will indeed be the “rogues” of society, such as cults, political dissidents, and even criminals. However, as far as mining and such are concerned, that may remain better done by machines guided by AIs.

Geoff March 27, 2013 at 2:44

In the present day, relatively energy-poor communities (i.e. the ones where most of us live) get most of their energy by importing energy-dense fuels. Instead of struggling to produce energy from meagre local resources, wouldn’t comet-settlers simply import uranium? (Or even fully-built, pre-fueled power plants, since a small community might not be capable of building such things on its own?)

Perhaps the future energy economy of the solar system will resemble that of present-day Earth, with the energy-rich inner system playing the role of the Middle East.

Marshall Eubanks March 27, 2013 at 11:35

What’s missing here is that there is increasing evidence that there are free ranging planets in deep space.Estimates range in the order of an equal mass in stars and free-ranging planets, with perhaps 10^5 Moon sized bodies per star,
http://arxiv.org/abs/1201.2687
and maybe 2 nomadic giant planets (Jupiter sized bodies) per star
http://arxiv.org/abs/1105.3544

A proportion of these nomadic bodies will be in the Oort cloud, either passing through or as residents. (A collapsing pre-solar Nebulae would capture some of the free-ranging objects in its vicinity, and much of that mass would probably remain in the outer reaches of the system, i.e., in the Oort cloud).

If there are 10^5 planets per star, then the nearest of these will be 5 – 10 thousand AU of the Sun, a much easier target for interstellar exploitation, especially as the larger of these bodies should retain deuterium and Helium-3.

Marshall Eubanks March 27, 2013 at 11:49

BTW, I too am curious about “Kuiper-Belt objects with unexpected and substantial red excess (infrared heat signature).” A search of google, bing and ADS does not reveal anything obvious.

GaryChurch March 27, 2013 at 12:14

“I am willing to bet they will indeed be the “rogues” of society, such as cults, political dissidents, and even criminals.”

I would take that bet; nuclear energy is going to be required to get out there and the only way said groups are going to get their hands on it is by stealing it- and in space you can run but you can’t hide. North Korea, Pakistan, and Iran have made the predictions of anti-nuclear activists in the 50′s valid. The powers that be are not about to let that happen in space.

The ultimate terrorist attack would be to divert a comet or asteroid toward Earth. This has actually been cited as a reason NOT to have impact deflection capability. I disagree- and accept that a United Nations of Space will be fanatics about controlling fissionable material.

GaryChurch March 27, 2013 at 12:22

-the only way said groups are going to get their hands on it is by stealing it-

I would add that the exception may be thorium- which is difficult to make into a bomb. But it is still going to be under tight control- you can do many things with a thorium reactor and they do require some bomb material to start.
A comet community might be “dropped off” by a spaceship along with some small thorium reactors and other equipment. Perhaps for research of some kind. I would like to visit Sedna just to say I have been there.

scott s March 27, 2013 at 13:13

Think the Reverand Richard Prichard was referring to S. C. Tegler and W. Romanishin, ‘Two Distinct Populations of Kuiper Belt Objects’, Nature, 392, 49-51. (1998) Gregory Lee Matloff referenced it as a possible reason to do an SETI search of the Solar System on a paper posted in Crowlspace.

Eniac March 27, 2013 at 23:13

Alex Tolley:

Living in the Oort seems like the space age equivalent of wanting to live in the desert, or setting up a small, isolated commune in the country.

Yes, exactly. And we do have both of these on Earth, in surprising numbers. It makes perfect sense that this would also happen in space, once the technical problems are solved.

ljk March 28, 2013 at 9:10

The Nature paper is online here, with only natural explanations for the KBOs appearance mentioned:

S. C. Tegler and W. Romanishin, ‘Two Distinct Populations of Kuiper Belt Objects’, Nature, 392, 49-51. (1998)

http://www.physics.nau.edu/~tegler/research/nature1.pdf

Adam Crowl posted on his blog Crowlspace Dr. Gregory Lee Matloff’s paper “The Re-Enchantment of the Solar System: A Proposed Search for Local ETs” here:

http://crowlspace.com/?p=1670

58 references at the end.

david lewis March 28, 2013 at 13:41

I doubt a civilization capable of colonizing such bodies would use solar. Having to build such a large structure for 1 MW is unreasonable. Now the PACER concept sounds more reasonable, but scale it up, way up. Find one of the Pluto sized bodies of which there might be 100,000 per star. Then forget a 1000 ft diameter cavity and consider instead a 20 km diameter cavity. Forget 50 kt explosions and consider something in the megaton range, say 5 MT.

Each 5MT explosion would release 5 million x 4.184 x 1 billion joules of energy, or 5811 TWh. Even if there were insanely low efficiencies, which I doubt there would be, you would still get at worse 1000 TWh per bomb. Build 5 such power plants, for safety and redundancy, with 1 bomb a day in each and you got between 10,605,075 and 1,825,000 TWh, or 10 to 60 times the current global usage of energy on earth. Now you’ve got a power source with which to run a civilization.

Over time the comets could be moved to be closer to such main bodies and be used to build space habitats.

Practical? Maybe not. But fun to think about.

scott s March 28, 2013 at 13:43

Yep, that one. The Matloff paper is the only one I’ve seen that suggests an artificial origin, although there may be some blogs I havn’t seen that make the argument.

Andrew W March 28, 2013 at 14:46

The rotational energy of planetoids can be harvested by sending mass from the surface down long tethers.

Dmitri March 28, 2013 at 16:45

On Earth there are many very isolated human populations – remote island in Philippines, Amazonas river banks and forest, Greenland, Island, Faroe Islands, Siberia deep forest, polar region. People live there for very various reasons but mainly energy resources and rear elements – gold, diamonds etc. In the places there are not wealth as in California but people have come to terms with challenges environment offers. Yes, the people there are happy as well. If we look at natural drivers which will lead to KBO and Oort settlements, we’ll see “meaning” be there.

Eniac March 28, 2013 at 23:34

Andrew W:

The rotational energy of planetoids can be harvested by sending mass from the surface down long tethers.

Right. Also: gravitational and orbital kinetic energy could be harvested by bringing planetoids together and coalesce them into bigger ones.

GaryChurch March 29, 2013 at 11:45

“Build 5 such power plants, for safety and redundancy, with 1 bomb a day in each and you got between 10,605,075 and 1,825,000 TWh, or 10 to 60 times the current global usage of energy on earth.”

And if you could make a He3 bomb work that gave off electrical energy you would do away with the entire generator complex. Transmit it to close by habitats and you have a little solar system without a sun.

Brett Bellmore March 31, 2013 at 18:06

I’m not at all sure scaling up the size gains you more in efficiency than scaling up the number of PACER plants gains you in redundancy. You’re going to want a good deal of “waste” heat to keep your habitats warm anyway. (Mind, it’s all destined to be “waste heat” in the end, courtesy of thermodynamics.)

PACER does not strike me as so much “the” way Ort cloud settlements would generate their power, as a demonstration that, in principle, fusion power is absolutely not infeasible. Given that we know how to do it already…

Nuclear power is understandably under serious restrictions on Earth. We live in a common biosphere with our industry, rather than hermetic bubbles. We have plenty of options aside from nuclear for our power needs. And our power needs are, per capita, fairly modest.

In space the considerations are rather different: The sealed nature of space habitats makes accidental nuclear contamination much less of an issue, especially as they’d exist in a moderately challenging radiation environment to begin with. There are no fossil fuels, and once you get past the inner solar system, solar power becomes infeasible, leaving only nuclear. (And, yes, stored angular momentum for larger bodies, but this is inherently not a very dense source of energy.) And energy requirements will be greater due to the lack of already provided heat and light from the environment, and the massive energy requirements where travel beyond the body you’re currently on is involved.

I’m expecting that, once any sort of self-sufficient settlements exist in space, they will get quite used to the routine use of nuclear energy, and much more casual about it, and won’t let ground based governments impose irrational restrictions on them.

And, after all, those restrictions aside, it’s not as though fission were particularly difficult, and fusion will probably be in routine use before we start colonizing the outer solar system, too, with people familiar with how to exploit it. The knowledge of how to build fusion bombs, for instance, can’t be kept out of the public domain forever.

And that alone provides a strong motive to leave the inner solar system, because with that knowledge widespread, the inner solar system is likely to not remain a very free place. There are a lot of liberties we can take for granted just exactly because we don’t know how to build city destroying weapons in our garages…

GaryChurch April 1, 2013 at 13:03

“There are a lot of liberties we can take for granted just exactly because we don’t know how to build city destroying weapons in our garages…”

I will go with Stephen Hawking on this one and admit I am more afraid of lab equipment than radioactive material. Unlike some who post here who seem to be knowledgable about epidemiology and biology and have doubts, I am fairly convinced that bioterror can do us all in.

An engineered pathogen or an impact are my first two worries and the unknown event- just one example being a new volcanic epoch, is my third.

Our collective problem IMO is our optimism bias- an evolutionary mechanism that keeps us thinking we can make it no matter what. These blinders probably evolved alongside self-awareness to keep us from worrying about how “all stories end” to paraphrase Hemingway. If we do not address the inevitable extinction event it is how our collective story will end. There is a movie called “Finding a friend at the end of the World” about that rock or ball of ice discovered on it’s way here one day. I have not seen the movie. But I have seen “The Road” and that was enough to put the fear into me.

Brett Bellmore April 1, 2013 at 20:18

“I will go with Stephen Hawking on this one and admit I am more afraid of lab equipment than radioactive material.”

A reasonable view, IMO; The point I’m making is that the nature of living on Earth with ever improving technology seems likely to drive ever more restrictive polices. You can already see it happening, when I was a kid you could walk into any pharmacy and stock a decent chemistry lab, even if you had to order some things. My son would probably get sucked into the juvenile justice system for some of the things I got extra credit for in high school chemistry. Order lab glassware for your home and a SWAT team will probably kick your door down at 3AM a week later.

It’s likely to be different in space communities, with the need for widespread advanced tech, and in some respects a more resilient environment. (Though only in some respects.) And that may drive exactly the sort of conflict between ground based society and space society which would drive people to colonize the outer solar system to get beyond the reach of planetary governments.

GaryChurch April 2, 2013 at 12:31

“-that may drive exactly the sort of conflict between ground based society and space society which would drive people to colonize-”

I think using past historical events as examples of what may happen in space are not valid. Interesting, but space is not an ocean- it is a hard vacuum seething with radiation- no king george and 13 colonies are likely.

Brett Bellmore April 2, 2013 at 18:10

In some respects the differences between space and the Earth’s surface favor runaway colonies: On the Earth, you can only get so far away from the “King” before you start getting closer again. (And it hasn’t been far enough for a good long time.) While in space, not only can you get arbitrarily far away, once you start moving you can KEEP getting further away.

The chief unfavorable difference is that we can’t yet “live off the land”. And until we can, it will be so clearly impossible for any colony to be independent that I doubt any would try. But I think the necessary technology is not so far distant, more a matter of decades than centuries.

GaryChurch April 3, 2013 at 11:43

“-we can’t yet “live off the land”.

Not to argue just to keep arguing with you Brett (even though it is fun) there may be only a few problems. The first is excavating underground habitats on the Moon since it is only from the Moon that nuclear missions of deflection or exploration will be launched. In Dandridge Cole’s Beyond Tomorrow, nuclear weapons are used to blast caverns under the surface of another body.

If I was to pitch a book it would be a revisioning of Dandridge Coles, Beyond Tomorrow. I must have seen that book when I was in elementary school because so much of what is in that book was in my head from an early age. I believe a nuclear power plant- a small one- could keep warm and light up sunlamps in an underground habitat. There are raw elements and with enough energy plasma converters can recycle metabolic waste. A sports arena sized cavern maintained as an oxygen garden could support a small population.

In regards to hypogravity debilitation, in my opinion these settlements on low gravity bodies will all feature a circular train- actually a spinning apartment building on the outer edge of the spherical under ground/ice habitat. What is needed is water most of all. In Earth orbit or closer to the Sun the opportunity to harvest solar energy is huge and nuclear power may not even be necessary. The Moon has ice deposits and is the place to launch nuclear missions to colonize other moons. I would start building on Neptune’s largest moon, Triton. It is way out there.

Brett Bellmore April 3, 2013 at 20:06

Regarding excavating cavities on the Moon, it appears that lunar lava tubes have already been located, and in the Moon’s lesser gravity, they have the potential to be quite large enough for underground habitats.

I agree with the circular train concept. IMO, often expressed, the greatest unresolved issue for human colonization of space is exactly how much gravity we need for health. It’s a crying shame that nobody has yet built the sort of spinning space station needed to do sustained fractional G health studies.

GaryChurch April 3, 2013 at 21:45

“-lunar lava tubes have already been located,-”

Nowhere near the ice unfortunately- and the ice is what makes a Moon base practical. My plan B would be to put a swimming pool 15 feet deep on top of a natural crater; this would shield the base from radiation. Conventional explosives could be used to dig side tunnels.

“-the greatest unresolved issue for human colonization of space is exactly how much gravity we need for health-”

I can resolve that for you; exactly how much gravity we evolved in is how much we need for health. I can also resolve the radiation issue; how much shielding is necessary? The amount that provides Earth levels of radiation.

The way to succeed is to provide an Earth environment. The way to fail is to go cheap and lower these gravity and shielding requirements. The way to succeed is to use nuclear propulsion and to launch from the Moon. They way to fail is to use chemical propulsion and to launch from Earth.

Eniac April 5, 2013 at 22:17

Gary Church:

I can resolve that for you; exactly how much gravity we evolved in is how much we need for health.

People have lived for years in zero gravity with very manageable side-effects. So, unless in your vocabulary “need” means the same as “nice to have”, you are dead wrong.

The same goes for radiation. We have discussed that one to death, already. Apparently without much success.

GaryChurch April 7, 2013 at 16:55

“-years in zero gravity with very manageable side-effects-
The same goes for radiation.”

Like the guy who smoked 2 packs a day for 60 years and did not get cancer- your idea of “success” has more to do with playing roulette at a casino than space travel.

There is no way to prove that Sally Ride did not get cancer from her occupation. All the other 400 odd astronauts will die eventually and how those numbers add up will be interpreted according to each evaluators own agenda.
The history of industry in regards to occupational hazards make the correct course crystal clear.
Shortening lives is too high a price. We need to do it right, not go cheap and laugh at the losers in the statistics game who end up in hospices.

Eniac April 9, 2013 at 3:20

It will be a while until space travel is completely risk free. You seem to be saying that we should not go until it is. That might well mean we will never go.

GaryChurch April 9, 2013 at 20:08

“You seem to be saying that we should not go until it is.”

Not at all. Space is an extremely dangerous place; you go on multi-year missions it is not like low earth orbit or going to the moon.

After, say, 4 years on a mission to the outer system- you can be healthy and ready for any emergency or you can be debilitated and irradiated from zero gravity and cosmic rays. You can also spend decades out there (coming home occasionally for some R&R) but not if you are going out in a tiny tin can- humans have psychological limits as well as quickly accumulating a lifetime dose that ends any more trips.

GaryChurch April 10, 2013 at 3:50

“It will be a while until space travel is completely risk free.”

It just became risk free because there will be no space travel. The space age is over. Bolden has announced no lunar operations and without a Moon base we will no be launching any missions…..anywhere.
It is over.

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