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The Closed Loop Conundrum

In Stephen Baxter’s novel Ultima (Roc, 2015), Ceres is moved by a human civilization in a parallel universe toward Mars, the immediate notion being to use the dwarf planet’s volatiles to help terraform the Red Planet. Or is that really the motive? I don’t want to give too much away (and in any case, I haven’t finished the book myself), but naturally the biggest question is how to move an object the size of Ceres into an entirely new orbit.

Baxter sets up an alternate-world civilization that has discovered energy sources it doesn’t understand but can nonetheless use for interstellar propulsion and the numerous demands of a growing technological society, though one that is backward in comparison to our own. That juxtaposition is interesting because we tend to assume technologies emerge at the same pace, supporting each other. What if they don’t, or what if we simply stumble upon a natural phenomenon we can tap into without being able to reproduce its effects through any known science?

Something of the same juxtaposition occurs in Kim Stanley Robinson’s Aurora (Orbit, 2015), where we find a society that has the propulsion technologies to enable travel at a pace that can get a worldship to Tau Ceti in a few human generations. We’ve discussed Aurora in these pages recently, looking at some of the problems in its science — I’ll let those better qualified than myself have the final word on those — but what I found compelling about the novel was its depiction of what happens aboard that worldship.

Because it’s not at all inconceivable that we might solve the propulsion problem before we solve the closed-loop life support problem, and that is more or less what we see happening in Aurora. A worldship could house habitats of choice, and if you think of some visions of O’Neill cylinders, you’ll recall depictions that made space living seem almost idyllic. But Robinson shows us a ship that’s simply too small for its enclosed ecologies to flourish. Travel between the stars in such a ship would be harrowing, as indeed it turns out to be in the book. Micro-managing a biosphere is no small matter, and we have yet to demonstrate the ability.

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Image: The O’Neill cylinder depicted here is one take on what might eventually become an interstellar worldship. Keeping its systems and crew healthy is a skill that will demand space-based experimentation, and plenty of it. Credit: Rick Guidice/NASA.

In Baxter’s Ultima, what happens with Ceres is compounded by the fact that just as humans don’t fully understand their power source, they also have to deal with an artificial intelligence whose motives are opaque. Put the two together and you can see why the movement of Ceres to a new position in the Solar System takes on an aura of menace. Various notions of a ‘singularity’ posit a human future in which our computers are creating entirely new generations of themselves that are designed according to principles we cannot begin to fathom. What happens then, and how do we ensure that the resulting machines want us to survive?

With Ceres very much in mind, I was delighted to receive the new imagery from the Dawn spacecraft at the present-day Ceres (in our non-alternate reality), showing us the bright spots that have commanded so much attention. Here we’re looking at a composite of two different images of Occator crater, one made with a short exposure to capture as much detail as possible, the other a longer exposure that best captures the background surface.

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Image: Occator crater on Ceres, home to a collection of intriguing bright spots. The images were obtained by Dawn during the mission’s High Altitude Mapping Orbit (HAMO) phase, from which the spacecraft imaged the surface at a resolution of about 140 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

We’re looking at the view from 1470 kilometers, with images offering three times better resolution than we had from the spacecraft’s previous orbit in June. Two eleven-day cycles of surface mapping have now been completed at this altitude, with the third beginning on September 9. All of Ceres is to be mapped six times over the next two months, with each cycle consisting of fourteen orbits. Changing angles in each mapping cycle will allow the Dawn researchers to put together 3-D maps from the resulting imagery.

So we’re learning more about the real Ceres every day. Given our lack of Baxter’s ‘kernels’ — the enigmatic power sources that energize his future civilization as well as the unusual but related culture they encounter — we may do better to consider this dwarf planet as a terraforming possibility in its own right, rather than a candidate for future use near Mars. On that score, I remind you of Robert Kennedy, Ken Roy and David Fields, who have written up a terraforming concept that could be applied to small bodies in or outside of the habitable zone (see Terraforming: Enter the ‘Shell World’ for background and citation).

It will be through myriad experiments in creating sustainable ecologies off-world that we finally conquer the life support problem. It always surprises me that it has received as little attention as it has in science fiction, given that any permanent human presence in space depends upon robust, recyclable systems that reliably sustain large populations. Our earliest attempts at closed-loop life support (think of the BIOS-3 experiments in the 1970s and 80s, and the Biosphere 2 attempt in the 1990s) have revealed how tricky such systems are. Robinson’s faltering starship in Aurora offers a useful cautionary narrative. We’ll need orbital habitats of considerable complexity as we learn how to master the closed-loop conundrum.

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  • Richard September 10, 2015, 11:19

    Really entertaining two books from Baxter. I loved the cliffhanger when Proxima ended and when the Romans entered the storyline (SPQR. I loved it even more because I went to Rome just when reading Ultima!) . Even though the storytelling of Ultima feels a bit hurried in the end I still enjoyed it thoroughly!!

  • BRS September 10, 2015, 12:24

    “It will be through myriad experiments in creating sustainable ecologies off-world that we finally conquer the life support problem.”
    Through modifying the passengers to simplify or eliminate life-support requirements, the need for complete, functioning ecosystems to accompany them may be abrogated. The “myriad experiments” needed to perfect advanced biotechnologies such as brain/machine interfaces or novel organs with enhanced metabolic capabilities (such as synthesizing “essential” amino-acids) would have additional advantages such as enhancing productivity, eliminating suffering and saving lives that would be realized fully as much here on Earth as on any prospective colonization mission.

  • Hop David September 10, 2015, 12:26

    One atmosphere is about 100,000 newtons/square meter. Mars gravity is about 3.7 meters/second^2, so each kilogram exerts 3.7 newtons. To achieve 100,000 pascals, there must be a very tall column of air over each square meter. A column massing 27,000 kilograms.

    Now let’s look at an O’Neill cylinder 8000 meters in diameter and and 32000 meters long. Filling this volume with air at density of 1.225 kg/cubic meter would take 1.61 e12 kg of air. Cylinder surface excluding end caps is 8.04e8 square meters. So we need 2450 kg of air for each square meter of real estate.

    So for this sized O’Neill cylinder we get 11 times as much earth pressure real estate per kilogram of air than Mars.

    An 8 kilometer diameter O’Neill cylinder is very ambitious! Near term habitats will be much smaller. A 1 kilometer diameter O’Neill cylinder would need 306 kg of air per square meter. So a kilogram of air gets us 88 times as much real estate as Mars.

    So here is my suggestion. Mars atmosphere could be harvested with a scoop at the bottom of a Phobos anchored tether. These harvested volatiles could climb a Phobos elevator. The top of a Phobos elevator could throw Martian volatiles to the Main Belt where they would do much more good. Over millenia or even centuries we might luna-form Mars thus making it a more useful body.

    Two related blog posts:

    http://hopsblog-hop.blogspot.com/2014/02/terraforming-mars-vs-orbital-habs.html The numbers in this post assume Mars volatiles remain where they are. This differs somewhat from the calculations above that compare kilograms of air per square meter on a planetary surface vs within a cylinder.

    http://hopsblog-hop.blogspot.com/2015/06/phobos-panama-canal-of-inner-solar.html Phobos is ~1.1e16 kilograms relatively deep in Mars gravity well. It is well positioned to be the anchor of a very able sling. A sling that could thrown stuff to the Main Belt or down to Earth. This sling would also make Mars much more accessible.

  • Michael September 10, 2015, 12:34

    In order to bring Ceres close to Mars you would need to change its velocity by about 6.2km/s, that is a serious amount of momentum change. Around 5 766 000 000 000 000 000 000 000 kg.m/s! If D-D fusion rockets are used with an exhaust velocity of 20 000 km/s and 100% efficient you would need 288 300 000 000 000 000 kg of fuel ejected. There is not enough Deuterium in Ceres to allow for the transfer and it would be better to para-form Ceres or use it as a dumping ground to soak up all those pesky menacing asteroids.

  • Alex Tolley September 10, 2015, 12:46

    I’ve read his “Proxima” where teh kernel power sources have opened up teh solar system. In many ways, he is returning to his early work “Anti-Ice” positing a magical power source.

    As for terraforming Ceres as a “shell world”, it still seems more reasonable to build habs that offer full g and Earthlike conditions. The habs could even be built largely of reinforced ice (like pykrete) to shield the inhabitants from radiation and meteors. The habs can not only be individually tailored to climatic conditions, they prevent single point of failure, allowing the inhabitants to get to another habitat in the case of an major accident.

    What we need to know from Ceres is an inventory of elements and minerals, so that we can determine what it is lacking in order to “terraform”. My guess is that it could be a largely robotic mining facility long before humans decide to live on or near it. It could export water and possibly organic carbon to space industries and space tourist destinations at a potentially lower cost than other sources.

    I hope that by the end of this year we will have more information on the composition of those bright spots, as well as some answers on composition.

  • Brett September 10, 2015, 13:10

    In the case of Aurora, it was an outgrowth of KSR’s premise that human beings need exposure to biodiverse environments (like the Earth), lest they otherwise weaken – the setting has the same “sabbatical” idea that 2312 had. If you don’t think that’s a problem (or decide that getting to the stars reliably is more important than shorter life-spans), then you could probably rely more heavily on mechanical systems with lots of redundancy to maintain life-support.

    @Alex Tolley

    That’s what I’m thinking as well. Honestly, by the time you’re seriously thinking about “hollowing out Ceres”, you probably have the technology and space capabilities to strip apart small asteroids (which are only weakly held together in the first place) and turn them into habitats anyways. The only thing Ceres would offer is free radiation shielding and a very small amount of free gravity (as in 0.03 g).

    I’m rather skeptical they’ll ever exist unless serious life-extension/medical immortality becomes common on Earth for humans, but that’s another topic.

  • Michael September 10, 2015, 14:31

    I don’t believe the closed loop problems is as great a problem as people think. So long as you have energy and plenty of it you can use it to re-stabilise an environment, say for instance the enclosure leaks air we could use electricity to break water apart for oxygen to re-pressurise the enclosure. A lot of the rocks could be made of high nitrate content which again could be used to form the nitrogen, as long as you use materials that have multiple uses it allows for a lot of redundancy.

    As for Ceres there is plenty of water to make an oxygen atmosphere. It looks like Ceres has a lot of dust on its surface, maybe hundreds of meters thick from the constant rain of materials from the asteroid belt.

    If we smoothed the surface of dust over and deposited a layer of suitable metals on top of this dust to a sizable thickness we could then remove the dust from underneath and put it on top to act as a pressuriser. We then decomposed some water at the same time to form a supportive oxygen atmosphere underneath. 1 g environments could be formed on the surface in the shape of rotating torus’s, eventually we could melt the whole ice shell to form a water world for fish and the like with us living on the outer shell in comfy 1g environments.

  • Andrew Palfreyman September 10, 2015, 15:20

    I have never understood why it’s thought that a shell could be stable. The gravitational potential energy of the state with one side of the shell touching ground is lower than the gravitational potential energy of the spherically symmetric state.

  • Larry Kennedy September 10, 2015, 15:28

    To me taking the biosystem itself into the cosmos would be more important even than the mark one humans that were included.

  • Matt September 10, 2015, 16:37

    “Because it’s not at all inconceivable that we might solve the propulsion problem before we solve the closed-loop life support problem…”

    I think this is something we could start researching here on Earth, before we ever try them off-world. These could start small and grow incrementally. Since we would still be on Earth the danger to the participants would be small. We could not simulate the radiation or low gravity we would need to deal with off Earth, but we could still learn a lot.

    I hope some researcher takes this up.

  • Hop David September 10, 2015, 16:37

    Shell worlds are mega-engineering projects where payoff is postponed until a huge investment in time and energy is invested. Implausible IMHO. I haven’t closely examined the arguments in the prior post, but I’m also of the opinion a globe encompassing shell would have formidable engineering challenges.

    Near term any human habitation will be burrowing. Whether humans are on the moon, mars, or asteroids, they’ll be in artificial environments buried in regolith. For gradually expanding populations, we’ll continually enjoy returns on our investment as incremental growth proceeds. This is plausible.

    Ceres can eventually be hollowed out. Not by a single mega-engineering project, but by gradual growth of sub Ceresean tunnels.

    Unlike generation star ships, habs in the main belt can enjoy commerce with neighboring habs as well as with Earth, Moon and Mars. Eco-systems would not have to be completely closed and self sufficient.

    Same goes for gas giant moons and Kuiper Belt Objects. We can spread out to 40 A.U.and we’d still have trade with neighboring city states. Humanity expand for thousands of years without the need for totally self sufficient artificial eco-systems.

  • Wojciech J September 10, 2015, 17:18

    Out of the top of my head two other SF books that deal with the necessity of upkeeping biosphere and issues facing attempt to transport Earth’s biological system into closed environments are Bruce Sterling’s “Schizmatrix” and Paul J. McAuley in Quiet War series. “Schizmatrix” has some paragraphs about ecological system failures on habitats and how they need to be kept sustained.
    McAuley is a botanist and his books have lengthy descriptions about how difficult and detailed the process is for transferring biosphere into space from Earth, going as far as detailing processes involving soil and making it liveable. It actually forms an important part of the main story.
    Amusingly both books have many elements that Robinson seems to have copied.
    Personally I don’t think interstellar exploration will be done by generation ships so don’t consider that problem vital, but still it is important for initial stage of Solar System colonization and eventual habitat building in other explored systems.

  • Charlie September 10, 2015, 18:32

    Interesting thing about Aurora was the fact that the authors seem to indicate that he wasn’t really too big of a fan of interstellar travel. And he makes a good point it would be very, very difficult to find any body which would give a good approximation to what earth is like. While one can speak of terraforming a planet and all that there is always the problem that there would be a difference in gravity and that the people on it would begin to diverge from the rest of the human race. Along with, many other, many other problems

  • Alex Tolley September 10, 2015, 19:18

    Livuing beneath Ceres surface in habs is a good idea, but you will either have to live in low g, or build centrifuges. How hard would it bee to do that with all the necessary interfaces compared to building a rotating structure in free space? If we can build centrifuges easily, then this is definitely the way I would go, as they could be housed in airtight, insulated habs, and be lightweight open structures with minimal mass – just a frame and flooring strong enough to support the interior fixtures and fittings, the crew and the systems to adjust the mass balance to prevent wobbling (plenty of water for such systems). I would even use the Ceresian ice for the main airtight walls of the hab, with foamed insulation to keep it warm inside.. Spread the habs out enough with lots of air-locked connections and it would be resilient enough even in the face of an asteroid impact.

    For such a vision, we are going to need to know what the interior structure of Ceres is like. A relatively undifferentiated snowball, or an icy crust over a slushy/watery ocean. We will also need to know the structure if the purpose is to extract water. Scrape the subsurface ice or drill to a more liquid layer and pump up the water/slush for processing and transport.

  • J. Jason Wentworth September 10, 2015, 20:02

    Paul Gilster wrote (in part):

    “It will be through myriad experiments in creating sustainable ecologies off-world that we finally conquer the life support problem. It always surprises me that it has received as little attention as it has in science fiction, given that any permanent human presence in space depends upon robust, recyclable systems that reliably sustain large populations.”

    My guess is that most science fiction story and screenplay writers are “hardware people,” for whom the ‘mushy biology problem’ (keeping humans and any brought-along food plants alive in spaceships, space stations, and colonies on other worlds) is an annoying problem that they prefer to solve through straightforward engineering rather than by applying the more complicated, inter-related solutions that a botanist or a biologist would. Also:

    Real-life applications of such “brute-force” life support methods do work–nuclear submarines remain submerged for months at a time and keep their crews alive via simple engineering. Adapting that technology to space use (including regenerating oxygen from the carbon dioxide absorber, which was known technology in the 1960s but wasn’t implemented because it wasn’t necessary even for lunar missions) and adding centrifugal gardens to produce fresh produce (hydroponic and/or aeroponic methods would work well, and would be compact and lightweight) would suffice for interplanetary missions and permanent space stations.

  • J. Jason Wentworth September 10, 2015, 20:23

    As an addendum to my comment above (I didn’t recall this until after I’d submitted it):

    Even the smallest, earliest space colonies that Dr. Gerard O’Neill and his study group designed (the Bernal Sphere and Hatbox types, in particular) were also designed to support their human, farm animal, and plant populations via straighforward engineering solutions that are already in use or are familiar. The Stanford Torus colony design also had this “mechanical”-type life support system. Their “rain” was to be supplied by pumped-water spray nozzles located above the farm areas and arbors, and the water–as well as the air–would have been filtered or re-processed so that they could be used over and over. Also:

    While the plant and animal selections were to be made with an eye toward having their cycles assist the maintenance of the colonies’ atmospheres, this was seen as a way of only reducing the level of artificial life support equipment that would be needed, which would reduce the colonies’ construction costs and recurring operational costs. The larger colonies (such as the 20 mile-long dual-cylinder habitats) were envisioned as possibly being able to house enough plants and animals (with sufficient diversity) for their natural biological cycles to maintain breathable atmospheres, with little or no artificial life support assistance being necessary.

  • Sara September 10, 2015, 22:00

    I am completely fascinated by those bright spots on Ceres. The overhead shot almost – well, nearly almost – implies that they might be underlit, or that they are subsurface light sources, almost like a subterranean city.

    Obviously, it’s NOT a natural formation… is it? Oh, come on! Where is your imagination? I think that moving a dwarf planet like Ceres is less practical than something more simple, such as using it as a way-station.

    Using Ceres as a means of terraforming Mars won’t do much good if Mars has no magnetic field to keep its atmosphere from being eroded by solar wind. And what is lying on the surface? The red dust of Mars, probably oxidized taconite or something similar. An article in Sky & Telescope some years ago – 1990s, I think – said that the orbiters found the entire surface of Mars to be magnetic. When the first set of people emigrate from Earth to Mars to set up housekeeping, they will be faced with practical problems such as whether or not there are nutrients in Martian soil that can support plant growth, and where to find and make use of water sources, if there are any. These are practicalities, not theories. Now what are you going to do with that? And in addition, a magnetic field is necessary to prevent destruction of brain cells. Since Mars doesn’t have that, how is that going to be dealt with?

    You have to find a way to control gravity on Mars or compensate for the lower gravity IF humans are going to use that little planet at all. Unless that is somehow dealt with, the habitat ideas don’t matter. It would be more practical to try to terraform Titan, starting with introducing O2 into its atmosphere, because right now, it’s just a planet with a methane envelope.

    Those bright spots on Ceres are… oh! I know! It’s a spaceport for the Colonial Marines.

  • Eniac September 10, 2015, 23:30

    I agree with Brett and Hop David. Even without considering how hard they would be to maintain, natural ecosystems are extremely inefficient as life support systems. We have long begun moving away from them. We get water from pipes instead of streams, air from vents instead of the wind, and we control our environment (temperature, humidity, particulate levels, etc) using elaborate HVAC systems.

    Many of us love being outdoors, but we do not need to be. We could quite easily stay indoors, all the time. I suspect at some point this will become common, even here on Earth.

    Thus, considering the many orders of magnitude of efficiency involved, space habitats will likely look like cities, growing “down” from a central, rotating hub in the form of hermetically sealed buildings. Or, as Brett has suggested, dug into the ground. In this latter case, we’d have to adapt to low gravity, too. Which, again, I think will be much easier than many here seem to think. No changes in human biology are necessary for any of this, just more advanced HVAC systems, really.

    Those habitats with the lakes and forests and back yards are dreams, and forever will be. Unless, that is, the ultra-rich build them just for fun, in spite of the economics, like the golf courses we find in deserts, these days.

  • Eniac September 10, 2015, 23:39

    Note that I am not forgetting that water does not originate in pipes, and air does not originate in vents. Once you receive them this way, it lessens the difference between the water originating in a mountain range 100 miles upstream, or in an icy asteroid parked nearby. Sure, in space we cannot just vent air inside from the atmosphere, but we can design an industrial plant that extracts it from raw materials, and reduce the need by efficient recirculation. A forest would be nice, but is not required and would be way too extravagant.

  • Eniac September 10, 2015, 23:41

    I made an attribution error: It was Hop David suggesting burrowing, not Brett. Apologies.

  • Jim Strom September 11, 2015, 2:51

    Why are exotic generation-ships better than the transit of biosuspension or biogeneration machinery? Why send a frail expensive space-terrarium? What advantage would such a ship have, upon arriving at an exoplanet, over a factory-ship that makes and raises humans from scratch, or over a ship that wakes up humans upon arrival after imperceptible passage of eons?

    And how much thought has been given to the question: what qualities would a ship need in order to allow _worthwhile_ lifetimes to pass within it?

  • Antonio September 11, 2015, 3:55

    I think we will master cryonics or other form of suspended animation much sooner than we start the first interestellar manned trip, so no need to build closed loop ecologies in ships. Also, another route to interestellar manned travel is production of artificial food and cure of aging, so the crew and passengers can live in an artificial environment during all the journey.

  • Cambias September 11, 2015, 7:53

    I suspect the closed-loop ecosystem will be solved by brute force: breaking down CO2 by chemical/electrical means and “printing” food. The fresh stuff from the farming decks will be a nice treat. And it’s looking more and more feasible to simply ship all but a skeleton crew in hibernation.

  • ljk September 11, 2015, 9:24

    J. Jason Wentworth said on September 10, 2015 at 20:02:

    “My guess is that most science fiction story and screenplay writers are “hardware people,” for whom the ‘mushy biology problem’ (keeping humans and any brought-along food plants alive in spaceships, space stations, and colonies on other worlds) is an annoying problem that they prefer to solve through straightforward engineering rather than by applying the more complicated, inter-related solutions that a botanist or a biologist would.”

    Not just the science fiction authors (who are still comprised mostly of white males) but the real space technologists as well. The idea of multidisciplinary fields working together is still a novelty to many on both sides of the fence. This is why I have more than a little concern about any long-term human space endeavors. NASA thinks having a few astronauts living aboard the ISS circling just a few hundred kilometers above Earth for one year is going to teach everything we need to know about a multiyear mission to Mars and elsewhere. I say camping in one’s backyard is a lot different than camping in a remote jungle or desert.

    The idea of the John Wayne attitude towards living and working in space needs to end, otherwise even a lunar colony is going to have major problems to say nothing of an interstellar multigenerational mission. Then again every human endeavor will have its flaws, the problem is in deep space the margin for error is far less than anything done on Earth, the only place humans are truly capable of surviving upon without major modifications.

  • Stan Erickson September 11, 2015, 9:27

    If you want to design a synthetic ecology, one of the first things should be incorporating feedback loops so that the system is self-sustaining, instead of requiring intervention. The idea now seems to be achieving an equilibrium, rather than a self-correcting system.
    By the way, is it even conceivable to have the OP ideas reversed, so that gravity is used as an energy source, rather than a sink (moving dwarf planets outward)?
    http://stanericksonsblog.blogspot.com/2015/06/hot-jupiters-whodunit.html

  • Hop David September 11, 2015, 11:06

    I’ve done a few drawings of spin habs built from asteroidal materials.

    http://hop41.deviantart.com/art/Sol-Comics-Page-8-193650847 The early spin hab might be a torus. Then by adding successive tori, it can be stretched to a cylinder. Clicking on the image will embiggen.

    http://hop41.deviantart.com/art/Sol-Comics-Page-1-193651395 Renderings of the same hab.

    In these illustrations I imagine parabolic mirrors to harvest sunlight. It would be a step towards a Dyson Swarm. Which, unlike a Dyson Shell, is remotely plausible. I know that even if every asteroid had a whopping big mirror, the surface area intercepting sunlight would be a tenuous cloud hugging the ecliptic plane. But even if asteroid cities intercept only a tiny fraction of the sun’s output, that still increases humanities available energy by many orders of magnitude.

    Ceres would be different than these illustrations. Besides spin habs embedded in Ceres’ surface I also imagine spin hab tori beneath Ceres’ surface. Unlike a planet, we can burrow quite deep. It might even be possible to burrow all the way to Ceres’ center. Thinking we’re restricted to Ceres’ surface is a bad habit from a planetary chauvinist mindset. For asteroidal real estate, *volume* is the metric, not area.

  • Larry Kennedy September 11, 2015, 11:17

    @ Alex Tolley
    I don’t see centrifuges on small bodies as any larger problem than others. Really just a subway train with a track of equal length. No reason to believe everything needs to be on the train. Unfortunately the experiments haven’t been done to determine how much time at full gee is actually needed.
    It would’ve been nice to have had a short radius centrifuge on the space station. Work stations or exercise stations could be designed to get around the short radius problems. Then we would’ve had data instead of just guessing.

  • Hop David September 11, 2015, 12:11

    Larry Kennedy wrote “Unfortunately the experiments haven’t been done to determine how much time at full gee is actually needed.”

    Larry, I agree an orbital centrifuge is desirable. At this time we only have two data points: Full g and zero g. It would be good to test the effects 1/6 g and 1/3 g to give us an idea if humans could thrive with lunar or Martian gravity.

    Do we need any time at all in full g? This is still an open question. Again, we only two data points.

    I would want enough g for water to flow downhill. Conventional plumbing and easy hygiene would be a big morale booster. It’d also help with the circulatory problems associated with weightlessness and other bodily functions — it’d be good for sinuses to drain, for example. I suspect lunar gravity or even less is adequate for this.

    Another goal is to prevent muscle and bone atrophy. Valeri Polyakov has already demonstrated exercise can mostly mitigate atrophy associated with weightlessness.

    There are folks here on earth who live most of their sedentary lives in the tiny volumes of their apartments. They have demonstrated muscle and bone atrophy can occur even with a full g.

    In my opinion, a full g is not needed for human health. Again, I acknowledge this is still an open question.

    If less than a g is needed for human health, that makes adequate spin habs more doable.

  • Alex Tolley September 11, 2015, 13:01

    @Larry – so you envisage a tunnel with tracks that a circular train runs on. The train is joined end to end so that there is no major net force on the tunnel walls.

    Nice idea, but how do you get on an off this thing while it is moving? If the tunnel is a cylinder, I can see a possibility of walking up a ladder or tube to the center, but that seems to defeat the idea as I visualize it, because it then becomes a centrifuge again, albeit with the drive in the train/walls rather than at the axis.

    Another possibility is to have a parallel track so that an elevator “train” can speed up/slow down to allow transfers from a fixed point entry to the train.

    Any further thoughts on how this might work? I an always looking for elegant solutions that use minimal materials for such ideas, as I expect much of the technology will need to be transported from earth, rather than made locally. So tensioned fibers rather than steel compression members, inflatable skins rather than rigid metal hulls, tensioned fabric floors rather than rigid metal or plastic, growing materials like plant fibers rather than bulk materials from earth, etc, etc.

    Karl Shroeder’s Virga series inspired me in this regard – steam punk-ish wood and steel centrifuges in a large bubble of air as habitats. Low tech rather than high. Our Ceres inhabitants will need to use ISRU as much as possible, with simple manufacturing technology, e.g. looms for making fabrics, spinning wheels to make fibers, and so forth. Simple stills for making alcohol from easily grown starchy vegetables. High tech where it is needed, like computers, but low tech for habitat expansion.

    Unless Ceres will be run with lots of control from Earth, like the ISS, I would expect that our miners will be minimal equipment and facilities to do their job profitably, but being human they will endeavor to make their lives as comfortable as possible for their tour or longer.

  • Alex Tolley September 11, 2015, 13:23

    Simple tech for biology. IIRC, O’Neill proposed to deal with disease outbreaks in farm modules by spacing the module and heat sterilizing it. Simple, brute force method, not unlike using fire on Earth (worked for the great plague in London in 1666). Whether this really makes sense I don’t know, but he was a physicist which may have shaped his thoughts on the matter.

    Apart from experiments like Biosphere II, we really have very little knowledge of closed ecosystems at all. Cities are not enclosed, so really don’t apply as models. We may build closed arcologies on Earth as experiments to test out ideas before building ones in space. My guess is that we will stick to mixed systems – Earth foods with some small scale vegetable framing for fresh food. Air and water recycling will be physical/chemical with less than 100% efficiency so reserves will be needed. Good enough will be better than perfect if we want to get moving. Repairability will be important (The ISS water recycler regularly breaks down. So does the toilet on occasion). Having artificial gravity avoids the unknowns of of lack of g and makes living easier as well as allowing simpler appliances, furniture etc. If beds can be simple, gravity hung hammocks, that makes them easy to make and repair in situ.

    My 2 cents for human space living if robots are not sufficient alone.

  • Larry Kennedy September 11, 2015, 14:39

    @ Alex Tolley
    One of the first things to do would be to determine whether everyone would live on “the train” or would 4 or 6 or 8 hr. shifts do the trick. In the latter if you had plenty of power and energy recovery you could just “stop the train”.
    Of course given a comfortable radius there would certainly be lots of room and elevator car type transfer is what I had in mind. Logistics could even be taken care of this way. After all thousands of people at fairs, festivals and such are taken care of by small trucks. That’s another one of those design tradeoffs that would need to be worked out.
    Of course once you run with the idea you can go crazy with all the specifics of how to actually build it all.

  • Eniac September 11, 2015, 22:50

    Hop David

    Do we need any time at all in full g? This is still an open question. Again, we only two data points.

    To be fair, one of those data points if quite conclusive: Humans can live and work without any gravity at all (nor any time at all in full g) for more than a year.

  • Eniac September 11, 2015, 23:00

    I don’t think people will want to go on that gravity train, much less live in it. They’ll find funner ways to spend their time. Swimming in a “giant drop” spherical pool, perhaps, or playing weightless 3d ball games in elaborate 3d courts. Or flying around the city, with wings.

    Speaking of swimming, no matter the shape of the pool, I bet a lot of fun is to be had with low-gravity water.

  • Michael September 12, 2015, 2:50

    @Sara September 10, 2015 at 22:00

    ‘I am completely fascinated by those bright spots on Ceres. The overhead shot almost – well, nearly almost – implies that they might be underlit, or that they are subsurface light sources, almost like a subterranean city. ‘

    I am wondering if the central peak of the crater has been hit by an asteroid and shattered in a forward low inclined direction.

    ‘Using Ceres as a means of terraforming Mars won’t do much good if Mars has no magnetic field to keep its atmosphere from being eroded by solar wind. Now what are you going to do with that? And in addition, a magnetic field is necessary to prevent destruction of brain cells. Since Mars doesn’t have that, how is that going to be dealt with? ‘

    We can give some planets, asteroids and habitats magnetic fields by using superconductors at the poles, Mars is cold enough to use super conductors that we have today and the iron cores may aid the fields size. All that is ‘required’ after setup is a maintenance current which would be several gigawatts if even that. I was once thinking of an idea to deflect iron asteroids by using superconductor coils wrapped around their waists, the large iron content of the asteroid helping to create a huge field that could interact with the solar wind to move it about.

    ‘It would be more practical to try to terraform Titan, starting with introducing O2 into its atmosphere, because right now, it’s just a planet with a methane envelope.’

    Titan is just so cold.

    @Andrew Palfreyman September 10, 2015 at 15:20

    ‘I have never understood why it’s thought that a shell could be stable. The gravitational potential energy of the state with one side of the shell touching ground is lower than the gravitational potential energy of the spherically symmetric state.’

    As one side comes closer to the surface the density of the air beneath increases countering the gravity but there will be oscillations no doubt. there is also the possibility of large towers deep into the core of Ceres as the gravity is so low.

    @Alex Tolley September 10, 2015 at 12:46

    ‘As for terraforming Ceres as a “shell world”, it still seems more reasonable to build habs that offer full g and Earthlike conditions. The habs could even be built largely of reinforced ice (like pykrete) to shield the inhabitants from radiation and meteors. The habs can not only be individually tailored to climatic conditions, they prevent single point of failure, allowing the inhabitants to get to another habitat in the case of an major accident.’

    With the shell idea the torus’s could be embedded on the surface and as Hop David said inside the shell with each rotating torus connected at the hub by a pressurised tube system running all over the shell inlayers. We could possibly use ice bearings at the hub tube connectors which are very low friction and easy to repair. As for stiffening the shell it would have to be in a honeycomb configuration for added rigidity with the waste material inside these honeycombs.

    If we do not think big we will forever remain small.

  • Larry Kennedy September 12, 2015, 11:51

    @ Eniac
    The data also gives little hope allowing people to live at zero gee without serious effects.
    As far as the gravity train, even if proved necessary, I would be amazed if people didn’t spend a good deal of time “off the wheel”. I still harbor hope that much shorter periods of higher gees could take care of health effects.

  • Charlie September 12, 2015, 15:08

    Steps to Interstellar laser pushed propulsion and a 16 year trip to Alpha Centauri

    http://nextbigfuture.com/2015/09/steps-to-interstellar-laser-pushed.html

  • Abelard Lindsey September 13, 2015, 11:53

    Keeping its systems and crew healthy is a skill that will demand space-based experimentation, and plenty of it.

    Developing self-sustaining biomemes (for lack of a better term) will require lots of research involving considerable trial and error. The SSI people are well-aware of this issue. The good news is that habitats built near large asteroids do not have to be 100% self-contained in terms of resources to begin with. One can always mine the asteroid for more materials as the biomeme process gets more refined and closers to true recycling sustainability.

  • Larry Kennedy September 13, 2015, 13:15

    I would like to float an idea here that I previously posted elsewhere.

    We need to get a bunch of high school classes to build gloveboxes and design their own experiments.