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Envisioning the Interstellar Ark

Strange Paths offers a robust essay on the topic of interstellar arks, one that considers our future among the stars without warp drives or other breakthroughs that get us past the speed of light barrier. Star Trek and its ilk offer familiar, short-term travel analogous to our own relatively brief journeys in the Solar System. The real thing may be different:

The way toward stars becomes however quite unfamiliar if we consider that such Triumph of Physics could possibly not happen, and that the famous constant of Einstein c, the speed of light (3E8 m/s), represents an horizon speed which is impossible to exceed and which is even extraordinarily difficult to approach, so that we would begin to see outer space like it is seen by astronomers: a vastness compared to which that of terrestrial oceans is nothing.

The author looks at two alternatives, the first being a relativistic rocket able to take advantage of time dilation at velocities close to light speed so that the crew experiences a much shortened interstellar journey. Such a craft (the author assumes a vehicle driven by antimatter) is well beyond our technology, but it offers up the kind of mind-bending travel Carl Sagan was among the first to describe. Says Strange Paths, “Thus, in just 12 years of proper time (but 113,243 years for the stationary observer), which is a long time but still bearable in a comfortable spaceship, one could traverse the whole Galaxy, whose diameter is 100 000 light-years.” The relevant mathematical arguments are supplied.

But what energizes the essay is the long-haul ark, a vessel driven by a what the author calls thermonucleoelectric propulsion, channeling fusion plasma through a magnetic conduit for thrust. The beauty of the ark is that it is a self-contained world, housing its own society and capable of maintaining itself in stellar systems unlike our own. Thus the author’s choice of Epsilon Eridani as a target, it being relatively close to the Sun at 10.5 light years and, as a K2 star, not terribly dissimilar from ours.

Could a gas giant around Epsilon Eridani, even one in as eccentric an orbit as the one we now know to be there, provide satellites that could be used as a resource base for an interstellar ark? There seems to be no reason why not, though I think the author is overly pessimistic about the possibility of nearby terrestrial worlds, the Centauri stars now looking more and more promising in that regard, especially as we consider Proxima Centauri’s possible role in delivering volatiles to inner system planets around both Centauri A and B (if they do indeed exist).

But it will take another decade or so before we start to accumulate enough terrestrial-style worlds to draw even the most preliminary judgments about their frequency. Until then, speculation like this, richly detailed and backed by solid mathematical description, offers us a look at how humans can reach the stars with technology that could reasonably develop absent major breakthroughs in our understanding of physics.

On the societal level, the discussion of human psychology in such enclosed spaces is fascinating, and I would also offer up a paper by Edward Regis Jr. called “The Moral Status of Multigenerational Interstellar Exploration.” This one was in the Finney and Jones volume Interstellar Migration and the Human Experience (Berkeley: University of California Press, 1985). Regis considers the psychological and ethical questions interstellar arks present and finds no show-stoppers:

We conclude then that just as no rights of Earthlings are infringed by their not being included as passengers on a space ark leaving for the stars, no rights of star voyagers are infringed by their not living their lives on Earth. A multigenerational interstellar expedition is no more and no less morally permissible than the very existence of human life on our own planet.

Strange Paths has more to say about how life aboard an interstellar ark would be conducted, and how the ark can be constructed in such a way as to maximize livability in terms of environment and social interaction. And here’s something to ponder that may awaken old memories:

Compared to the Present, the spiritual horizon is identified to the horizon of social activity previously discussed. Arkonauts live a morally new situation, in lived and in long-term aims. They should develop an original mentality. The need of getting along would come first. The word trajectory reminds of “transient”. But such transient is a whole life and a whole civilization, with the result that the stellar goal will become almost secondary. The majority of individuals populating this travel will belong to a generation “not leaving, not arriving”. For this majority, the end of the way would just appear like a distant future. Certainly, in background the reach of targets will structure the community, but the stake making the happiness of the travellers will remain for the humankind its present.

The science fiction trope from way back is the interstellar ship whose inhabitants have forgotten their mission; indeed, they no longer recall that they are on a ship at all. Think Heinlein’s story ‘Universe’ (later part of Orphans in the Sky) or Aldiss’ Non-Stop (published here in the US as Starship). But we can hope for outcomes better than this. Alan Bond and Anthony Martin, of Project Daedalus fame, have written about so-called ‘worldships’ powered by nuclear pulse engines or solar sails, and Gregory Matloff has speculated on sail-driven craft on a 1000-year journey to the Centauri stars. These are voyages that may one day prove viable with manufacturing help from nanotechnology.

Strange Paths concludes this energizing essay with the thought that no matter how extravagant the propulsion and structural demands of an interstellar ark may be, the examination of its parameters now may somehow contribute to a future in which it happens. So it is with interstellar studies, which routinely posit technologies that are, at the least, next-generation, and extrapolate from them to show what could be done. We are in the lengthy but critical stage of base-building, creating the intellectual framework from which great things may one day grow.

Comments on this entry are closed.

  • andy February 20, 2007, 9:40

    Actually, I don’t think the author is being pessimistic about habitable terrestrial worlds at all. It depends how you define the word “habitable” – we must ask: “habitable by what?”

    If we require the target planet to be habitable by humans such that a self-sustaining colony could exist without prohibitive environmental control measures, that severely restricts the habitable zone: while planets in the outer regions of habitable zones could retain oceans, this comes at the cost of elevated levels of carbon dioxide in their atmospheres, which would not be pleasant for the colonists. There is then the issue of oxygen: an oxygen atmosphere on a terrestrial planet probably implies a native biosphere, which will at the least compete with imported organisms, probably more effectively since they will be adapted to the peculiarities of the precise atmospheric composition, radiation and chemical balances, rotation rates and orbital period. Not to mention how human biology and an alien biosphere would interact (anaphylaxis? poisoning?) The alien biosphere would presumably have its own feedback processes and “Gaia-homeostasis” which would tend to resist conversion to an environment suitable for Earth-derived organisms.

    I would suggest that human-habitable planets, as opposed to planets capable of supporting some form of biosphere, are very rare indeed. The best type of planet to colonise might be a young planet with photosynthetic organsims but before large-scale colonisation of the land surface by the planet’s biosphere, which would give the advantage of a pre-existing oxygen atmosphere but without so much competition on land for the crop-plants to deal with. How far would we need to travel to find such a planet?

  • Administrator February 20, 2007, 9:44

    Point taken, Andy, and you’re right that ‘human-habitable’ isn’t the same thing as ‘habitable’ in the broader sense!

  • Darnell Clayton February 20, 2007, 12:59

    Instead of an ark, wouldn’t it be more reasonable to develop worm holes to “cut the distance” between two objects?

    If humanity is to ever become an interstellar species, then we need to develop technology that can get us from point A to point B in a relatively short amount of time, otherwise it will take thousands of years to colonize our part of the galaxy with speeds barely approaching that of light.

  • Chris Wren February 20, 2007, 13:00

    My guess is we’d have to travel pretty far – and arrive on time. If travellers had arrived in our system a few months or years after the impact that wiped out the dinosaurs, they’d have found a much less hospitable world than the one their long range probes might have reported to them a century or so earlier!

    My guess is that we’ll have to “make do” with worlds that are less than ideal. Colonists might have to remain in orbit for decades while the world is prepared for them. The ideal situation would be to identify a borderline acceptable world (probably more of them out there than “just right” ones) and launch a swarm of autonomous terraforming robots to arrive a century or two in advance of the ark ship. This could be something as simple as a photosynthetic lifeform, or microbes that enjoy eating methane. It should be possible to get a pretty clear idea of what tweaking needs to be done to the target biosphere even before construction of the ark ship is complete.

  • Ron S February 20, 2007, 13:19

    One thing about these arks that I keep thinking about is… what is the destination?

    By this I don’t necessarily mean which exoplanet or similar physical place. As noted any reasonable trajectory means many generations worth of travel(*). This implies that life would have to be pretty good on the ark. If not there would be a catastrophe, whether it be sociological, medical, or whatever.

    So if life is good, and the ark inhabitants have no memory of Earth, and likely don’t pine for it, what will they do when they reach that brave new world? I suspect there is a strong probability they will look on the planet as a hostile or at least unappealing place, or at least some of them will. Even in the best possible scenario the personal risks would be higher on-planet for the colonizing generation than life on the ark.

    They could simply choose to stay on the ark, do a bit of exploring and replenishing of resources, beam back some data to mommy Earth, and then go and or do something other than become an exoplanet colony.

    (*) We don’t have a wormhole, couldn’t get to it easily if we did see signs of one out there somewhere, and we have no prospects of building one or even knowing if it is possible to build one if it is theoretically possible. It’s an interesting speculation but wholly unactionable. An ark can be planned now and perhaps even get to an actual design in the foreseeable future.

  • Adam February 20, 2007, 14:11

    Hi All

    The other problem of wormholes is that they’re not FTL by themselves – they have to be towed to your destination. If you’re waiting millennia for a wormhole to arrive anyway, why not travel along?

    There’s no guarantee that some kind of immortalisation process won’t be developed before an Ark launches, making “multi-generation” moot.

  • Warren February 20, 2007, 14:15

    There may be many reasons to go to the stars but I doubt that a need for finding living space is one of them. Given time, can’t we design and construct much better living spaces than even the earth itself; and probably way before we can talk seriously about a trip to Tau Ceti? Whatever happened to Gerard O’Neill? Out of fashion?

    Why will any naturally occurring “habitable” planet we find circling another star provide resources for a life more comfortable than is already available on the “ark” the day it is launched? Why would anyone able to build this ark have any need whatsoever to find ‘natural’ planets to live on no matter how common they are? (But especially when, as Adam suggests, they are probably extremely rare and would need much terra forming anyway). Anyone traveling in an ark through interstellar space is already living well there.

    We are on our way back to the moon to learn to “live off the land”, build living spaces for upper class tourists, then ships comfortable enough to live in for years in order to explore the solar system. The technology is under development now. Why contemplate a move to a “habitable” planet? We can probably design and build a paradise for billions in the oort cloud, in orbit around an earthlike planet, or wherever we want.

  • philw February 20, 2007, 21:19

    Include me in the group that believes that very Earth-like habitable planets where we could walkabout Star Trek style are rare and distant, like 1,000 LY or more. Uploading ourselves to AI aside, the good news is that we will have the ability to modify our genome to adapt to what we’d today call ‘unihabitable’ oceanic O2 planets today, ones with toxic levels of CO2 or whatever.

    Should C prove to be the ultimate law, there’s no question that some decedent form of humainit ‘could’ migrate to the stars. It’s a matter of politics.

  • Administrator February 21, 2007, 10:02

    Good point, Phil. We should also factor in this: any civilization that could build a true interstellar ark may well be capable of at least limited terraforming upon arrival. Thus a potentially habitable world, though not human-ready in the beginning, could be developed while the ark’s inhabitants continue living as before within the confines of their vessel. This, of course, assumes no existing ecosystem, and raises all kinds of intriguing ethical issues about planetary manipulation.

  • Jose February 21, 2007, 10:20

    “There’s no guarantee that some kind of immortalisation process won’t be developed before an Ark launches, making “multi-generation” moot. ”

    Well you’re just changing one unique and unusual “What if” scenario for another in that case.

  • ljk February 21, 2007, 12:13

    What if… a multigenerational ark from another star system
    arrives in our system and the inhabitants decide this would
    be a great place to settle down?

    I find myself in agreement with those who asked why would
    people who have spent their whole lives in a giant, enclosed
    artificial environment in space want to land on and settle a
    distant planet, especially when there is no guarantee that
    any other worlds could support life from Earth? Nor can we
    assume that those travelers would have the means or the
    desire to terraform another planet.

    Would it not be better and safer to roam the galaxy in a
    giant space ark, seeing new places and avoiding potentially
    hazardous zones. Being stuck on a single dirty little planet
    for life seems boring and even cruel by comparison. Most
    humans certainly lack a true appreciation for the wider
    Cosmos being stuck on Earth, as an example.

    Maybe this is why no ETI have made it clear that they
    colonized Earth and the rest of the galaxy: Settling down
    on a planet with all its uncontrolable natural dangers is both
    unnecessary and so gouche. All the truly advanced beings
    of the Universe would never soil their feet/tentacles/pads
    with actual dirt and breath unfiltered air.

    The other idea of adapting our descendants to live in almost
    any cosmic environment also has merit, certainly at least to
    ensure our survival and gain a knowledge of alien places that
    no spacesuited astronaut ever could. It would be hard for the
    galaxy to destroy a being that could live on the surface of
    Venus or swims in the Europan global ocean or float in the
    clouds of Jupiter, or dwells in space itself.

    Personally I still think that all these ideas will be surpassed by
    our technological advancements, the kind that will create Artilects
    and rearrange the Sol system into something more useful for
    such intelligences.

    Just because humans can barely conceive of how to do such
    things and seem to inherit a rather primitive fear of the unknown
    and those more powerful than us does not mean it has not already
    happened somewhere or that our descendants will make them a
    reality some day – especially when the galactic parameters change.

    After all, we know that in just a few billion years Sol will make life
    in the inner planetary system unbearable, so hopefully long before
    then somebody has decided that the space program is in need of
    a budget increase for conducting a mass exodus. Or maybe they
    will find a way to keep our star and others under control and
    fusioning properly way beyond its natural years.

    Or maybe our descendants won’t need a sun at all.

  • Warren February 21, 2007, 12:47

    -good points from Phil, Jose, Administrator. Yes, we are talking about a system, that is in control of it’s own evolution. These “folks” can modify their form(s) to suit the environment and the environment to suit their forms. Yes, it is a matter of economics, politics and religion. I suggest, though, that any descendants who migrate to the stars will have adapted themselves to the intersteller environment long before they arrive at another star with an earthlike planet. They will be able to make what they need using only the resources of interstellar space. Maybe they are interested in small rocky planets with complex organic chemistry near a sun but how many would want to live there any more than we want to live near a hydrothermal vent? I’d be very surprised if many shared our romantic fantasies. They are no longer human, after all.

  • Warren February 21, 2007, 13:35

    ljk, I think that is exactly right, they almost certainly don’t need a natural sun at all. They have been traveling with one they built themselves for a long time. We’re trying our best to build a hydrogen fusion reactor now and we are, I assume, still the primitive result of mindless natural evolution.

    When I think about those who may indeed share our star wars dreams after light years of travel in their ark, the image I get isn’t pretty. Unfortunately we can imagine a very rigid and degenerate kind of religious cult, obsessed with spreading trillions of hairless chimpanzee troops with oxygen, “freedom”, “god” and/or “free enterprise”, transforming earthlike planets from here to the Virgo cluster. (The fact that we find this “pink goo” scenario even remotely plausible might be reason to wonder seriously if we are being carefully watched. Maybe the killer comet has already been diverted, timed to arrive before the cancer can spread.)

  • X February 21, 2007, 13:37

    ET worlds full of life should be off limits to colonization. Life on such planets should be given a chance to develop in its own right without interference from humanity or any other Earth life.

  • Administrator February 21, 2007, 13:49

    Here are two references by Robert Freitas on ethical issues in terraforming and other human exploratory scenarios:

    Freitas’s “The Legal Rights of Extraterrestrials,” Analog Science Fiction and Fact (April 1977), pp. 54–67. Freitas also discusses the issues in “Metalaw and Interstellar Relations,” Mercury 6 (March/April 1977), pp. 15–17.

  • Timothy J Mayes March 8, 2007, 15:19

    Unlesss we can get a lot of antimatter together, or we develop the medical technology to create “sleeper ships” with crew in suspended animation
    the most practical approach to interstellar space flight is to become interstellar nomads traveling on a multigenerational journey to the stars
    at perhaps 10 % of light velocity possibly using thermonuclear pulse
    drives for propulsion .

  • Bruce April 8, 2007, 12:51

    Even with multigenerational ships, I have a hard time believing that human beings could look down on a world capable of being settled (and by that I mean anything between Mars and a somewhat cooler Venus) and not take the chance. Compared to even the largest of ships, the resources would seem limitless. The enormous available land space, with the opportunity to “spread out” would be irresistable. Further, no ship could endlessly recycle ALL of its resources. A few decades of settlement would allow resupply and even improvements which had been designed with the experience of the trip behind them. No, I think they would settle. Five hundred to a thousand years later, they might even lauch their own ships.

    The issue I find fascinating is how we would react to an alien biosphere and how it would react to us. There is a coninuum of possibilites from immediate hostility and rapid death of either the invader or the native (or both); through the midrange reactions where adaptation will take place and a new balance found; to complete immunity, where we cannot be attacked by their bugs and they are immune to our diseases. I regard the two extreems as unlikely. Life is too adaptable for such absolutes. However, even small shits from the midpoint could make a hugh difference in the difficulty and style of colonization. Until we go to such a world, it is unlikely we will ever know. Perhaps, if we find primitive life somewhere in our own solor system, we could at least get some insight.

  • Interstellar Travel Fanatic April 27, 2007, 8:15

    I have always been fascinated by this stuff, ever since I first rad Carl Sagan etc., but nowadays I have a doubt… what if we all that way, using any of the abovementioned methods, and arrive just to find out that in the new environment to be colonized, there is a critical shortage or total lack of such elements that are indispensable for humans to survive, that can be found in our bodies in ever so small amounts, like selenium or whatever, you got my point, the very rare, heavy metal elements… would we synthesize them on site by some alchemist version of a fusion reactor? Think how hard it was for the first American settlers to just survive on the new continent… you just can’t think of eveything you will possible need to survive in your new, presumably totally virgin environment/habitat…

  • ljk April 27, 2007, 9:01

    I think it would only be logical to assume that any exoplanets
    our descendants want to colonize would be thorougly checked
    out first by robot missions before sending humans there.

    And see my post above why substituting one planet for another
    may not be the solution to galactic colonization.

  • ljk February 25, 2008, 13:02

    The Ultimate Project Web site, a multigenerational vessel
    to be sent off to a system with an Earth-like planet with
    one million colonists in about 500 years: