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The Ethics of Interstellar Journeying

We usually picture the far future in terms of the most exotic possibilities. And why not: Getting to the stars with warp drive or wormhole makes the entire galaxy accessible. But while we work toward such goals, a raft of technologies continue to develop that can get us to another star with currently understood physics. Imagine, for example, a starship pushed to ten percent of lightspeed by a powerful laser array, a tiny vessel enabled by nanotechnology to carry a cargo of human genetic material.

I played around with the concept years ago in a story called “Until Anna Changed,” which dealt with a colony around another star whose inhabitants had all been raised upon arrival by their starship’s crew, beings called Adepts who were manifestations of artificial intelligence. The Adepts were to move on to another star when the colony was mature enough to survive, but the story looked at what happened to a particular colonist when his own Adept unexpectedly returned. The dynamics of growth and ‘parenthood’ in such a situation were fascinating to play around with in a society where death was nothing but an option.

Flash Frozen Humanity

Recently reader John Hunt wrote with some ideas that triggered memories of that story. A Canadian study looked at rapid freezing of human eggs, and 200 children who had been conceived in this way. The classic problem with freezing eggs has always been the formation of ice crystals in liquids within the egg, but ‘vitrification’ removes those liquids and replaces them with a kind of ‘antifreeze,’ after which they can be flash frozen in liquid nitrogen. Remarkably, 95 percent of eggs seem to survive this process, which is now available in the UK. This BBC story looks at the Canadian work and notes why people might use it today:

Aside from the wish to delay motherhood beyond their 30s and 40s, some women may use this technique for medical reasons, perhaps if they are facing cancer treatment which will render them infertile, or a premature menopause.

The researchers, from McGill university in Montreal found that the rate of birth defects among the 200 children conceived using vitrified eggs as 2.5%, roughly the same as in natural pregnancies and IVF.

Frozen eggs last how long, exactly? I suppose we don’t know, but both sperm and actual embryos have been frozen and successfully thawed as well. So if we could develop a technology to push something to a significant percentage of lightspeed — not unthinkable given our current understanding of physics — then a small craft, as Hunt suggests, could theoretically carry a human cargo. An interstellar transit of several hundred years should be workable in terms of survival, the trick being child-rearing at the destination. Here we make the leap to artificial intelligence and advanced robotics for a solution.

A ‘Coke Can’ to the Stars

It wasn’t so long ago that former NASA administrator Dan Goldin was raising eyebrows by talking about entirely new concepts for interstellar missions. Speaking to the 100th anniversary meeting of the American Astronomical Society in 1999, Goldin brought together lightsail technologies, genetic algorithms that ‘learn’ and adapt as they process code, and hyrbid systems that fuse biology with silicon. Throw in advances in neural nets and you wind up with an interstellar probe the size of a Coke can that builds itself into a full-sized probe when it mines carbon, iron and other materials in its destination star system.

“This reconfigurable hybrid system can adapt form and function to deal with changes and unanticipated problems,” said Goldin. “Eventually it will leave its host carrier and travel at a good fraction of the speed of light out to the stars and other solar systems… Such a spacecraft sounds like an ambitious dream, but it could be possible if we effectively utilize hybridized technologies.”

No one would argue that planting a human colony via frozen genetic materials and robotic childrearing is the optimal way to go. We’d all rather see fast transport via warp drive or other methods, and here’s hoping we find a way to achieve it. But as a hedge against species extinction, the possibility that we could create a human colony around another star without making any breakthroughs in the laws of physics is a notable prospect to consider. It firms up the belief that one way or another, we will see a human presence around nearby stars.

An Emerging Interstellar Ethic

While our goal should be to consider as many different ways of making an interstellar journey happen as possible, whether we would proceed with a mission like this may one day depend upon our understanding of the ethical issues involved. Do we have the right to subject human beings to these conditions, raised without true parents in a potentially hostile enviroment? The same question is posed by so-called ‘generation’ ships, in which crewmembers live entire lives on the vessel on a journey of thousands of years. We have yet to develop guidelines for what might be called a code of interstellar ethics, but one day we may have to do so. After all, we’re talking about what we owe to our descendants

While I know of no papers on rearing children via robots, Edward Regis Jr. has written a fascinating study of the multi-generational starship question. Regis concludes that there is no fundamental ethical distinction between raising children aboard such a ship and raising them aboard our own planet. He goes on to say this:

It is true that in the designing, outfitting, and launching of a space ark, planners will be committing others to conditions not of their own choosing. But this… is just what happens, and necessarily happens, on Earth… A multigenerational interstellar expedition is no more and no less than a microcosm of human life on our own planet. Launching one is like beginning Genesis anew: It is to place human beings on another heavenly body for its inhabitants to make of what they will. To do this, to put humans on a microplanet upon which they can live, procreate, dispose of their affairs under their own governance, and die, is to bestow upon them conditions quite analogous to those on our own planet, conditions they may use for good or for ill, just as we use the planet Earth.

There is much to mull over in Regis’ paper. It’s “The Moral Status of Multigenerational Interstellar Exploration,” in Interstellar Migration and the Human Experience (Berkeley: University of California Press, 1985), pp. 248-259. And it strikes me as just the opening wedge of what will one day be a major and contentious debate. A code of interstellar ethics is waiting to be written as we confront issues our technology will one day make possible. Science fiction is the only current venue for their study.

Further Reading

A wider consideration of interstellar ethics has been begun by Robert Freitas. See his “The Legal Rights of Extraterrestrials,” in Analog Science Fiction and Fact (April 1977), pp. 54–67 (available online). Freitas also discusses the issues in “Metalaw and Interstellar Relations,” Mercury 6 (March/April 1977), pp. 15–17 (available here) — thanks to Dave Weeden for the links! Compelling questions continue to surface: If we send a nano-assembler probe to another star system, do we have the right to mine local resources in the presence of a potential intelligent species within that system?

Addendum: Tibor Pacher passes along this interesting reference: C. Cockell, “Essay on Extraterrestrial Liberty,” in the July Journal of the British Interplanetary Society. I haven’t had the chance to look at it yet. but an abstract is here.

Comments on this entry are closed.

  • Ross July 7, 2008, 11:01

    When considiering the ethics of sending colonists to another star, should we consider the ethics of “colonizing” other worlds around other stars with respect to the life that might already be there? Do we send our can of colonists out as soon as we find a habitable planet? Do we consider that life at all when talking about the survival of our own species or is it either not considered, or considered irrelevant? And isn’t “colonization” an 18th century term and really a step backwards for the human race? Wouldn’t a step forward be to remove human dependence on planets atltogether? We could start ensuring our survival in greater numbers a lot sooner with current technology and physics, by building movable, rotatable space colonies, near earth to begin with and gradually moving out. Use resources from the moon, asteroids, comets, rather than lock ourselves on to another sitting target, which in the end the colonists would have to move off of anyway. Of course it would be a lot cheaper to send out a coke can full of embryos, but that doesn’t really help those of us left here in terms of survivability. What are the ethics of condemning the billions left here to destruction if we don’t move a large number of us off this planet?

  • dad2059 July 7, 2008, 12:26

    Excellent treatise. I don’t think any one method will be used for interstellar travel, if we chose to go.

    One organization or group might choose a way that suits their goals or purposes at the time.

    I don’t believe a government entity like NASA or Roskosmos will plan something this audacious in the future unless there is a perceived survival imperative for the human race to do so.

    And if there’s enough time.

  • tacitus July 7, 2008, 12:49

    Regis concludes that there is no fundamental ethical distinction between raising children aboard such a ship and raising them aboard our own planet.

    Hmm. Well I can think of one – at least one that’s distinct from living just about anywhere on Earth these days. Interstellar missions will, essentially, be completely cut off from the rest of humanity with a good chance that it’s for ever. If the mission was set up as a pluralistic society then fine, but if it was funded, designed, and crewed by a fundamentalist religion or sect, the morals and ethics of the resulting society could be twisted beyond all recognition within a couple of generations. There would be no outside influences for the grandchildren to draw upon and challenge their elders — there would likely be profound indoctrination with no recourse to deprogramming or rebellion. Even the scientific and educational materials would be not help — just think of the wealth of creationist material swilling around this country — they would have little choice but to believe whatever crackpot beliefs were foisted upon them.

    Sure that has happened on Earth many times in the past, but these days the vast majority of people do at least have a chance of hearing a dissenting viewpoint. There would be no escape for those trapped in a religious or cultic interstellar mission.

    Given the wealth and power of some of these fundamentalist religions, it’s certainly not beyond the bounds of possibility that one or more of them will want to colonize space with a societies isolated from the “baleful” influence of a sinful and apostate world. The ethics employed during the setting of interstellar missions is the most vital issue. Should fundamentalists groups be allowed to create and operate their own missions when the welfare of countless unborn children is at stake?

  • tacitus July 7, 2008, 12:52

    The classic BBC radio drama “Earthsearch” (which enthralled me back when I was a teenager), those on some of the issues. It’s about an interstellar mission that’s gone terribly wrong and only four children are left alive on a ship on a ship run only by a pair of AI computers.

    Well worth a listen if you get the chance.

  • Tim July 7, 2008, 13:04

    Perhaps there exists another path to the stars using currently understood physics. The rapid development of life extension technologies that seems likely to occur during the 21st century may produce a life expectancy of several centuries. Earlier in human history, some groups of hominids undertook to wander across uncharted territory for decades, a very significant portion of their lifetimes, before finding a suitable place to settle. Similarly an interstellar voyage of two or three hundred years will not seem to be so daunting for people who might expect to live for three or four hundred years.

  • david lewis July 7, 2008, 13:24

    Within 50 years one might expect to see micro-probes sent to other stars. Technology is changing so rapidly.

    Imagine, just 62 years ago ENIAC was built and it did an amazing 5000 simple additions/subtractions per second. Not too long ago the world’s fastest supercomputer broke the 1000 trillion instructions per second mark. In just a little over 60 years.

    Compare the phones of today with the first phone built. Something you can slip into your pocket and forget about compared to something you would not want to lug around all day.

    Even if nanotech isn’t the miracle many believe it will be it may still offer us the stars. We don’t need to work on the scale of billionths of a meter in order to build probes that individual nations would have the resources to send to the stars. Even cutting things down to 1/10th of what they can be done today would mean the same device being built at 1/1000 the size and 1/1000 the mass. (there being three basic directions)

    As for ethics. If we eventually do launch such probes, with the capacity to seed human life what would be the ethical thing to do if a world already has intelligent life? A society in the stone age would not be detectable via any instruments we are likely to build, and the introduction of humans into such a society would have drastic consequences. Especially if those humans have access to the technology capable of putting them on that world in the first place.

  • Administrator July 7, 2008, 13:46

    Ross, I just added a few references at the end of the interstellar ethics piece that discuss the very questions you raise. The issues many of you are talking about are going to take a lot of consideration. As David says, “what would be the ethical thing to do if a world already has intelligent life?” That question may become huge depending upon what we find around nearby stars. Our own history offers some guidance and also some dismaying examples of what can go wrong when people make too many assumptions about where they can settle.

    And tacitus, where can I find ‘Earthsearch?’

  • kurt9 July 7, 2008, 13:46

    “Coke Can” interstellar colonization is the technology basis of Jim Hogan’s SF novel “Voyage from Yesteryear”, one of my favorite SF novels.

  • Administrator July 7, 2008, 13:48

    Thanks for the recommendation, kurt9. Have not read the Hogan novel, but it now goes onto my list.

  • andy July 7, 2008, 13:57

    When considiering the ethics of sending colonists to another star, should we consider the ethics of “colonizing” other worlds around other stars with respect to the life that might already be there? Do we send our can of colonists out as soon as we find a habitable planet? Do we consider that life at all when talking about the survival of our own species or is it either not considered, or considered irrelevant?

    I suspect that the last thing anyone wants to do is colonise a planet with an advanced biosphere… for a start, the local life would have a major advantage when it comes to local chemical quirks, and then there’s the problem that our immune systems would be completely unused to the local microbial life (sure, the local microbial life would be unused to our chemical quirks, but it may be that they’d just see us as a big bag of nutrients for the taking, slipping by the immune system perfectly fine). Needless to say, this could be very unpleasant. (Note also that unless the alien life is very similar to our own in how its heredity is stored, the local equivalent of viruses should not be an issue)

    In short, I suspect inhabited (i.e. by organisms, not necessarily intelligent or technological ones) worlds would be of immense scientific (and perhaps commercial) interest, but be very bad as places for humans to live, at least without serious re-engineering of the human organism. If we wanted to convert them to host humans, the best policy might be to hit the planet with a relativistic bomb to sterilise most of the surface (and even that might not necessarily work to get rid of the pre-existing lifeforms), and such total extermination of a biosphere has serious ethical issues.

    The best prospect for interstellar travel would be a universe where Earthlike worlds are common, but life itself is rare. Of course, this raises the question of how to detect anoxic biospheres at interstellar distances…

  • ljk July 7, 2008, 14:51

    Tacitus – If the crew of a multigenerational ship were strict
    creationists, I would be surprised if they survived for very
    long. Though it will be groups exactly like them that will
    probably be among the first to leave Earth and either settle
    elsewhere in the Sol system or set off to another star system

    If they encounter an alien society and attempt to convert
    them, it will be interesting (in the Chinese proverb sense)
    what the reaction may be. Just as likely they could be on
    the receiving end of a similar missionary action.

    As for the ethics of stopping such rigid groups – now there
    are some deep and murky ethical waters. However, if they
    fly off into the galaxy and remove all methods of contact,
    what are the folks “back home” supposed to do?

    And what if we encounter alien species that do things we
    might find objectionable, such as sacrificing their children
    to a god? Are we to become the policemen of the galaxy?

    As for multigenerational ships in general, why do we only
    look at the negatives of such projects? I think a lot of it
    has to do with the fact that science fiction stories need
    some kind of conflict to be considered interesting enough
    to read. And while they do bring up some good points on
    potentially negative situations, at the same time such
    crews might be better off than we on Earth. After all,
    they will be in a relatively small, controlled environment
    for starters. Plus they will have a defined purpose with a
    tangible goal (colonizing a new world). Even those who
    will live and die in the interim will know they are making
    a contribution to their direct descendants’ futures.

    As someone else in this thread said, there may be more
    than one way we will reach for the stars. Perhaps the
    most effective way will be via AI, or Artilects. They
    certainly have the potential to do the job better and
    last much longer.

    See this recent article on a related subject:


    Tacitus, thank you for bringing up the Earthsearch series,
    which I had not heard of before. However, I do question
    the idea of the ship’s Artilects wanting to conquer Earth.
    After all, they could easily go just about anywhere in the
    galaxy, why focus on one little planet? Just as I question
    why aliens in most SF stories want to take over Earth and
    humanity in a galaxy with 400 billion star systems.

    About a starship mining a solar system for resources that
    may have intelligent beings on one of its planets: I would
    say it depends on not only what we might consider to be
    intelligent but just how much a few rocks in their solar
    systems actually “belong” to them. Look at humanity: Do
    we actually own anything in the Sol system, and just how
    put out would we be if a passing alien ship mined a few
    comets in the Kuiper Belt, or even a planetoid or two in
    orbit between Mars and Jupiter? We wouldn’t even know
    about such activity at this stage of the game. If said alien
    ship needed those resources not only to move on but just
    to survive, is it wrong for them to take apart a few space
    rocks where nothing already lives?

  • Dave Weeden July 7, 2008, 14:52

    A bit of googling finds The Legal Rights of Extraterrestrials and Metalaw and Interstellar Relations. Good stuff and deserves links. :-)

  • dad2059 July 7, 2008, 15:25

    but if it was funded, designed, and crewed by a fundamentalist religion or sect, the morals and ethics of the resulting society could be twisted beyond all recognition within a couple of generations…

    And who would prevent them from doing so if they provided their own financing?

    Whom are we to judge if a certain group is fit to colonize other planets or star systems?

    No one corners the market on morality or ethics in my view. If a group chooses to fund their own way to the stars, more power to them I say!

    If it fails, they paid the cost more ways than one.

    Besides, in recent history religious groups are usually second to attempt colonization of different lands. Does a whacko group of religious nuts from England in 1620 called “Puritans” (Pilgrims) ring a bell?

    BTW, the first group to attempt to colonize new (to them) lands are people looking to get rich.

  • Administrator July 7, 2008, 15:35

    Dave, both are already listed at the end of the article, but I’ve added the Web links. Thanks for passing those along!

  • tacitus July 7, 2008, 16:18

    Looks like you can get Earthsearch and Earthsearch II from Amazon as a digital download: click here.

    I also just found out that it’s being repeated right now on BBC Radio 7. Unfortunately the first episode available is part 2:

    http://www.bbc.co.uk/bbc7/listenagain/tuesday/ – scan down the schedule, which you will have to listen to (or download) *today* within the next few hours at most – remember the UK is 5 hours ahead of the EST.

    You can catch up with the rest of the eps broadcast in the last week too. (You can probably find the first one or two eps elsewhere on the web, but I will leave that decision up to you.)

    Each series was ten half-hour episodes, the second series isn’t as good as the first, but would certainly while away the hours on a long flight or car journey. Don’t expect anything too deep, but I certainly enjoyed it.

  • andy July 7, 2008, 17:11

    If the crew of a multigenerational ship were strict creationists, I would be surprised if they survived for very long.

    Why? Remember, creationists are NOT (necessarily) stupid – this is also good to keep in mind if you ever feel like debating one. Is the theory of evolution going to be particularly relevant to colonising a new world or travelling interstellar space? I see no particular reason why a creationist interstellar mission would necessarily fail…

  • kurt9 July 7, 2008, 17:56

    “Voyage from Yesteryear” (James P. Hogan) is a wonderful novel describing a wonderful idea for a “post-scarcity” society based on fusion power and self-replicating robotics technology. It was written in 1982.

    The “coke can” colonization idea (in the novel) was inspired by a paper that Robert Frietas wrote in 1980 about the possibilities of self-replication manufacturing by 2000! Although it is now 2008 and we still do not have self-replication manufacturing, nanotech or non-nanotech, we are getting closer to having it.

    Nevertheless, the novel is quite good and I likely recommend it. You can find it at any used bookshop or on Amazon.

    I think the idea of generational starships sucks. The concept essentially condemns one or more generations to having to live their entire lives within the fixed confines of a starship. I find this notion to be quite intolerable, no matter how large you make the starship. It would be like having to live your life in a small college town, without the possibility of moving away and creating a new life for yourself.

  • Ronald July 7, 2008, 18:16

    Ref. to Ross and others, when it comes to the rationale of star travel, I think there are some good reasons to go forward.

    However, solving our present earthly problems, particularly environmental, energy, overpopulation and the like, are *not* among them. Any of those problems can always be dealt with better and cheaper here on earth, than by sending people off into space.
    Sending people to the stars is not meant to directly help the billions left here and moving people off the planet is not a solution to any overpopulation problem.
    Furthermore, as argued before, relatively small space colonies are probably not very good means of survival for humankind, because limited space (island biogeography) greatly increases chance of extinction events (stochastic extinction).
    To survive long-term, large and stable platforms, like planets and their abundant energy sources, being their mother stars, are probably natures greatest gift by far.

    I agree with andy, that our best prospect would probably be terrestrial planets that are (potentially) habitable but still uninhabited, i.e. planets that are (relatively) easily terraformable adn can be seeded with adapted lifeforms. Planetary engineering in combination with bio-engineering might well be thé sciences of the future.

    I like the vision of Marshall Savage and his Living Universe Foundation (or Millennial Project) to spread life acroos the Milky Way galaxy.

    I believe the two main justifications to ‘colonize’ the MW galaxy are indeed:
    1) to ensure survival of humankind and earthly life.
    2) to spread (earthly) life, intelligence and civilization across the universe, or at least across barren parts of it.

    In order to be able to do so, we will first have to learn to live on a planet sustainably and be able to deal with our major problems here. Going to the stars is passing the ultimate test, not escaping it.

  • Ronald July 7, 2008, 18:27

    Just for clarity, an addition to my previous post, ref. to ‘dealing with our problems here’:
    when I mention our earthly problems, I mean our internal, relatively small, temporary and surmountable ones, that are inherent to a growing civilization, such as in particular food, water, energy, pollution, conflict, and the like.
    I was not referring to the large-impact cosmic or geological events, such as meteorite impacts, supervolcanoes, drastic climate changes, supernovae, solar changes, etc.
    Those might exactly be good justifications to move.

  • david lewis July 7, 2008, 18:38

    I am so used to religious fundamentalists being a barrier to space exploration and colonization that I didn’t think of what resources a religious group whose aim is colonization might have.

    There are 1.13 billion roman catholics worldwide. Imagine if on average each was able to donate 1000 dollars a year to the church at the pope’s request for that purpose. Just how many orion type vessels could that fund? Imagine a 8 megaton orion type vessel with a 2 percent light speed capacity. Model the ship after a monastery with 20 people, using 1 megaton of the ship as a biosphere for them.

    As for how humans might cope with such a different biosphere. I wonder if those biospheres will be as different as we believe. With spores able to exist for millions of years in frozen comets and such those worlds might use the same building blocks for life as here on earth. Different germs and bacteria but ones which operate the same as here on earth, and hence with vaccinations possible for them with only a little tweaking needed for the human immune system.

    While I believe the resources of a solar system are too rich for us to ignore, and that we will eventually use them for the building of habitats, having several interstellar missions as insurance would be nice. Just in case …

  • Benjamin July 7, 2008, 20:59

    In Alastair Reynolds’ series of sci-fi novels in the Revelation Space universe, he has it that the first attempts to colonise a number of systems were by just such “coke-can” probes sent by the “Amerikanos”. They construct the artificial wombs and nurse the colonists to birth and then the AIs raise them. However he raises the interesting point that human beings are generally socialised in a community of a variety of ages and occupations; he has it that the overwhelming majority of Amerikano settlers develop as psychologically unbalanced.

    I think this could well be an issue – is it right or even sensible to try and develop a human society from nothing but fertilised eggs and machines? What does it do to the psychology of the settlers?

  • ljk July 7, 2008, 21:37

    Marshall Savage assumes there are no other living beings –
    at least intelligent ones – anywhere in the galaxy. I find
    his reasoning on this more wishful thinking (that humans
    get to spread their seeds everywhere without having to
    deal with any natives) than anything else.

    I am surprised that they even still exist. They seemed
    to be turning into a cult more than a serious space group.

    Maybe a tightly wound religious group would do best on
    a multigenerational starship. As for creationists, if they
    strictly adhere to their beliefs, then they must reject
    certain tenants of science that could ultimately prove

    But if God is on their side, then I guess anything is
    possible. :^)

  • James M. Essig July 7, 2008, 22:56

    Hi Folks;

    Good discussion by the way!

    It occurred to me to mention a hypothetical way in which mankind might reach ultra high gamma factors, perhaps even runaway gamma factors, would be to launch a craft to relativistic velocities wherein the craft would have the length to cross-section aspect ratio of a long thin string further incorporating a long selonoidal coil made of high temperature superconducting materials wherein a tremendous electrical current would build within the superconducting coils.

    One or more continuous coils which may have a path-length as great as multiple to several light-years but a relatively low mass and an incredibly high current density capability, or current criticality coefficient under extreme magnetic field intensities, would gradually build up electrical current as the craft slipped through space at ever increasing velocities: a sort of an analogue example of a electric dynamo with circumferential rotation speed approaching C within a very weak magnetic field of perhaps 10 EXP – 10 Tesla, which is similar to the background field of interstellar space.

    Now comes the hard part and that is how to use the electrical energy or power within the electrified coils to produce a net gain in propulsive force instead of resulting in drag and velocity reduction through magnetic breaking or at least allowing a net break even or positive acceleration instead of simply neutral kinetic energy gain.

    The above conjectured mechanism would be awesome if some electro-dynamic action or configuration could be made manifest that would result in a kind of runaway acceleration or ship-based kinetic energy gain. The problem is, I am not sure how to make it work without violating the conservative aspects of electro-dynamic fields as such is currently understood by even college sophomore level students of electro-magnetic theory and associated Maxwell’s equations.

    The “What ifs ?” of the above conjecture lead to back to thinking about this concept from time to time, and in fact, it may prove a violation of conservative aspects of magnetic and electric fields, but in the off chance that it could be made to work, we could have one heck of a field effect propulsion system, perhaps with very little additional applied electromagnetic theory physics beyond present day state of the art.



  • John Hunt July 8, 2008, 1:59


    Thanks for referencing my ideas.

    Wouldn’t y’all like to see a true interstellar mission launched within your lifetime? But it has been 40 years since we went to the moon and we haven’t sent people back since. Let’s get real. Unless we can figure out an interstellar mission plan using current technology, within approximately current space budgets, and with a good rationale for spending that money…then it ain’t gonna happen! Not within our lifetimes.

    So when I think about interstellar missions I can’t afford to think about missions that rely upon uncertain physics or which are implausible from a cost, risk, and rationale standpoint such as:
    – trillion dollar multi-generation ships,
    – multi-ton ships using exotic fuel and fusion which we haven’t even been able to get to work on Earth,
    – life-extended astronauts whose life-support systems prone to break down repeatedly,
    – science probes requiring extensive launch architecture competing with much less expensive discovery missions in Sol system,
    – worm holes, etc

    So what sort of mission design would meet the requirements I list in the first paragraph?
    – Push the travel time out to what equipment can survive,
    – Use the fastest propulsion method that doesn’t require too expensive an architecture,
    – Keep craft mass as low as possible,
    – Travel at speeds where collisions with dust and micrometeorites are survivable,
    – Try and avoid any thing like prone-to-fail life-support systems,

    But even then there is the issue of rationale – a huge issue. A near-term interstellar discovery mission won’t get funded for two reasons:
    1) there’s a lot of less expensive discovery left in Sol system, and
    2) a later mission traveling faster negates the earlier mission.

    So the only imperative I see for a near-term interstellar mission is the survival of the human species. It is reasonable to fear that in the next few decades we may face an existential risk (xRisk) due to self-replicating technologies such as chemical, biologic, nano-tech, or AI.

    But perhaps one could survive an xRisk without having to travel to a nearby star. (i.e. underground ark, lunar base, etc). Here’s where I appeal to Fermi’s Paradox. Where are all the other civilizations who survived their xRisks? Can’t say that we see them. Sure, there are alternate explanations to Fermi’s Paradox but nobody has convincingly ruled out the universal self-extinction of intelligent civilizations prior to interstellar space colonization. So long as this explanation remains, it behooves us to shoot for the stars in the near-term even if that Coke can has to take 10,000 years to arrive.

    But including frozen embryos, automated gestation, childrearing, and life support systems at destination increases the complexity of an interstellar mission immensely. True. But it would seem as though all of these technologies are within reach especially if included in the development budget of the mission.

    Someone with the ability needs to write-up such an interstellar mission plan. If it would help move things along I’d like to suggest a name for the project. It could be called Project Arrow with an interim Project Boomerang which would be a similar mission but would loop back to Sol System so as to be out of the solar system for a few decades but then return in case humanity had destroyed itself in the interim but Mars or somewhere else could still be colonized.

  • John Hunt July 8, 2008, 2:49

    The ethics of automated childrearing poses significant challenges but ones which I think can be overcome.

    Life on a Mar-like world might be dangerous, difficult, and lack opportunities. What right do we have to subject people to grow up in that environment. The mission could be set up in such a way that, upon arrival and communication with Earth is established, if no signal is received from Earth then it is presumed that humanity has self-destructed. If so, the ethics of risking the establishment of another human civilization is not problematic.

    What about having adequate social stimulation? What sort of child would result from having been raised by an android mother with, perhaps, limited “social skills”? I think that if funded adequately, a highly interactive android mother could be produced today. Writing subroutines for numerous situations could be opened up for contributions from the world via the web. Also, updates could be sent after launch. I do wonder what would happen if the child were to see his/her mother mechanically break down.

    Although introducing other ethical challenges, one could first raise a mother baboon which could be a real-life mother for human children. Verbal training could be provided by an android or virtually. One could wonder how a child might feel when it finds out that it was raised by an animal when later generations were raised by humans. But today people learn that they were adopted, had an anonymous donor as a father, were test tube babies, were raised by same-sex parents, had a surrogate mother, was abandoned by a parent, had parents who where murderers, etc. It can be tough but isn’t a show stopper.

    Then there’s the children of Adam and Eve dilemma! Who would the children marry, their siblings? Every child could and probably should be genetically unique via frozen embryos and/or invitro fertilization. So genetically there probably isn’t a problem. But emotionally, siblings are who you grow up with. So there should probably be at least two separate colonies where, upon arriving at puberty, children could meet young people from the other colony.

    Limited opportunity would be a real problem. But this is not a great deal different than the lack of opportunity experienced by much of humanity throughout the ages and in many rural parts of the world today. The new civilization could be provide with a digital copy of all sorts of information. So the development of their civilization could be fairly rapid (e.g. 200-300 years). Also, if they could not establish contact with Earth then they would know something that we don’t. That is that an existential threat is very real and something that they needs to protect against and to launch another interstellar mission early on.

  • msadesign July 8, 2008, 7:53

    What did we do to deserve such treatment?

    I know that I’ve been a very good reader, even singing paeans to our illustrious leader, praising his blog [ok, well-deserved paeans, but still].

    And what do I get in return? A reference to a delicious story– a story replete with Adepts, no less– but no hint whatsoever of where to find it!

    How can you look so coldly on your loving and ever-faithful readers? How do you even sleep at night?

    Just askin’.

  • Adam July 8, 2008, 8:02

    Hi All

    Has anyone read Ken Macleod’s “Learning the World”? It’s about the arrival of a generation ship full of aliens in a star system with an already inhabited planet – the twist being that the ‘aliens’ on the starship are humans, while the story is from the point of view of the planet’s inhabitants.

    Technically I’m sceptical of the viability of frozen embryoes after a long interstellar mission – the cosmic ray caused molecular damage might be too much for the cells to handle on revival. Protecting them from the flux would require a LOT of mass-shielding or very elaborate magnetic shielding that would quickly erode the advantage of trying to save mass by freezing the colonists as embryoes. Perhaps sequencing technology and “cloning” would allow the recreation of genetic material from a hardier medium and its transference into a “generic ovum” that the vehicle doesn’t have to try to hard to preserve the genetic material of. Perhaps a live culture of precursor cells to ova can be maintained, thus able to self-repair, and eventually stimulated into action when the time is right?

    If Craig Venter’s efforts with making cells advances over the next ~ 25-50 years we might be able to make viable ova from scratch via souped-up versions of current sequencing technology. Thus we could store the requisite data on something more durable and have no nightmares about reaching journey’s end with a clutch of utterly mutated eggs…

  • Administrator July 8, 2008, 8:22

    msadesign, you are too kind, but “Until Anna Changed” remains unpublished. I sent it off to Asimov’s, got it back, then resolved to tweak it and never got around to the necessary work. I should go back and make the changes I’ve been thinking of and send it off again, I suppose. Thanks for the encouragement!

  • ljk July 8, 2008, 9:55

    By the time we are able to send humans into the galaxy and
    if they require “android” parents, the technology level to make
    proper ones will make them indistinguishable from so-called
    real human parents – and probably much better than the
    organic versions.

    But I still say imaginations are being limited here. By the time
    we have real interstellar travel (not a few probes that will take
    77,000 years to go the distance of Alpha Centauri and have
    already been “dead” for millenia), humans may be radically
    different and probably not even the ones that make such
    journeys, rendering android parents obsolete.

    Artilects are making progress in the real world. One can now
    beat champion poker players:


    Ya know, Artilects do not necessarily have to be truly intelligent
    and aware to still be effective space explorers. They will
    certainly do better than humans.

    And for those of you who still say we need humans up there
    to make it seem “real” down here, today’s tech-savvy
    generation of humans may actually prefer the virtual experience
    via a pair of electronic eyes and other sensors to actually going
    into the Final Frontier on their own. Humans in bulky spacesuits
    walking on other planets may become so old school. An
    advanced rover clanking around Mars or a planetoid with
    technology allowing viewers to feel like they are really there –
    that is the wave of the future.

    The only reason I advocate the multigenerational starship
    idea is in the event there are no other feasible ways to get
    humans to the stars faster.

    As for wanting an interstellar mission in our lifetimes – yeah,
    it would be nice, but even if one were built and launched
    tomorrow, none of us would be alive to see the probe make
    it to its destination, as we cannot even come close to 99%
    of lightspeed with anything even remotely feasible for now.
    And such a speed still leaves most of the galaxy very very
    far away.

    But as said above, a starship won’t happen anytime soon
    as it is. And we cannot rely on the major space nations to
    build one, while the private space industry has yet to get
    a ship into Earth orbit. I will consider myself lucky to see
    humans on Mars in my life time at this point, forget Alpha

    The only thing that might stir the major space powers into
    making an interstellar mission is the discovery of a truly
    Earthlike planet around another star. Even then the odds
    of one being conveniently nearby (as in a few tens of light
    years away at most) are slim. And of course if it is already
    inhabited, we will need to look elsewhere if we want to
    colonize such a world, which only stretches out the distance
    and time.

    The best hope I see in my lifetime is a small interstellar
    probe being readied for launch. Look elsewhere in this
    forum for the ChipSat and needles ideas, where a cluster
    of small probes can be sent out very fast to return a bit
    or two of data which could still return very important info
    on an alien star system.


  • James M. Essig July 8, 2008, 9:57

    Hi Folks;

    If we can have efficient fusion rockets developed, hopefully with strong efforts toward such within the next 10 years, that could mean everything near term in our journey to our stellar neighbors. At 0.1 C, which is often stated as a practical limit to known fusion rocket concepts, we could still send humans to the Proxima Centauri System in 40 years. I have read a detailed paper to the effect that a 5 stage fusion rocket, a sort of autophage craft based on a self consuming comet, wherein each stage is 10 times the mass of the next stage but wherein 10 percent of each stage is inert or dry weight such as fuels tanks etc., could reach a terminal velocity of about 0.67 C; about 2/3 C!.

    Since gamma factors for fusion powered space craft wherein all of the fuel is carried aboard the space craft is sensitive to specific impulse, if an effectively five stage fusion craft such as the one I conjecture about above could completely consume each stage, then perhaps velocities as high as 3/4 C might be obtained. With more stages, perhaps 4/5 C could be obtained.

    Now such five stage space craft might require 10 billion metric tons of fuel to accelerate a 100,000 metric ton capsule to 2/3 C wherein part of the mass of the final payload would be magnetic breaking mechanisms, thus avoiding the need for a large final supply of fuel to slow to the target star system. However, hydrogen, deuterium, and Helium-3 are very plentiful at certain locations in the solar system, and especially hydrogen within the water make-up etc of comets.

    I certainly hope and pray for wormholes and warp drives and we should continue our mathematical and experimental quests to verify their feasibility although I will be greatly pleased if we even where to somehow decide as a civilization to undertake a vast effort to launch manned fusion rockets to all 10 of our nearest 10 stellar neighbors say by 2040. I will be 78 years old by then but if I am still alive, I would have to through one heck of a block party.

    I can imagine that fusion pellet runways could allow very high gamma factors thus opening up the entire Milky Way to human exploration ships’ reference frame. Hopefully by then we will start experimental programs to test real wormhole and space warp generating hardware.



  • John Hunt July 8, 2008, 12:56


    You mention “the viability of frozen embryoes after a long interstellar mission”. Clearly this is an issue that would need to be solved for such a mission.

    To date our warmest superconductor does so at about 138 K. I believe that those ambient temperatures exist at about Jupiter and beyond. So we wouldn’t need massive refrigeration equipment. Without electrical resistance, couldn’t the superconductor hold a massive charge producing a powerful magnetic field without producing significant heat? I read somewhere that without resistance it could be able to maintain a magnetic field for a very long time (years as I recall) without needing to be recharged. I’m guessing that the superconducing material could be within the craft which would need minimal shielding from micrometeorites if traveling at Pioneer x 10 speeds (i.e. travel time about 7,700 yrs).

    Adam, as I reviewed that cosmic ray shielding paper you posted on CD (https://centauri-dreams.org/?p=1933) it seems as though using superconductors is easily able to produce magnetic fields strong enough to protect against cosmic rays to the levels so as to get radiation exposure levels down to 0.5 rem/year. Of course 7,700 years of acceptable radiation levels might become unacceptable. So on what basis do you say, “Technically I’m sceptical of the viability of frozen embryoes after a long interstellar mission”?

    Even if there is no technical way of preserving viable frozen embryos for 7,700 yrs there still might be a way within reach to figure out what mechanism Deinococcus radiodurans uses to repair it’s DNA. Then the embryos could be thawed periodically, they repair themselves and they are frozen again.


  • andy July 8, 2008, 13:04

    There seems to be an assumption that going to computer-based mechanical systems will somehow magically get around the radiation problem. This is not the case: electronics are also susceptible to radiation damage. The Galileo probe lasted about 8 years in the Jovian system, by which point several systems were showing severe radiation damage. An interstellar journey would last orders of magnitude longer (trade the Jovian magnetosphere for travelling through space at relativistic velocities…) A small probe would be at great risk from radiation, especially if it contains highly complex systems.

  • James M. Essig July 8, 2008, 15:47

    Hi Folks;

    It is interesting to realize that sometime in the relatively near term, we may be setting boots down on Earth like planets around other stars. If perchance we are able to devise, build, and launch reactionary propulsion craft capable of 0.867 C and thus a gamma factor of 2, any star system within a 60 light year radius becomes fair game for human landing within a disciplined, well trained, healthy, robust, and young crew, in just one average modern-day human generation, ship time. Note that there are about 2,000 stars within a 50 LY radius of Earth. Thus, a lot of ground could be covered by gamma factor 2 manned space craft.

    The point I am trying to make is that there is a very real possibility that some time in the 21st Century, we could be the ETs landing on these other planets. Perhaps we will be more advanced than the inhabitants of these extra-solar worlds, more advanced then them in some ways and less advanced then them in other ways. It might be possible that some of these advanced beings that we might discover would have a less advanced knowledge and technology with respect to nuclear physics, quantum physics, sub-nuclear physics but yet have figured out how to travel interstellar space with technologies such as warp drive, hyper space travel, and the like. Thus ironically, any radically motivated anthropocentric nationist human agendas might result some how in the subjugation of these advanced ETs by means such as advanced and exotic nuclear weapons, matter-antimatter bombs, antimatter bombs and God knows what else we may be able to develop from knowledge of particle and sun-nuclear physics gleaned from devices such as the CERN LHC and future even more capable machines.

    Our track record in encountering cultures less advanced then our has often resulted in forced occupation, enslavement, and the robbery of resources from indigenous peoples thus occupied. We need to develop some sort of political bill of rights for any such beings we encounter on extra solar worlds that sees such beings in a very real sense as our brothers and sisters or whatever. We face an awesome pro-life responsibility as we learn to travel interstellar space and land on extra-solar planets. Some of our great grand-children may live to see the day when we will be called ETs by other planet based civilizations.



  • Adam July 8, 2008, 15:49

    Hi andy

    The problems you mention are real, but the difference between frozen cells and active electronics is that you can pick your choice of materials for one, but not the other. Some kind of micromechanical system might also be used in place of traditional electronics and self-annealing circuitry, but biochemistry is harder to replace.

  • kurt9 July 8, 2008, 18:27

    There is a near term possibility in fusion and that is Bussard’s polywell device. However, even if this works out, the cost of an interstellar trip will be tremendously expensive (billions of USD’s) as well as being decades away.

    I think it more practical to pursue relatively inexpensive research and experimentation in the development of new physics.

    The Earthtech guys are gearing up to replicate the Tajmar experiments. As I mentioned before, these guys are serious experimenters. If their replication is successful, we will know that there is something real here.

    The LHC goes online this summer with its first task to find the Higgs. This is relevant because if the Higgs is found, it is likely to falsify the Extended Heim Theory that Droecher and Hauser have developed, and we don’t even have to pay for it or do the work!

    Some of the ideas that Eric Davis and others at Earthtech have come up with are certainly unconventional. They might even be wrong. However, the cost of developing and conducting experiments to verify or falsify such ideas is most certainly cheaper than building spacecraft based on current technologies. We can’t even get into orbit for less than $100 million.

    If any of these ideas are verified, the implications for interstellar travel would be quite profound.

    In any case, star travel is decades away. It is more cost effective, in the near term, to do physics research than it is to do space stuff. If the physics research can produce more prosaic products, these can be licensed and you have a revenue stream to continue your research.

  • Benjamin July 8, 2008, 22:53


    “Learning the World” is one of my favourite science-fiction books, and the only first-contact book I like more is “State of the Art” by Iain Banks.

    John Hunt makes the point that a superconducting loop could produce magnetic fields to deflect energetic particles. I have scant knowledge of superconductors, but just the conservation of energy makes me skeptical as to whether a viable radiation shield could be made with a superconducting loop. You say it could be maintained indefinitely without heat, but surely the energy used to deflect particles would add up – even a very long mean free path would nevertheless contribute a large energy loss over light-years when encountering the particles at very high speed and having to deflect them or reduce their energy. Regardless of the exact mechanism you use, you need to have some way of ensuring that you have the energy to keep doing it for a long time over a long distance.

    Ignore the above if there’s some crucial aspect of superconductors which I’ve overlooked.

    Another science fiction inspiration is how Greg Egan has human interstellar travel done in “Schild’s Ladder” (a good book, by the way, notable for having the worst use of quantum entanglement to get out of a plot hole in any otherwise good book, and for using a theorem of elliptical geometry to explain two characters’ relationship). What happens is they send “spores” – self-replicating constructors – to a system, which build an infrastructure for humans to live in, themselves being nanotech and small but macroscopic devices which mine asteroids etc to replicate. Then if sentient creatures want to travel there, they do it at the speed of light, or rather AS light, by sending the data necessary to construct them at the other side. Egan’s future is one of AI so this is plausible, but how about this: to construct biological humans, first send small constructors which will replicate until ready… then send at the speed of light the information about how to construct artificial wombs and the other support equipment, and the required genome and anything else, as a digital signal with a laser, radio array, or other signalling device.

    Seems to me that Egan’s right: if you just established some kind of adaptable presence in the system, you’d be able to send whatever else you like later, at the speed of light, rather than actually worrying about getting fragile things through the radiation. You don’t need to have something which can be autonomous at the other end: so long as it’s robust enough to survive and start building apparatus to receive data and to construct machinery, you can squirt all the mission information later.

    There is the objection that perhaps our civilisation would have faced some crisis and either ceased to exist or been unable to muster the technology to send data at that kind of bandwidth, or our priorities may have shifted; there is a way to get around this. Just send a big, heavily-shielded chunk of transmission and data storage equipment out into space, no need for any particular velocity, all you need is to chuck some computers and lasers on an asteroid, and programme it to squirt the data on a loop as soon as it’s likely the other end will receive it.

  • James M. Essig July 9, 2008, 5:27

    Hi Folks;

    It is interesting to consider that technologies such as those based on electrodynamics, known quantum mechanics, and the like could seem like magic or perhaps be viewed as just as far out as any future workable concepts involving antigravity concepts or other gravity modification concepts, warp drives, and the like.

    For instance, one can imagine the possibility of an interstellar ramjet that would constantly accelerate at a rate of anywhere between 1 G and 10 Gs and perform a huge circumlinear travel itinerary that would take the craft on a loop with a radius of anywhere from 13 billion light-years to trillions of light years, provided any improvements to the interstellar ramjet can be worked out in order to permit such high associated gamma factors and long duration flight paths. Obviously, some novel ways of dealing with CMBR, starlight, and baryonic matter induced drag would have to be dealt with. But can you imagine if, by chance, our descendants trillions years from know actually forgetting about the launch of such a craft wherein the craft would show up at their door step trillions of years from now with representatives from our era! I could imagine that such would seem extremely freaky to them.

    Another possibility is the acceleration by reactionary means, such as by any workable forms of perpetually accelerating ISR, beam ship, planetary sized and planetary massed matter/antimatter rocket powered craft, etc., whereupon such a craft would reach a high enough gamma factor wherein Lorenz contraction along the length of its direction of travel would cause an area specific density high enough for the craft to become a black hole along tits direction of travel with respect to the stationary background reference frame. There might even pose a cosmic danger to such high gamma factors in producing such an area specific density in terms of forming a naked singularity of large macroscopic massed-scale with all of the dangers that such could expose the cosmos to.

    Another idea involves reactionary propelled craft, whether in rocket form, electromagnetic field effect propulsion form, etc., that accelerate with super high values. Perhaps onboard magnetic and/or electrical fields could be used to induce dipole moments in the atoms and molecules with which the contents of the craft are composed wherein additional magnetic and/or electric fields would be oriented to react against the dipole moment configured atoms or molecules to cancel out acceleration, perhaps even acceleration of thousands or even millions of Gs.



  • Ronald July 9, 2008, 5:38

    @ljk, July 8th, 2008 at 9:55: I agree with you that intelligent robots could (nearly) always do a better job at interstellar exploration that humans, but the main rationale and justification for humna sto go there would not be just exploration, but settlement and perpetuation of our species and civilization.

    I agree that it would already be a great thing in our lifetimes to so see humans on Mars; one step at a time!

    Indeed, also, the discovery of an earthlike planet with clear spectral biosignature would probably constitute a tremendous boost for interstellar exploration, both telescopic and (later) robotic.
    Therefore I always say, first things first: lets put all our present emphasis and effort, including advocacy, on a thorough and complete survey of planetary systems in our galactic neighborhood.

    @kurt9: thanks for mentioning Earthtech, I perused their site last noght, quite fascinating. I also follow Polywell closely and agree that this offers real hope, both for future energy provision and space propulsion. We live in exciting times.

    BTW, I think that, once we find other habitable or easily terraformable planets, just ‘billions of USD’ would be considered peanuts for interstellar travel.

    Maybe a bit corny to repeat the same political refrain, but the USA spends about 800 billion USD on defense and related budget lines (including Iraq). Iraq alone has cost anywhere between 500 and 800 billion USD so far, enough to establish a permanent presence on Mars, even according to some older and very high estimates (the ‘living of the land’ approach of Zubrin would be much cheaper). It is all a matter of priority. I mean, for some 20-30 billion USD per year (net present value) for the coming decades we could establish a permanent presence on Mars, offering a tantalizing new challenge and focus for humankind! I am sometimes afraid that humans cannot set their priorities right and do not realize what crucial and decisive period of time we live in.

    @Jim: I always love your optimism and ‘big’ thinking, we are the same age, we share the dream and I would love to join your party in 2040. However, I would already be partying, if and when we found the mentioned earthlike planet(s) and/or set foot on Mars.

  • ljk July 9, 2008, 10:39

    Ronald said:

    “@ljk, July 8th, 2008 at 9:55: I agree with you that intelligent robots could (nearly) always do a better job at interstellar exploration that humans, but the main rationale and justification for humna sto go there would not be just exploration, but settlement and perpetuation of our species and civilization.”

    Do not expect the “humans” who may one day journey to the
    stars to be anything like us.

    The only exceptions will be groups of “baseline” humans who
    refuse to change and decide to leave Earth and perhaps even
    the Sol system to preserve themselves and they way of life.

    Otherwise, expect the galaxy to look like this some day:


    Even if this scenario is ultimately wrong, I still find it more
    likely than what we see most often in Star Trek.

  • david lewis July 9, 2008, 11:00

    Maybe a bit corny to repeat the same political refrain, but the USA spends about 800 billion USD on defense and related budget lines (including Iraq). Iraq alone has cost anywhere between 500 and 800 billion USD so far,

    Maybe corny, also very depressing. Around 1.6 “million” US soldiers have served in iraq. The medical costs from those injured, physically or mentally, from the conflict will be a drain on the US treasury for decades after the last soldier leaves.

    The trillion the US spends on its military, matched by the trillion the rest of the world spends on their various militaries, is around 2 trillion a year our species wastes. Half of that spent on space, with half spent to modernize the third world countries, would give us bases on several moons and planets within the next 25 years. After that when we are ready to tackle interstellar travel we could easily spend 3-4 trillion a year as a species.

    The biggest challenge we face in exploring and colonizing space is not the technological one, it’s our own nature. The technology we can eventually develop, but our nature ….

    That nature might also be one of the biggest threat people on a generation ship face. The earth is large enough and has a resilient enough biosphere that up until recently it could handle our wars and conflicts. A single person on a generation ship might be able to wipe out the entire ship.

  • John Hunt July 9, 2008, 14:18


    I’m doubting that we’ll find an exoplanet with a biosignature any time soon. Our system contains a planet teaming with life and yet Mars and Venus probably show no biosignature. And if 5% or more of exoplanets containing liquid water spontaneously evolved life then I think we’ve got a huge Fermi Paradox issue. Rather, I think that the big breakthrough will be the discovery of a planet that calculates to have liquid water. I think that it will be unlikely to show a biosignature and yet would still be a candidate for colonization. I just wish that at that moment of public excitement that we could come forward with a practical (e.g. ISS cost-level) interstellar mission plan.



    Very good point about energy lost due to particle deflection. Hadn’t thought about that. Perhaps someone here could hazard an educated guess as to whether deflecting 5,000 years worth of high-speed but very low mass particles would significantly slow the craft. I understand that “A few cosmic rays pass through your body every second of every day, no matter where you are.”

    Your point also makes me wonder about what sort of drag a magnetic field would place on the interstellar medium although our craft would not be traveling at relativistic speeds so I don’t know if we’d be inducing ionization nor do I know if there are a lot of ions out there apart from cosmic rays.


    I agree that it makes a lot of sense to send small constructors then beaming genetic info later rather than actually worrying about getting fragile things through the radiation. But the premise of a Project Arrow (i.e. moderately long duration, frozen embryo mission) is that it is insurance for humanity in case we self-destruct due to technologic advancement. I myself have no confidence that humanity will not develop self-replicating chemical, biologic, or nanotech threats within the next 100 or so years. Hence the rationale for seeing if we can protect fragile biologic things from the radiation of interstellar travel.



    > There seems to be an assumption that going to computer-based mechanical systems will somehow magically get around the radiation problem…The Galileo probe lasted about 8 years in the Jovian system.

    I understand that around Io radiation is about 1,314,000 rems per year. The average value for background radiation on Earth is around 0.36 rems per year. If the Galileo probe could last 8 years then our craft should do fine even on extended trips if it had magnetic protection against cosmic rays and had electronic equipment designed to be rugged against radiation and any “sclerosis from dormancy” (I made that up, can you tell?).

  • ljk July 9, 2008, 15:10

    What Fermi Paradox? If there are planets that produced ETI
    that can traverse the galaxy, why would they want to visit
    Earth with 400 billion other star systems to choose from?

    And if they don’t have a space program but still developed
    radio telescopes and lasers, what motivations would they
    have to contact us?

    I don’t meant this to sound quite so negative, but while a
    more advanced ETI might want to study us as another data
    point in their Encyclopaedia Galactica, how many real
    motivations would they have to contact or visit us?

    How about putting a collection of water tanks around a star
    probe to protect it from radiation? And is there any way to
    turn radiation from our enemy into our friend, such as
    somehow using it for propulsion?

  • ljk July 9, 2008, 16:36

    As a side note, here’s an interesting tidbit I learned from
    Freitas “The Legal Rights of Extraterrestrials” – and I quote:

    The United States is presently in a state of national emergency.
    (It has been continuously since the early 1930s!) This fact is not
    generally known or appreciated by the public. The Presidential
    proclamations of national emergency issued under Roosevelt
    (1933), Truman (1950), and Nixon (1970, 1971) were not
    terminated when the crises that spawned them had passed.
    Our country remains under four separate active declarations
    of emergency.

    Is this still true 31 years after the article came out?

  • Benjamin July 10, 2008, 0:53


    As for your radiation problem, water tanks (or ice) is how most suggestions I’ve seen do it. At the risk of sounding like a Reynolds junkie, that’s how they do it in his Revelation Space series, they just cover the outside of their ship with tonnes and tonnes of ice. However there’s a catch. Water’s pretty heavy stuff. It doesn’t have really big nuclei or really tight core electrons to soak up the radiation like, say, lead does, and I suppose the idea is mainly to stick a lot of it there because it’s cheap and easily replenished. However, all of that is mass. If you want to accelerate your ship up to any appreciable speed you really don’t want it to be carrying a few thousand tonnes of dead weight. They only do it in the aforementioned Reynolds book because they have arbitrarily powerful drives which draw energy from the vacuum… Fantasy science which we couldn’t use in real life.

    And using radiation to accelerate you, I think there’d be some kind of conservation of momentum problem there… right?

    I think, and I mean this to ljk and John Hunt, that the most important thing is to get the smallest possible mass accelerated to relativistic velocities. But then there’s the above radiation problem, which would be much worse than in-system flights if you’re travelling long distances for a long time at high speeds, upping the energy and the total dose. That’s why I think that if you sent the most robust possible probe you’d get the best result.

    This has been well discussed in the New Scientist article “Space Mission Impossible”, 25 February 1995, the 1966th issue. (Available online with subscription)

    If self-replicating probes sound like fantasy, remember that life already does things just as remarkable. I think something packed with mesoscale replicators – things the size and complexity of ants – and the ability to decelerate them without killing them (killing being the right word for things this close to organisms) is what’s needed. The chemistry shouldn’t be impossible – find a way to make it assimilate the organic and inorganic matter on the asteroids and comets (or holy of holies, planets), and there are biological pathways bacteria have used to assimilate nearly anything, and as for coordination, ants and termites, things with this level of complexity, already run dumb programs to make marvellous mounds. Now they don’t need to store this data in their cells, and you don’t need to mess around with chemical signals – you beam it to them. Nanoscale radio transmitters and receivers are already on the table – see New Scientist, 17 September 2005 for example – and you just need to equip them to receive the data and tell them to organise to do X, Y and Z.

    The benefit of this is you could engineer these things with DNA-equivalent repair enzymes like you find in radiodurans, and you don’t particularly care what happens to them so long as one or two get there intact, whereas with baseline human embryos, you need to take a lot more care.

  • John Hunt July 10, 2008, 2:32

    ljk, Yes, it’s possible that intelligence is so common and mundane that 100% of ETIs have no interest in contacting us and that they coincidentally show no obvious evidence of their existence.

    But my argument is that, so long as we cannot rule out universal self-extinction then it behooves us to “purchase the insurance policy” that a near-term, frozen embryo, interstellar mission offers.

  • Ronald July 10, 2008, 9:03

    In my knowledge the Fermi paradox deals with (highly) intelligent life only, not with biological life in general. The MW galaxy and the universe at large may be teeming with life, but with exceedingly little advanced intelligence.
    So that would not necessarily make biosignatures a rare thing.

    Besides, even a planet with a reasonably amiable temperature (say, -50 C to +50 C), water (either frozen or liquid) and something resembling a (convertible) atmosphere would do for terraforming.

    As for an insurance against global-scale human stupidity, even a self-sustaining Mars base might do.

    @david lewis: straight from my heart!

  • ljk July 10, 2008, 12:14

    John Hunt said:

    “ljk, Yes, it’s possible that intelligence is so common and mundane that 100% of ETIs have no interest in contacting us and that they coincidentally show no obvious evidence of their existence.”

    Actually I was mainly referring to the fact that the Milky Way
    galaxy is so big and so full of so many star systems and other
    neat objects that an ETI society might easily miss us among all
    those wonders.

    However, if there are lots of intelligent beings, and especially
    if they are ahead of us, then that too might explain why we
    aren’t being contacted or visited – or at least certainly not
    figuring it out if we are being waved at.

    I am certainly all for preserving our history, knowledge, and
    especially ourselves from potential future disaster. I also
    pointed out that by the time that real interstellar travel is
    made possible, humans may be radically different from
    what we are now or have been superceded by much more
    advanced beings originated by us.

    As for water and ice being heavy – that’s what we should do,
    hollow out a bunch of comets and fling ourselves into the galaxy!
    We will have shielding and a water and fuel supply all in one
    package. And if we have to move a bit slower to get where
    we want to go – hey, the galaxy is over 10 billion years old,
    what’s a few thousand years?