Diaspore would be the proper scale for said generation ship relative to the Earth, but I suspect engineers would object to that even more than starship. Want to call them an argosy or something? An Earthship? Yes, I know that means something else.

Which was fascinating, but required the ability to drink from five simultaneous fire-hoses if you wanted to get a grip on what was going on

So a lot like reading something by Stephenson then?

Am currently reading REAMDE; there's no comparison. This conference was like reading ANATHEM and all three volumes of THE BAROQUE CYCLE in parallel.

As much as I hate to use the religiously freighted term, I think "ark" is an appropriate word for what this machine would be doing.

Speaking of religious freighting, I was quite disappointed by what I've seen about "space Jesii" (http://www.christianpost.com/news/professor-asks-did-jesus-die-for-klingons-too-57285/) coming out of the conference. What a waste of a time slot.

General Contact Vehicle :)

Wouldn't we want a full-on General Systems Vehicle?

DARPA is famous for pissing away money on things like red mercury. I fearless say nothing will come of this.

Species Transit in Orion Space System

DARPA's remit is to do the blue sky stuff.

a colony ship arrives at a habitable planet. this ship has never had passengers though. only a library of genomes and what's needed to synthesize dna and grow life from that in vitro. it begins spitting out feral humans.

now, can feral humans reacquire our culture over generations of exposure to passive media?

the ship provides a constant supply of nutrition and is also replete with touch screens connected to a library of all videos / music / videogames / books / etc.

there is no babysitting ai on board, so assume generations without language and prone to horrendous violence.

could some permutation of this work as a colony "seed"?

a colony ship arrives at a habitable planet.

The last two words are the really implausible part of this scenario.

Now I'm stuck on the religious themes. Noop, imagine your scenario, decanted feral humans released into a "garden" on the new planet and tempted to acquire "knowledge" after which they're kicked out of the "garden". Now, go reread Genesis.

Would we be able to have this discussion without ARPANET?

And I still think DARPA's X-29 is a thing of beauty.

A few years ago, I wondered when New Horizons would take the record for most distant man-made object in space (as some news accounts called New Horizons the "fastest spacecraft ever launched"). Soberingly, the calculation was that it would need 126 years to match Voyager 1's distance.

Without future propulsion technology (and maybe ion rockets are such a technology—you get a lot of speed from say a 1/1000g acceleration over 3 years, at least compared to Voyager or New Horizons speeds) it's not clear why we should bother thinking much about things like human travel to the oort cloud.

On the subject of the unlikelyhood of arriving at a habitable planet: I recently watched the sci-fi horror movie Pandorum and I was surprised the final reveal was not that the destination planet itself was a fiction…

Possible non-starship names? Mobile colony? Nomad colony?

What was the general tendency in terms of destinations and what to do when you get there? What are minimum requirements? (There are probably several rocky planets and gas giants of unknown description within less than 10 light years.)

Finally, was there any discussion on point two of the master plan?

I would consider myself to be a subscriber to the idea of Kim Stanley Robinson, that it would be an outgrowth of a colonization effort in the solar system (basically proving all the requirements except for longterm propulsion).

If you can make a space habitat that is big enough to support a civilization and has a working life of centuries in interstellar space, why return that civilization to a planet's surface at all? Far easier to spend your time and energy making small bits of matter (asteroids and comets) into new habitats than trying to find an "earthlike" planet and "terraform" it.

By all means, though, spread around the galaxy in this type of habitat in order to get all our eggs out of the one basket…

Hm, do we have any evidence of whether features like the asteroid belt, Kuiper belt, and Oort cloud are common features of planetary systems? Or, as always, are the only things we can see the massive objects?

It would suck to attempt to colonize space based on using matter from the Oort cloud of another star to create habitations for a few trillion humans, but on arriving there discover that there's not enough usable mass outside of the sun and a gas giant or two.

a colony ship arrives at a habitable planet

And that is where they usually lose me. If you can build an interstellar ark ship that can transplant human civilization (including supporting ecosystem) anywhere, then what you have is a biological Von Neuman machine.

You don't NEED a habitable planet. What you need is a solar system that has readily accessible mineral resources and a good habitable zone so that you can build more habitats. Several iterations of this and the descendants of original colonists will begin to forget they were ever planet bound.

Rick Cook did a good treatment of this idea in his book LIMBO SYSTEM

Did the conference just confirm your thoughts, or did it challenge them, perhaps sufficiently to make you change your mind on some of your ideas?

Well, I got smacked upside the head with at least two interesting ideas that mean I have to rewrite bits of the world-book (and plot) for NEPTUNE'S BROOD ...

Something with habitat in it... Massively Mobile Habitat?

Alternatively, how about something more symbolic and less technical, like a Waka? Here, I'm thinking of the canoes the Polynesians historically used to cross massive distances, carrying entire families. Wikipedia tells me that "waka ama" is the Maori term, with variations like "bangka" or "wa'a" used in other parts.

I like Ark, too.

I am just totally pessimistic. We are actually regressing in terms of capability, and I doubt whether we will even get to Mars before some kind of tech singularity/AGI appears. I also have a stinking cold.

The interstellar thing is interesting, but I suspect that if we do manage to colonize the solar system (radical human re-engineering probably needed), then interstellar colonization will be a given, though on tremendously long/slow time scales.

From what I gather about the Oort cloud, it extends far out into interstellar space, probably overlapping Oort clouds around other near-by stars. A wave of colonization from small-ice world to small-ice-world would nicely spread a population out into interstellar space eventually, all using somewhat more feasible technologies (nothing relativistic). 10's or 100's of thousands of years later, and boom! We're an interstellar species (maybe with most of us having no close interests in space nearby stars anyway).

Of course, we'd have to master fusion energy first. I hear it's only 20 years away. :)

Also, wait long enough and every million years or so sees a star pass within about 1 light year of our sun.

Really, the key is getting a small portion of people off the Earth, and have them independent enough to start expanding in the solar system. If you can live (even as a robot) on a moon of Saturn, you're probably just fine with interstellar space.

I would love to hear more about Philosophical and Religious Considerations that were brought up. What religion (if any) would you set up, or prohibit, for thousands of people living in a generation ship?

Also the Social, Economic and Legal Considerations would be fascinating. What types of systems would you set up, if you could start from scratch?

reliable nuclear-thermal rocket motors that have undergone extensive static test firing

Have there been any tests since the shutdown of the US program in 1972?

See Paul J. McAuley's "Second Skin": the damn sf writers always get there first. (",)

I second Stephanos' suggestion of a Polynesian reference, as they did something fairly similar at the time, given relative tech levels, down to the terraforming. The difference is they took the safety precaution of exploring into the wind, and had Micronesia as a backstop if they gave up and turned around.

Interesting point about having a cold. I would think that 100 years of living in closed environments could create some real nightmares for an epidemiologist. I know a lot of people /already/ believe we're losing the antibiotic race. Mind you, it's not even remotely my field but I would think that increased (but human-survivable) radiation in our environment might elevate both bacterial and viral survival-mutation rates. Flying Dutchman anyone?

I agree up to a point. A planet with some kind of existing life is going to be a useful source of minerals forged through biogeological forces (chalk, limestone etc). Provided they have the means to create structures that can bring up massive amount of cargo (and people) into space it's probably more cost-efficient to mine than artificially create some of these minerals. So mining outposts still make a lot of sense.

Of course, in the long-run these outposts could be the seeds of a planetary colony. Which might require a bit of genetic engineering of the human colonists. But the basic advantage of space habitats remains, you can build a new one relatively quickly and each habitat will have an environment perfectly suited to human life. The planet on the other hand will require a very long process of terraforming, and even at the end of it will probably not be perfect (for example gravity is likely to be noticeably different than Earth's).

Yes. First, there was the Timberwind project during the 1980s -- part of the SDI, it was a military project and is still classified. More recently, Gregory Benford was telling me that the Soviet nuclear thermal program ran their motors a lot more extensively than NERVA, racking up a thousand hours of continuous firing; their data is now accessible in the west, and some development work based on the Russian program is available. His conclusion is that nuclear thermal is a mature enough technology for outer-planets unmanned missions -- we have a buttload more experience with it than most people realize, despite not actually having flown such a motor.

I know a lot of people /already/ believe we're losing the antibiotic race.

s/we're losing the antibiotic race/we have lost the antibiotic race/

Unfortunately the arrival of XDR-TB and horrors like the NDM-1 metallo-beta-lactamase trait spreading around, it looks very much as if our current antibiotic strategies have collapsed. We may be able to regain the initiative, but it's going to take a radically different strategic approach to do so, and in the meantime the commercial pharmaceutical R&D industry is Unfit For Purpose -- antibiotics aren't profitable (you give a patient a course that lasts 1-2 weeks and then they're healthy again; compare with chemotherapy agents or better still, anti-depressants, where the patient is on the hook for months or years of treatment).

I caught something on the topic of antibiotic resistance on radio 4, and it was made quite clear that the relying on pharmaceutical companies idea was totally broken, because of exactly the reasons you give. However the gvt response seemed to be, umm, bureacratic in the extreme, rather than extremely worried and didn't exactly seem to be planning to deal with market failure, since that would mean admitting that markets are not perfect and private companies have limitations in their capabilities and uses, whilst at the same time promoting private companies to take over all aspects of gvt work. Bastards.

Vessel for the Gaian Diaspora, aka a Gaiaspore. At the very least, vessel is a nice, neutral term, and it's appropriate for the thing's function as a container.

While I'll admit I'm fond of vaka and its cognates, it really just translates as boat or ship.

Interesting news about nuclear thermal rockets. Somehow, I would have thought that some sort of atmospheric sniffer would have picked up on that exhaust, at some point.

I really like heteromeles' suggestion of "Diaspore" as an alternative to "generation ship" (which is a cool term in itself).

I've been bouncing between Project Icarus' blog, Centauri Dreams, and Athena Andreadis' blog checking for updates on 100YSS, and I look forward to the upcoming papers. In the meantime I've been trying to read up on the subject a bit. Some of the proposed interstellar ark schemes are pretty cool:

http://strangepaths.com/interstellar-ark/2007/02/14/en/

A friend of mine has a draft doc on just this subject. He knew about this conference but couldn't afford to get there. It's pretty damn huge, but has some interesting things in it. It's (still!) just a draft, but do have a poke about if you've some time to kill (but it does run to a 100+ pages)! Interstellar Travel 'Per Ardua Ad Astra'

Just do the inevitable and cut it down to 'spore already.

And while you're at it, you might introduce some seeds as well. Though in this case the Seeds should be manned and the Spores unmanned.

Actually, there was a technical reason I chose diaspore, rather than seed. A diaspore is a "plant (or fungal) dispersal unit consisting of a seed or spore plus any additional tissues that assist dispersal." Sometimes it's a seed. Sometimes, as with a tumbleweed, it's most of the plant.

Something like "gaiaspore" gets the point across a little bit better, although as a portmanteau word, it has some issues..

The basic idea is that you can't really disperse humans. At best, you can disperse a small chunk of the Gaian biosphere. That's the advantage of using a biological term. The other nice thing is it gets at the idea of a diaspora, which is what starships are about. They're not going to be commuter ships, unless someone really does figure out good FTL.

Of course we could. It'd be in the letter pages of Analog or Astounding, and it'd take months instead of hours.

Oh, and there'd be an editor selecting which letters he had room to publish.

why return that civilization to a planet's surface at all?

To take a walk in the Muir woods. To sit on a summer day and listen to a mocking bird 1/2 mile away. To watch a thunder storm approach and pass. To sit on the beach in a warm breeze while the waves lap at your feet.

And a few hundred other reasons. Assuming such options are available on said planet.

Sad news flash: Steve Jobs is dead.

It seems like all questions about Steve Jobs health have been answered. My condolences.

I stopped reading when I got to where it says "In the longer term, Sol (the Sun) will go nova. We are pretty certain of this." Reading a treatise on interstellar travel from someone so ignorant of elementary astronomy would be like reading a treatise on genetic engineering by someone who thought Splice was a documentary.

(The earlier section on overpopulation didn't exactly fill me with confidence either. This thing was clearly written by someone who thinks regurgitating tired cliches is a good substitute for actual research.)

You must carry a lot of something to heat for a NERVA. If you can get it up it would probity be great. For around here, not out there. I think I read Freeman Dyson saying it worked but not well enough to do anything with, Maybe you could dig into a BIG rock and start feeding the inside out the back for a long time.
DARPA is famous for pissing away money on things like red mercury, not things that could do any good. Look up red mercury and see what I think they still dreaming of doing with it. SUGER WOULD BE BETTER.
There was a group of real scientists that was given papers to grade on how likely it was they would work if supported, from DARPA I think. They all said main parts of Star Wars were a joke. They stopped getting anything from the Feds. And the big time pissing away started. They knew what they wanted to hear, and what they did not want to hear.
Jobs partner was the idea man who made it work. jobs pushed him out. And worked making sure he would never compete. That's what the partner's book said in a indirect way.

You must carry a lot of something to heat for a NERVA. If you can get it up it would probity be great. For around here, not out there. I think I read Freeman Dyson saying it worked but not well enough to do anything with, Maybe you could dig into a BIG rock and start feeding the inside out the back for a long time.

Is this yet another zombie idea that just won't stay properly dead? There really ought to be a FAQ on this one. The usual tradeoff for any advanced propulsion mechanism (read: propellant decoupled from the power source) is more mass vs less time in transit. Guess what? Most of the time - unless the propulsion system is very advanced indeed - "more mass" is going to win hands down every time.

So what if trip times to the Oort cloud go from twenty years to just five? Machines don't care and for human beings you still need to have that magic closed loop life support system regardless for missions that stretch on into a decade or more.[1]

The bottom line is that except for very peculiar mission profiles NERVA, DUMBO, et. al. just aren't going to cut down your trip times by any significant factor.

[1]Into Deepest Space

Jeff,

There are about 900 known or suspected debris disks which are the extrasolar analogs to Kuiper belts. A few also orbit stars which have planets. Analogs to our asteroid belt are also known, but are fewer in number. The wikipedia article is decent, http://en.wikipedia.org/wiki/Debris_disk. The nearest known debris disk is around AU Microscopium which is 32 light years distant.

You are correct that because of sensitivity limits of telescopes, the great bulk of the known debris disks are more massive than our Kuiper Belt. I expect that the soon to be completed ALMA telescope will find a lot more of the less massive debris disks.

Many thanks for linking to our Icarus Interstellar site Charlie.

It was a fascinating conference, and we learned a lot from it. We realised that there are some misconceptions about Icarus Interstellar that we need to work on. Principally, we appear to have given people the impression that we are advocating fusion pulse propulsion. That's definitely not the case. We are pursuing it in one specific design study, Project Icarus, but we are not assuming anything about whether it is the right way to do interstellar travel.

We're currently working on a variety of topics coming out of the symposium, based on the feedback we received from amazing people there, both critical and supportive.

(BTW I was the chap who said hi to you at breakfast in the 19th floor lounge on Monday after you were talking to Greg, but I didn't want to take up your time. I was afraid I might go into fanboi mode. :-) )

for those not familiar:

http://www.netwrx1.com/skunk-works/v02.n067

third post in the digest.

Hey Ross, So we don't think the Sun will eventually destroy us? I thought that was the whole point of trying to get off this rock?

I suspect he has just spent some time thinking about the problem, and maybe pulled together various memes that are related to the problem space, but I'd agree that maybe his style doesn't necessarily make for easy reading for anyone with specific knowledge in any of those areas. Hey Ho ... Thanks for having a little look anyway.

So we don't think the Sun will eventually destroy us? I thought that was the whole point of trying to get off this rock?

No, we don't think the Sun is going to go nova. Because it's the wrong stellar class; G2 dwarfs just don't do that. Instead they exhaust their hydrogen, begin fusing helium -- the core gets very hot and pumps heat into the upper layers, causing them to expand and cool somewhat, and the newly bloated red giant star is so large that the inner planets orbit within the photosphere, which tends to melt and then vapourize them over a period of millions of years.

We have around 4-5 billion years before this happens. As the average life expectancy of a mammalian species is on the order of one thousandth of a billion years, it is very unlikely that any humans will be around to see it. Indeed, this event lies about six to ten times as far into our future as the Cambrian explosion (and the Burgess shale fauna) lie in our past.

Ah ... thanks Charlie. This average life expectancy thing though, do we not get to play the Joker on this one? Could we not be sufficiently cleverer than our erstwhile mammalian cousins to be able to last at least a bit longer than others have managed? That said, it's a good point and I'll put it to him :-)

My emphasis:

six to ten times as far into our future as the Cambrian explosion (and the Burgess shale fauna) lie in our past.

General point - I'd like to thank DARPA for Charlie's attendance at their conference too. I suspect that both my blog reading and my fiction reading will be the richer for it.

This average life expectancy thing though, do we not get to play the Joker on this one? Could we not be sufficiently cleverer than our erstwhile mammalian cousins to be able to last at least a bit longer than others have managed?

My money is on us lasting a lot less time than most other mammalian species.

We've only been around for about 200Ky, and we've already triggered a once-per-100My mass extinction event. Doesn't bode well for our stability, does it?

Thanks for the info, Broca. There doesn't seem to be a link on wikipedia between "debris disk" and "oort cloud" in either direction, so I doubt I would have found the right term and article on my own.

Charlie said "We've only been around for about 200Ky, and we've already triggered a once-per-100My mass extinction event."

Is it too late already? I certainly know many people who work in, or near, the field who think so! Well, we do seem to have got the key in the ignition, and are stubbornly turning the engine over! If we don't figure out that the coughing and spluttering is the sound of the engine of our demise trying to start then perhaps we should just hand over the keys to the Dolphins and let them drive for a bit, as it turns out we're not the cleverest after all!

Actually, many of them think it's not actually too late yet, but that nothing will be done until it is too late!

> My contribution, to the extent that I've got one, is simply to suggest that we should stop talking about "starships" and select another term that doesn't come with a lot of preconceptive baggage: "interstellar autonomous probe", or maybe "interstellar colony vehicle". (But preferably something a bit snappier!)

For the autonomous habitats: arcologies. I got the term from Stefan Gagne's anachronauts, and it seems appropriate, understood as an architectured ecology.

(I was going to suggest starwisp, from Accelerando, for the robot probe, but that seems to be specific to their propulsion system.)

Dude, there was undoubtedly life on land in the Cambrian: bacteria and fungi. Probably slime molds and similar.

It gets annoying when people say "life" when they mean "animals." To paraphrase Stephen Jay Gould, it's been the Age of prokaryotes for the last 4 billion years, and age that will probably continue until life on Earth disappears.

As for destructiveness and tenacity, the last group of organisms to cause global destruction were the cyanobacteria, when they (over the course of hundreds of millions of years) flipped the atmosphere to oxygen, helped precipitate a couple of global ice ages much larger (global) and longer (up to 60 million years) than anything we've seen recently.

Cyanobacteria are not only still around, they and their descendents (chloroplasts) are more common than ever.

The only reason I'd bet against the human species as it currently exists is that our clade has been evolving quite quickly over the last million years. The genetic evidence says we're still evolving quickly, so I suspect that we're nowhere near a stable configuration. Since we're nowhere near as tough as cyanobacteria, I doubt we'll be around four billion years from now (absent time travel), but I suspect our descendents will make six million years.

attendees were discussing two classes of vehicle: a high-speed long-range robot probe (think Galileo, Cassini, or Voyager on steroids), or generation ships functionally indistinguishable from a space colony with a motor on one end

Everyone's given up on coldsleep, then? Serious question. If you could drop the body temperature to just above freezing (no lower: ice crystals are not good things in the body), metabolic reactions are going to slow a lot. Hypothermia victims (generally children who fall under ice) have survived going down to heart rates of 1 per minute - almost 1% of normal rate - for hours. And that's without prior preparation and medical oversight. Research on VO2 of warm-blooded creatures implies that it is 30 times higher at normal body temp than it would be at just above freezing.

That's going to cut the demand for consumables, and potentially the consequences of spending several years in coldsleep could be no worse than those of, say, spending a few months bedridden. Not ideal, but not lethal. Have a rota to thaw out every ten years and do some physio for a couple of months.

The trouble with cold sleep is that it would require long duration testing, which is ethically suspect and even if it worked their would be a requirement for monitoring the crew and equipment for problems. It would be hard to make an automated system that could fix an unforeseen glitch.

The other thing is that a lot of work still would need to be done deciding how to organize things and what to take along.

You don't want to get to another solar system and wake up to find out that due to the bad effects of long duration cold sleep your frontal lobes have deteriorated past the point where you could make rational decisions. Long duration hibernation is a magic wand at this point, though maybe not as much of one as strong AI or warp drives.

Well, the spread of photosynthesis was a much bigger deal.

Not merely poisoning the planet and killing off most of the existing species near the surface of the oceans (including most of those doing photosynthesis themselves), but even that only after depleting all the oceans of huge quantities of iron that existing species depended on. (Forming hundred meter deep deposits.)

Sounds a lot like a success story, right?

(There are implications of this that I won't spell out - because during the last century people have proven incapable of dealing with them and I don't think this has changed yet.)

Agreed that the Red Giant phase of solar evolution won't start for another 4 or 5 gigayears, we still have the slight issue of solar warming - the gradual increase in solar luminosity whilst still on the main sequence. That will drive earth's temperatures above the livable point somewhat quicker. I have seen estimates ranging from 100 megayears to 2 gigayears.

The best solution to this that I have seen, so far, is to expand the earth's orbit, and move us farther from the furnace. The rate needed is so slow that a dirigible-asteroid flyby of earth once every century or so (IIRC - I may be an order of magnitude or so off) will be sufficient).

And, hey, even if humanity isn't around then, then do it for the children! Give rats a chance!

Now you've piqued my curiosity.

Sorry. Should have stuck with my original contention of "since trilobites" instead of catching a phrase while Wikitrawling a quick fact-check on my comment...

There were some papers on the biomedical track on the topic of suspended animation. Actual freezing seems like a bad idea, but chilling and/or use of H2S-induced coma might help. However, as noted, we're sort of at the heroic Otto Lilienthal stage, rather than the Boeing-747 stage.

I suspect that maybe somewhere in China the bureaucracy and ethics committee has been bypassed in favor of testing on prisoners.

Freezing someone for 100 years to see what happens is unlikely, but there might be operational requirements which would allow us to work towards it in stages.

If Enceladus and Titan look interesting, we might want to be going to visit Saturn. Hohmann transfer orbits are about 6 years. This seems an ideal timescale to test cold-sleep methods. Unethical if untried, but there's a clear benefit (far fewer consumables there and back) that might outweigh the massive potential problems. I suspect that volunteers would be easy to find for the precursor experiments (run these all concurrently, unfreezing a batch at a time, and thawing the lot if this batch appears damaged): the problem would be the ethics committees.

A few iterations of the '5 years asleep, 3 working on Titan, 5 years asleep' cycle should tell us a bit about whether we could scale it up to 10 years/6 months (Yo! Pluto!), or 20y/6m (Sedna!) at which point things might get interesting.

China don't need no stinkin ethics committees. If there is going to be a starship launched, bet on the Chinese. The USA is going backwards thanks to being a risk averse lawyer infested blame society. And Europe is close behind on that front.

Well, ethics committees are one thing, but has anyone even done this on rats?

Seriously, how long do you think it would take to get the relevent permissions to do that expt here?

Although mice have been put in suspended animation using 80ppm of H2S. Higher mammals? Not a word AFAIK

IIRC they've completed H2S testing on pigs and are proceeding to phase 1 human trials. Said trials to be restricted to life-threatening emergencies remote from an ICU, where the patient is likely to die before they reach intensive care unless they're subjected to this dangerous procedure.

(This is the same protocol by which we test out new anti-cancer treatments: pick some folks who have terminal prognoses and see if it prolongs their life. Once there's some data, we can proceed to evaluate it on less urgent cases.)

Specifically a "Plate" or "Continent" class GSV is required...

Charlie @ 11 Sure about that, given that it appears that most(?) stars have planets .... I suspect habitables are quite common, it's just that we can't see them yet, being relatively small. @ 20 Oh dear? Or not?

Guthrie @ 31 Just for once, guvmint are not "bastards". They are massively incompetent. You are getting LAWYERS and BUREAUCRATS trying to solve a SCIENTIFIC/TECHNICAL problem-set. Of course they will screw up.

Dirk B @ 66 The US is going backwards because of the religious nutters. The lawyers are a minor irritant, I'm afraid!

That seems very unlikely ie a person in a near fatal condition, no ICU nearby, but with H2S on tap and the relevant permissions granted.

Greg, "habitable" doesn't just mean "roughly earthlike mass and orbiting in the liquid-water zone around its primary". "Habitable" also presupposes no runaway greenhouse effect, working plate tectonics, and an oxygen based atmosphere created by organisms that have oxidized all the reducing minerals in the upper crust. (But hopefully not gone so far that there's a flourishing human-incompatible biosphere already in residence.)

If any of those parameters are lacking, making the world habitable will involve terraforming operations on a scale rather more extensive than that required to give, say, Mars a habitable biosphere -- i.e. taking thousands to hundreds of thousands of years and major effort.

That seems very unlikely

Correct. Which is why it's going to take a long time to collect the relevant data. (IIRC they're talking about equipping emergency ambulances in remote wilderness areas of the USA and Canada with the necessary gear and trained staff.)

Everyone's given up on coldsleep, then? Serious question. If you could drop the body temperature to just above freezing (no lower: ice crystals are not good things in the body), metabolic reactions are going to slow a lot.

If you look at the relevant literature - science fiction - coldsleep, suspended animation, etc. remains hugely popular as a technique. The precise opposite, iow, of the teaching machines I was talking about in an earlier thread. I'm guessing this is because it's very easy to see medical freezing as a way of advancing The Dream of space travel, unlike mechanical education. But this seems exactly bass-ackwards.

We know how to ensure that a viable set of human reaches a destination hundreds or thousands of years away - just let them have kids, the old-fashioned way. Problem solved. No need to complicate it with suspended animation, because you're going to need a closed-loop life support system no matter what.

Otoh, Charlie has pointed out more than once something that I find extremely troubling: how many humans do you have to ship to maintain an adequate industrial base? I'm very much afraid that his estimates of millions, or tens or hundreds of millions are very likely to be spot-on accurate. Now, if you could use a mechanical educator to learn what you needed on the spot, maybe one human really could do the work of dozens of specialists . . .

ISTM that this would save far more resources than any sort of hibernation scheme.

de nada, and thanks for the clarification.

On a diffirent note, if we look at the things that have made evolution jump and ping, they include, oh, cyanobacteria (made multicellular life possible), eukaryotes (made sex possible), fungi (for obvious reasons), land plants (started the oxygen crank really churning), various animals that crawled onto land to feed on plants, trees (almost got all of the carbon dioxide out of the air. O2 levels skyrocketed and the bugs got huge), vertebrates (crawled out of the water and into the forests--do realize that the walking fish climbed up logs), dinosaurs (award for the most efficient lungs--and they're more numerous now than ever), ants and termites (eusociality is now dominant by biomass in the insect world), and humans (made cultural evolution more important than biological evolution for the first time, although we weren't the first to have culture).

Each of these is an addition, not a replacement or a step up the chain? My bet is that cultural evolution will remain part of the biosphere until the sun turns red. If the pattern holds, there's going to be a diversification of cultural species, and we cultured types will be a good chunk of the world's eukaryotic biomass until the Next Big Thing comes along and relegates us to the sidelines now shared by birds and trees (/sarcasm). Yes, we're transforming the world, and yes, it's going to take about 10 million years (most likely) for diversity to recover, whether or not humans go extinct. This is the way the Earth works.

Everyone's given up on coldsleep, then? Serious question. If you could drop the body temperature to just above freezing (no lower: ice crystals are not good things in the body), metabolic reactions are going to slow a lot.

If you look at the relevant literature - science fiction - coldsleep, suspended animation, etc. remains hugely popular as a technique. The precise opposite, iow, of the teaching machines I was talking about in an earlier thread. I'm guessing this is because it's very easy to see medical freezing as a way of advancing The Dream of space travel, unlike mechanical education. But this seems exactly bass-ackwards.

We know how to ensure that a viable set of human reaches a destination hundreds or thousands of years away - just let them have kids, the old-fashioned way. Problem solved. No need to complicate it with suspended animation, because you're going to need a closed-loop life support system no matter what.

Otoh, Charlie has pointed out more than once something that I find extremely troubling: how many humans do you have to ship to maintain an adequate industrial base? I'm very much afraid that his estimates of millions, or tens or hundreds of millions are very likely to be spot-on accurate. Now, if you could use a mechanical educator to learn what you needed on the spot, maybe one human really could do the work of dozens of specialists . . .

ISTM that this would save far more resources than any sort of hibernation scheme.

To maintain an industrial infrastructure circa 1970, Apollo, Orion, would probably need a minimum of 100,000 really clever, highly educated people.

From that, in order to go on from there given regression to the mean etc, you will probably need a very high breeding ratio right from the start.

we should stop talking about "starships" and select another term that doesn't come with a lot of preconceptive baggage

With a tip of the hat to James Blish, I suggest "cities in flight".

A volanurb? In chinese, that would be fēixíng chéngshì.

Charlie@48

Correct that the Sun won't go Nova, but that is because it is not a close companion to a white dwarf, not because of its spectral type. Nova occur in close binary systems where a white dwarf accretes Hydrogen gas from a companion star which may or may not be Solar-type. See http://en.wikipedia.org/wiki/Nova

Each of these is an addition, not a replacement or a step up the chain

On the relevant time scales, all of them today are a replacement of their former selves.

I think in standard chinese it would probably be something like 'xīngjìfēichéngshì' 星际飞城市 (interstellar flight city, flying star city, or starflightcity) (I guess 'xīngshì' 星市 for short? (startown, starcity :) I'm sure there must be a more poetic name...

Ref. medical induced comas; it's not as uncommon as you might think. ISTR that they are already using this (not using H2S, but it's being talked about as an application) for shipping serious casualties from Afghanistan. You stabilise them on the scene or in the MERT aircraft, get them back to Kandahar, and then put them into an induced coma so they don't deteriorate over the next 24 hours while you ship them back to hospitals in Europe.

The trouble with cold sleep is that it would require long duration testing, which is ethically suspect and even if it worked their would be a requirement for monitoring the crew and equipment for problems.

Once you've got past the testing-on-monkeys stage it should be feasible to get volunteers to be chilled for, say, a year or two. (Look at Mars 500.) And if they come out with no ill effects, I think you could make a good case that chilling for ten years would be reasonably safe.

As for the supervision thing: you have a few crew awake all the time, and operate on a rota. So everyone spends 20 years asleep, 1 month (or whatever) awake supervising the other sleepers and doing physio, 20 years asleep and so on. That way you can ship 10,000 people on a 200 year voyage but you only really need enough consumables for 20 or so, because the ones in coldsleep will barely consume anything. Makes your environment problem much easier. No worries about a society that can exist in isolation for hundreds of years - perceptually the crew will only be awake in flight for a few years.

Ref. medical induced comas; it's not as uncommon as you might think. ISTR that they are already using this (not using H2S, but it's being talked about as an application) for shipping serious casualties from Afghanistan. You stabilise them on the scene or in the MERT aircraft, get them back to Kandahar, and then put them into an induced coma so they don't deteriorate over the next 24 hours while you ship them back to hospitals in Europe. Isn't it normal practice now for cases of significant brain bruising, such as can happen in truly high speed vehicle crashes (we're talking 150+ mph at impact)?

I think the problem is, as Charlie pointed out a while ago, you might not get any prolongation of life through induced hibernation.

It's unclear whether mammals really follow environmental time. Environmental time measn that your lifespan is something like 2e9 heartbeats, and if you can slow down your heart rate, you live longer. It's equally possible that you actually live 70 clock years, regardless of what your heart rate is. There's not enough good data on mammals to answer this.

In the later case, hibernation is still useful in space, in that it lets people last through lean times. Unfortunately, hibernators have to binge before and after to make back the calories and nutrients they lost during hibernation, so it only makes sense if food is only periodically available.

In this regard, Larry Niven's scenario of sending obese people into space might be equally useful, if you can somehow help someone pack on 100 extra pounds, make it into space, and then starve back to normal weight while performing astronaut duties and staying healthy.

Two things that are easy to forget, though, I think easy to fix is the need for the means to start up some kind of agriculture and the possibility of pregnancy en route.

I might actually require the sterilization of male crew members, it's an easier operation. If more people are needed later they could be created from stored sperm.

While this squicky, it's the kind of thing you have to think about particularly on a colonization mission. For many guys, though certainly not all, caring for babies and young children is a blindspot. It does, however, have to be taken into account.

you might not get any prolongation of life through induced hibernation ... There's not enough good data on mammals to answer this.

Another serious worry -- wrt. space travel -- is that radiation damage is cumulative. So you might sidestep 200 years of physiological ageing via cold sleep, just to get sandbagged by a 200-year dose of cosmic radiation: go to sleep healthy, wake up with multiple brand new cancers and radiation sickness.

(High energy cosmic rays take a lot of shielding to attenuate -- figures I've seen suggest 10 metres of water or equivalent. And even with significant attenuation -- 1-2 orders of magnitude -- a 200-year dose could well be very serious.)

You'd have to balance the easier sterilisation op against the higher probability of successfully reversing the op in women.

Charlie, what's triggering mass extinction has to do with our own survival? We just need the biosphere, and it survived numerous extinction events. I'd understand the problem if humans were multiplying uncontrollably and destroying more and more natural environments, but in developed countries the reverse is true, former farmland turn into new forests as we speak. So we screwed the biodiversity of many small ecologies by introducing continental species. It sucks, but not the end of the world.

Farmland is turning into forest in a few places in the developed world. In many other places, it's turning into subdivisions, and where intensive farming is the norm, we're losing top soil.

In other words, because of various land use laws and practices which favor homes over food, we're going to have to feed more people on less land, and the farm land that remains is degraded or of lower quality, and further from the cities that it's feeding.

Why did this happen? Many cities grew out of towns that sprang up near plentiful water and exceptional farmland. As the cities grew, a farmer could always make more by selling his land than by growing crops on it, especially if developers had a hand in crafting the local planning ordinances that dictated how many houses could be built on farm land.

Note that this is happening all over the world.

That's part 1.

Here's part 2: mass extinction. The numbers appear to say that in the last 10,000 years, we've seen declines in animal species (the easiest fossils to find) that are comparable in scope to one of the big 5 mass extinctions.

Why does this matter? Some animals (especially elephants and top predators) are keystone species, which means that food webs change substantially when they disappear. Effects cascade, because they control which plants are dominant, and in the case of top predators, they control both herbivore populations and the populations of smaller predators. I'll also point out that humans evolved in this disappearing ecosystem.

A bigger reason why this matters is that humans, right now, are driving the swift evolution of a whole host of new species. They're called pests, pathogens, and weeds. They take advantage of the bounty we provide. The problem is that the species that win this particular lottery are capable of taking advantage of us whether we want them to or not. It takes a major effort to even control any of them. There are more of these every year, too.

Now, here's the question: if you had a choice, which ecosystem would you want to live in? Choice A is the system in which you evolved, where you are the baddest dude on the block, and if you don't exercise self control, you'll trash the place and make life harder for yourself. You live here by exercising self control. Choice B is the system that's evolved to take advantage of your worst excesses. You live here by a matter of luck and constant adaptation.

Personally, I prefer Choice A, but apparently society at large thinks Choice B is more fun. To each his own.

Hmmm ... let's run a BOTE calculation just for grins, to see how much shielding mass a really large space colony might be able to support. Going big, let's say that we're going to send out 1e6 people in a single "vehicle". On average, I can't see industrialized humans who are completely self-sufficient in terms of food and material goods production needing less than 300,000 meter³ per capita*. That's a sphere a little over 40 meters in radius, with a surface area of about 7000 meters². If we wrap that in a thin skin standing 10 meters away from the hull and fill the volume between with water to make a shield, that's 70,000 tons of water. A million people mass somewhat under 100,000 tons, and the ship itself is going to have mass quite a bit more than that, so carrying that much water for shielding doesn't seem too onerous.

Of course that's a crappy design for a colony; if we spin for gravity then we want it in the shape of a cylinder to get the most surface area at standard gravity, and we probably need a larger radius to keep the RPM for a reasonable gravity low enough to reduce Coriolis forces, and to reduce the gravity gradient on the living surface so standing up doesn't make you dizzy. But the spherical cow design gives a rough idea of the practicality of a water shield.

• Assuming that on Earth the industrialized nations have a complete footprint of somwhere between 1.7 hectares of land per capita (the estimate for the actual use in the Netherlands) and 5.3 hectares per capita (the estimate of what the Netherlands requires for long term sustainability). Source. Then I arbitrarily assumed a 10 meter ceiling average, which ought to allow for ventilation space, etc.

So we screwed the biodiversity of many small ecologies by introducing continental species. It sucks, but not the end of the world.

There speaks a person who is unfamiliar with the role of pharmacognosy in keeping us alive.

People would prefer option A as well, but we havn't exactly been given the choice.

Math error. (I'd quibble over the need for 10 metres of head space; but I'll take it as a starting point.) However, I notice that you went from a per-capita volume of 300,000m^3 to total volume (you need to multiply by 10^6 for a million people). So, we need 300^9 cubic metres. I make the radius of that sphere a whisker over 4Km, i.e. surface area of roughly 220 x 10^6 square metres. With 10 metres of water for shielding, that gives us roughly 2.2 gigatons of water needed to shield our ship. (That's 2.2 cubic kilometres.) (Have I dropped any digits?)

Actually, 22,000 tons of water shielding per colonist is a bit better than your original estimate of 70 kilotons per person -- square/cube law for the win.

But it underlines the fact that we're talking here about something the size of a large comet or a small asteroid, not a "ship" in any sense of the term we understand; something that masses a hundred times as much as the entire 21st century world-wide fleet of ULBC and ULCC cargo ships combined! And if it's going to go anywhere fast -- even reaching the dizzy pace of 1% of light speed -- it's probably going to need a reaction mass bunker the size of Ganymede.

As the cities grew, a farmer could always make more by selling his land than by growing crops on it, especially if developers had a hand in crafting the local planning ordinances that dictated how many houses could be built on farm land.

"Obsf": The Good Earth

Choice B is the system that's evolved to take advantage of your worst excesses. You live here by a matter of luck and constant adaptation.

Obsf: John Varley's Millennium. The book, not the movie.

It's a terrible waste of space to create largely empty single-layer spheres when you can shrink them by simply creating multiple-layer spheres. That way you get more surface area for a smaller total volume. Instead of traditional single-layer planetary agriculture you could have grain fields stacked a meter above each other. As for intensive vs sustainable agriculture, they'll probably not be too keen on soil in the first place, preferring hydroponics. Soil is basically a lot of useless matter for purposes of growing plants, it's only the small percentage of nutrients in the soil that plants need.

Tobu suggested "For the autonomous habitats: arcologies."

Hmmm. Didn't Sim City have Arcologies too? Indeed, once cities become sufficiently large won't there be some requirement for them to be more and more self sufficient anyway. Obviously, they won't need the shielding etc, being Earth-bound, but perhaps we could hone at least some of the skills required here on Earth? Perhaps an entire Arcology could move to live on the first hollowed out asteroid - they would already have a functioning government, etc, etc.

You might as well use aeroponics and do without the water entirely...

...Unless, of course, you've been paying attention to the plant science research that says that Leibig's idea (that plants only need nutrients from the soil, and otherwise the soil's useless) is radically incomplete. Just remember that the plants that do best in hydroponics typically have been bred to do well in hydroponics.

It's also unclear whether you can make a functioning closed ecosystem with hydroponics, particularly since with hydroponics (let alone aeroponics) you lose the soil-based decomposer ecosystem that would normally break down all the dead organic matter to things the plants would take up. Going from trash to the liquid fertilizers required by a hydroponics system isn't simple, and one thing you've got to be really good at in a closed system is recycling your nutrients efficiently.

Small brainstorm. It isn't a design for a livable formerly-known-as-starship. Rather, it's a test to see if the design will work.

Here's the test: the closed ecosystem within the ship has to be able to produce enough beer to satisfy all the beer consumers within the system.

The reason? Beer's pretty central to culture (see http://topdocumentaryfilms.com/how-beer-saved-the-world/ for a humorous and fairly accurate take on the role of beer in history). If things are so tight that there's not enough acreage to produce alcohol (beer or equivalent), then there's probably not enough surplus capacity within the system to withstand the inevitable problems they'll face. Ditto if everyone has to be sober all the time just to keep the ship running. In the later case, people will distill alcohol anyway, and it will be a problem, rather than a central part of the ecosystem.

Something to think about. If they can't drink, it probably won't fly.

I like the beer test.

Added ornate twiddle: the ship should be able to produce a passable lambic. (Or, instead of a beer, scrumpy: the same principle -- natural fermentation implies a robust detritivore ecosystem -- applies.)

Another serious worry -- wrt. space travel -- is that radiation damage is cumulative.

That is rather a good point. Yes, we've got error-checking mechanisms and so on which allow us to handle the damage caused by constant background levels of radiation, but if you're in coldsleep those will slow right down along with anything else; so even if the actual rate is only, say, 10 sieverts a year of ship time, which is perfectly OK, you're receiving 1000 sieverts per year of "physiological time" and you're probably toast.

So you'll need to shield your coldsleepers pretty well. Fortunately they won't be moving around too much so you can pack them in closely together in the centre of the ship, shielded by everything else. We won't need to shield the rest of the ship so much, because awake people are running at a higher metabolic clock rate and aren't as vulnerable.

You can get 200 years of radiation damage on Earth in 20 years if you live close to Chernobyl. The increase in cancer rate will be somewhat noticeable but not dramatically so. In interstellar space, the big problem is the cosmic rays, which we are shielded from by atmosphere; 10 metres of water or 3 metres of rock would be equivalent to the atmosphere. Seems entirely feasible to bring the radiation down to perhaps 0.03 microSieverts per hour (mostly from internal sources). '

Funny: for the inner shield, you would have to use steel from old sunken ships (all newly produced steel gets contaminated by cold war fallout, and radiation measurement equipment commonly uses steel from old shipwrecks). Starship Titanic.

At 0.03 microSieverts per hour, it would take 33 millions hours or over 3000 years to take dose of 1 Sievert, which is the radiation sickness threshold if you are exposed to it at once, and which raises cancer risk by 10%.