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Still on the road, sort-of

I'm back home today and tomorrow, but off again on Thursday to Novacon 39 in Nottingham. Oslo was about as cold as Edinburgh, and about as dark; although a good time was had by all, all this rushing around in the dark is leaving me somewhat tired, and even a portable battery-powered daylight lamp for dealing with SAD (which has begun hitting me earlier and harder with each passing year since I turned 40) isn't helping much. (No surprise, if you bear in mind that I live 50 miles or so north of Moscow, some way north of every significant city in North America except Anchorage).

In the meantime, I have little to say except that I'm still thinking about the long haul in extra-planetary travel. Running a biosphere (as the past couple of discussions suggest) looks to be a lot harder than most people imagine — we don't even know where all the critical paths lie, and the longer it has to operate the more complex it gets (with failure modes that mostly appear to be ghastly variations on dying painfully and slowly of exotic trace element and micronutrient deficiency diseases). But there's another question that occurs to me. What are the other problems with building and running a biosphere in space?

Here's one: waste heat dissipation.

Vacuum is, as has been noted in the past, a good insulator. At the same time, it looks likely that any long-term human space habitat is going to need shielding from high-energy cosmic radiation (which is probably going to be physical, rather than electromagnetic, given the multi-GeV energy spectrum of the radiation in question). And for long-duration habitability, biospheres are going to need to be complex, multiply-redundant, and to include pathways to recycling micronutrients and exotica (not just for cycling carbon dioxide and water back into oxygen and glucose).

Approximating a space-based biosphere to a sphere would seem sensible — you can maximize the inhabitable volume per unit of external surface area, and the mass of the radiation shielding goes up in proportion to the external surface, not the interior. But radiation shielding works in both directions: biospheres take short-frequency light and down-convert it into long-wavelength thermal energy (the second law of thermodynamics is in play, here). Don't underestimate the amount of heat we need to dump. Per kilogram, mammalian muscle tissue ("us") puts out more watts of waste heat than an equivalent mass of the sun generates through fusion reactions! The waste heat a biosphere produces ought to be proportional to the mass of metabolizing organisms; and that is going to scale with the volume of the biosphere.

So, while it might make sense to make our spherical biosphere as voluminous as possible (to make best use of the dead mass we're hauling around as shielding), it's going to need radiators to dump the waste heat into space (background temperature: 2.725 degrees Kelvin). Their area is going to go up in proportion to the volume of the biosphere, not its external surface area. And they're not going to be a useful contributory part of the biosphere — they have to be outside the cosmic radiation shielding.

What other gotchas associated with the mechanical supports for an in-space biosphere can we expect to run into? (NB: I'm deliberately ignoring propulsion, political/profit motivation, and crew. If you want to talk about the requirements of running a biosphere, that's the previous topic.)



Without doing the numbers, is there any advantage in using magnetic shielding to divert/attenuate as much of cosmic ray background as possible? This would reduce the amount of "dead" mass that needs to be invested in shielding. If the magnets are persistent mode superconductors, very little (almost zero) power is needed to maintain the field.

If shielding is no longer the dominant driver, then radiator surface wants to be proportional to biosphere volume, which takes you in the direction of something like Ringworld - a relatively shallow layer on the inside of a cylinder. This can be spun up around its symmetry axis to give gravity (or an approximation to it), which is useful, and even necessary for many species.


Will this biosphere be under constant acceleration?


How long time do you want your vessel to last ?

Whatever your exterior surface is made of, it will not last until you get anywhere interesting.

We're not quite certain if metals will actually sublimate in the long term exposure to space, but I would not want to trust them not to.

The accumulative effect of free hydrogen is also a good questoin, most metals get brittle when exposed to hydrogen.

Cosmic radiation may also be significant.

So you want an exterior surface that can be renewed, replaced or regenerated.

Somewhat similar concerns go for whatever provides the structural strength of the vessel, beams will loose their strength over time to all sorts of solid-state/crystaline effects.

So it sounds to me a replacable recycleable exoskeleton is in order.




I am intrigued by your battery powered lap, but perhaps this is too much information?

To minimise the heat dissipation problem, we should clearly send cold blooded organisms: perhaps our shadow cabinet? There's a well known chameleon who needs to be put somewhere safe before he does too much damage.

Sorry if this fails the tedious politics test. I quite understand.


I'd also take a good look at interior degradation - a biosphere that optimizes space and biomass should be quite warm and wet. Think Brazilian rain forest, not Finnish coniferous forest.

Also, several torusses should provide better surface area/volume ratios and not cost much more in terms of weight, while they can provide good artificial gravity by rotation. The need for gravitiy is not to be underestimated - it makes a lot of things easier. Plumbing, for a less obvious example. While some organisms can do fine without gravity, others do not (esp. humans).

They also provide multiple redundancy, which is always nice in such projects.


Can you see Santa Claus from your house?


Assuming there's some type of computer architecture integration with the biosphere, you'd want a minimum of AE-35 units. :)


I'm in the middle of Arthur C Clarke's "Sands of Mars" and the Ares ship (which reminded me strongly of the ship in 2001, and ships in other fictions I don't recall the title of now) lends an idea. Connect your biosphere via tunnel to a second sphere that has radiators on the outer surface. Perhaps keep any "difficult to live near" mechanisms/radiation sources down there as well. Dumbbell-shaped ship, but you could also spin it with the two spheres hurtling end-over-end to provide pseudo-gravity throughout the whole of the biosphere, rather than just at the "outer rim" if it were spun on-axis.

Sure, transporting the heat down the connecting structure may be hard, but we do heat-pumps and also steam-tunnels a lot on good 'ol Earth. A passive heat-pipe probably would not be good enough, unless you had all the heat-pump machinery in the radiator sphere, and just used the passive heat-pipe to move the heat out of the biosphere to the radiator sphere.

As for shielding against "interstellar friction" (ie the scouring of dust, sublimation effects, etc.) perhaps just plaster on crushed asteroid? (Borrowing from Stephenson's Anathem here) It'd be ablative, and you could renew the coating wherever suitable asteroids are found. It's difficult to shield radiators, though, at least with "end over end" spin. On-axis spin would just require a frontal shield (or just the shielding already on your biosphere) that leaves a relatively clean "wake" for the radiators to pass through.

Hmm. One of the other problems is keeping enough oxygen around. Sure, recycle, re-split water, etc. but you're going to have leaks. Over a long enough span, you will very likely need to periodically "top up". Need a way to store oxygen in a very leakproof way - would various oxides be good? If you have enough input energy you can break down the oxides to get the oxygen and the base material out. Could use oxides as your ablative shielding, just find a "cheap enough" way to replenish them - I don't know what the makeup of most asteroids is, but if you can find big enough chunks of ice (comets, etc.) and solids that oxidize then you can make more.

Somewhat off-topic - if your radiator was a big, dark, flat plate, with the opposite side being "lighter", would it provide (a small quantity of) thrust? I'm thinking about those little radiometer things, writ large.


How are you generating gravity? If indeed you are. My science background isn't strong enough to the maths, but if you're generating gravity by rotation in a sphere wouldn't things get a bid awkward out to the sides of the sphere that aren't in the direction of rotation. Poor phraseology, I know but hopefully you'll get what I mean.

Not sure if it counts as mechanical but, if you aren't generating gravity you're going to have problems with your biosphere down the line.

Also, along with your radiation shielding problem. The more radiation you shield against the less perception of your environment you're going to have. And indeed you're going to have to have some physical entries into the sphere, so you can't treat it as a single spherical object: it's going to have some imperfections in it's skin.


I find myself wondering when it becomes cheaper to shield from cosmic rays by making your "biosphere" large enough to retain an atmosphere via gravity - meaning planetary mass, albeit for a fairly small planet. I'm not talking about full terraforming here, just grabbing a spare planetoid that can carry enough gas to act as shielding, while you build smaller sealed habitats on the surface. That would also avoid the health problems that result from microgravity (obviously this is all assuming that you don't need microgravity for something). If you don't need to accelerate the thing, this may be practical.

Alternatively, maybe you could build it "inside" a gas giant. That would also let you dump heat via convection, which reduces the radiation problem, and give you a large supply of some essential chemicals (lots of methane and water in them, at low concentrations).

Another problem: if you're planning on building this biosphere near a star, you need to deal with the stellar wind somehow. It's lower energy than cosmic rays, but there's a lot more of it, and it will gradually erode anything it hits.

On magnetic shielding: superconductors are only near-zero maintenance when nothing is hitting their magnetic field. If it's getting bombarded with cosmic rays, there's going to be a significant energy cost. I'm not sure how to estimate the scale of that.


We're not quite certain if metals will actually sublimate in the long term exposure to space, but I would not want to trust them not to.
Yes we are.


I think there would be some pretty severe complexity issues with the superconducting radiation shield. Wasn't the LHC shut down by a baguette recently?

I'm not saying that you *couldn't* use superconductors, just that the current tech has a number of critical dependencies that would be challenging for redundancy's sake.

Despite Earth's limited habitability, it did a good enough job to allow for at least one species to evolve enough to take notice. I shouldn't just say 'it' though, I should add Jupiter in there for custodian's sake, and being lucky to be far enough from galactic center to not be too toasty.

From a 'long now' kind of view, wouldn't you have to take a fairly big bubble of spacetime as your design ecosphere?


Assuming a modern day level of technology, this could get messy.

Ideas to combat this vary, Ice-shields, super-armour, laser-defense, force-fields etc. Sticking with the modern-day theme however, the simplest answer is to drive real slow and don't put all your eggs in one basket.

Getting lost:
It's not hard to navigate by the stars until your external sensors get fried. What's your backup? Plus do you even know where you're supposed to be going or are you off exploring?

Be prepared:
Wherever you end up, the chances are that no one has been there fefore you, so you're going to be capable of landing/settling in an unknown environment, sand/sea/hot/cold/windy/high-G etc. You'll need a swiss-army knife for your landing gear to handle all that.

Obviously there are ways of dealing with this, but as a minimum you'll want to monitor every inch of every room, duct, pipe and wire ship-wide. Fires that cause an explosion could be bad. Will You want thick walls in case of shrapnell, or thin ones to save mass? Walls become your storage space for raw mats?

15 year old kid sets of fire alarm for fun, automated defenses jettison 3 decks into space. Oops.

No really, what's its retail value in scrap?

Changed my mind:
Do you have a way to turn around? Can a shuttle leave and go back, can you evacuate?

Who's cleaning this thing?

A lightbulb goes pop - you need a new one. That's silicon smelting, glass blowing, metal forging, and machining. Oops.

Advance to Mayfair:
Arriving at your destination in your banged up old colony ship only to find that in the 1000 years since you left someone back on earth invented a teleporter. Do you stay in touch with earth? How? With who? If they give you nanotech breakthroughs, could you make use of them?

Where did you get the materials to build this thing? And who's paying for it? Perhaps the biggest obstacle of all would be asking people to believe it might work in the first place.

Basically, I think that the less you give the travellers then the less there is to go wrong. It might be tempting to circumvent a problem by throwing mass at it, but everything we are used to is so interdependant it just won't last - short of hollowing out the moon and powering it off into space. I would want to start with a number of small nuclear submarines with extra stuff crammed into them. Then I'd send them out in a flotilla and they could trade spare lightbulbs for a travel-sized connect-4 game. There's some redundancy with a flotilla and the social/mental benefits of pitching people against each other in this way might also be useful.

I like this topic.


I wonder whether you can do any useful work with plasma to cool things.

Beyond that, I think it's a matter of meticulous good design. Surface area doesn't have to be flat to radiate, and a fair amount of the waste heat will get used by ectotherms (i.e. plants) as ambient warming so that they can work faster (remember, they work at ambient, they don't add a huge amount to it). Additionally, LEDs are getting better at producing photosynthetically useful radiation without a huge amount of waste heat, and I suspect that future technology will get at least as good (if not better) at providing useful light efficiently, in an environmentally benign manner.

In any case, I don't think waste heat is a huge show stopper, but as with the rest of these ecosphere beasties, it takes a heck of a lot of good design work to put it all together.

The real kicker is operating regime. I suspect that a ship that works in Earth orbit might have problems in interstellar space or in Mercury orbit, because the thermal and radiation regimes are different. To some degree, you can insulate a deep space habitat from a huge heat input by having it in the shadow of the engine pushing it away from the sun. Still, keeping an ecosphere viable will affect navigation and route choices, as well as spaceship design. But that's true already.


Oh noes! Intelligent design...[[rolls eyes at self. Sorry.]]

I think it would stand to reason that you'd want to make a pretty sophisticated computer simulation of the biosphere within it's operating regime as heteromeles puts it, and producing a 'five nines' end run. That would be a fun challenge in and of itself.


I don't see that radiator area has to be related to arkship-surface area at all; having christmas-tree- or cpu-cooler-shaped arrangements of radiator panels sticking out will allow you a radiative area potentially orders of magnitude larger than you actual ship surface. Of course, you do then need some extra shielding to stop too much of your cooling system getting blatted into atoms by passing spacedust :)

The other possibility, of course, is to use your waste heat constructively. Feed it into your engine system to generate extra thrust if possible, perhaps, or else store it and use it to power the communications laser for talking to Earth :) More of an engineering challenge, but probably a better idea in the long run.

Nick@11: Well, strictly no, actually. We know they don't sublime at all quickly, which isn't the same thing. The problem is that if, say, 16 Psyche (the largest and most easily measurable of the M-type asteroids) sublimes from every surface at a rate of 1cm per century*, we couldn't possibly detect the mass loss. (And I wouldn't expect any existing space vehicle to have suffered identifiable sublimation, either.) But that would represent a potentially serious loss of the protective envelope of a thousand-year generation ship - four extra inches of thickness is a lot of metal to boost into orbit. Of course, if you just hollow out an M-type asteroid, you can make the walls as thick as you like, and asteroid mining is arguably no more technically challenging than arkships. :)

*For the record, I regard this as implausibly fast but probably not absolutely impossible for heated metal**. There'll certainly be some mass loss over geological time, but whether it'll be measurable in mere centuries is another question.

**most asteroids are at interstellar background temperature, remember, while an arkship emphatically won't be. I'd expect it to lose mass faster than an otherwise-equivalent asteroid. But still very slowly.


The waste heat a biosphere produces ought to be proportional to the mass of metabolizing organisms; and that is going to scale with the volume of the biosphere.

Metabolic rate in mammals scales with the three-quarters power of the mass. A classic allometric law.

The amount of energy necessary for an internal ecosystem will be roughly the internal surface area of the habitat times some fraction of the solar constant. So the critical ratio will be internal area / external area. A habitat like a layer cake will have more problems than the hollow sphere or cylinder.

Thermal regulation is a known problem in crowded hives for insects. But I'm not seeing volume as a scarce resource in space.


This is one of the reasons I've never had much faith in the "generation ship" idea for interstellar travel. Besides the mass increase you get all that added complexity and associated problems.

Much more feasible is an automated sleeper ship. That only requires one breakthrough in addition to the basic ship -- some sort of reliable suspended animation technology. Which, given that it would have attractive uses here on earth and is an order of magnitude cheaper is a much more likely technology.

Even better would be storing a crew in a digital format and reconstructing them in the target system. But that would require a lot more new technologies. But it has the advantage of allowing much smaller ships.


Would the benefits of a successful biosphere implementation have ramifications for helping to regulate one's home planet? We seem to be having a bit of a problem with heat build up right now...


Chris @16: you're thinking of "radiator" in the usual sense of a heat-exchange surface that sheds heat to an environment via conduction or convection, not pure black-body radiation as is necessary in vacuum. Your "cpu cooler" arrangement has lots of fins that are side-on to each other; radiation emitted by one ends up being absorbed by neighbouring fins, not dumped into space. (This works here because the fins are surrounded by air, and convection applies. In space, that ain't going to work unless you continuously vent working fluid.)

Again: using waste heat productively depends on having a thermal gradient -- see "radiators" above.


First off...thanks Charlie, for helping me waste way too much time today.

That said,

@14: Doesn't it suck that we can design intelligently any more, because of those idiots. Granted, it's not as bad a crime as what the Nazis did to the swastika, but it's annoying that saying you believe in intelligent design means that's you're presumably a religious nutcase, rather than someone who likes to see engineers being clever.

Anyway, who needs a simulation? We'll know when we're getting ready for space when we start seeing the following:

--The Dorset Island Parc Hyatt becomes the new "in" destination, food grown on site.
--People grow fish in the Sahara for export, at competitive prices.
--The water's cleaner coming out of LA than it went in, and it goes out the Colorado River, not Santa Monica Bay.

--and, most critically, the environmentalists aren't bothered by any of this

Building a working interplanetary spaceship is actually an evolutionary process, although we keep thinking about it in terms of scientific exploration and make-work for missile engineers. If we can build even partially working ecospheres, we can do stunts like being water-efficient enough to take advantage of the high energy flux in the Sahara to grow things, or make a remote area of the Canadian Arctic fun to visit in the winter, and so on. And of course, we have to do these stunts in sustainable ways.

When stunt-pieces like the above start popping up, that's when I think we should start thinking seriously about space colonization again.

Not that I'm holding my breath.


One problem is optimizing mass. What you want to go for is a large volume/surface ratio, in order to minimize mass of structures and possibilities for leaks on the one hand - on the other hand you would like to have structures that don't require assembly in space.

So, you'll end up with "balloon" stations mostly limited by the dimensions of their launch vehicles - no Death Stars, rather pebbles on a thread. And you will end up transporting huge quantities of soil, seeds, water and fertilizer up there before you can start with anything whatsoever.

Then again, biomass depends mostly on surface area (because of light). The bigger your balloons, the less light you get, the worse things are for your biosphere.

So, with large spheres, there'll probably be a lot of mirrors to get as much light as possible into your station (even more the further away from the sun). This in turn aggravates your heat and ventilation problems (meaning that you'll have to add radiators to your mirrors), but all of this is probably preferable to having having a larger surface between pressurized areas and the outside.

In all cases, I guess that you'll end up with too much mass to move those things around a lot. So if you confine yourself to the solar system, you'll probably end up with several biomass carrying stations (enjoying the lack of a gravity well) and shuttles moving stuff and people between them. Possibly on some of the asteroids (alleviating the need for water and some other stuff).


Move to Australia, Charlie! The light in winter here is brighter than the English summer.

As to your question: I think mold and other fungi. Waste heat, and waste moisture from the living organisms, will encourage mold. Spaceships are traditionally depicted as clean and sterile; this may turn out to be way off.



Yes, very bad example; I wasn't thinking. A better model for radiative cooling would be hemispheres on the end of long poles. (With the hemispherical surface outwards and the flat side of the hemisphere towards the ship.) You can still have a cooling surface much larger than the surface of the arkship (although not as large or as easy to make as a conductive cooler:), and only a very small fraction of the outer (hemispherical) surface will radiate in the direction of other hemispheres. The flat side will be radiating back towards the ship, of course, but that's a relatively small portion of the whole.


1cm per century is 400km since the Hadean era, so every iron-nickel asteroid would be 800km smaller that it was when it was formed? This is absurd on the face of it, and should also be very easy to detect by statistical analysis of asteroid sizes.

It would also be naked-eye detectable on any metal structure which has been in orbit for more than a few months. Such as, for instance, the Hubble space telescope, or Cassini, or anything we have sent to Mars.

1cm per century is 3e-12 m/s. At that rate a micron-thick layer of metal would sublimate in under 4 days.

Any undergraduate in a solid-state physics lab could put hard limits, a couple of order of magnitudes better than this, on sublimation of common metals at a range of temperatures in vacuum.

Given the enormous value of understanding the behaviour of micro-electronic systems over many years in LEO and GEO, and (for instance) how much is known about tin whisker growth in on-orbit satellites, it is inconceivable to me that space systems engineers don't have very firm bounds on sublimation rates of common metals.


(disclaimer:not at all acquainted w/ medium-less heat exchange)
If our bio-dome is sufficiently large/complex, such that we have orcas (and therefore, let's say, an ocean) mightn't we want to take the earth model of deep-water hot-cold mixing as a model? I'm picturing some very high volume but very, very high surface area regions of our ship devoted to, essentially, icebergs. (We're going to need some active shielding from debris in the form of lasers, otherwise we're going to get diverted into water-prospecting for most of our journey to make up for losses)
Maintain a very, very large thermal mass at temperatures much lower than we want in our bio-dome, circulate our oceans past/through, chilling them and remixing into our faux-cean. If thick enough, might shield us from some radiation?


Poul@3: Corrosion of complex materials in complex environments over long duration will be a problem, but sublimation of metals in a vacuum? Citation needed, coz if you're making ultrahigh vacuum systems, you make them out of metals, specifically aluminium or stainless, coz it is pretty inert to a vacuum. As Nick@11 pointed out, nickel-iron is stable over at least a billion years.

Titanium sublimation occurs and is used to create getters for vacuum systems, but I understood that the titanium had to be at 400 C or more for this to occur. Anyone know what the rate is at more likely temperatures? Coz I'd be surprised if it's meaningful, even over decadal timescales.

And hydrogen embrittlement is a problem for steel, but rarely for aluminium.

Now, if you'd been concerned about polymers, then yup, degredation is a major issue due to atomic oxygen (in low Earth orbit) and UV damage (near the Sun, where "near" means inside the orbit of Jupiter. Other sources of surface damage are erosion from dust specs at multiple km/s. Surface engineering is going to be a problem, though there's no definite show stoppers here.

All this has been a topic of quite a bit of research (LDEF and MISSE, to name just a few projects).

But certainly, long term engineering of habitats is going to reveal a whole host of reliability issues that we won't discover until we try it. I'm keen on trying it with habitats that aren't going to kill everyone when they fail, coz engineering projects this complex will fail, repeatedly, and in unexpected ways, until we get it right. (And as for ecology projects this complex, ah, you're screwed...)

But back to the topic at hand, can everyone go and read the Atomic Rockets page on heat radiators before commenting? Numerous answers are found there to questions being raised here.

In a vacuum, you're cooling by radiation, which depends on the fourth power of your radiator temperature and increases with surface area. As Charlie points out, because of the surface area/volume issue, cooling becomes a bigger problem for bigger habitats.

However, it's simple to increase the effective surface area of the habitat, just make an extra spherical layer of radiators outside the shielding, well away from the structural surface. Make these radiators modular, for ease of maintenance, and support each modular pack of radiators with one long, tall column. Combine the radiators with tiltable solar cells, to gather power from whatever nearby sun. Bingo, you've got biological trees on the inside of the habitat, doing the ecological jobs, and engineered trees out the outside, doing the engineering jobs.


Competition. Unless the trip is so prohibitively expensive that it can only be performed by our species once, it will probably occur more than once. Competition could be accidental, in deep time.

As @13 and others have said, shielding, huge problem, not from cosmic rays but from all the stuff between the stars. If you're going sufficiently fast you'll have to reduce your cross section (long skinny ship).

Evolution. Over-adaptation to the environs of the ark.

Rogue Planets. (Wow, that would suck)

Information failure (All Human Knowledge Database wiped).

Navigation failure, not being lost, just choosing the wrong cosmological model, maybe something akin to the Pioneer Anomaly.

Things that go bump in the night. Maybe the Fermi Paradox has a concrete answer, and a body temperature of ~2.725 K.


I'm not sure about biomass scaling as some higher power of the volume. Would a generation ship look like the Heinlein version of nested cylinders, or would it be more like an O'Neill colony with jets? It seems the earlier generation ship stories are mostly about the former, while the later ones are more about the latter.

Just a gut feeling, but I would think O'Neill's are better than nested cylinders, even given the mass problem.


I agree that one of the challenges to long-duration space travel will be getting rid of waste heat, but I do have to disagree slightly with the notion that the biomass itself will be the major driver of the waste heat problem. Consider the rule of thumb that each human produces ~100 watts of waste heat. With a conservative 50kg of mass per person, this comes out to 2w/kg. Using this figure for a 1000 metric tons of biomass yields 2 megawatts to be radiated. For purposes of comparison, if you look at the engine list here:

the smallest power requirement listed is 10Mw for a Vasimr with an implied waste heat of ~4 megawatts and this for a level of thrust that is inadequate for a 1000 ton payload. The waste heat from your powerplant is likely to produce the vast majority of the waste heat you will need to radiate off. One useful aspect of this is that the waste heat produced by the vehicle's powerplant is very likely to be at high temperature and waste heat radiation scales with the temperature difference to the fourth power. At room temperature, a perfect radiator will dissipate ~ 1/2 kw per square meter whereas at 1600 degrees K you get more than 1/3 of a megawatt per square meter.

One interesting idea for killing two birds with one stone is a droplet shield/waste heat radiator system. The idea is to spray droplets with a low vapor pressure (e.g. lithium) ahead of the spacecraft. These will then radiate heat off into space, after which you collect the droplets. While you are accelerating gently you will overtake the droplets, facilitating this. While in the acceleration phase, these droplets also provide a shield, any dust motes are likely to encounter a droplet (catastrophically, a 1 gram droplet at .1c has 4.5 * 10^11J - more energy than the largest non-nuclear bomb ever designed) rather than the ship.


Greg@30 the Article seems to say that despite not being the major source of waste heat, it's relative low intensity is what makes it so hard to get rid of..... All energy gone to heatpumps. Also, apparently the shuttle uses much the same coolant as a car, propolene gycol..... I am still picturing a LOT of water in..... Big black fins??


This might be the solution to your problem:

They say there that the device can work either as an electricity generator or a cooler (if electricity is applied to it).


Meat, in space? That makes sense for short trips, but multi generational pan galactic flights for meat are just insane.

Why not pack adaptable information up into a tiny spore? Something small enough that 0.0001% can survive to reach a planet's surface or float in its gassy embrace. RNA, DNA, Virii, Bacteria, a little blister of dense dessicated life. Produce it by the megaton and spray it all over space with unmanned ram scoop ships in every direction. Think coral.

Humans are finally getting to the seeding other planets stage,. IMHO it's just very unlikely that it will be our monkey bodies that make it else where in the bodies that evolved for this little blue rock.

Never teach meat to fly generational ships. It wastes your time and annoys the meat.


Charlie, as an ex-Alaskan may I recommend Saint John's Wort? I have a predisposition for mild depression, a 300mg. capsule a day helps me. I've also noticed (for me) that the "sweetener" aspartame has a BAD effect on my mood. Of course, I'm not a doctor (or on topic!) your mileage may vary! Meditation can help too :)


Why not just hollow out a moon or something else whose mass alone will create the kind of gravity necessary to keep everything where its supposed to be. Plus it will act as a radiation shield. I like the idea of using oceans inside the sphere as radiators and thermal control. You would have to genetically engineer to support it but you could make the oceans out of 10-25% heavy water for use in a fusion reaction later. Yes the rock would be slow and probably be out paced by tech changes in your main system but it could be seen as a biological and cultural ark as well. I'm thinking something along the lines of a mini Dyson sphere.

Propulsion use antimatter, antimatter that you construct on site. If you don't have at least the kind of tech that can make practical amounts of antimatter I don't see why we should be out on the starlanes in the first place. Don't plan on any huge acceleration just constant thrust. Keep swinging around the local system for the first hundred years building up speed. That way if something goes completely wrong at least it will take less than 100 years to find out about it. You could even rendezvous your final colonists once it has picked up speed. You could also allow for crew that rotate off the ship (at greater and greater cost as it sped up) but it would be possible. Think of dozens of these things orbiting out with the comets, a fleet of colony ships in waiting. Yes I see the danger and if one of them was commandeered and hit Earth it would make nuclear war look like a barroom brawl. That's why you have more than one. So you have a chance at stopping one.

Meanwhile keep sending out Von Neumann style starwisp scouts. Then send unmanned terraforming probes to worthwhile targets. Eventually in the nanotech age you will only need a few grams of smart stuff to start terraforming a system. Then your manned rock can be sent with the colonists.

For older more advanced civilizations just pack up your solar system into a Dyson sphere and spend your golden years traveling the galaxy. Sure its slow but why rush, all the comforts of home including your home are packed with you. (also a good way to get out of the way if a neighbor is going to go nova.)


On vaguely related (read: probOT)technological futurist items, highly recommend the singularian technophilic blogfeast going on over @ .... Also among the twitterafflicted, @tedgreenwald mining asteroids? But not w/meat.



That difficulty can be viewed as the other side of my point about the waste heat from the powerplant. At 310K you are only dissipating 1/2kw per square meter for a perfect radiator, as opposed to more than a third of a megawatt that it would dissipate at 1600K.

While there is likely to be a lot less of it, waste heat from biota will require far more surface area than powerplant waste, watt for watt. Fortunately, there is no great limitation on the surface area available for radiators on a spaceship (keeping the mass of the system from getting out of hand is really what is imperative). As Atomic Rocket puts it


"Rockets Got Wings"

or droplet rigs.


Charlie said he was ignoring propulsion, BUT... unless you're talking about a Bussard ramjet (could those actually be made to work, tech gurus?) or a lightsail, you're going to have to carry some reaction mass long. Depending on what form that takes, you could use the reaction mass tanks/lumps/whatever as part of your surface area. A sphere of biome balanced atop a long cylinder of inert stuff would have much better heat dissipation properties than the sphere on its own, I imagine.


NASA is currently researching magnetic shielding for long term space travel. Their early vacuum tank experiments with particle beam assault indicates that a superconductor generated magnetic field of approximately 2 Tesla is adequate to protect a biological cargo from most cosmic radiation and solar wind. Polyethylene as an additional shielding material works well for alpha/beta radiation, water for other, harder radiation.

Dr. David Brin, in his story, Sundiver, postulated a laser pumped by waste heat, that would then radiate that energy away at effective temperatures of a million degrees or so. That may actually work.

I must note: I have just finished your 5th novel in the Merchant Princes series.My Son, the software engineer, turned me on to this series by forwarding to me The Clan Corporate, so, of course, I had to read the succeeding novels. I am really looking forward to the 6th book.

GAry 7


I bow to your expertise in vacuum technology, but I would like to point out that we have very little experience with long duration hard vacuum exposure.

While we can undoubtedly find alloys that have good properties, I would not expect us to be able to use a single alloy for the entire exterior surface, a number of technical gadgets would need to be present, (such as star-trackers, radiators etc).

In practice, as I mentioned, in interstellar space I would be far more worried about atomic hydrogen with high impact speeds: You are essentially travelling in a low-intensity proton beam, and no metals or their structures like that very much.

But even if you find your good numbers for some alloy, are you willing to trust them to scale to multiple thousands of years ?

You are going to be the first ship out there testing our assumptions, the voyagers have very little instrumentation left to give us guidance.

I wouldn't do it, without an regenerable exoskeleton, just on principles.



Re: Things that go bump in the night. Maybe the Fermi Paradox has a concrete answer, and a body temperature of ~2.725 K

That would be Cthulhu.


Gary @ #39:

You'd still need a heat gradient to "use" the heat to pump the laser.

This leads me to one possible idea. Use big radiation domes, with a "wrinkled" surface (such that the normal from the wrinkle flats do not intersect any other wrinkle, I guess an easy initial design would be π/2 angles, like stair-steps, that should give you somewhere in the region of 50% surface without increasing volume), connected with thermal conductors. In the thermal conductors, insert Peltier elements to extract electricity. Use this electricity to pump a light source (lasers? bright visible-light LEDs? dunno).

That would allow you to radiate more, I would've thought. But there's probably a catch I am NOT thinking of.


JParkerKC @35: you might want to ask what happens to the gravitational field inside a hollow sphere before you go hollowing out any moons. (Also, ask yourself just how much energy this involves. Even the relatively tiny Phobos and Deimos are mindfuckingly huge in human terms.)

If we can trivially manufacture antimatter in bulk, my inner pessimist says that we as a species are dead (or transcended by Someone Else).

You might want to scale back your ambitions a little ...

Gary @39: David pulled the refrigeration laser out of his ass, to make the plot of a novel work. It violates basic thermodynamics, and he's said as much in public. (It's a good idea to apply a physics-based bullshit detector to any neat idea you read in SF, Just In Case.)


I have an idea I'd like to float - with the fair warning that I don't know much physics and what I did learn is long in the past!

Is there any reason you can't plaster the outside of the minimal amount of hard shielding with pretty damn thick layer of ice?

As far as I can see, it would act as an extra layer of shielding. Heat build up could be disipated by creating a "cometary tail". Finally, if it all goes pear shaped you have an emergency reservoir of volatiles for the biosphere.

Alright, I'm sure it isn't as simple as that and even I can see that there are a number of engineering issues with it. But, in principle...?


@3,40 - I like the regenerating exoskeleton. unless it's alive, things always, eventually, break. I understood Charlie got round this in Saturns Children with nanomachines. even if the onboard repair factory was something a bit cruder though, as a closed system, depending on how much waste you were willing to tolerate you might end up with an ecology of feedstocks (structural member A being eaten to make shielding B because it had some valuable alloying element) that might get almost as complex as the onboard biological ecosystem.


Wouldn't it be practical to solve the heat dissipation problem by using a big heatpump and a very hot radiator ?

Radiated power goes as T^4, so as long as you get the temperature up you can easily afford to radiate the energy used to run the heatpump.

I assume you have energy to spare, if you have any kind of a stardrive.

Other gotchas - to my mind, the problem of plumbing, specifically keeping all the air in all of the time, will be the biggest one, and I suspect the solution will be to take a load of extra mass along to make air & water as required.

Also, the problem of spare parts. Unless you have magic fabricator tech, you are going to need bits that you don't have the industrial base to manufacture. O-rings and faceplates and liquid-nitrogen plumbing and bimetallic strips and transistors and kernel patches.

That effect might actually set the smallest practical size for a truly long-duration mission, since a bigger ship can carry more of its industrial base.


Use big radiation domes, with a "wrinkled" surface (such that the normal from the wrinkle flats do not intersect any other wrinkle,

I can't see the wrinkles working, since every point on the surface emits (infrared) light in all directions. More in general, you cannot expect to emit most of your energy at more than about 300K, since any process to increase its temperature (or light frequency) will out of necessity generate waste heat at less than the original temperature.

Is there any reason you can't plaster the outside of the minimal amount of hard shielding with pretty damn thick layer of ice?

As far as I can see, it would act as an extra layer of shielding. Heat build up could be disipated by creating a "cometary tail". Finally, if it all goes pear shaped you have an emergency reservoir of volatiles for the biosphere.

This is really two separate ideas: using ice as protection, and heating mass from interstellar temperature to 300K as heat sink.

A quick calculation (please recheck this!): ice has a specific heat of 2kJ/K/kg. So raising its temperature from 2.7K to 300K takes about 600kJ/kg.

Organisms like us produce around 2W/kg, so you have to heat your own mass every 300,000 seconds to dump your heat. Using something else than ice might change that a bit, but I am sure no space ship can afford to carry enough mass to dump a mass equivalent to its living payload every few days.

As for using ice as shield: a shield for high-energy particles is at first approximation just mass. Whether that mass is a thinner layer of high-density metal or a thicker layer of ice or miles of gas is a secondary effect. Ice could work, altough it might disappear into space quicker than metal.

More in general, what kind of radiation are we talking about? Presumably, your spaceship hitting floating particles at a significant speed is the main source. Does anyone have a quick calculation how much radiation that would be at say 0.01c, compared to solar wind etc inside a solar system?


environmentalists aren't bothered by any of this

Heheheh. Hrmm...

I think you have an excellent point about the evolution of the necessary systems, but I also think that having a real-time model to compare with the full-scale operation would be valuable at least as an early warning system of possible failures. Or maybe it's not failures, and it's just that your model wasn't as accurate as it needed to be.

If anything, a tweaked-over-time record of the final, successful, biosphere might prove handy for mass production of more spheres...


I can't remember the details of the laser cooling Brin used in the series, so it very much could have been pop science. At the same time waste heat could hypothetically be converted into photons, maybe through a kind of reverse fluorescent material. In fact, converting this heat into photons might then allow it to be reconverted to sugar or electricity, and the energy in the heat is not "wasted."

Given that you wanted to create a self sustaining biosphere where all materials were recycled, it seems like it would be important to recycle the heat as well.


@48: I love doing models, which is why I'm so suspicious of the little buggers. I agree that not cranking the numbers as part of the design process is extremely stupid. Your system has to run under normal operating conditions. Beyond that...

Unless we're using some yet-to-be-invented quantum supercomputer thingie to run the model, it's going to be less detailed than reality, and we're going to have to choose which details to leave out to make the model work (and if we have a quantum supercomputer-thingie, why don't we just upload ourselves and save everyone the trouble?).

It's the assumptions that kill you.

There's a nasty little truism, which is that if you create a system based on models that absolutely will not fail, what you are guaranteeing is that the failure modes will be (by definition) totally unpredictable, and their solutions will be (by definition) a matter of guesswork and luck.

If you're really cynical about designing one of these things, you want to set it up so that when it fails, it tends to fall into a predictable failure mode, and then set it up so that you can recover from this mode.


Well the assumption for me is that energy is going to be abundant, so you could consider using Peltier elements to tackle the heat issue.

You can also consider a variety of electochemical cycles to dispose of waste heat, with emission of light as a waste heat disposal, leading to luminol regeneration or something similar, there are several luminescent chemical reactions, it would probably be possible to link that to some light endothermic process. It would probably be bulky.

Another possibility is by dumping a coolant, which would severely affect the resources of any ship and set a limit to endurance. But then you could use ramscoop to collect interstellar matter, it is considered only for ions, but matter is matter and non ionised but magnetically sensitive matter would be picked up/influenced too. Then divert the matter collected as to serve as coolant before either dumping it or using it to accelerate the ship, action-reaction works just as well with hot matter. And anyway a huge magnetic field covering the ship is a boon considering radiation hazards.

I wonder if some heat dissipation/recycling method would be possible by using Brownian motion.


> emission of light as waste heat disposal
sounds like you're working up to a violation of the 2nd Law, and that never ends well.

I suspect @49 is leaning in that direction, too.

I like the idea of using ramscoopings as coolant, but I do wonder if you would ever find a way to do the scooping without warming up your collected mass. Your scoop has had to do something violently energetic to it to get it up to your cruising speed.


Getting the whole thing airtight is going to be a problem. The larger your surface, the more rivets etc. you have, the bigger it gets. Assembly in space is a major problem right now and production in space is one of those things I keep thinking about when I happen to forget reality ...

I also don't think that you could power the thing without using nuclear fission or fusion once you get too far away from the sun. So you would have to deal with radiation from the outside *and* the inside, both as a health hazard and deteriorating the material after a couple of decades or centuries.

So you would have to either store or scoop up some additional material on the way. I'm not sure if you are talking about spacefare in the solar system or much further out. In the latter case you need to find a way of finding such material - real powerful radar maybe?

Also, has anybody brought up evolution yet? I mean, we're putting a rather limited genome pool in a bottle and let it run for a couple of hundred, even thousands of generations.

Lots of species in a very strange environment and you would have to wonder if *all* the plants and animals coming out of the biosphere after a hundred or a thousand years would still be recognizable for what they were at the beginning of the trip. I'm especially concerned about small and microorganisms. (Not to mention all the little critters in our stomachs etc.)


Say we use a water shield, we could pipe it through twisty little passages (like the wrinkles mentioned before by 42) made of silicone or ETFE.

Something like this, though spherical.

And I think 28 mentioned evolution.


@49,51 - all heat disposal in a vacuum is through the generation of photons, just normally less energetic photons than you can see. From memory, it is simply impossible to move heat from a colder body to a warmer body without a heat pump which generates more heat still.

the only way I'd see of increasing heat disposal is simply to keep the whole ship as warm as possible (biosphere of tropical jungle rather than northern temperate?). perhaps we're quite lucky that as a species we already have 300K to play with.


Honestly, I'm getting a terrible vision of "Just flush it down the time loop!" as a solution. Waste heat: the dioxin of space.

...Yeah, I got nothin'.


I see one really big, glaringly bright problem with the premise of disapating excess heat into the vacuum of space.

Such an activity will undoubtedly contriubte to interstellar/galactic warming. It's bad enough that we're killing the polar bears here on Earth, but we have no right to go around and start heating up the vacuum of empty space. Who knows what implications such actions would have?


Pockets of explosive gas ramdomly squatting in vacuum. Fly into one and BOOM! Then again, if you're going too fast even non-reactive gas is going to hurt. Oh and when I say pockets, I'm not thinking 'fits in one' I'm thinking bigger.

The degradation of the hull on the outside of the ship might be less of a concern than the degradation internally, where oxygenation can occur ~ markus@5 mentioned this also. Many substances become brittle, rubber for instance, and stress-fractures might weaken an airtight seal etc.

Relativity - as speed increases you're going to find your perception in front of you will change. Might this make it tricky to work out when you should start slowing down? Redshifted signals is an obvious one, but are any other problems with this?


Woet: you're pointing at non-existant threats (with the exception of oxidation, which is a phenomenon we're intimately familiar with).


I'm very sad to see such a lack of evolutionary thinking.
From bird wings giving us flight to star fish's eyes inspiring excellent optical fiber lenses Nature has show us more than enough to be humbled for a thousand generations and yet I still see most conversation steered to human engineering feats. Sure, we're really smart, but why not crib off Nature? There's no points off for cheating here.

I think the best bet for trans star system lies in breeding organisms to span those distances. I'm not blathering here about "beings of pure energy", but real physical solutions to the problem presented.

I think my biggest beef is that the most successful solution to the problem of waste heat dissipation may be to have none at all.


It would require special circumstances to make the first large scale space habitat a starship. It is much more likely that Earth orbiting habitats will be done first, and inner system (with access to Earth on a few year's scale) habs second, and out system habs third. (Earth may be a decade away, and expensive to access.)

So barring weirdnesses (which are of course fine sources of SF novels), by the time anyone sends out interstellar canned monkeys, if indeed that is ever done at all, there will be a lot of practical monkey canning knowledge floating (literally) around.

Additionally, such a ship is a rather big ticket item, so people will *think* about it, and plan. Smart people, with resources, and decades or (more likely) centuries of science, technology, and practical space experience we don't have.

Charlie has his work cut out for him if this is indeed his project.


61: If Charlie wants to settle interplanetary or interstellar space, yes. (From novelist to Interplanetary Overlord?) If he just wants to write about it now, he only needs to be smarter than the smart readers who *don't* have expensive resources and decades of experience and planning.

Like the story about the two hikers and the grizzly bear: "I don't need to outrun the bear, I only need to outrun you."


@60: The question is about engineering, specifically the engineering of long-duration habitats, so it's not surprising that most people start thinking about...well, engineering!

@21: I get what you're saying, but there isn't any incentive to do that sort of thing on Earth (well, there is, a little, but not to the extent needed for any major development), while there is in space. We have the evolved and developed ecosystem of an entire planet to make the thing habitable (if barely), after all, with no maintenance needed from us. Of course, as Charlie has pointed out before space is really like an ocean in ways which science fictions writers have not necessarily been eager to point out; that is, it's a hostile environment with valuable resources, but not somewhere you want to live. Nevertheless, it seems...well, possible that there will be significant advantages to building medium-term (years) stable biospheres to enable those resource-exploitation activities.


What if there is a big "rock" in your way? If your gravity comes from rotation wouldn't that make evasive maneuvering tricky? Fire up the Inertial Damper Scotty!


As I implied in my previous comment (37), for the purposes of space travel the mass required for radiators is of greater concern than the amount of space it will take up (after all, space is one thing you have plenty of, once you are out of a gravity well).

Fortunately, it sounds like there will not be too big a hit for this. The numbers I got from Atomic Rocket were .01 to .05 kg per kw so that radiating a gigawatt of waste heat will only be a 10 to 50 metric ton hit to your mass budget. I wasn't really clear on the provenance for those numbers so to do a comparison, I located a paper by Bob Bussard on his IEC Fusion concept in a space vehicle:

He uses 3kg/m^2 for his radiator mass budget, which he looks to operate at 1050K, which gives a figure in the area of .045 kg/kw (or .022 if, as he seems to do in the paper, you allow the radiator to operate double sided at no mass penalty) depending on what you emissivity he is counting on, which gives a nice sanity check on the numbers I got from Atomic Rocket.

My takeaway is that while waste heat radiation is definitely something that designers of such a space mission will have to pay attention to, it is nowhere near as worrisome as the questions posed in Charlie's previous inquiry about how you keep an adequate degree of ecological closure for the needed time scales.


Tetrarch@51: Peltiers are just inefficient heat pumps that don't take up much room. A proper heat pump, based on refrigeration technology, works much better and is probably more reliable. Although you might have to hook up multiple stages of phase-change to get your radiators really hot.

Zamfir@47: heating the ice isn't the whole story. I'm pretty sure water sublimes at less than 37 degrees in a vacuum, and that sucks up LOTS of heat. More than evaporation, for instance. Still probably not a viable long-term strategy for cooling a spaceship, unless you stop every year or two to scrape up comets.


I still keep wondering about whether you can get enough conductance from plasma to make it a halfway reasonable way to get rid of heat. I'm thinking here of a spaceship going something above 0.05c, to the point where the interstellar medium starts being a real problem. Is there ever enough stuff flowing by the ship to offload heat into it at a reasonable rate?

I'm also looking at propulsion systems. A solar sail solves the radiator problem, although how you keep it from exploding from micrometeor hits is something I don't understand. One of those beamriders that they have over on Orion's Arm has enough (apparently cold) mass flowing into it that thermal control is apparently not an issue (not that they talk about it in the article). But for things like anti-matter drives, how much is the heat from the life system compared to the heat from the drive? If it's less than a few percent, the radiator surface pretty much gets lost in the safety margin for the drive.

AFAIK we're talking about somewhere between 100,000-1,000,000 watts/person input, based on how much solar energy flows into the proverbial half hectare that can support a human for a year. A fair amount of that energy gets caught in the system as biomass, but the energy all eventually goes somewhere. We're also talking about on order 1-10 tonnes biomass/person for the biosphere (most of that is plants and decomposers).


Have you tried cod liver oil? I found I couldn't stay awake in Oslo during the winter. They had great commercials for the fish-oil. :).


Just standing on the shoulders of giants here, but if the figures are right, you have a human radiating 2 W/kg, and a radiator at 310 absolute radiating 500 W/m^2. Being conservative, that's a heat load of two people per square meter, so 10,000 people can be taken care of 5,000 m^2. A factor of 20 from the supporting biomass gives us 100,000 m^2 of radiative surface area. Sounds like a lot, right?

Now look at the size of this thing. If it's just one kilometer long and one kilometer in circumference, that's 10^6 m^2 of area on the sides, plus extra area for the end caps. Hard to tell of course, but I'd say something that size would be rather small if it was going to house that many people on a trip lasting a century or more. Waste heat from the biosphere doesn't appear to be much of a problem then, though of course there's other components to think of - raw power for the lights, fans, elevators, communications, etc is going to be associated with a certain amount of low-grade warmth as well.


Another thought that I'm surprised no one has voiced yet - cleaning. I don't have any relatives on active duty in the Navy any more, but to here them tell it then, the minimum wage service motto "You got time to lean you got time to clean" didn't hold a candle to what was expected for seamen far out at sea.

I don't know how true these stories are or to what extent the cleaning duties were supposed to tire out a young man and keep his hands occupied, but I'd say it's a pretty safe bet that there will several man-centuries burnt up in polishing the brass work, keeping the passageways and paths litter-free, pulling belly-button lint out from behind bamboo panelling and out of the electrical wiring, etc.

Considering the human body as a rather complex vessel in and of itself, just how much of our internal resources are spent on the equivalent of basic cleaning procedures?


>>A solar sail solves the radiator problem, although how you keep it from exploding from micrometeor hits is something I don't understand.

That part is simple, any lightsail is going to be so tenuous that the micrometeor will go through and not even "notice" that it encountered anything. The effect on the sail will be very localized and, so long as the sail is properly designed with ripstops, no big problem.


Crinkly surface heat-sink doesn't help, but a long tail or great big wings would.

But... keeping animals alive in deep space. Why would you even want to do that? That's insane.


Charlie thanks for response @45
Sorry didn't think the hollow earth style moon out very well just a flight of fancy. But I'm optimistic that human scale will continue to grow with our technology. After all Deimos(dinky by moon standards) is only roughly 25 times the volume of the Three Gorges Reservoir which is itself more than a 1000 times the volume of the Great Pyramid.
I think everyone can agree humanity would have to grow up more than we have to colonize the system or to handle tonnes of antimatter. Although our experience with thermonuclear bombs should allow a little optimism. After all there have been fewer than a direct deaths from nuclear energy in its first 70 years then there were from the internal combustion engine or alternating current. Humans haven't used VX gas,GE plagues or nation wide EMP in war yet so maybe we have grown up a little. The ten million shades of the victims of the Central African wars in the 90's would probably disagree with my optimism.

@31 kleer001 (best pessimistic comment so far)I agree the medium term even long term prospects for light-speed canned meat does not seem very promising.

And no offense to anyone but only certain death would make me choose spend the rest of my life traveling between stars with less than a thousand people for company. If you can cure death or let me sleep all the way I'll reconsider.

Why should humans or any other species travel between the stars?
When humans explored our own planet, They had ideas of the resources available at the other end spices,silk,opium,gold etc. and they had an idea of how to send it back in there own lifetimes. Of course the things they weren't expecting like tobacco,maize, kangaroos, and Pekingese dogs were interesting too.

Which means it would have to be a religious / psychological rationalization that would make a civilization spend the trillions necessary to launch a ship. Philosophy and politics will be more important than engineering. Perhaps it could be sold as the species equivalent to reproduction. But then which biological model? An oak tree, whales, an octopus, coral, people?

If there is an anthropologist in our midst perhaps they could explain Polynesian expansion and migration, or recommend some reading. Why did they do it? What kind of success rate did they have? How expensive was it for an expedition to be launched? Of course the Polynesians were not trying to raise three generations on the canoe trip but they did take everything with them to create a colony at the destination including domesticated plants and animals.


@73: Jared Diamond's Guns, Germs, and Steel is probably the most easily accessible summary of the settling of Oceania (you'll want chapter 17, "Speedboat to Polynesia"). Otherwise, you need to hit the technical books covering archeology of Oceania. The really early history of settlement (the Lapita culture, and the archeology of the Solomons and related islands) is at least as interesting, because the evidence says that some of the Melanesian islands were colonized more than once before the settlers succeeded.

As a freebie, McGhee's Ancient Peoples of the Arctic is a fairly non-technical summary of the archeology of that region. It's interesting for explorations of tech transfer, loss of technology, adapting to extreme environments, and how environmental shifts apparently drove cultural change and innovation.


Here's your heatsink:
I betcha you could grow that through gold leaf or some photosensitive medium. Gnarly energy cells.
Pebble goes up in space, turd maybe. Seeded, spoored, eggs. Warm enough to expand and spread out and make a sail.
Aphid like as larvae, scale adults with magnetic ceramic shells explode hermaphrodite seed propels the whole thing into orbit.
Eventually enough adult shells snap together. Their angular momentum adds and multiplies, accelerates and bursts out at escape velocity from compressed handwavium.
Space is for frozen sperms.
Get on warm wet planet, get live again. That's where the fun's at!
Lather. Rise. Repeat.


heteromeles@74: I think the state of knowledge has moved on a fair bit from Guns, Germs and Steel. I know for a fact that the gene flows and so on are now fairly well established, whereas the technology to do that barely existed when the GGS was published. There's a book called Vaka Moana, Voyages of the Ancestors that deals with some of this stuff, published last year out of Auckland Museum. It's a bit $$$ or I'd own a copy.

And Diamond is a bit of a nut, let's be honest.


Halting State reference

Todays NY Times has an article on smart phone delivered reality related games - its spooks ,its here but its probably not steaming - yet


Cphi, you are probably right then again, it was just speculation, but i never considered going directly from heat to light, which would of course be quite impossible, but you could have some large energy cycle that absorbs a great deal of heat, and nudge a final reaction along. Just finding a reaction where the activation energy can be partially delivered by heat, that neads a little extra to reach the necessary levels and with the final energy states lower than before the heat was added. Anyway you are quit right about the temperature difference, which made me think of the previous topic, we could also tailor our biosphere in such a way as to gain 25 % more efficiency in thermal dissipation terms. We could haven an outer layer of biosphere involving extremophiles, they are better at recycling a selection of compounds and often need the high temperature for the metabolism, therefore justifying an even warmer outer layer. Assuming of course that it can be managed without cooking everybody else.

@Richard Sewel, well there is that, but I suppose it would also depend on the size of the magnetic field, a small field would have to deploy quite a lot of energy on the matter to collect it since the ship is moving and therefore displacement vectors have to be quite sharp, a very large collection area would allow for the collected matter to be much more gently treated wouldn't it, since it has more time/distance to be collected. Anyway, It would depend on the temperature on collection, but wouldn't it be simpler to transfer energy to a already hot medium and dump that then radiating heat in such a radiator as vacuum.

I also read that the Thermosphere, while poor in particle is in fact extremely hot, as in the particle are very excited, stimulated by sunlight, cosmic radiation and whatnot. Would there similar particles or clouds, in space? That would severely affect any space ship with cooling issues. Not cool.


Re. @34 (SAD):

It's St. John's Wort for me too, but 3x300mg capsules a day i.e. 900mg extract with 0.3% hypericin (that's not the active compound, but it's what it has been standardised to and tested before the active compound was known).

I've been on it for 5-odd years, November to March (unless I'm travelling to somewhere sunny), and it does the job.


Tetrach@78: The temperature of clouds is not a problem. However hot they are, they will not prevent your radiators from radiating. They're only going to add heat to you by conduction and by radiation themselves, which they will do at a very low level because they are very very tenuous. If they are not very very tenuous, the problem of hitting them at 0.1c is not materially worsened by their temperature.


Denni @79 One capsule works for me (at least during the summer) probably because I'm a blue-eyed redhead, 2 sunblock levels below Dracula! Also I've been taking it for about 15 years. Although, I've forgotten to restock a few times, after about 4 days I feel a difference. Now,back to your regularly scheduled program ;)


Why assume a closed system? Why not use a lot of ice as both external shielding (cosmic rays, etc) and as a heat sink. The heat sink would eventually just dump the hot water generated away from the vessel. No radiators required. The trade off is the extra energy required to move all that extra mass, although the mass may be what you want anyway for propulsion.

I think my bigger concern would be the biospheric actions on the non-living infrastructure. Almost anything will degrade under the action of water and critters. This will impact everything from the strength of materials to the circulation of metals, chemicals and plastics in the biosphere, The design really should be as simple as possible using living systems as regulation mechanisms, rather than mechanical systems. But related to the previous thread, how will genetic drift and evolution of small populations impact the stability of the biosphere?

The one thing we know is that lifeless rocks are almost primordial, whereas earth changes very rapidly under biogenic action.


Vic @81

That is really interesting! I once switched to another brand of SJW and noticed a drop in mood after 3-4 days and it turned out to be a rubbish formulation with no potency. It also happened when I ran out of the stuff.

I promise I'll stop changing the subject now ;)


@76: Yes, Chris, absolutely agreed. I've been eyeballing Vaka Moana and some of the other recent books myself. Nice thing about GGS is that it's readily available almost everywhere (including Google Books), so if someone wants to spend a few minutes getting an overview, it's a good place to start. There are a lot of good books out there, but most of them are either expensive or available in the libraries of universities with decent anthropology departments.

The basic point about GGS Chapter 17 (Speedboat to Polynesia, hint for the Google crowd) is that it shows how the fairly uniform Polynesian culture adapted to different types of islands. To me, it's a good starting point for any SF writers who want to think about how environment influences cultural complexity.


How does the earth (yupp, the planet) do this (heat-regulation with vacuum and so on)?


@76 @84 K.R Howe (editor of Vaka Moana) has an interesting book called "Quest for Origins: Who First Discovered and Settled the Pacific Islands?"
Half of this book is a very polite description of various non-standard answers to the question. The rest is a description of the state of evidence when it was written (2002). Doesn't directly answer the questions asked at @73 however.
"This book is a thoughtful and devastating critique of such 'new' learning, and a careful and accessible survey of modern archeological, anthropological, genetic and linguistic findings about the origins of Pacific Islanders.
Why have there been such extreme and diverse opinions on this subject? Professor Kerry Howe also examines the 200-year-old history of Western ideas about Polynesian origins in the context of ever-changing fads and intellectual fashions."

Perhaps look at the reading lists for appropriate courses at Massey (Albany) and Auckland Universities?

The author list for Vaka Moana is very impressive. VM also contains some top-quality academic sniping, amusing to read - I bought it when Borders had a 40% off voucher.


@86: Thanks Errol. For once, my public library has a copy of something useful. I just reserved Quest for Origins


Just how big can the colony expand population-wise before scarcity of materials starts in?


@88: Assuming the colony is a closed system, to a first approximation there will be no room for expansion. However, as a simple safety factor you would want to have surplus capacity in the systems, and as now, there's always some bright bulb who thinks the best use for surplus capacity is to make more people or other productive systems.

So the bottom line is: yes, there is room to expand, at the expense of your safety margin. If your safety margin is the engineer's traditional factor of two, that's roughly how much you could expand your population.

Personally, I wish more economists and business planners would get stuck in survival situations (or reincarnated back in time at Easter Island), so that they could begin to understand that surpluses have a function too. But that's a rant for another day.


Assuming you build a Spherical Habitat. Heat dissipation could be conducted by a single tether (aka Space elevator) from the center of mass. We already know that tethers in space can conduct electricity. The tether (with a moonlet? attached) can radiate heat and produce power. Obvious advantages are an elevator from your gravity well as well as orbital propulsion. (exchange of momentum) A tether also provides a convenient way to (land at your destination) Assuming current technologies (i.e. no warp drives) once your habitat comes to another planet it will need to have a easy way down to and back up the planets gravity well. The tether / elevator makes good sense.

The trick will be the (shell) of the habitat. My thoughts are smart nano materials (think balloon or atmospheric swarms) that can be controlled. It will need to be a conductor of heat, assist in providing a habitat magnetosphere, optionally provide UV protection from solar radiation and be flexible. If the habitat is a traveling ship the shell will deform into an ovoid. As per my previous post, I envisage the habitat to be liquid water. Which is also an excellent conductor of heat.

IF the habitat is a generation ship the tether idea can regulate heat both out and in. In deep space orbital friction will generate heat which can be piped back to the core of the habitat. The habitat orbital shell could also be used as a deformable LENS that can magnify distant light once out in deep space.

Having a Moonlet with mass attached to the end of the tether also gives you tides and dynamics in your habitat.

I keep thinking it could also be the principal propulsion mechanism but my ideas there are vague.

Perhaps a pulsed energy discharge from the moonlet can (pull / push) the orbital resonance of the two masses in the direction you desire.? The tether would have to be amazingly strong.



I still like the idea from Greg(#30) of using the heat to blow material off the front of the ship, where it will also serve to intercept incoming particles before they damage the rest of the ship, and then scooping up them up as the ship plows through to more-or-less regenerate the system. It lets you have high surface area and shielding in one package.

Of course, the whole ship should be powered by a spindizzy 3.5, powered by pure narrativium/anti-narrativium reactions...


I live at latitude N45 deg. My SAD cleared right up when I started taking vitamin D. Here's a study:



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