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Microbes grow the starship

Could microbes grow the starship? Starships grow as organisms in George Zebrowski's Macrolife, and in Octavia Butler's Lilith's Brood. A single cell could multiply into a living starship made of trillions of cells. The starship could divide and form a whole fleet of them, enough to sustain generations of human travelers. Any damage could be repaired, since every cell's DNA would contain all the blueprint of the entire structure. Our own teeth grow biofilms that survive decades of brushing and dentistry--maybe they could survive outer space.

So far, most synthetic biology looks at one molecule at a time. Synthetic biology basically extends what microbiologists call the fermentation industry. The original fermentation product was ethanol, in yeast-fermented beverages that kept water safe to drink. Today, microbes make all kinds of products, most notably antibiotics like penicillin. Pharma companies send explorers to remote parts of the globe to find exotic drug-producing strains. My students discovered a new drug producer growing from a crack in a bar counter at the local college hangout. To prove it, they first spread tester bacteria on a Petri plate; then spotted four different bar isolates on top of the testers. The isolate at left shows a clear ring where its antibiotic diffused out and killed the tester. We don't yet know what the antibiotic is, but if it's new we could patent it for Kenyon.

We imagine making products "not found in nature"--but even natural microbes make molecules that organic chemists would never dream of. Look at this antitumor agent discovered from a filamentous soil bacterium, the kind of bacteria that give soil that new smell in the springtime (Science 297:1170). Those sets of three parallel lines are each triple bonds, within a nine-carbon ring. Who would even think to draw such a thing, let alone make it? To make it, the bacteria use modular enzymes, nanoscale assembly lines that condense one functional part after another. The original nanotechnology.

In principle, microbes could produce any organic molecule. In The Highest Frontier, microbial machines "print out" any molecule or complex--even viruses, unfortunately, like flu or Ebola. A new twist on "computer virus." And in Brain Plague, where the microbes grow buildings, they develop cancers--blobs of building material that crawl off to tap a power line. Still, is it worth a try to grow a microbial starship?



I would suggest "growing" a starship requires development which really means you need a eukaryote, not a prokaryote.

You might just get away with yeast to start with, although I suspect you want some some of higher plant as your starting point.

It may prove "extremely difficult" to fully develop a full starship biologically, but I do think that biology will be most useful for creating parts, even if that is a crude as growing trees for lumber to create the hull, or microbes to synthesize a host of chemical feed stocks for various plastics.

Should we ever get a starship to reproduce, it will not fission, but rather gestate [cloned?] daughters from a single cell.


'A single cell could multiply into a
living star ship'

A fascinating (and oddly poetic) notion

My understanding is that lab grown
cellular and microbial colonies
require an organic substrate on
which to grow and multiply.

How would one provide the nutrients
needed to grow and sustain a cell
colony massive enough to constitute
a star ship?

As a variant on the notion of 'growing'
a starship from a cellular colony might
one instead program a colony of microbial
machines to convert, molecule-by-molecule,
a mass of raw organic matter into one;
the organic matter would provide
nutritional sustenance to the microbial
colony as well as the raw building matter.


Oooh, pretty pretty. Got those molecules in RasMol format?

(I've loved o-chem and biochem for decades -- if I hadn't realized I was better at computers and taken a detour, that's what I'd still be working on.)


Take a while to work the bugs out of it.


If it wriggles, it's biology.
If it stinks, it's chemistry.
If it doesn't work, it's physics.

I am way better with stuff that stinks or doesn't work than with stuff that wriggles.

"living ships" as distinct from structures with AIs are a small but continual theme in SF. AFAIK this is the closest anyone has ever come to discussing how you actually get one though.


Also Alan Dean Foster in "Sentenced to Prism" IIRC.
Except there the life-forms are crystalline ...


Or Peter F. Hamilton's Bitek in the Night's Dawn Trilogy, although I think you were proposing something simpler, like a space coral that would grow into a starship?


Stargate Atlantis Season 5 Episode 2 had a similar idea with the Wraith spaceship growing out of a human host consuming them in the process.

For Organic computers there is the old classic Blood Music by Greg Bear.

For Complex simple organisms using nanotech there was the silly but fun Warstrider books by William H. Keith.

Further reading is also out there in the Cthulhu Mythos with the various Alien races growing and harvesting their organic machines.


The most powerful results would be produced by using bottom-up, evolutionary, networked biology for things it is good at, and analytical, top-down, engineering solutions for what they are good at.

Consider it with brains today - for instance, computers are bad at face recognition, but good at math. People are bad at math but good at face recognition. It's complimentary.


I like the idea of a living starship being a bacterial colony. A stromatolite rather than a whale. But, some problems we would need to solve for a bacterial starship:

1) a source of material. Perhaps water and organic molecules mined from comets and ice-moons like Europa? You'd need a lot of this stuff. Maybe the starship is surrounded by a host of smaller ships that go out and collect water. Maybe it carries a shield of ice in front of it (there was an Arthur C. Clarke book with that concept)

2) conflicts of interest between different communities of bacteria in the starship, and between starship and human passengers. What do we do when natural selection stops the production of nanotubes (or whatever) in part of the hull?


Prokaryotic starship? Hmmmm. I think the comparison between stromatolites and corals shows the problem with that. Corals grow bigger, faster. Or you can compare them with reef-building algae, which do the same thing. This shows the benefits of being able to translocate nutrients long distances. Prokaryotes don't do this well. Therefore, if I wanted a living vessel of any sort, I'd call it a eukaryote.

The bigger problem with biological space ships, however they grow, is that it isn't just vacuum, it's a whole bestiary of high energy particles, high velocity meteroids bigger than particles, massive temperature differences (even higher if it's a rocket), and powerful magnetic fields.

And worse, the bioship can't just sit there in anhydrobiotic stasis, it has to metabolize and grow in space. There are organisms like tardigrades that can survive such conditions in anhydrobiosis (basically, they either die or come close, and then resurrect when the water shows up again). However, I don't know of any life form bacteria that actively metabolizes in a vacuum.

Obviously, you can hypothetically design a ship that has a non-living outer pressure vessel, and living tissue inside. The challenge there is a nasty one: you are building your ship from the inside out. If it wants to grow, how does it grow without weakening the vessel walls to the point that they rupture? The pressure difference between the outside vacuum and the inside living pressure is going to be substantial. Remember, the pressure vessel isn't just a balloon, it's a bullet-proof, radiation resistant balloon that may have a >100 degree temperature difference between the sun and shade sides. It's not impossible to build this way, but it's a difficult engineering challenge, even before you turn to the biological part.


I work at a company that makes software for, amongst other things, producing 3D models of small molecules from descriptions. If I have the SMILES string for that compound right as


then there's a PDB-format representation at

The 'who-ordered-that' microbial compound that amazes me is the ladderane found in some ammonium-oxidising bacteria (see wikipedia 'ladderane')


"growing trees"

Stage trees?


It's a thought, but you need a lot of nitrogen to make it work.

Trees, incidentally, have a neat trick. I did a little modeling of plant grown (based on C,N, and P), and I found that under a wide variety of parameters, the plant accumulated a huge surplus of C. The thing is that growth is stoichiometric: to grow cells, you need the proper ratio of elements. A surplus of C is wasted.

Or not. Wood in a tree is mostly carbon, it's close to metabolically inert, and it's a great support material. That's what trees are, basically: they're a thin skin of highly active tissue (cambium and leaves) with ablative bark on the outside, and wood on the inside. The wood not only supports the growing tissue on the sides and top, it passively moves water around. Wood's neat, because it takes a surplus element (C) and puts it to good use.

Getting back to stage trees, that's the problem. A stage tree is supposed to be a solid-fuel rocket, basically. For that to work, you need to take out some of the wood, and put in some sort of complex, probably nitrogenous, hydrocarbon to serve as fuel. All that rocket fuel (in chemical terms) could have been additional leaves, so you're sacrificing a lot of plant growth to make the rocket fuel, and it's going to grow quite slowly. Additionally, the stage tree will probably have to fix nitrogen (either symbiotically or not), and that's also an energy intensive process, meaning the stage tree grows even slower still.

In theory this is possible. However, you're going to have to do quite a lot of weeding on a stage tree farm, because just about anything else will grow faster than your growing rocket. You might also want to grow them next to a sewage treatment plant, just to get more nitrogen as manure. And don't forget to keep all fires away while the tree is growing, and it may be growing for a thousand years to grow a stage tree to, say, Saturn V size.


I can imagine how this would work in practice, beginning with the idea that we don't want to waste delta-vee by shipping everything up from the Earth into orbit (or wherever.) So we find a comet coming toward the sun. We fire off a bacterial colony that uses the hydrogen and oxygen of the comet to build an engine that changes the course of the comet. The nice thing about waiting until we have a comet heading toward the sun is that we don't have to design our bacteria to operate where it's REALLY cold.

The engine puts the comet into orbit around the earth. Now our comet is in the liquid water zone and we can easily ship trace elements up if they are needed, or apply antibiotics to misbehaving bacteria, or otherwise debug problems.

We wrap the comet in a balloon and inflate the balloon. The balloon keeps useful elements from boiling off into space, it helps regulate temperature, and forms a scaffolding on which the bacteria will build the ship. (Or ships, if we're being really ambitious...)


If we're talking about television, well, Farscape not only featured living ships, but based some episodes around them. There was a bit of handwaving about exactly how Talyn grew his weapons (and why the Peacekeepers wouldn't use that technology on Sebaceans), but aside from that, I thought the concept brought up some pretty interesting ideas about being on a living ship.

If there is a degree of sentience, then travel isn't as simple as "Let's go thataway", but then you don't have to have crew assigned to check on every aspect of the ship at all times. (This isn't true, I think, with non-sentient ships: no matter how many systems you build into the ship to monitor and possibly repair it, you still have to have people check on the systems.)


Of course, a living ship means being very careful about ecologies; any new passenger could have a boatload of microorganisms that Do Not Play Well with the ship (or, on the other hand, get the ship higher than a kite without leaving orbit. Either one could be...exciting). I remember an episode of Voyager where Neelix acquired some cheese whose set of bacteria interfered with the biological components of the computing system, and not in a nice way, either. Since he brought up by way of a shuttle or his own little ship, the cheese didn't go through the transporter--which may or may not have a filter for such micro-organisms. Granted, a transporter buffer of that kind would be needed for a living ship, and would likely cut down on some of the long-term effects of going on shore leave.

Gives a whole new twist to the term 'plague ship', doesn't it?


I agree that a eukaryote something like a coral sounds more practical than what would have to be a very complex soup of different bacteria (some grow the external walls, which have to be airtight, good thermal insulators, strong, and probably rigid, some grow internal structures which should probably be lighter to save mass, some grow the engines, which need to withstand high temperatures and pressures1, etc.). And if the organism has a simple nervous system you can use that to carry control and sensor signals from one part of the ship to another (hopefully faster than most animal nerves propagate their signals).

1. I wonder if it would be possible to design an organism that could handle enough current flow to generate the RF fields required for a VASIMR plasma engine. Because the engine doesn't need to come in contact with the plasma the organism wouldn't have to withstand both vacuum and very high temperatures.


Well, it works for Dr. Who - they grow TARDIS time machines that way.

I'd be surprised if some of the molecules used for starship components aren't grown that way by the time they're needed, we're already growing enzymes etc. that way, but building the entire thing may be a little bit ambitious.


If you can capture a comet then you can probably gain an advantage from building organic solids as a kind of industrial process. I'm not sure about putting the design in the genes, it may make more sense to grow the members as deposited organic materiel on a starter wire or starter panel, to control the shape. Using different grown stages, it might be possible to grow the whole ship hull at once, but I think we wouldn't want to abandon previous technologies, so we'd end up adding electricity and wiring.


Even if all the bacteria can do is grow an airtight shell that has things like appropriate spaces for cable runs, windows, and sensors we're ahead of the game in a major way. Grow it in orbit and move on in!


I don't think (says he, with trad English understatement) that we're absolutely on top of the whole morphogenesis thing yet. Surely we're miles closer to programmable chemical synthesis than to programmable macrostructure!

The two problems don't even seem, except in the most trivial and necessary senses, to be clearly linked.


Regarding ladderane - a germ that makes rocket fuel?


The first time I read of the idea of a biological spaceship was Benford's "Beyond the Fall of Night", which had an enormous Redwood skyhook, and a ship that was another tree.

Would it be possible to engineer microbes that can digest/process rock or metal? Send a bucketful to an asteroid, it reproduces until it reaches a certain population density, and switches to another part of its genetic programming to build a shell, or more, so long as you're in no hurry. I don't know how you'd guard against the chance of mutations, which could give strange results.


This whole discussion is awesome--Keep it up!
>I don't think (says he, with trad English understatement) that we're absolutely on top of the whole morphogenesis thing yet. Surely we're miles closer to programmable chemical synthesis than to programmable macrostructure!

Actually, we're onto molecular programming of macrostructure (homeobox etc.) Will post later.

>if I wanted a living vessel of any sort, I'd call it a eukaryote.

Prokaryotes and eukaryotes turn out to be less different than we thought. There are prokaryotes that develop complex structures (Myxococcus) and there are vast populations of marine eukaryotes as small as bacteria.


>I work at a company that makes software for, amongst other things, producing 3D models of small molecules from descriptions.

Thanks for the PDB--that looks beautiful.

Here's what we do with PDBs at Kenyon:


"We don't yet know what the antibiotic is, but if it's new we could patent it for Kenyon."

Instead of reopening the usual debate about whether patents foster or hinder innovation, I'd like to ask how you figure Kenyon has the rights. It seems to me that the "invention" belongs either to the bar that developed it or to the student(s) who discovered it. "College that happens to be nearby" doesn't seem as compelling. But IANAL, of course.


You'll need a huge uterus, and a complex one at that, with the placenta alone being a huge feat of design. We still don't understand fully what the mammalian placentas do, but we know they're important. If you build in space you'll need a monster sized shell for the uterus to start things off, something like the hollowed out center of a big asteroid.

Human beings and other mammals are incredibly complex organisms. We have symbionts living in us, helping with digestion and other matters. A biologically grown spaceship would have to also use an array of several symbiotic organisms, with extras for generating and recycling air and other esentials that mammals usually don't produce. THis means more DNA design and more "creature" design in addition to the basic ship design. Having a ship reproduce itself would be more complex than having amoeba split up.

I'm not too worried about zoonotic diseases but that also would be an important design issue from the start.


True, there are certainly multicellular prokaryotes (even ones with cell specialization, such as some cyanobacteria), but they don't get as big as, say Siberian Armillaria mycelia or aspen clones.

Since people keep bringing up comets and asteroids, I'll admit that I'm quite fond of Heart of the Comet, even though I don't think it would quite work. Still, the idea of growing stuff on such bodies does lead to a couple of good questions, some of which could be answered by Kenyon students.

The best simple question is how to make regolith into something that will grow plants. I suspect NASA has enough data to simulate lunar or martian regolith in a lab (extra points for an asteroid, after NEAR does its work). Heck, comet ice might even be an interesting starting material.

Going from raw regolith and ice to growing plants may not be quite as simple as we think. Still, it would be fun to figure out what one needs to get a garden growing from indigenous material in space, and simple versions could be done as bottle experiments in the classroom or undergrad lab.

As for growing a ship out of an asteroid, see that first post about growing bacteria in a vacuum. I think that's the first issue to solve.


Universities typically have fairly draconian rules regarding the rights to anything that is developed using their facilities by their students and staff. By agreeing to work or study there, you've signed up to those rules. They don't necessarily go out of their way to make students aware of this unless they have to.

An acquaintance of mine fell foul of this back when I was a student; a piece of software he had written on his own time was appropriated by the university computer science department without his permission. (I believe it was some kind of tool for working with Haskell and TeX.)


I'm not so sure. I think the bacteria may not be able to operate in a vacuum, and may have to be left in water instead, along with some sort of nutrition cycle. I also think that producing genuinely airtight materials by biological means would be hard, perhaps even impossible. There has to be water to make life as we know it work, so unless that water is part of the structure, it has to be removed somehow. I'm reminded of amber. Perhaps the structural members could be wood or bone (also tooth enamel or keratin), with an inner sealant layer of something, maybee even non-optical glass.

I could see ships that were mostly ex-living matter, and the presence of lots of life outside of the usual human life cycle would indicate that part of the ship is being re-modelled or re-engineered.


The other problem with farming stage trees?

Lightning strikes ...


I think it's interesting to consider the roads not traveled by organisms, both on the molecular level and on a larger scale.

Fluorine, in the form of fluoride-containing minerals, is common and widely distributed on earth. It has proven an extremely valuable modifier of small molecules in the hands of human chemists. Yet out of the multitude of natural products identified from organisms, only about a dozen containing fluorine have been found, and only 2 bacteria species and a few plants produce them. It appears that the leap from local maxima based on other chemistries to organofluorine compounds is rarely accomplished.

Biopolymers have incredible richness and diversity, despite using only 3 great motifs (peptide, saccharide, nucleotide). But organisms missed out on some much simpler chemistries that have proven powerful in human hands: polyolefins, phenolic resins, and nylons, for examples. The necessary precursor chemicals are already known as natural products, but none of the polymers. For how many megayears have organisms produced ethylene without stumbling across polyethylene?

Finally, it is in some ways amazing that we know of phototrophic and chemotrophic organisms, but no kinetotrophs. In many environments the energy flux carried by the movement of wind and water is orders of magnitude greater than that available from sunlight or minerals. Wind and rivers are some of the earliest energy sources tapped by humans and still among the more powerful. But not a single organism, other than humans in conjunction with their machines, can feed even partially from these rich energy sources.


Not through chemical transduction, but plenty of organisms use wind and water currents for transportation. When a bird catches the updraft, it is using wind energy.


>Instead of reopening the usual debate about whether patents foster or hinder innovation, I'd like to ask how you figure Kenyon has the rights. It seems to me that the "invention" belongs either to the bar that developed it or to the student(s) who discovered it.

You're right, the student or faculty could patent it. Kenyon has no patent participation rule, so far. However, given that Kenyon provided the class and materials, I would feel ethically bound to include the college.

Of course, realistically speaking, it takes tens of thousands of dollars even to begin to think about a patent; and then years of backlog.


You'd need lightning-rod trees next to each stage tree. Either that, or some way to render the tree chemically inert until you wanted to use it. Also, try using a bean plant as your starting point if you want to fix nitrogen.


As for growing a ship out of an asteroid, see that first post about growing bacteria in a vacuum. I think that's the first issue to solve.

That's among the things I thought of after hitting submit. So...
How about if the microbes form a biofilm that skins over--a frozen layer protecting the rest of the colony underneath as it goes about its business.

And picking an asteroid of the carbonaceous type might be helpful?


Personally, I'd advocate growing rocket potatoes (or if you want the bean version, modify jicama to grow huge and make a rocket, then grow it in soil without rocks. Or gophers.). That said, I believe someone's eventually going to mention that liquid H and liquid O are better fuels, so it might make more energetic sense to simply use biomass-based fuel to refrigerate propellant gases, rather than spending a century growing some sort of organic solid rocket.


Thus, by a maze of twisty passages, the habit of some Computer Science students of GPLing their essays. (",)


I can imagine how this would work in practice, beginning with the idea that we don't want to waste delta-vee by shipping everything up from the Earth into orbit (or wherever.)

Delta vee of roughly 10 km/s for Earth orbit from surface.

So we find a comet coming toward the sun.

Delta vee of comet (absent aerobraking) to Earth orbit, something like 40 to 70 km/s.


Except that we will be sending a small load of bacteria to rendezvous with the comet. The bacteria will use existing hydrogen and oxygen on the comet to fuel an engine that will de-orbit the comet.


V.exhaust of LOX/H2 rocket: About 4,500 m/s.

Rocket mass ratio equation:

m.fueled/m.dry = e^(delta vee/exhaust velocity)

= e^(40,000 m/s/4500 m/s)

= 7,251.

One 7,250/7,251th would be reaction mass; the last 1/7,251 would be what got delivered to Earth orbit.


I think I'd look for a multicelluar space-going organism, and modify it somehow. I mean, why do the whole job from scratch if you don't have to?


Fluorine isn't in use by living organisms because there's no free fluorine on Earth, it's all in compounds like CaF2, and it costs a lot more energy to break it free than it does to get oxygen from the air.


That's not good. Do you have any ideas about something the bacteria could build us that's better than an oxy-hydrogen rocket? My math isn't great, but I'd guess we need to decelerate the comet while approaching the sun, then perform a massive course-correction to bring the comet into Earth's orbit. I suppose we could decelerate the comet with a light-sail while approaching the sun, but matching courses with Earth probably still requires a massive burn, which doesn't leave us much comet to build stuff with.

On the other hand, if we don't need to do the job quickly, we can probably use less delta-vee. Do you have any thoughts on how that might work?


Redirecting a comet with an organic drive to come into a near Earth orbit after orbiting the sun is a really bad idea.

One minor muck-up in programming the flight plan into the proto-ship and instead of circling the Earth it collides with us instead, send most life on Earth the way of the dinosaurs.

Or it strikes the Moon moving it out of orbit destabilising planetary rotation also wiping out most life on Earth.

A better plan would be to direct it to near the Asteroid belt where it could harvest minerals off of the asteroids until it is fully grown. Then we direct it to come closer to pick up a crew when it is more fully grown.


There's no free chlorine or bromine on Earth either, but many more organisms produce halogenated compounds containing them and many more distinct chlorine and bromine compounds are known from natural sources. It probably comes down to bond energy: simple fluoride salts are bonded 40-50% more strongly than the corresponding chlorides. That's apparently enough of a difference to make exploring the fertile but harder-to-reach landscape of fluorine compounds a rare thing in organisms.


re: bulding on stage tree criticisms

So we need Giant Beanstalks, with Conductor Vines, that somehow synthesise Dioxygen Difluoride for maximum lols, and which naturally kill all competing plants in the area (for it is slow to grow to launch size).

If it's going to fly, it might as well be ambulatory and carnivorous in it's juvenile stage, what the hell, why not? A Venus FOOF Trap.


Less delta-V? All else being equal, it's tricky, since the delta-V is inherent in the comet's dance between potential and kinetic energy during the course of an orbit which is close to escape velocity for the solar system as a whole.

However, all else is not equal and there is a way out, which is to use gravitational slingshot braking. In the same way that space probes are repeatedly boomeranged between the planets to get them out to the outer planets, you should be able to use Jupiter and other planets (nnot the Earth, please!) to slow a comet right down.


The lack of kinetotrophs is surely a similar issue to wheels being very rare in nature. A lot of the best structures, including the absolute best (the turbine), involve something that needs to rotate through 360 degrees all the time and that's difficult for a living structure.

Although, I do remember asking a biologist why none of the cephalopods had evolved axial flow for their jet propulsion and got rid of having the intake half of the cycle acting against the power half, using something like a peristaltic pump. I wonder if the opposite would work - external fluid flow driving internal, rather than internal driving external?


I guess one of the key questions would be the need for Oxygen? what needs for both the growth and during travel - does the outside of a living spaceship (organic material) constantly die from lack of oxygen and dessication in the vacuum of space?

Is it constantly growing new layers to replace old - the introduction of shark DNA perhaps could start off as well intentioned maintenance based design and end up with behavioural transferance to some of your ships. ?


You'll need a huge uterus, and a complex one at that, with the placenta alone being a huge feat of design.

I take issue with the "huge", and note that you're thinking in terms of placental mammals. Why not make it oviparous, and start with an egg? (Consider how small many dinosaur eggs are, and consider that the growth potential of a spaceship isn't limited by its ability to maintain structural integrity in a constant 1 g field.) Alternatively, if you can manage a full placenta, why not go for a marsupial design -- have parturition as early as possible, but then incubate it in a pouch and feed it until it's big enough to feed itself outside?


Or it strikes the Moon moving it out of orbit destabilising planetary rotation also wiping out most life on Earth.

I think you need to look up how massive the Moon is; it's quite a bit bigger and harder to shift than most people seem to think! Please can we try to keep our options in this discussion within the realm of the plausible, at least wrt. the physics?


Why not go the whole hog, and equip your ship with a set of 'wings'. The wings wrap around the ship and then seal, allowing for a redesign. The small area left outside isn't removed, it just becomes the ship's keel, and you can tell how many times the ship's been remodeled by how many layers the keel has.


Some form of exoskeleton seems appropriate for the environment. Perhaps it's appropriate to take a page out of the crustacean's book and have some way to moult off the outer shell, rapidly inflate a still-flexible shell packed just inside it, and then harden off that new shell. This allows growth from a small egg or the like up to a 'final' size.

(Do we have to have a final size?)


Seems to me a monolithic starship is doomed to failure. To quote Terry Pratchet, one in a million chances happen nine times out of ten. What I'm trying to say is given enough time any starship will suffer a catacylismic failure.

But imagine a million individual biological starships travelling as a pod. You'd lose lots but perhaps you'd have a greater chance getting some people to the destination.

And you could have your own music per pod.


Perhaps we could throw snowballs at Simon until he gets the idea that one comet isn't going to move the Moon a whole lot? ;-)


>But imagine a million individual biological starships travelling as a pod.

That's the right idea. Most life is modular; break off a piece, and it reproduces more. The vast majority of microbes, plants, and many invertebrate animals are modular.

Whatever the starship is made of, for long distance survival it had better be modular in some sense.


"Uterus" ideas seem to come up a lot.

Let's be clear: the mammalian uterus is nothing more than a crash helmet/ejection device.
*Not* needed for development.

A man can easily implant and grow a baby from the abdominal wall. It's been done in monkeys--and in mice, they've even grown babies off testes.


Shouldn't have said "easy" -- significant medical management is needed (in abdominal pregnancy) to keep the fetus healthy. But then, look what Sophia Loren had to go through to get a baby to term.

Just curious, any volunteers?

Anyway, by the time we have starships maybe the babies would be grown in tanks. Or maybe not--we're still trying to figure out what communication goes on between the fetus and the person carrying it.


Why do we want living starships? There's no obvious source of energy out in interstellar space, and I can't see the benefit of carrying food for the ship as well as fuel for the engines, just so we can get some notional advantage in repairing nonfatal damage.

No, I reckon we want organisms that shed starships - that grow them as shells, and then moult out of them. Then we capture the shells, retrofit them with engines and off we go...


As JDN says, that is a huge delta V cost in resources.

Probably better to find a dead comet with a much lower eccentricity and use a solar sail to move the ship when it has developed. So much teh better if the sail can be grown in situ.


If we could grow starships, I think it would make more sense, at least in the short run, to grow them on Earth. Sure, they would then need to be launched to orbit, but let's think a moment on why launching today is so expensive: it's not the fuel, it's the costly, non-reusable, insanely complex hardware. If you grow your hardware, then the price goes way down. And growing organics in space is difficult: no air, extreme temperatures, no available resources. The best way to go about it is to design several organisms, each producing a different part of the spaceship, launch the parts on a cheap organic rocket, and assemble them in space.


Venus FOOF trap. I love it!

The criticism of stage trees is based on plant physiology, which is relevant to this discussion.

Thing is, plants (and all life forms) have a budget, not of money, but of energy and elements. Moreover (and more interesting), tissues have specific ratios of elements. If the elements aren't available in those ratios, you don't get efficient use of the elements. Growth is limited by whatever is in short supply.

This is why, for instance, nitrogen-fixing corn is probably a bad idea. It can probably be done, but nitrogen fixation is energy intensive, and producing grain is energy intensive. If the plant is fixing its own nitrogen, it's going to produce fewer kernels.

It also explains why you don't see a lot of redwood giant-sized trees in the tropics (I'm talking about the 75-100m tall class). Plants respire, and since they are (generally) ectothermic, they respire more when they're hot, as in the tropics. Wood, to some degree, is surplus respiration (carbon stored rather than carbon out), so oddly enough, the biggest redwoods grow where temperatures are low for part of the year and nothing else is limited. As global warming bites down, I'd expect the tops of the tallest trees to die back, simply because the plant will be respiring more.

For anyone who's serious about growing a starship (by any kind of nanotech, bio, hylo, or whatever), these are the issues to consider. Is the growing starship endothermic or ectothermic, and if it's endothermic, how is the energy being supplied to keep it warm? Equally important, will the ship embryo have the elements it needs to grow?

The nice thing about such an analysis is you don't have to know *how* the ship grows. The analysis tells you whether such growth is possible at all.

That's why I suggested that growing plants from simulated regolith as a first experiment. It tells you what a lot of the issues are, without a huge expenditure of effort or planning.


On the other hand, if we don't need to do the job quickly, we can probably use less delta-vee. Do you have any thoughts on how that might work?

Yes. Step one is "ditch the idea of using comets for an Earth orbit market". Even if you solve the problem of delta vee by using Jupiter THE PANAMA CANAL OF SPACE!, the Kuiper is far enough out we're talking many decades for the payloads to show up, much longer if we use the smexy ultra-low delta tricks. The second is, having ditched stupid ideas possibly picked up from SF authors who couldn't be bothered to run the numbers [1], look around to see if there's a more reasonable source we could tap.

There's a population of bodies called the Near Earth Objects; return orbits from them can be extremely cheap, to the point where it requires more delta vee than Nolan Ryan's best pitch but not a lot more (220 km/hr vs Ryan peak of 160 km/hr)[2]. This assumes aerobraking at the Earth end so keep the payloads small enough navigational mishaps cannot lead to deep excursions within the atmosphere; failing that, make sure city-killing impacts are kept south of 41┬░41'N.

The catch with these is getting there will cost 4ish km/s and the return windows tend to have long intervals between them.

It's also possible the Moon has volatiles worth tapping.

1: I'm thinking of Ben Bova and M.K. Locke here, in case anyone cares, but I can come up with more names if pressed.

2: Meaning it's easy for these to be perturbed into an Earth impacting orbit. Currently it is estimated there are about 20,000 NEOs, any one of which could scream its way directly to where you are sitting given a surprisingly small delta vee.


Another possibility for kinetotrophes might involve piezoelectric materials.


ISTR an Arnold Schwartzenegger comedy in which he (yes he, no typo) was pregnant, and the "doctor" responsible had a line something like "It's perfectly possible for man to have a baby, given a sufficiently narcisistic male".

Also, and being entirely serious (better say that, because you're coming across as the least po-faced academic I know, and several of my best friends are academics. Also, I have made several intendedly humourous comments in response) ISTR a case of a man being reported as pregnant in the Philippines about 15 years ago.


By the way, here's the reference for FOOF, for those who didn't see it the first time:

(worth a read, even if chemistry normally makes you cringe)


'Why do we want living starships?'

> It is easier to grow something than to
build it.

Start with a single cell who's DNA is
programmed with a starship's 'genetic
blueprint' and who's RNA transcription
process can implement pre-programmed
building instructions (using built-in
cellular machinery), add an adequate
feedstock, and then watch your new
starship grow.

>An organic construct is,within limits,
self-repairing (self-healing?)

'There's no obvious source of energy out
in interstellar space, and I can't see
the benefit of carrying food for the ship
as well as fuel for the engines'

This may be a bit fanciful but perhaps
one could design an organic version of
a hydrogen ramscoop/ramjet, a starship
that would harvest interstelllar hydro-
gen gas, using it both as food and as
fuel for a fusion torch?


On the other hand, if we don't need to do the job quickly, we can probably use less delta-vee.
HUH!!? The delta-v to get from orbit 1 to orbit 2 is a constant.
If you can do the transfer slowly, you can use less specific impulse for a given payload.

Similarly, by using gravity wells intelligently, you can do the job more quickly by using them and a lower specific impulse, but if you need to lose 60K kps to get £comet from its cometary orbit to, say, Earth geo-stationary, then on this pass you always need to reduce the speed of $comet by 60K kps.


HUH!!? The delta-v to get from orbit 1 to orbit 2 is a constant.

A: There are ways (Oberth manuevers, flybys, aerobraking, lithobraking) to get nature to pony up the necessary delta vees.

B: There is a class of extremely low delta vee orbits (see the so-called Interplanetary Transport Network) whose delta vees are extremely low. The catch is what you save in reaction mass you pay in time: Hiten, which used a low energy transfer orbit, took five months to make a trip Apollo missons took days to accomplish.


For a living starship: The problems of energy and substrates are distinct. Energy needs resupply, whereas components (mass) can be recycled.

--A "crustacean" starship ought to be able to conserve and recycle most of its material. For instance, a cactus can conserve its water for decades.

--The ship could coast between stars, getting by without needing energy inbetween. Actually, that is how most organisms live in nature. They use energy for brief periods, then go dormant for long stretches until the next energy source appears.

--It may help to look at the vast underground ecology of endoliths (microbes growing within rock). They subsist off radioactive decay, and may double only once in a hundred years.


...they've even grown babies off testes.

YEEE-OWCH!! My testicals just withdrew so far into my body cavity that I'm having liver spasms!


Also, to keep beating on the damp patch that used to be a horse: it's an interesting question to ponder where the energy to turn cometary ice into H2 and LOX is going to come from.


Hi James,

I know about Near Earth Objects. The reason I picked a comet is because there's a lot more water, plus frozen gases and fairly complex organic chemicals available. One probe even found amino acids. If we're going to grow our spacecraft out of organic material, this seems like the best approach. An asteroid gives you a lot less gas and organic compounds, though it does give you more rock and metal... something to think about.

Note also that I'm not suggesting that we go out to the Kuiper Belt and get the comets - arguments about delta-vee aside, that's obviously way too much work. I propose that we intercept one that's headed sunward, as this gives us a much shorter command and control loop.


Hi James,

We use a comet that is inbound towards the sun. That way we have decent amounts of energy available from somewhere near Earth's orbit and back again. (This was specified, BTW, in my very first post.)


I think the hard-shell approach would be easiest to get started.

Blow a large bubble in space from a suitable polymer, statically charge the surface and paint layers of metals to get suitable albedo. Keep it spinning to even heat distribution, and fill it with appropriate filler (water, oxidizer, whatever). Power could be supplied by solar surface materials or kilometer long copper wires drifting out from the sphere. Depending on how much effort needed to stabilize the interior one could stop there or loop superconducting wires around the sphere to generate a mag field to deflect charged particles.. one could even deflect them into storage if you wanted extra building material.

Feed cometary material and the hard crunchy stuff in as needed.

Scale up from an initial start of basic construction material growth (thinking boards, girders, and the like via tree-like biology). Once you've mastered growing building blocks you could convert these object growth farms into placenta's.

It starts as a factory for girders and panels (tinker-toy objects) being grown (think tree's or crustacean shells) in a zero-gravity environment. Toxic atmosphere, reducing environment, radioactive material consolidation, etc... all could be done in different 'factory spheres'.

Automated assembly or following a complete object genetic blueprint could await advancements biotechnology.
But ultimately the vision would be giant protein factories in space or cells with mitochondria, dna, and 'proteins' being produced that float around awaiting assembly.


Oh, come now Boss ..this is so, so, CRUEL - not even to mention, leave alone Mock, in a late Great Bob Shaw sort of faint echo kind of way " Space 1999 " ??? ...

Do you know that of all the Sciffy Writers that are currently alive and kicking bottom you are probably the only man who could do a Serious and Scientific Talk after the Manner of Bob Shaw ...

" Most of Shaw's novels and short stories are serious, but he was known in the fan community for his wit. His early fanwriting career was as a member of Irish Fandom, aka the Wheels of IF, along with Walt Willis, and James White. He always remained a keen reader of and contributor to fanzines. Later, and for many years, at the British science fiction convention Eastercon, he would deliver a humorous speech (often part of his famous series known by the tongue-in-cheek label of "Serious Scientific Talks"); these were eventually collected in The Eastercon Speeches (1979) and A Load of Old Bosh (1995), which also included a similar talk from the 1979 Worldcon in Brighton, 37th World Science Fiction Convention "

This from Wikipedia.

Hard Work though ..very Hard Work!


There are probably LOTS of variations on ..

" It's also possible the Moon has volatiles worth tapping. " but the one that sticks in my mind is in Lloyd Biggle Jr. s " The Fury Out of Time " not his best novel - my choice would be " Watchers of the Dark " (1966) even though he did rather paint himself into a corner with a truly Beautiful idea in crossover SF/Detective fiction - but none the less his Volatiles on the Moon in " The Fury Out of Time " is Wonderfully Silly for all that.


In extremis a bacterium "starship" is the panspermia theory. We can certainly launch those.


Do you have a reference for cactus conserving water for decades? The cacti I'm watching in a nearby park (prickly pears and barrel cacti) are noticeably thinner now than they were when the winter rains ended six months ago. I'm pretty sure they wouldn't last a decade without rain. I'm watching them to make sure poachers don't grab the (rather rare) barrel cacti.

The other thing is that plants have open circulatory systems. Water generally goes in the roots and out the stomata (except when the soil is drier than the plant). Cacti have some neat tricks for conserving water which I won't elaborate on here, but they're still open to their environment.

One of those "space trees" needs something to close its circulatory system, either a closed circulatory system and a heart, or some sort of external membrane and a way to return water to the roots.


For cactus survival without water, I can't put my hand on a research reference. This site says "three years" is common:
The ones in my office go for months without water and they look the same.

You're right that some loss always happens. Actually, that's true of our planet as well. We're still losing hydrogen all the time. What will happen to Earth some day when our molecules start to run out of hydrogen? (I'm sure someone will tell me this takes a while, and I'll sleep easier.)


Charlie's already written about it, in Palimpsest.

I don't know that it will make you sleep easier, though.


I used to tell me biology and biochemistry students [when I was still an academic] that "not found in nature" means you get to file a claim with the Bacterial Patent Authority, but nobody else.


Paul Laffoley did a lot of (as far as I can tell, entirely infeasible and drug-fueled, but extremely pretty) designs for organic space elevators. I can see why such things aren't feasible the way he planned -- with naturally existing vines and such. However, we are aware of some fairly odd exophilic organisms, and I could see breeding a whole ecosystem intended for outer space, living off trace nutrients. It's been demonstrated that, for instance, water bears (which are certainly multicellular) can not only survive in but actually reproduce in the vacuum of space.


I hadn't thought about marsupials. Come to think of it, they're good models. All the growth, the juvenile and adult stages are covered, along with the room for years of good parenting a biological interstellar craft would need.

I rejected birds (or dinosaurs) out of hand because while I can always see 8 million people going off to the stars inside a giant whale, I just can't see them doing this in a cosmic chicken.


you know if you had a inflatable form and planted something inside it maybe it would grow a shell.


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This page contains a single entry by Joan Slonczewski published on September 29, 2011 2:16 PM.

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