Aurora - a critique by Stephen Baxter and others

[stevebowers]

Kim Stanley Robinson has written an intriguing novel about interstellar colonisation, which some of you might be already familiar with.
http://www.amazon.com/gp/product/B00NERQ...GHXDY3BCXA

Now Centauri Dreams has published an important analysis and critique of the science by
Stephen Baxter, James Benford and Joseph Miller
http://www.centauri-dreams.org/?p=33838

The Ship is accelerated to the cruise speed of 0.1c by means of electromagnetic ‘scissors’ slingshot at Titan, imposing a brief’ acceleration of about 10g, and then a laser impulse for 60 years.
The Ship decelerates at the Tau Ceti system using its on-board fusion propulsion system. The technology, like that used by Daedalus, is known as ‘inertial confinement fusion’ (ICF), in which pellets of fuel are compressed, perhaps with laser or electron beams, until they undergo fusion; the high-speed products provide a rocket exhaust. For twenty years the Ship is decelerated by the detonation of fusion pellets at a rate of two per second. The fusion fuel is a mix of D and He3, as was the case for Daedalus (Chapter 1).

Some interesting ideas there, not all of them plausible; the eventual deceleration by Oberth Manouevre is analysed and dismissed as unworkable.

Robinson suggests that planets with life are likely to be too dangerous or problematic to colonise, something I largely agree with; however the 'prion-like' pathogen he describes is probably not realistic by itself.

[stevebowers]

A few more points;
An abiotic oxygen atmosphere would be possible on a waterworld, because the water would provide a barrier to prevent the oxygen ‘rusting out’ (to use Baxter’s phrase). But presumably the planet would be mapped beforehand to determine if there were any landmasses.
Mapping a planet at interstellar distances would be challenging, but surely not as challenging as getting 74 million tonnes up to 0.1c.
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An abiotic oxygen atmosphere would be possible on a waterworld, because the water would provide a barrier to prevent the oxygen ‘rusting out’ (to use Baxter’s phrase). But presumably the planet would be mapped beforehand to determine if there were any landmasses.
Mapping a planet at interstellar distances would be challenging, but surely not as challenging as getting 74 million tonnes up to 0.1c.
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Braking the ship could be possible if a rambrake (magbrake) were used- as described on this page
http://www.orionsarm.com/eg-article/54ee3dd3291c0
but this would need some advanced planning.

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I would suggest that life-bearing planets be treated with caution and respect - complex biospheres are likely to contain pathogens, predators and/or be in edible or toxic. But a small fraction of biospheres might be compatible with terragen life; a larger proportion of biospheres could perhaps be compatible with modified terragens of various kinds, although this would be a technology for the slightly more distant future.

Planets with microbial populations or even prebiotic biospheres might be dangerous as well, but it might be slightly more acceptable from an ethical standpoint to sterilise a planet with this sort of basic biosphere, so long as samples of the original biota are preserved.

[Drashner1]

Reading through the critique, several other issues and thoughts come to mind. In no particular order:

a) Why assume that planets are necessary for colonization? The very existence of the ship indicates that large, rotating, space colonies are another option. With access to local resources, such as asteroids and moons, and the right equipment, the ship and its population could sustain and expand/replicate itself without bothering with a planet at all.

b) The issue of maintaining a closed ecosystem is brought up. I suppose this might also impact the issue of building space colonies, but:

i) In 500yrs of working on the problem, it seems likely that the state-of-the-art in this area would have improved considerably.

ii) A space colony could be even larger than the ship and so presumably could be more robust in this department.

iii) A space colony needn't be as perfectly closed since it can extract materials, energy, and such from local space to sustain itself.

c) It's mentioned that for the ship to be built in the first place a pretty well developed and wealthy solar civilization would need to already be in existence. This raises several questions/issues:

i) Shouldn't there already be fairly extensive experience with closed ecosystem management already in place? Ok, the ship is as closed as you can get and maybe running longer than has ever been attempted. There should still be some pretty extensive know-how on these things.

ii) The resource base is large enough to send a full colony mission, but not sufficient to send a probe first to check out the planet/system beforehand and report back? Admittedly, if that had been done the story kind of goes away, but much like the whole issue of the 'prion-like' life-form, this comes across as rather contrived in the service of the book being an author-tract.

iii) Why bother with interstellar colonization in the first place at this point? Assuming the book doesn't describe some factor(s) or event(s) forcing the issue, why are these people going to another star instead of just across the solar system to somewhere they can develop while actually having help fairly close to hand? For the ship to exist in the first place, there needs to be a pretty massive amount of solar system development - but it's doubtful that all the good spots have already been taken (or if they have, that's a factor that would be forcing things).

Overall, it sounds like the book somewhat loses something in the way of logic and contrived circumstances in its quest to make a point or argument vs just telling a good story.

On a somewhat related note - a magbrake would work at the speeds described but would be much less capable (they get better the faster you're going and taper off as you slow down). So it might or might not have taken too long to slow down for the ship to survive. Although, since such isn't apparently mentioned in the story, we can't assume that it even plays a role.

Similarly, if the solar civ in the book can field 100,000TW (which is really about standard for starships - maybe a little high), then it could use beamrider tech to send a whole fleet of vessels, probably at a higher speed (and using mag-brakes to slow down) and saved themselves a lot of headaches.

Anyway.

Todd

[Rynn]

I can't say I've been impressed with anything KSR has written aside from the Mars Trilogy, which is unfortunate. I've not read this but a few points based on the feedback:

1) Colonising an earthlike planet with an existing ecosystem could very well be dangerous from a medical perspective. Whilst infections might be unlikely due to lack of co-evolution overstimulation of the innate immune system could be a huge problem. If the biochemistry is similar to Earth then the entire ecosystem is going to be soaked with material that could provoke a (lethal) allergic response.

2) Agreed with Todd. If you can build an interstellar colony ship you have to be able to build a self-sustaining ecosystem (one good enough to support a large population of humans). There's no requirement for a planet with a biosphere. You could built a closed city on a moon, planet or mine an asteroid to build a hab.

[stevebowers]

The point raised by Baxter about predators is a good one. If you are trying to take entire chunks of a biosphere along with you on an interstellar trip, then to take pack predators like wolves you would need to take many, many square kilometres, which would require very large ships indeed. Any large predators or other animals with extensive ranges would need to be taken as DNA or gametes/zygotes, along with gestation technology.

If you have access to gestation technology, then you don't need a massive generation ship; a moderately small one would do, even if cryogenic tech is not available. I call this the hybrid generation ship concept- you can still have a multigeneration ship, but with only a fraction of the number of living sophonts on board. You need take no living presapients at all.

[Rynn]

The point raised by Baxter about predators is a good one. If you are trying to take entire chunks of a biosphere along with you on an interstellar trip, then to take pack predators like wolves you would need to take many, many square kilometres, which woul require very large ships indeed. Any large predators or other animals with extensive ranges would need to be taken as DNA or gametes/zygotes, along with gestation technology.

Problem is predators serve a very important role in ecosystems. If you don't have them then you're going to find yourself over-run with animals whose populations are normally controlled and that could lead to ecosystem collapse. Hmm...mission failure due to explosive rabbit population :p never thought of that as a failure mode for space travel before.

Ways round this would involve increasing technological intervention of the ecosystem. You could replace the predators with culling bots that do little more than kill the prey and deposit the bodies appropriately (don't want to leave too many lying around or you'll have to spend resources culling scavengers and dealing with the problem of excessive rotten meat). I imagine that most of the small ecosystems in OA have a substantial mechology supporting them.

If you have access to gestation technology, then you don't need a massive generation ship; a moderately small one would do, even if cryogenic tech is not available. I call this the hybrid generation ship concept- you can still have a multigeneration ship, but with only a fraction of the number of living sophonts on board.

I disagree, slightly. To check I understand do you mean gestation technology for growing colonists at the other end? If so I disagree that this allows you to have a small ship. Automation is what shrinks ship size by decreasing the amount of colonists you need to maintain a ship.

Space habs (and I'd class generation ships as this, they're just habs going places) designed to be closed ecosystems are going to require a large amount of technological infrastructure to maintain. As I said above you'll need bots to manage animal/plant/etc populations, you'll need smart dust of some sort to monitor species levels, O2 levels, soil health, track any emerging diseases etc. You'll need chemical plants, preservation like areas to safely breed up population numbers, transport, utilities, recycling plants, factories to maintain the bots and infrastructure etc. All of that is going to require a labour force. With low levels of automation the number of people it would require to maintain a technological economy sufficient enough to maintain the ecosystem that supports them likely ranges in the millions.

The more automation you add, the lower this number becomes. That's the only real way you're going to get smaller interstellar colony ships. Without that you need to take a small city's worth of people just to keep everything ticking over.

[stevebowers]

Absolutely.
Automation is the key to reducing the size of a generation ship to manageable levels; automation that allows artificial gestation (including non-human species) and automation that allows the maintenance of a minimal CELSS or some other life support system. Eventually, on arrival, these automated systems can construct a large enough habitat to house pack predators or any other arrangement of species.

This newly constructed habitat would need to be larger than the largest range area of the species included in it; preferably many times larger.

[Rynn]

Something to bear in mind is that many species won't thrive if you take a bunch of juveniles and release them into the wild. Many animals require periods of socialisation and education with kin groups. Given this another aspect of automation needed to properly introduce some new species into an ecosystem would be to have bots that look and behave like adults to raise the young.

Raising human by robot...well I'm skeptical that anything less than a human equivalent intelligence could do so (at least doing it properly, humans need a lot of interaction with other humans to develop socialisation skills. Less than human equivalent you're going to end up with a person to social disorder ratio of 1:1). Along those lines do we have any examples in the setting of robotic interstellar ships, lead by an AI, that build an ecosystem and raise human children in it? I'm feeling some good scope for OA level weirdness there

[Drashner1]

So, reading through the thread, various thoughts:

a) I would suggest that rather than trying to fit a full planetary ecosystem into a ship, a better approach might be to create a smaller, custom designed, and possibly engineered, ecosystem instead.

Such a 'shipsystem' would be viable within the small and closed environment of the ship, but might not fair so well if it had to operate on a planet. It might consist of a mix of organisms, some naturally evolved, some evolved, but then gengineered to fit better into the shipsystem and some totally artificial (if the tech allows for that).

One element of such a shipsystem might be that it 'tops out' with its largest organisms and/or apex predators actually being rather small and harmless by our standards. Cats or weasels instead of wolves or lions (or tigers or bears, oh my). Another might be lifeforms engineered to work better in the closed environment of the ship. Perhaps a rabbit gengineered to have a slower breeding rate, for example.

Such systems might be partially modeled on urban ecologies, in which organisms that do well around lots of humans (and generally need much less space and 'nature' to thrive) dominate.

b) I would also suggest that for a fairly short range/short duration ship such as Aurora (I've seen discussions of ships taking centuries to thousands of years to get around and SF back in the 70s and 80s had many stories about such), that a better approach would be to go for less of an ecosystem and more of a system designed to support humans reliably over a fairly long time scale. So perhaps something more like farmland, living areas, some amount of plants and animals, but not trying to cram whole self-sustaining ecosystems into such a small space. A certain amount of machinery doing some jobs as well might be in order, if that turns out to be easier and more reliable than attempting to manage a purely biological set up. The elements of an ecosystem, including large animals of all types could be brought along in a genebank, embryo store, or some other method.

c) In terms of generation ships, I've seen some discussions that suggest that, at least for early starships, any trip taking more than a century should not be undertaken since there is some chance the travelers will arrive to find that advances in propulsion tech have resulted in other people getting there first.

d) On a different note, worldships are an element of the OA setting (although a little used one). I agree with Rynn that it would be interesting to explore these kinds of vessels and that some novel and 'OAesque' ideas might grow out of the discussion. For one thing, there would be the issue of making use of the entire volume of the ship, rather than just a single spinning open space ala an O'Neil cylinder. For another, there would be the question of how the inhabitants would continue to feel such things as a connection with the wider universe, a sense of horizons or growth, avoid stagnation, etc. All while operating inside something much smaller than a planet.

Just some thoughts,

Todd

[stevebowers]

Along those lines do we have any examples in the setting of robotic interstellar ships, lead by an AI, that build an ecosystem and raise human children in it? I'm feeling some good scope for OA level weirdness there.

A few early missions used the Parental Vec system.
Uoagranyu was mostly a success;
Pandya nearly failed because of inadequate immunology;
Diwali here the environment was deemed too dangerous for biological humans so it became a purely vec colony;
On Caph the system worked too well, and a population explosion occurred.