They are fundamentally different things. Structural engineering is complicated, ecosystem engineering is complex. They’re broadly different problem domains requiring different approaches and skills.
The biggest challenge with complexity is that all the feedback loops mean it’s impossible to predict outcomes from inputs. Theory isn’t a great guide here. What’s needed is empirical observation, and lots of it, over a long period of time, and nobody’s doing the work. We had a couple of Biosphere projects fail, and nothing to replace it AFAIK.
I’m not saying it can’t be done. I’m saying that if a person says they want to colonize Mars, and they’re not already working on habitat, then they’re obviously lying about their intent.
ETA: though they might not be deliberately lying; they might be fool enough to think that building a functional habitat is a trivial problem.
Quite a lot of science fiction stories seem to assume they’ve just got one. There may (or may not) be some mention of growing plants stuck in there somewhere; but there’s almost never any discussion that implies that figuring out a functioning ecology for the space station or asteroid or generation ship or terraformed planet was particularly difficult. Often there’s just some piece of machinery that magically produces meals and air; and that’s assumed to be all that’s needed.
ISTM that the sort of empirical observation needed is going to only be able to be done in situ with supplied bases as the start.
Small environments, like ships or biospheres, are going to be the most challenging and difficult. Not the easiest ones to learn on. Ecological systems generally are stable because large size and complexity provides buffering. If we someday colonize Mars into a place with self sustaining ecosystems those will be large structures with redundant networks and systems inclusive of plants, fungi, selected microorganisms, so on. A larger system will be more fault tolerant. Self sustaining ship environments will be more brittle and will wait on having the experience with larger ones. Small is harder. Paraterraforming just hard.
Much will have to trust modeling and then investing based on testing in those models.
Yes, this. If space and energy are at a premium - and on a generation ship they definitely are - then tanks of genetically modified algae are probably the only viable solution. In terms of mass required per calorie generated, we’re talking about orders pf magnitude of efficiency above piling up dirt on a rotating disk and trying to grow crops in fields.
I think that’s called a seed ship. And yeah, if you have the ability to grow embryos and live animals from DNA, it seems like a much better method for interstellar colonization.
While this is true, a seed ship is a much smaller, simpler devicie than a generation ship. It can be a tiny fraction of the size and cost, and requires no human lives to be risked. For the same effort that a generation ship requires one could build a whole fleet of seed ships to go to to each neighboring star.
There’s also the concept of a gardener ship - a generation ship with all the capabilities of a seed ship. It coasts along with a stable and permanent population until arriving at another star, where it starts building habitats and printing up life. Then once the colony is established the gardener ship departs for another century on its way to the next star system.i
Anything not used up by the flowers would accumulate in the soil (or water if you go hydroponic) that you’re growing them in. Presumably you’d be treating the soil to remove these substances and replenish compost.
So maybe every X cycles you completely replace the soil when you’re adding compost, and you put what you take out through some other processes to try and get back the calcium etc. This was a problem that came up often in the novel Aurora. Hydroponics would obviously make this easier.
Of course you’d probably be engineering all the species you’re using in this project almost as heavily as the ship’s components. So maybe your genetically engineered memorial flowers are specifically designed to use up nutrients in the exact ratios found in decomposing human slurry.
Yes, this is one name for the concept.
Here’s a previous post in this thread, where I mention a list of options I wrote about 20 years ago.
Note that these aren’t the only options, and probably the most likely option is that no-one ever travels between the stars in any form whatsoever. The boring option.
This is a good idea, although it does remain the case that generation ships are much slower than other strategies. If you are not in a hurry this would be a fairly reliable way to populate the galaxy.
This is a great point, and one that applies to domestic animals as well.
It’s very possible to imagine a generation ship with rolling fields of wheat, where colonists can spend their days tending to crops and domestic animals… but where only a fraction of the actual food supply comes from these farms, and hidden vats of algae make up the very significant deficit.
Yep, it’s a safe bet that the crew of a generation ship will be the best farmers/gardeners/genetic engineers the human race is capable of producing. They’ll be routinely solving problems we probably can’t even guess at today.
I think the default answer to every “Should we include specific product X, that has some useful and near-unique traits?” will be “Yes”. Yes, algae, yes fungus, yes wheat, yes potatoes, yes genetically engineered legless cows, yes four-winged chickens, yes nutritionally useful shades of the color blue. Multiple fall back systems, so when an inevitable problem arises, you have something else to fall back on while you try to fix the problem.
Then you need to consider the trophic levels in the closed environment on board the ship. If you use saprophytes to break down organic material, the amount of available energy in that material decreases somewhat. Any closed environmental life-support system needs an input of energy into that system, either in the form of chemical energy or light energy, otherwise you will be stuck with diminishing returns and decreasing amounts of food.
Even if it is less efficient from a mass standpoint (and it’s hard to imagine anything more important than mass efficiency when it comes to space travel), this is likely a point in favor of having multiple interconnected habitats.
One option would be to launch multiple ships and put them on the same trajectory. This has other benefits - in the event that one ship suffers a catastrophic failure, you could evacuate people to the other ships. You could bring different sorts of species by maintaining different habitats. And I think five societies a thousand strong each will be more stable than one society five thousand strong, for the reasons you mention. People who feel like misfits on one ship could travel to another to find their place.
This goes back to what @Alessan and others have said, but I doubt we will be sending out colony ships before we get a LOT more experience in living in space here in our own solar system.
By the time the first generation ship leaves our star, I expect we will have had people who live their whole lives in space, as have their ancestors for at least a few generations back. They wouldn’t be looking for a habitable rock; just a warm sun, and a whole solar system full of untapped resources.
Maybe if the AI doesn’t like what the first society of humans is doing it can just pick one family to save and then flood the whole planet.
This is a pretty good and thorough list (obviously we can think of many more ideas but most just seem like variants of these).
And this is an excellent rebuttal to the “how can we think about other planets when we’ve screwed up Earth” objection. We have been practicing environmental engineering unwittingly for… well, for many thousands of years, ever since we started pooping out the seeds of our favorite berries alongside our regularly traveled paths. But more specifically, since the Industrial Revolution. We cannot save the Earth without coming to grips with our impact on the planet and then consciously directing our impact going forward. The same exact skills we build by messing around with pie-in-the-sky ideas like long term habitats or terraforming can be used to save the Earth. For example - the aforementioned concrete curing processes that messed up Biosphere 2 also impact the environment.
Yes, this is very true. Case in point - one area where even a hobbyist may have some experience with building a semi-contained ecosystem is in aquarium keeping. Remember that aquariums, unlike spaceships, get their oxygen through exchange with the atmosphere - so aside from keeping the surface agitated to ensure aeration this is not a problem. But you are dealing with the nitrogen cycle. I’ve heard it said that when you successfully keep an aquarium, you aren’t really keeping healthy fish - you are keeping healthy bacteria, who ensure that harmful waste is broken down through the nitrogen cycle.
One very valuable piece of advice for the starting aquarist is that bigger is easier. Keeping all parameters nominal enough for the nitrogen cycle to take place in a 75 gallon tank is far easier than doing so in a 2 gallon betta bowl.
I’d imagine the same principle applies to spaceships (although like with fish tanks the 75 gallon is much more expensive to begin with than that betta bowl!)
You might do better with a generation of android parents who never tell their kids that they were actually robots (assuming your AI can pull that off).
All of these are good points. And even if we don’t end up using chickens or cows on the ship, if we are able to grow embryos then taking their genetic sequences (and a library with the genetic sequence of every living thing we can get our hands on) is absolutely worthwhile.
Fungi are especially interesting if it turns out that claims of radiotrophy are true (or if radiotrophic organisms are possible to engineer even if none currently exist). If the ship is using nuclear power or propulsion, this would be a way to turn waste energy into food.
And if that “something” isn’t humans: you need to first figure out what, exactly, is necessary to raise humans from birth to adulthood in a fashion that results in reasonably sane and recognizably human adults; and to provide the “something” with the ability to provide all of that. The first part is probably the hardest, but the second’s likely not to be easy either; and certainly neither of them would be simple.
We know some things that don’t work. But that’s not at all the same thing as consciously understanding all the combinations of things that do work.
You wouldn’t need to hide the algae. As long as the other crops and animals are providing variety and nutrients not in the algae, even if as a relatively minor part of the diet, the need to be doing something useful (as well as the need to be around plants and non-human animals) can be satisfied.
Sure – if we come at it with that attitude. I don’t think anybody in this thread is objecting to building skills that can be used both here and in off-Earth habitats. We’re objecting to presenting the idea of off-Earth habitats as a solution for messing up this one.
Isn’t it also generally necessary to routinely add food to the tank, and to occasionally perform cleaning functions?
The overall point that it’s easier to keep a large tank stable than a small one still holds, though.