What to do with with dead bodies on Generation Ships

Don’t ask about Soylent Brown.

I expect there would be vat grown meat, depending on the energy cost to create it. With sufficient nuclear power, or whatever, energy may not be a limiting factor.

We have small quantities of very expensive vat grown meat now, and companies that are working to make it a consumer product, so it is reasonable to assume that by the time we can build a generation ship, it will be cheap and plentiful.

Possible, but if true in this scenario, they’d likely be more horrified by the thought of eating meat from animals/grandma (unless it was socially preserved / added) in that case. After all, given all the ethically ‘clean’ meat (for various values of clean) I suspect the thought of eating meat directly derived from death would be terrifying.

For that matter, given hundreds/thousands of years, nothing is free. The effort to gather hydrogen for fusion, via Bussard options or other vaguely probable technologies are going to come at a cost of weight if nothing else. The simplest options are more likely to be the ones that dominate the average generation ship, which would be growing GMO veggies that meet (meat?) human’s nutritional needs.

Yuck! I suspect they are working on it now because we have actual meat. Take that off the table and I’d rather have a plant protein substitute.

Personally, I find it to be a stressor to know that I was born on Earth, and was never given any choice in the matter.

And on any interstellar ship, the energy needed for life support is not going to be a big deal. It won’t matter if bioengineered algae or vat-grown meat is more energy-efficient than actual dead animals, because if we have a stardrive, then the energy needed for inefficient foods will be a rounding error.

You certainly wouldn’t want to lose any water, but there is actually water in interstellar space that might be harvestable. In molecular clouds the water density can be as high as 10,000 water molecules per cubic centimeter, but even in open interstellar space there are water molecules floating around. Whether it’s a significant amount and how to harvest it is still an open question.

The most valuable chemical in the human body for space travellers is probably phosphorous. Nitrogen is critical to plant life, and the human body has 3% nitrogen by weight. Potassium is another necessary chemical we wouldn’t want to throw away.

My vote would be for the ‘memorial garden’, with the plant mass from that going into standard compost. But if you needed specific chemicals, you’d have to figure out how to process the body to reclaim them.

Life as we know it cannot exist without nitrogen (which is part of every amino acid, the building blocks of protein) or phosphorus (which is part of DNA and RNA, as well as ATP, the chemical that cells directly use for energy). Sulfur is probably also essential, being part of some amino acids, but one could conceivably have life-as-we-know-it that just happens to not use those particular amino acids.

Everything beyond CHONPS, you can probably find some living thing that doesn’t need it. Though humans, specifically, need a bunch of others.

And we don’t need to figure out how to process bodies to reclaim specific chemicals, because that’s a solved problem. It was solved long before we were even capable of figuring it out. We get the chemicals we need from the plants we eat (or from the animals that also eat those plants), and the plants get them from the soil. In some cases, they need to be in the soil in the right form, but any way they’d be left over from a dead body is a “right form”.

Flower gardens seem to be a popular idea in this thread. Would flower plants draw calcium from the corpse fast enough to recycle it?

From Wikipedia

So water ice is a mineral. Some designs of generation ship have a layer of ice in the outer shell, or on the front end, to protect against radiation and high-speed dust impacts.

The savings in mass, rather than energy, favour vat-grown food.

Algae tanks and meat vats both require much less space and infrastructure than farms with enough space to raise cows. Maybe there will be room for farms growing edible insects or fish, which could live on human garbage; but acres and acres of pasture would require much larger ship designs.

Even on a generation ship, every gram will need to be accounted for.

Isn’t the whole point of building a generation ship because we don’t have a stardrive?

Areas growing plants, however, are growing oxygen as well as food; and may well provide enough net benefit to make it worth allowing the space.

There are also psychological benefits for humans from being around growing plants, which I don’t think extend to being around tanks of algae.

I agree that raising cows on a generation ship is implausible. Rabbits, maybe; though they might be way too likely to be perceived as pets, which would cause other problems. Having no pets, however, might also cause problems; although there are some humans who actively don’t want to be around anyone other than humans, living with other species in some fashion seems overall to be one of the Things People Do, even people who don’t treat them well. I suppose it might well not be practical to bring obligate-carnivore cats. (Not the only reason I’m not volunteering for a generation ship; but certainly one of the reasons.)

It’s been proposed as an answer to the Fermi Paradox

Algae vats produce oxygen too, and they can be stacked into much smaller spaces.
Humans do have a psychological need for space, but I expect there will be ways to simulate wide open spaces and combat claustrophobia long before we can build generation ships.

There is a ways to go on that front (yes, the whole generation ship as well, but), remember Biosphere 2?

“Many scientists looked back at the original Biosphere 2 as a colossal failure. “In short, the Biosphere 2 experiment failed to generate sufficient breathable air, drinkable water and adequate food for just eight humans, despite an expenditure of $200 million,” the ecologist Rebecca Stewart and her colleagues declared.”

All I saying is might be better to use new tech and science than trying to re-create earth in a spaceship. Still it’s an interesting read.
.

Holodeck!?

The issue of collapsing ecosystems such as what happened with Biosphere is a big deal. Ecologies are complex systems, and we still don’t understand them very well. In Biosphere they kept running into various crashes - suddenly CO2 would spike, or some other thing would happen that they didn’t understand.

It may be that artificial ecosystems outside of Earth are extremely hard to keep going over years or decades. Too much diversity required, too many little important interactions that we don’t understand.

Or maybe not. We will learn a lot more once we start building permanent stations on the Moon and Mars.

You still have to accelerate to speeds much greater than humanity has achieved to date, and then decelerate before you arrive. Otherwise, your trip will take millions of years instead of just thousands.

Space is big.

I think it is a mistake to expect the plants in a generation ship or a habitat to generate enough oxygen to support a biosphere. On Earth the atmosphere contains about two orders of magnitude more oxygen than the total mass of the biosphere; most of this oxygen is ‘fossil’ oxygen, created millions of years ago by plants which are now dead and buried in sediments. If we burned the entire biosphere of Earth to produce carbon dioxide, the amount of oxygen in the atmosphere would only decrease by a couple of percent. In a generation ship or space habitat most of the oxygen would need to be supplied by chemical processing.

On the other hand plants and/or algae could help maintain a comfortably low level of carbon dioxide, especially if they are well illuminated. Even then we might need artificial CO2 scrubbers to even things out.

If you’re getting to other stars, then what you’re using to get there is, by definition, a stardrive. Now, we could in principle do it using low-energy techniques like planetary flybys, but just because you’ve got a generation ship doesn’t mean you want your trip to take longer than all of recorded history. Most likely, you’ll have some sort of fusion-powered drive.

I’m curious if anyone’s ever followed up on that… We know why and how Biosphere 2 failed. It was partly constructed from concrete, and concrete actually continues to cure for decades after it’s hardened enough for use, and the original designers didn’t account for that. Just because the first experiment failed doesn’t mean the project as a whole failed: You take the failures of the first try, fix them, and try again, until you get it to succeed.

The amount of plants necessary to supply sufficient oxygen for a population of heterotrophs (like us) is exactly the same amount of plants as are necessary to supply sufficient food for that same population of heterotrophs. It can’t be otherwise. Of course the plants on board the ship won’t create the ship’s initial atmosphere, but there’s no need for them to do that. All that’s needed is for them to maintain that, a much easier task.

Are you saying yuck because you’ve tasted it and dislike it? Or does the idea of it disgust you?

I’m curious as to how it tastes. But I know some people who are squicked out by the thought of it.