As a background, a team of seven astronauts embark on a journey through space. Their aim is to find the source of radio waves that have been attributed to communication from a distant planet (referring to an exoplanet). The astronauts reach their destination in six months in a powerful space ship, with "faster than light" traveling capability (through warping of space). Upon arrival, they find no sign of life. Disappointed, they bein their return journey, but due to some accidents on the planet, run out of their food supply.

This is where I am stuck:

How do they find food ?

It can be assumed that they have enough water (through a recycling module) and their ship has capabilities to very efficiently convert the star's light energy to electricity.

Assuming they can traverse much of space but have a limited food supply (let's say the recycling module's organic matter recycling part broke), how do they successfully return?

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    $\begingroup$ Does everyone need to return? Because without miraculously stranded ships filled with food, unless their spaceship is capable of converting inorganic matter into organic one, it'd seem like we have too many people to feed and not enough organic matter to use. As I see, the most likely outcome would be whoever dies of starvation first being converted into food for the rest to last a little longer. $\endgroup$ Jun 18, 2020 at 17:51
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    $\begingroup$ Give them some emergency farming things, seeds and so on, and then have them look around in the system or whatever for water. That way if a planet supports it, they can set up farms. Sun and water and seeds should be enough. Maybe have them look for that source of the signal. Maybe they can discover something they can use. But honestly sending a whole space ship without a contingency for that seems pretty stupid. $\endgroup$
    – Seallussus
    Jun 18, 2020 at 19:16
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    $\begingroup$ Have you seen the movie or read the book "the martian" $\endgroup$
    – John
    Jun 18, 2020 at 20:25
  • $\begingroup$ similar question on chemistry, though it too has no answers chemistry.stackexchange.com/questions/70791/… $\endgroup$
    – James K
    Jun 19, 2020 at 8:46
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    $\begingroup$ i.imgur.com/srsHwTU.gif $\endgroup$ Jun 19, 2020 at 17:49

12 Answers 12


Water and electricity is not enough to produce food. Sure, lack of water kills way faster than lack of food, but if they have no means of producing food, they don't have many options.

Space apart it sounds like the history of the Essex

Essex was an American whaler from Nantucket, Massachusetts, which was launched in 1799. In 1820, while at sea in the southern Pacific Ocean under the command of Captain George Pollard Jr., she was attacked and sunk by a sperm whale. Stranded thousands of miles from the coast of South America with little food and water, the 20-man crew was forced to make for land in the ship's surviving whaleboats.

The men suffered severe dehydration, starvation, and exposure on the open ocean, and the survivors eventually resorted to eating the bodies of the crewmen who had died. When that proved insufficient, members of the crew drew lots to determine whom they would sacrifice so that the others could live. A total of seven crew members were cannibalized before the last of the eight survivors were rescued, more than three months after the sinking of the Essex.

Apparently, based on the numbers above, in 3 months half of the survivors were cannibalized. This would mean that your crew could maybe have one or two survivors reaching back home.

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    $\begingroup$ Yup... my first thought upon reading the question was "now paging the Donner party...". Not the best storytelling, perhaps, but possibly the most realistic. $\endgroup$
    – Matthew
    Jun 18, 2020 at 19:00
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    $\begingroup$ @Matthew that depends on how you tell the story now doesn’t it? $\endgroup$
    – Joe Bloggs
    Jun 19, 2020 at 7:51
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    $\begingroup$ @David258, to grow plants you need seeds and some nutrients for the plants. Electrons and water alone are not nutrients. $\endgroup$
    – L.Dutch
    Jun 19, 2020 at 16:21
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    $\begingroup$ @JoeBloggs, true! I was using a definition of "best" which was something like "less likely to result in my needing therapy" 😉. $\endgroup$
    – Matthew
    Jun 19, 2020 at 17:53
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    $\begingroup$ @David258, I recommend reading (or watching!) The Martian. You need more than water and light. You need more than water, light and CO₂, even, especially in space. There's a lot actually needed to grow plants that can be taken for granted on a living planet. $\endgroup$
    – Matthew
    Jun 19, 2020 at 17:55

It definitely sets a tone that you may or may not want in your story, but to quote an Orc - "What about their legs? They don't need those". That's 14 legs that are made of meat! Given they're in space, they're entirely capable of manoeuvring around using only their arms. If the ship has an artificial gravity system, it could be turned off to enable the poor volunteer to move around.

They'll lose the ability to kick off surfaces, and have a significant amount of trauma but they'll not die (assuming there's a medic/medbay on board to perform the butchery).

However, that is pretty grim and doesn't have a place in many stories.

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    $\begingroup$ The problem is that the "volunteer" will get little or no net benefit from eating part of their own body. Whatever fat/muscle they cut off to serve was already available to them as an energy reserve, and consuming it as food will not yield that full amount of energy. There might be some benefit to the reduced energy requirements of being a legless torso, but any "food" that comes out of someone's body is just a less efficient redistribution of the food that already went into their body. You can't feed everyone in this way, so you may as well just kill the volunteer and eat them whole. $\endgroup$ Jun 19, 2020 at 13:51
  • $\begingroup$ @NuclearWang On a strictly caloric standpoint you are correct, but if you ask me whether I want to lose a leg or be killed... you may get a different answer. $\endgroup$
    – Michael
    Jun 20, 2020 at 12:52
  • $\begingroup$ @Michael-Where'sClayShirky You're missing the point, it's not lose your legs or die - it's lose your legs then die. The person who gives up their legs doesn't starve any slower. That person will go through the ordeal of being cut in half, only to die of starvation anyway. I'd rather be killed than cut in half and then die of starvation while everyone around has a full stomach (of me). $\endgroup$ Jun 22, 2020 at 5:04

If there is no life on the planet then maybe they track down an earlier failed mission. A derelict spacecraft and its stock of unused provisions is an excellent source of story potential. If the previous mission is far enough off their path, the crew might need to decide that one or more people would have to be left behind to preserve supplies

Of course for a one year round trip just carrying that much food would be much easier and safer then trying to recycle solid waste and organic matter back into food.

If their source of water was destroyed instead of their food, then they could look for icy comets and asteroids, even a single small asteroid might hold decades of water.


The ship is edible

I refer you to the Japanese game show Candy or Not. Contestants have to guess whether incredibly genuine-looking objects are edible or real. There are plenty of videos to be found. enter image description here

They can start by eating the less vital equipment maybe tables, chairs and entertainment facilities. As long as the hull, motors and navigational equipment are non-edible, they can return, even though in straitened circumstances.

In this future age, it is quite feasible to make a durable plastic-like substance which can also provide nutrition when broken down by saliva and stomach juices.

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    $\begingroup$ Wouldn't this go against the "no food supply" requirement? $\endgroup$ Jun 19, 2020 at 8:45
  • $\begingroup$ One of Stanislaw Lem's stories has Ijon Tichy recalling his family history, and recognizing the with of one of his ancestors who did invented edible spaceship furniture. $\endgroup$
    – SJuan76
    Jun 20, 2020 at 14:10

The scenario, if I may summarize it from the OP in my own words:

  • a closed system (the spaceship) that needs to remain closed for 6 months.
  • 7 people inside that need to eat to stay alive for that period.
  • some food cycle system did exist in the ship, but some part is now broken.
  • thus a severely diminished food supply that will not sustain the lives of the 7 for that duration - but not completely zero.

I'm also going to assume that:

  • no resupply from the target planet was possible, either through lifelessness or incompatibility of native organic matter with the Earth-originated ecology.
  • the spaceship can't make any intermediate stops for resupply either (myriad of reasons possible).
  • the ship has some form of artificial gravity, as that will make some of the processes much easier and a known quantity (already done on Earth).

What I propose is alluded to in some other answers and comments, but I'm going to flesh it out in practical terms:

Do nutrient recycling as it is done on Earth by natural processes

(enhanced by human intervention, as needed).

  1. Time: What people often underestimate regarding growing plant crops is the time that is needed. It's not simple sticking some seeds in soil and watering them, and voilà the next day (or month) a fully-developed, nutritious potato has appeared. Same goes for breaking down biomass until it is suitable as a growing medium that provides nutrition to the plants that grow in it. You need to provide some means for the initially needed time to ramp up the system - perhaps by having some remaining foodstuffs, strictly rationed; perhaps by having the crew fast (30-40 days is probably realistic without adverse long-term health effects).

    a) I'm not sure how you will get very hungry humans to abstain from "touching" the not fully grown plants. The crop needs time to develop to full potential where it can feed the entire crew. If I were to write such a story, maybe I'd have the expert/hobby botanist on the crew locking/barricading him/herself into the agri section (with some rations) were s/he gets the process going, only coming out once food supply has been guaranteed. At least there is enough plot potential for an entire book right there - tough love, hard choices between two suboptimal options, isolation, conflict, power dynamics and politics, human nature, and all that.

  2. Converting biomass to growing medium can be accomplished in a myriad of ways.

    a) Lasagna containers: People I know build "lasagna beds" in plastic tote cases, old truck tires, or similar containers, which can be done in small courtyards or even in sunny indoor places. Recommended depth around 40 cm / 16 inch, and would be done in a continuous fashion as biomass becomes available and new crops need to be established. Read up on the lasagna method, but it entails alternating layers of "green" (nitrogen rich) and "brown" (carbon rich) biomass, which triggers the composting process. Paper and cardboard generally count under "browns". Can be enhanced with some soil, compost (from previous batches), minerals. Can be planted immediately if the top layer is an appropriate compost/soil mixture, by the time the roots have reached the lower levels, they should be well underway to compost state. Needs sufficient space for the composting process to develop (depth x width x length) so a tote-size case is probably minimum per iteration.

    b) One can also make compost outright. The speediest compost piles are "warm piles", i.e. microbe-rich (more on that later) which are given optimal circumstances to do the decomposition at optimal rate and generate quite some heat in the process. You'd need a space of dimensions about 1 m / 3.5 ft min to 1.5 m / 5 ft max, to contain the composting material, and some means to ventilate it (blowing air through it mechanically should work). "Dimension" means length, width, height and/or diameter, as applicable - it's a flexible guideline. Again "greens" and "browns", mixed well, in a ratio of around 1:1 to 1:2, and quite a lot of moisture (water) - wet but not soggy or dripping. One or two "turn-overs" (remixing the pile) are often needed to keep the decomposition going, so you'd (temporarily) need that extra space to keep the material. Let's say you can have growing medium ready in about 6 weeks. Composters are usually discouraged from putting anything other than plant material in it, but "warm" compost piles as above have been known to decompose various dairy products, meat (raw and cooked), cooked leftovers, oily foods, hair, bones, blood, and even (small) animal carcasses and human waste products (urine and excrement). Warm piles have been known to ignite in rare cases, which is usually prevented by not going too big (or monitoring them like a baby).

    c) Another way that is used in many kitchens (including small apartments) to handle biomass is the Bokashi method. This can also handle all of the above non-plant materials. A filled container, mixed with the bokashi "bran", is closed air-tight for 2 weeks to allow an anaerobic fermentation process to complete, which is performed by various microbes with which the "bran" was inoculated. Do note however that this is not a complete process, and would require finishing-off by one of the other methods - the benefit however is that it preprocessed some biomass that the other methods would not like, or take much longer with, so the recycling is sped up.

    d) Earthworms are marvelous little creatures that in 24 hours can turn biomass of half their body weight to the absolute best compost (often wonderingly called "black gold"). However, they work best on half-rotted material (compost pile or bokashi thus works well as a preprocess step).

  3. Once you've got your biomass nutrients turned into growth medium in this way, I think you're past the biggest obstacle since this nutrient and microbe-rich material grows plants that are usually disease free and producing abundantly (provided the right minerals and trace elements are present). Since it is so nutrient-rich, it lends itself to higher plant densities or smaller growing containers, which may be appropriate in a space where space is at a premium. Of course, this assumes that the necessary seeds/seedlings/cloneable plant material is on board in the first place...

    a) The earthworms also produce "castings", a mass of little roundish particles that some have converted hydroponics systems to use instead of the usual growing salts - see vermiponics. Otherwise they could just be added to the growing medium. You would probably still get such medium out of your worm farms (and/or other systems) in addition to the castings.

  4. Apart from eating plants, I have heard earthworms are also considered a good source of complete proteins and a delicacy in some places - prepared in the right way. (No first-hand knowledge here, (un)fortunately...) Guesstimates are that you can keep not more than 5 kg of Eisenia fetida worms per 1 m² (about 1 pound per sq ft). You'll have to research reproduction rate yourself if you want to go this route, but they can be quite good breeders under the right circumstances.

Some problems and other notes

  1. The above processes do depend on microbes (viruses, bacteria, yeasts; and optionally but preferably also nematodes, worms, insects) to work at all. They occur on Earth simply in the environment, but what about on a spaceship that's presumably sterilized? Although, the International Space Station has shown that it is quite hard to keep all microbes out. All living organisms on Earth live in symbiosis and we humans probably carry more microbes than our own cells around with us. So some mix of luck, microbiology knowledge, accidentally or deliberately brought-along microbiomes would be needed to get the right critters for the process. Maybe have bokashi be a part of the original waste conversion process, some on-board experiments, a smuggled-in pot plant, fecal swabs of the whole crew by the microbiologist....

  2. Same goes for earthworms. Why would there be Eisenia fetida on board? Some reason to be thought of.

  3. Same goes for having viable (reproducable) foodstuff plant material on board. Maybe from an existing food production facility (hidroponics?), maybe experiments, supplies for a colony of sorts, etc.

  4. Human waste products (urine and excrement) are a nutrient resource that should not go to waste in a closed system like this spaceship. Warm compost piles and bokashi fermentation both have the potential to neutralize harmful pathogens and help return the material to the food chain. It has already been done on Earth. If you need more background, I strongly recommend The Humanure Handbook as a starting point, in addition to websearch for the right terms. This book also provides a wealth of information about warm compost piles and microbial life, even if one does not plan to bring any animal dung near it. Although, 3-4 months (6 months minus the old rations/fasting rampup period) might not deplete nutrients in the cycle enough to matter. So to make it more interesting, the travel time could be extended...

  • $\begingroup$ many of the right microbes are present in the crew own digestive tract. $\endgroup$
    – John
    Jun 21, 2020 at 15:01

For a voyage of >6 months (each way?) I might actually expect that the ship is designed to be able to grow food; otherwise that's a lot of wasted weight, an extra mechanism for waste disposal, and the risk of food loss that you're explicitly worried about here.

In the general case life on a spaceship (or anywhere) is sustainable if energy-in is equal to energy-out, and there is a closed nutrient cycle. The energy-balance hasn't changed so you should be good on that front, solar lamps to grow plants seem pretty reasonable in space if you don't have better tech. A big food loss will disrupt the nutrient cycle; but given all the humans are currently alive there are definitely enough total nutrients remaining, even if everything is running a bit closer to the wire than the crew might hope for.

If the crew is particularly worried, they may have the grim task of bringing back corpses from the site of the accident for use as fertiliser. In the very worst case you might need to make some corpses for fertiliser to kick start the process, but that might not need to be very many of the crew.


I have several ideas, though all of the hinge on mission and spacecraft design

Mainly, since the vessel has a warp drive, we don't really have to care as much about the rocket equation. Meaning that bringing more elaborate equipment is justifiable. Furthermore I'm going to assume that thed setting has some near and far future technologies. Disregard options that do not fit your setting.

1. Do you want to eat canned food for a year? Can you imagine the effects that would have on morale? Yes? Good that this is an easy problem to solve. Try hydroponics and vat grown meat. Both are technologies that are rapidly maturing today and bringing a farming module on such a mission is quite justifiable. Maybe the rations were just the carbon component of the meals and now the hydrocarbons need to be expanded/repaired. Alternatively you could feed everyone out of a yeast and alge based agriculture. Aquaculture can also be done in some of the inner water tanks.

Just have the mission planners be a bit more creative about feeding everyone.

2. Build some sort of "farming". Let's assume that Tey have a lot of blueprints, really good design AI and decent, 3d printer based, manufacturing capabilities. Even if they don't have lab meat growing capabilities to bed in with, these highly skilled individuals (probability there is at least one biologist) and the vast databases of their vessel should be capable of setting such a system up. Then you would only need some blood and you can start growing meat. Farming labrats or alge used in the recycling systems you'd work as well.

3. Cannibalism, but we'll planned and organised. Amputations shouldn't be too hard in a property equipped medical bay. Calculate how much food (arms and legs) is needed to feed none or one or two people, depending on what's the minimum crew, for 6 months. Then cut of what you need, put everyone who's not required into an artifical coma to reduce food consumption and set up the medbays machines and the shops robots to feed the astronauts. They should all come home, all be it malnourished and a few limbs short.

4. If cryonics exists in your setting, they are a great option here. Even if they exist, there are good reasons for why they aren't standard procedure for space travel. Maybe there are religious or cultural biases against litteraly dying and beeing conserved in a state where reanimation of the frozen corpse (not wakeing up the sleeper, you are certifiably dead when in cryostasis) is possible. Or there is an significant failure rate, something like 20% don't come back and 40% have brain damage. If it is possible, construct freezers and medical equipment, mix up the antidepressants that will prevent brain damage and decapitate the crewmen going into cryostasis. You only need the brain with the head anyway. Might as well use the bodies to feed the guy who will fly the vessel back. The others might have to wait a hundred years longer, until unfreezing has become saver, but they'll live (again).

5. Use the medical printer or synthetiser. If the technology is sufficiently advanced the medbay should have a way to grow replacement organs. Just programm that maschine to produce steak. Maybe one can even use the medicine synthetyser to produce something edibile.

  • $\begingroup$ +1 for farming. $\endgroup$
    – Pere
    Jun 19, 2020 at 14:38
  • $\begingroup$ Antidepressants don't prevent brain damage during cryonics; I think you mean antifreeze (though not the substance we generally call antifreeze, like alcohol v.s. propanol). $\endgroup$
    – wizzwizz4
    Jun 21, 2020 at 0:08
  • $\begingroup$ @wizzwizz4 Ups, my autocorrect must have gone wild. Well considering the situation the astronauts are in antidepressants might be in order as well. ;) $\endgroup$ Jun 21, 2020 at 9:52

The Russian and American space agencies both had a look at this (1960-70s I think). Short answer is: I hope they like glycerol and starch!

This is the closest I know of that we have come to producing synthetic food from water and electricity (apart from 'electro single cell protein') and even then you would slowly be dying from vitamin deficiencies.

FYI I would hope that crew morale is good or future technology has improved the flavour as having this all day everyday would be interesting!


One or more unmanned/automated resupply ships/cargo pods with reserve fuel that were sent ahead and are parked in handy locations along the route such that it could reach a crew before they starve to death. In the event that they are not put to use, they return to earth or something such they aren't a total loss.


By "no signs of life" does that mean that there is nothing edible on the planet? Like is it just a barren rock, or is there vegetation on it?

Extending this idea further, are there other planets along the way back that have vegetation or maybe some kinds of animals they could eat?



tholins on europa

Tholins are a wild mix of thousands of different organic chemicals. Deposits of tholin on planetary surfaces is thought to be common throughout the universe, because the elemental precursors of tholins and the energy to make them are common thru the universe. Titan is covered with thick deposits of tholin. Depicted: cracks in Europa, crammed with tholiny goodness.

Bacteria can eat tholin.


Tholins have been a scientific pet project for decades. “This tholin material has been made in labs for about forty years, but the stuff is so complex that we couldn’t analyze thoroughly until recently,” says Dale Cruikshank, an astronomer and planetary scientist at NASA's Ames Research Center. Now they know that when you hydrolyze tholins, those complex bonds between hydrogens, carbons, nitrogens, and oxygens can recombine to form amino acids.

Nobody knows exactly how life got started, but most scientists agree that amino acids were probably involved. “It’s also edible, in a way. People have made the this stuff and exposed it to different kinds of bacteria, and some can metabolize and even thrive on it,” Cruikshank says. "To me, that drives this connection to pre-biology even closer.” So, tholin soup, anyone?

So too your scientists! Now - tholins probably contain a lot of stuff that is not good to eat. OK, mostly not good to eat. But there are amino acids in there, and those are good to eat!

Presented with enormous mounts of tholins, your castaways could

1: Use science to purify the amino acid fraction. Then chow down. Even if it is only 0.1% they have mountains of the stuff.

2: Grow yeast or bacterial on tholin slurry, rinse off unmetabolized tholins, and eat the bugs.

3: Warm up the tholin to drive off the worst stuff, eat the rest and hope for the best.

4: Give up on 1 (too hard), 2 (making grow vats did not work) and 3 (one time project). Instead, distill off volatiles, retaining only the ethanol fraction. Get drunk. Wake up; repeat.

In unexpected discovery, comet contains alcohol, sugar

"We found that comet Lovejoy was releasing as much alcohol as in at least 500 bottles of wine every second during its peak activity," said Nicolas Biver of the Paris Observatory, France...

Ethanol has plenty of caloric value. Your tholin brew will have piquant notes of ethanol, ammonia, melamine and hexane.

Korolev looked appraisingly at the clear fluid in the beaker, tilting it back and forth. He took a careful sniff. He lifted an eyebrow. Then he raised the beaker in a silent toast to his crewmates and downed the whole thing in a gulp. He ran his tongue over his teeth, regarded the empty beaker phlegmatically and nodded. "A little ice will help."



If they are at the level of technology in which they have faster than light travel via warping space, it would be unsurprising to introduce some form of matter replication. They could have a basic nano-level molecular assembler expected to be used for spare parts and other inorganic structures that could be hacked to produce simple foods. In fact you could come up with some explanation involving the molecular assembler being a component of the faster than light drive. If you want them to not have an inexhaustible source of food make the hacked food replicator depend on a finite supply of raw materials they extracted from the planet for this purpose.


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