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Assuming that

  • the planet is 20 light years away (so back and forth trips would be impractical)

  • we have no clue whether there is any edible life forms on the new planet

  • hibernation (freezing/thawing etc.) of our bodies isn't invented

  • we carry 100 people

  • The ship can travel up to 1/2 the speed of light

I know that in order to maintain a good gene pool, we will need at least 100 healthy people, who may grow old during the journey and have their kids (extra mouths to feed) to keep the generations going. Even if it is high energy food, people need to eat a lot and drink a lot.

About how much would any space colonists need to bring?

Would we need to balance between space craft fuel and food for the crew?

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    $\begingroup$ "I know that in order to maintain a good gene pool, we will need at least 100 healthy people" - there was a question on this very site, and I am sure that the answer was 6,000. Alas, I can't find it again, but maybe someone else can $\endgroup$
    – Mawg says reinstate Monica
    Apr 12, 2017 at 12:14
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    $\begingroup$ "we have no clue whether there is any edible life forms on the new planet" - do you if you will be able to farm on a large scale? If not, it doesn't matter how much food you bring, everyone will starve eventually $\endgroup$
    – Mawg says reinstate Monica
    Apr 12, 2017 at 12:17
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    $\begingroup$ @Mawg I believe you're looking for this: worldbuilding.stackexchange.com/questions/3/…. Not quite 6,000, but certainly more than 100. $\endgroup$
    – Nuclear Hoagie
    Apr 12, 2017 at 12:33
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    $\begingroup$ @NuclearWang Do note that the number can be much smaller if the colonists are selected based on their genetic profile, and their breeding is controlled. I'm not sure if 100 is possible with near-future technology for humans, but I wouldn't discard it outright either. $\endgroup$
    – Luaan
    Apr 12, 2017 at 13:06
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    $\begingroup$ they could carry a lot of frozen eggs and sperm in a small freezer, no need to bring more people than required to get started. $\endgroup$
    – PatFromCanada
    Apr 12, 2017 at 21:03

5 Answers 5

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If the average person had 2kg of food a day, and 1 liter of water, you'd need about 2,922,000kg of food and 1,461,000L of water for the trip. Not feasible on a spaceship, which has to conserve space and weight. Rather, what you need are renewable supplies of nutrients and water.

For drinking water, http://mentalfloss.com/article/67854/how-do-astronauts-get-drinking-water-iss

and for food https://en.wikipedia.org/wiki/Cellular_agriculture

the matter for this food would have to come from recycled waste, so the supply of food would have to last longer than the time it takes to break down human waste into parts that can be used to regrow the cell cultures.

Water is a bit funnier since it's used for so many different purposes, but you'd always need a supply of it in store while recycling used water.

A good thing to keep in mind is that everything in space travel triple and quadruple redundancy, so much can and often does go wrong, that your backup plans need a last resort emergency plan, which has backups.

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    $\begingroup$ 1 liter per person per day seems to be a bit n the short side? $\endgroup$
    – Burki
    Apr 12, 2017 at 7:54
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    $\begingroup$ Definitely it's closer to a minimum, that highlights how improbable it is to haul a large enough supply for single use on this type of trip $\endgroup$
    – Eloc
    Apr 12, 2017 at 8:01
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    $\begingroup$ Two kilograms of food per day? Are they all weightlifters? I'd estimate my daily food intake is more like 500g and I am an average person. $\endgroup$
    – Michael Vehrs
    Apr 12, 2017 at 9:20
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    $\begingroup$ nationalgeographic.com/what-the-world-eats The calculations aren't super important, feel free to edit that, since the amount of supplies for 100 people for 40 years is too large to carry on conventional spaceships $\endgroup$
    – Eloc
    Apr 12, 2017 at 9:40
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    $\begingroup$ @Burki if people sit around and do nothing 1 liter is enough. However, you're correct if they try to stay in shape, not become like the people in Wall-E $\endgroup$
    – arthurz12345
    Apr 12, 2017 at 20:00
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Using this as a reference: One km^3 of aeroponics bays can feed can potentially feed 49,210,000 people on sweet potatoes at 2k calories per person per day, from there its simple mathematics. Still using my reference, we multiply that number by 54/70 to get from sweet potatoes to potatoes (which contain all the nutrients you need in a healthy diet), to get to 37,962,000 people fed by 1 km^3 of aeroponics bays, from there we divide down the area we need to feed 200 people (assuming a huge redundancy because this is space), then multiply that by 37,962,000/200 to get 189810, then take 1/189810 km^3 in m^3 to get 5268.43m^3 of ship space needed to feed your crew of 100 people.

Additional problems: you need to have a huge supply of vitamins and supplements in case someone has a dietrey problem and ends up requiring some.

Also you are going to need to coat your ship in solar panels to be able to power these aeroponics bays.

Also i'm not quite sure on how to work out how much water you are going to need, but it has to be a continuous process (like BSG), else you may have shortages.

The final problem is you have to have a ship vaguely similar in design to that seein in The Martian, as you need to keep these people in an environment where they can experience gravity and do exercise, else their muscles will waste away into nothing and you will enver be able to land

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    $\begingroup$ This is an interstellar journey, meaning at first you move away from the nearest sun. This greatly reduces the efficiency of solar cells. $\endgroup$
    – Burki
    Apr 12, 2017 at 7:54
  • $\begingroup$ @Burki I am aware, but i am going to assume that a species that can build a 0.5 C speed spaceship (generation ship) can also build super high efficiency solar panels and probably fusion generators $\endgroup$
    – Alex Robinson
    Apr 12, 2017 at 8:15
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    $\begingroup$ You should probably assume fusion power (or hand-wave power) by this point. $\endgroup$
    – Chris H
    Apr 12, 2017 at 9:15
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    $\begingroup$ efficiency of solar panels is absolutely irrelevant if there is basically no light to work with. $\endgroup$
    – MolbOrg
    Apr 12, 2017 at 11:34
  • $\begingroup$ You get the caloric requirement from this, but still miss important nutrients. For example proteins. While 3rd world countries seem to have no issues with vegan diets, they don't work well in 1st world countries because 1st world countries limit the amount of insect contamination in your veggies. You will need "hand wave" power for a journey like this. teh good news is that any engine capable of pushing a ship to 0.5C will have oodles of capacity to spare for aeroponics. $\endgroup$
    – pojo-guy
    Apr 13, 2017 at 3:53
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As usual, Star Trek got it right. You can't carry enough food, so you need a replicator. You need a machine which can take human waste (both solid and liquid), break it down into its component chemicals and minerals, add a little energy from the ship's fusion reactors and somehow reconstitute it into something that humans can digest. It doesn't need to have openings into each crew member's quarters (like the ones on the Enterprise) but it needs to perform that basic function efficiently and reliably.

Now comes the tough part... you need to recycle your crew. There is a limited amount of biological materials on-board and at some point in the journey, somebody is going to get pregnant. Where will the material for the new baby come from? You either need to carry extra biomass in storage (which is only a short term solution) or you need to somehow culturally link the birth and death process. For an expecting mother to get the extra food she needs to build a new person and for that person to get the extra food needed to grow and mature... somebody will have to die.

Closed loop systems are not for the faint of heart.

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    $\begingroup$ Fully closed loop systems are not for the faint of heart, but these people only need to make it for 40 years. I think a few extra tons of biomass to replace the dead people can be done. $\endgroup$
    – BobTheAverage
    Apr 12, 2017 at 6:05
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    $\begingroup$ and when they get there, what biomass do they use for increasing the colony? Surely if it was closed-loop they wouldn't be able to increase population over 100? $\endgroup$
    – marcellothearcane
    Apr 12, 2017 at 8:48
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    $\begingroup$ @marcellothearcane The loop no longer needs to be closed in their destination. Ammonia, methane, carbon dioxide, nitrogen fixation, ... are all raw materials to grow the food supply once they arrive. Micro-nutrients might be trickier, but they can also take a lot bigger supply of those, since they are only required in much lower numbers. $\endgroup$
    – Luaan
    Apr 12, 2017 at 13:10
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You cannot simply pack food for a 40 years travel and some years to settle on the planet.

You will need to grow food on your ship, mostly plants.

You will not bring along livestock, they require too many resources. You will better use bugs and insects for protein supply: they grow fast and in large number.

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    $\begingroup$ @Cursed1701, didn't I say this? $\endgroup$
    – L.Dutch ♦
    Apr 12, 2017 at 7:56
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Hmmm... I'm gonna keep this answer short because it's late on my end, but I guess the two big things I have to say is that firstly, you wouldn't need to bring much "food" at all (at least not in the way I think you mean it), and secondly, as an incidental bit of constructive criticism, 100 is hardly adequate for long-term colonization. I'll get to the food in a second, but if you want a truly sustainable population that'll last long enough to establish a permanent human presence on your planet without the need to bring in any new people a few generations down the line, you'll need a few thousand people. 20,000 to 40,000 is usually a good number, while 100 is only suitable for establishing small colonies you intend to use only as temporary scientific/mining outposts or that you plan on sending more people to in the future. Basically, a colony of a few hundred is only feasible for in-system settlement where you can expect frequent communication with Earth and a steady influx of new people as they become needed. Interstellar or intergalactic colonization requires large numbers.

As for food, there are a number of great videos on Isaac Arthur's Youtube channel explaining the basics of interplanetary and interstellar colonization, including your desired population size, multiple methods of getting people there, the likely design of your colony ship (if you're sticking to known physics), and most importantly, food and living space aboard your ship. Here's a hint: it involves genetic engineering and tofu-burgers.

Here's a link to the most relevant video. There should be links to others included in it, but I'd also recommend watching the Terraforming, Bioforming, and Interstellar Travel Challenges videos, as well as the other Life in a Space Colony videos: https://m.youtube.com/watch?list=PLIIOUpOge0Lvr26RCeM_6mq72KFhPWEkG&v=THqtAQOicQI

Hopefully this'll help!

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