Until food can be grown or synthesized reliably and effectively in space, a manned deep space mission needs to bring all of the food with it, or cache some of it ahead of time.

Roughly what would be the mass of "space food" per year per astronaut? Possibly an answer for current supplies used on the ISS would be larger than a supply optimized for absolute minimum weight - I don't know.

For example, if I take 5 Calories per gram (carb/protein/fat mix) and 2500 Calories/day as ballpark figures I get about 200 kg/year, or about 3x the mass of the astronaut per year, but food is not necessarily pure carb/protein/fat. The water content could be ignored here and considered as part of the "make up" water necessary for system losses.

How would that ballpark number compare to reality?

note: the answer needs to include some estimate of the "mass overhead" — additional items necessary to contain, maintain, and eat the food; anything that scales with time. Reusable items that don't scale with time (like a heating device or utensil) don't count.

The motivation of the question stems from reading Kate Greene's 2014 Slate.com article An All-Female Mission to Mars; As a NASA guinea pig, I verified that women would be cheaper to launch than men. where the conclusion comes in part from an overall lower caloric requirement.

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    $\begingroup$ slightly related; Dried beans, rice and oats, jerky, olive oil, salt, vitamins, electrolytes, water; anything else? $\endgroup$ – uhoh Dec 15 '17 at 11:06
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    $\begingroup$ If projects like biosphere someday become a reality, you're left with "mass per astronaut" regardless of time. There must be one space flight duration limit, where a longer non food autonomous stock, becomes heavier. It would also be interesting to know how number of astronauts affects mass per astronaut. $\endgroup$ – qq jkztd Dec 15 '17 at 14:48
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    $\begingroup$ Another problem: shelf life. I was about to say that for absolute minimum weight you could do it for a little over 640g/person/day. That's the weight of a commercially available source of complete nutrition, albeit rather unpalatable! Since you're trying to minimize weight store it in something like ziploc bags, very carefully arranged to avoid breaking during launch. However, it doesn't have the shelf life to go to Mars and back. $\endgroup$ – Loren Pechtel Dec 16 '17 at 5:32
  • $\begingroup$ @LorenPechtel the 640g/day figure is really interesting to hear! It's a good benchmark; as you point out, elevating the palatability (for lack of a better word) and the longevity may have a weight penalty. $\endgroup$ – uhoh Dec 16 '17 at 5:53
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    $\begingroup$ The nutrition of astronauts could not be done with water and (carb/protein/fat mix) alone. Minerals and vitamins are also essential. Scurvy killed millions of sailors some centuries ago. But smell and taste of food is also essential for missions lasting years. The weight of vitamins, minerals and spices will be very small but essential. $\endgroup$ – Uwe Dec 16 '17 at 22:58

So, after a lot of searching after what are the recommended daily intake in terms of nutrient requirements and other stuff, I used a couple of sources to make an average of what is actually needed, and starting from this extrapolated a need.

Here are my basis per day, for the average astronaut (average between male and female need) with a moderate physical activity:

  • Proteins: 50 grams
  • Fat: 65 grams
  • Carbohydrates: 320 grams
  • Sugars: 60 grams
  • Sodium: 1.5 grams
  • Fiber: 25 grams
  • Mixed vitamins: 1 gram (wild shot here based on what is needed and could not be provided by the rest of the ingested food)

The sources for these were from an average of several documents, mainly this document from the European Food Safety Authority, this document from WHO and this document from UK FDF. The amounts where chosen with respect for the upper limits proposed by those authorities.

Overall physical activity in space is usually lower than on Earth, since there are no gravity, but there are some forced physical activity to maintain the state of bones and muscles, so I tended to a moderate physical activity.

This should amount to about 10000 kJ per day (using the 9.4kcal/g for fat, 4.7kcal/g for protein, 3.9kcal/g for carbohydrates and sugar and 2.5kcal/g for fiber). Source for these value are this document.

The bulk of this food amount to a total of 522.5 grams per day, per astronaut. Please note this is dry food only.

This NASA Document (from the previous answer) gives the information of 120 grams for packaging for the meals. The same document also gives a reference value of 710 grams of food. However, this amount does seem to include some water since most of the food on the ISS is not dried food.

So per year, this gives about 191kg worth of food and 44kg worth of packaging (or 235kg overall).

Your ballpark was not that far off, and in the right range. The NASA Document for the ISS gives a bit more (260kg of food per year), but this probably includes wet food.

This estimate could probably be reduced by better controlling the activity of the astronauts and a better control of the environment (a bit hotter than needed to reduce the thermogenesis of the body for example).

Small edit to add a bit more information. I fell into the powder food trap and spent the last few days looking for more information.

Some companies are creating their own mix of powdered food, where you just need to add water. If we don't take into account the impact of food quality on astronauts morale, this could be a viable solution to reduce the weight, since they manage to achieve about 150gr of dry powder per meal. This would take the food weight down to 164kg. Also, this kind of powdered food is usually packaged in pouches, so this could significantly lighten the load too if we have a 50gr pouch for each day, that would be a total of 18kg of packaging and a total weight of 182kg.

  • $\begingroup$ This is a great answer, thank your for the links (these are quite interesting) and also the intriguing tidbit that the environmental temperature could be kept slightly higher reduce thermogenesis. That reminds me that the caloric intake of many of the outdoor workers building stations in Antarctica (e.g. Admusen) consumed significantly higher calories for similar reasons. $\endgroup$ – uhoh Feb 20 '18 at 15:03

By searching "ISS food intake" on Google, I found this, which mostly answers you question: https://www.nasa.gov/vision/earth/everydaylife/jamestown-needs-fs.html

  • $\begingroup$ Can you summarize what the page says (so the answer will still be readable if that site goes down - nasa.gov is unreachable for me at the moment) $\endgroup$ – Hobbes Dec 23 '17 at 19:08
  • $\begingroup$ Thanks @Daniel. In stackexchange the answer needs to be at least a minimally stand-alone answer, not just a link. You need to include at the minimum a number for an estimate of mass of food per astronaut per year (subject to the constraints of the question) in your answer in order for it to be a stackexchange answer. $\endgroup$ – uhoh Dec 24 '17 at 3:46
  • $\begingroup$ @Hobbes looks like no response is forthcoming. Care to post at least a speculative answer? (I've added a bounty) $\endgroup$ – uhoh Feb 20 '18 at 3:01

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