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It seems to me that weight and size would be important in choosing spacefarers for many reasons; I came across this Wikipedia article where the Chinese astronauts (taikonauts) have to be between 50 and 70 kg, which makes sense to me, but other countries don't seem to stipulate a size requirement.

I would think that it would be easier and cheaper to get the person into space if they weigh less, and could survive on less food for a given time frame so you also save on the provisions.

Cramped conditions would be less of a problem.

All else being equal, is there any reason why sending bigger people into space would be an advantage?

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    $\begingroup$ Space suits themselves are expensive. If you want to be a NASA astronaut, you have to fit into the suits they have. They most likely will not go through the expense of making a new one just for you. You have to fit inside the launch vehicle, and be able to sit in the chair properly, and anything else you will be inside of, as well. So, yes, these considerations are important, but I do not know a full list or good references for them. $\endgroup$ – zibadawa timmy Sep 28 '15 at 7:12
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    $\begingroup$ Using the Soyez rocket they build the chair and suite specially for you. $\endgroup$ – Jakob Sep 28 '15 at 7:20
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    $\begingroup$ To answer the question - can height be an advantage. Allowing a wider range of people does increase the choice of suitable candidates, so I guess this is the advantage. I read there used to be tighter restrictions on height, for example 6ft maximum for the early NASA astronauts. But these days there seems to be a wider range of shapes and sizes that are acceptable. Smaller people don't necessarily save that much weight on food, oxygen, water intake, clothing and miscellaneous equipment. And suits are a small expense compared to the costs of several years of training. $\endgroup$ – Andy Sep 28 '15 at 10:38
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    $\begingroup$ US EVA suits are put together from a selection of "generic" sizing components to best fit individual crewmembers. $\endgroup$ – Organic Marble Sep 28 '15 at 19:24
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In the early days of crewed space exploration, size and weight of crew was an issue. The original batch of Soviet cosmonauts selected were restricted to 1.75m height and 72kg mass, for example, and US astronauts to 1.80m and 82kg.

As launchers got bigger and spacecraft got more complex (and roomier), these restrictions became less important because the crew represented a progressively smaller share of the mass budget.

For example, in the Mercury program, the astronaut's mass was ~5.8% of the spacecraft mass; in Gemini, the crew was ~4.3%; in Apollo earth-orbit configurations, ~1.2%.

At some point in that progression, it makes sense to start relaxing the astronaut height/mass restrictions. China's space program simply hasn't advanced far enough for them to do so yet.

As for inherent advantages of a larger crew member, all other things being equal, larger people in good health are generally stronger, which can be important during certain EVA operations. In most other criteria a smaller crew member would probably be very slightly preferable primarily due to resource consumption rates.

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  • $\begingroup$ I expect those EVA operations to be rare, while the slight reduction in resource consumption would be a constant and over time, say a couple of years or so add up to quite a substantial reduction. Perhaps so rare that over a lengthy period I could actually afford to have 2 smaller spacefarers to handle the EVA operation. I'm thinking long term space travel not a trip to the moon. Strength in many cases apart from weight lifting is often in practice a product of leverage, particularly in cramped quarters. You have given the best answer so far though. $\endgroup$ – Kilisi Sep 29 '15 at 2:48
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    $\begingroup$ I would expect that consumable usage (food, water, air) would be pretty close to linear with body mass, so there's no point at which two 75kg crewmembers would be more mass-effective than one 100kg crewmember; if you want to replace 3 100kg crewmembers with 4 75kg crewmembers, you need an extra seat, an extra sleep compartment, an extra spacesuit, and so on. I'm not saying there's no advantage in smaller crew members, just that at some point it's not worth worrying about. $\endgroup$ – Russell Borogove Sep 29 '15 at 3:01
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    $\begingroup$ I disagree, my brother in law easily out eats me by a factor of three, I'm just under 80kg, he is 124kg but not at all obese. But I didn't really put my question properly either (I thought of interplanetary missions or one way colonisation where there's also a factor of landing with a bigger gene pool) and shorter term spaceflight I agree that the difference isn't a big issue, I hadn't thought of short missions at all. All in all your answer covers the question so I'll accept it. And probably pose a new question. $\endgroup$ – Kilisi Sep 29 '15 at 3:10
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    $\begingroup$ @Kilisi what are your relative activity levels? Some years back I found an exercise vs calories burned table that had columns for multiple weights spanning from small skinny people to very fat ones (IIRC a 3-4x range from min to max); and for most if not all activities listed energy consumed scaled roughly linearly with weight. Eg, your BiL would need ~50% more energy than you to run a marathon and would also burn calories twice as fast when you're both sitting on a couch watching TV. $\endgroup$ – Dan Is Fiddling By Firelight Sep 30 '15 at 20:53
  • $\begingroup$ I probably train a bit harder than him, he's a soccer coach so pretty fit, I used to box and still train. But he's full Samoan and I'm half Samoan, so we may well have a difference there. The main difference I can see is that I stop eating when I'm no longer hungry, many people here stop eating when the foods finished. $\endgroup$ – Kilisi Sep 30 '15 at 21:10
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Not a complete answer, but Shuttle height restrictions reflected the initial requirements of not restricting most of the US population and were generous: minimum of 4 ft 10 1/2 inches for mission specialists, 5 ft 4 inches for pilots and commanders, maximum of 6 ft 4 inches.

This is quite a wide range, as this picture from STS-86 indicates. Russian requirements were not so generous and this fact caused issues for this crew (it was a mission to Mir).

enter image description here

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    $\begingroup$ I was trying to indicate that for Shuttle program I do not believe that size was a criterion for selection, as long as a person met the generous requirements. In other words, the requirements were set such that anyone passing the gate was considered equally qualified. But I cannot speak for other programs so I acknowledge that my answer is incomplete. $\endgroup$ – Organic Marble Sep 28 '15 at 21:40
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    $\begingroup$ You made your point well, hence the +1. My question is hypothetical in that it assumes that you have a pool of equally qualified astronauts of different sizes already. Perhaps I should change my question a bit, but it's already been migrated once, and might end up being migrated to oblivion. And I need a logical answer because I've already told my brother in law that I'm not letting him in my space ship because he's too big. Which made me wonder what advantages there could be if I did allow him on my hypothetical spacecraft. $\endgroup$ – Kilisi Sep 28 '15 at 21:43
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    $\begingroup$ Edited my answer to address your real question. I would not expect a larger crewmember to be more useful as a net source of food; by the time you get around to cannibalism, the larger crewmember will have eaten more food relative to the smaller than you'd get back by eating him first. Also, planning for cannibalism suggests an overall lack of confidence in the mission. $\endgroup$ – Russell Borogove Sep 28 '15 at 22:13
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    $\begingroup$ Or could be a cultural thing, Polynesian emergency rations, but yes good point on the fact that he'd consume more than he's worth in that respect $\endgroup$ – Kilisi Sep 29 '15 at 2:35
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    $\begingroup$ I tried reverse image searching the inline image and was unable to find it. Could you add attribution and a link to details? $\endgroup$ – Dan Oct 2 '15 at 21:57

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