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Spaceships are a peculiar thing; as are the things inside them. Humans... Humids... Humies - the colloquial term for those crazy enough to make a living by crewing these hulks of metal. A special breed. Hardy folks. Not only smart but ingenious - able to calculate trajectories and fix & maintain everything from computers to microwaves. Tough, and crazy, enough to withstand the heat inside these buckets for months at a time. Sleeping and working in temperatures us norms can barely manage with the help of ice cold coconut milk..

But how hot & humid does it actually get inside these ships..

Q: How high a temperature (and humidty) can I keep the insides of my spaceships at before the crew start taking too much1 permanent damage?

1Some people willingly damage themselves by ingesting toxins such as alcohol or tobacco. Others work in areas with particulate contaminants without wearing respirator masks. So everything that doesn't kill in less than 20-30 years is perfectly fine.

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  • $\begingroup$ inside a spaceship you may not sweat as much as you do on Earth, in microgravity environment and especially with high humidity cause our body to overheat itself (sweat cannot evaporate fast enough) $\endgroup$ – user6760 Aug 25 '17 at 1:58
  • $\begingroup$ This seems like a real world question that would be better on the Anatomy or Biology sites. $\endgroup$ – DJClayworth Aug 25 '17 at 15:05
  • $\begingroup$ @DJClayworth I see where you come from. The reason I would still keep it on here is because I don't see a way for the not too much damage requirement to fit into the mindset of a biologist. Any scientist will talk about spherical humans in a vacuum :/ $\endgroup$ – dot_Sp0T Aug 25 '17 at 19:31
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Humans like a temperature of about 20 to about 24 °C (68 to 75°F) and a relative humidity of 25% to 60%. They can function long term in temperatures from about 16 to about 30 °C (61 to 86 °F) and relative humidity from about 15% to about 75%, but they may not like it. (With humidity the limits are not that strict, people can survive close to 0% and 100% relative humidity, with a decrease in productivity.)

They won't really thrive if kept long term outside those limits, but they can work for a limited time in temperatures up to 40 °C (even much higher for a short time, especially with low humidity and good ventilation) and relative humidities from 0% to 100%; the key to the maintenance of your humans is not to keep them for too long outside their confort zone.

Note than humans use devices called clothes which enable them to function long term at lower temperature, or for shorter terms at much lower temperatures; but they don't cope well with long-term exposure to temperatures higher than 34 °C (93 °F).

From "Human heat tolerance in simulated environment" by Nag PK, Ashtekar SP et al., Indian J. Med. Res. 1997 May;105:226-34:

The study suggests the acceptable and tolerable limits for human exposure in heat: (i) acceptable at 38 to 38.2 degrees C Tcr [body core temperature] for a tolerance time of 80 to 85 min; and (ii) the tolerable limit of short duration (40-45 min) at 39 degrees C Tcr that corresponded to 31.5 and 36.5 degrees C ET(B). [effective air temperature (basic)]

From "What Are the Limits of Human Survival by Natalie Wolchover, August 9, 2012, published on the Web by LiveScience:

According to a 1958 NASA report, people can live indefinitely in environments that range between roughly 40 degrees F and 95 degrees F (4 and 35 degrees C), if the latter temperature occurs at no more than 50 percent relative humidity.

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  • $\begingroup$ So if I read the data in your answer correctly I can keep the insides at 35C as long as I don't surpass 50% humidity; and everything above will kill them too fast? $\endgroup$ – dot_Sp0T Aug 25 '17 at 7:17
  • $\begingroup$ @dot_Sp0T: Yes you can as long as you don't expect them to do anything much. If you want them to work you really shoudn't get above 28-30C with 50% humidity, $\endgroup$ – AlexP Aug 25 '17 at 7:56
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    $\begingroup$ Can humans acoelomate with 24/7 exposure? $\endgroup$ – Andrey Aug 25 '17 at 20:45
  • $\begingroup$ @Andrey: "Acoelomate" means "having no cœlome or body-cavity". I don't understand the question. If you meant "acclimate", then the problem is that humans need to keep their internal temperature between 36.5 and 37.5 °C or they die; the basal metabolism (and any kind of effort) produces heat which must be dissipated; so that when the environment approaches (or goes above) this temperature, dissipating the internally produced heat becomes harder and harder. With good ventilation, low humidity and lots of water intake the built-in head-shedding mechanisms may cope for a while. $\endgroup$ – AlexP Aug 25 '17 at 20:56

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