# What does the physiology and biochemistry of a vacuum adapted post-human look like? Part 2: Temperature control

I am a post-human adapted for permanent life in vacuum and micro-gravity. How might my physiology and biochemistry overcome the following challenges?

Please note I have a strong cultural aversion to augmenting my body in order to help me survive: i.e. enclosing myself in artificially-constructed protective shells, etc.

See Part 1 on radiation resistance

Part 2 Temperature control: Space is cold, but vacuum is also highly insulating. How do I stop myself from both freezing and overheating?

See Part 3 on metabolism

See part 4 on movement

See part 5 on senses

• I think the bigger problem is stopping all the air in your lungs from being pulled out into the vacuum of space when you open your mouth, and the evaporation of moisture from your eyes, etc in an environment with no ambient pressure. Cold and heat are probably not the biggest problems here. forbes.com/sites/startswithabang/2016/12/23/… Nov 5 '18 at 14:21
• without gas exchange, no metabolism. space is short on gases. Nov 5 '18 at 14:45
• @theRiley metabolism of organism to be addressed in part 3. Nov 5 '18 at 14:58
• @TylerS.Loeper thanks, metabolism and biochemistry will be looked at it in part 3 Nov 5 '18 at 14:59
• Is becoming cold-blooded an option? Nov 5 '18 at 15:28

As you pointed out, space is cold and insulating.

You cannot rely on matter to exchange heat, this rules out conduction (you don't like shells) and convection.

What remains is radiation: your body will emit thermal radiation and lose power according to Stefan Boltzmann law, $$I=\epsilon \sigma T^4$$.

Since you want to keep this lost power low and not freeze, you can only work on $$\epsilon$$, your emissivity. The lower you make it, the less radiative power you will emit.

Basically your skin has to be pigmented in a proper way so that its emissivity can be as close as possible to 0, but not 0, else you will boil up. You also want to be able to control this emissivity, for those cases when you want to emit excess heat and cool down.

You can refer to this table for the emissivity of some common materials.

• Actually the problem is not freezing, it's overheating. At the normal temperature of a human the black body radiation is utterly insufficient to dissipate the hundred watts or so of waste heat. Nov 5 '18 at 11:26
• I don't like artificial shells - but that doesn't rule out a shell that is organically grown, perhaps using raw material common in deep space environments. One of the suggestions given for Part 1 involves a plate-armour incorporating heavy metals to insulate against ionizing radiation. Could this be relevant? On emissivity, what kind of skin pigmentation might help bring it close to zero? Nov 5 '18 at 11:36
• Control of emissivity should be the key here. In goldilocks zone, humanoid will be freezing when in shade and overheating when in direct starlight. Nov 5 '18 at 18:13
• It would be a more complete answer if it also put the difference of heat generation vs the heat dissipation. Also imagine trying to keep your emission as low as possible and then generating more heat than you dissipate without a way to suddenly increase your emissions... Nov 5 '18 at 18:59

# Nothing needed

You just need to keep things as they are and keep your people hydrated. Oh, and compressed.

See research on Space Activity Suit:

Cooling of the astronaut with an SAS is generally achieved with evaporation from body perspiration which is emitted from the suit in all directions.

That's scientific way to say that he would sweat. And that's it.

Because space suit designs discuss cooling at great lengths, and heating rarely if ever, I believe it's safe to assume that freezing is not a real problem, overheating is.

• Looking at this site: nasa.gov/audience/foreducators/spacesuits/home/…, you can see that keeping the body warm is easy by simply having layers. But cooling is a much more intricate system. The hands of astronauts also get cold and need heating elements to stay warm as theres few layers on the gloves in order to keep the hands nimble and ready. So I think that "only needs cooling" is a foregone conclusion. Nov 5 '18 at 19:04
• @Demogan whole body except hsnds is cooled, and fingertips needs heaters. I believe minor biological adjustment would take care of that. As for cooling being more intricate — it is. In a suit that basically shuts down natural cooling. If you don't shut down natural one, you don't need to replace its function. Nov 5 '18 at 21:38
• the natural one is shut down anyway because vacuüm. My point about the hands wasnt that it wasnt solveable but that without proper insulation such as the little that the gloves provide a human form and skin might lose heat rather than gain it. Nov 5 '18 at 22:04
• @Demigan no, according to NASA vacuum is not a problem. Problem is that classic suit don't let sweat out. And vacuum is insulator. Human body can't radiate enough not to overheat. You can read linked article and its sources for details, your claims in previous comments are almost entirely false. Nov 6 '18 at 7:37
• I wasn't sure if a vacuum was a problem for staying warm (or cold), so could you link to some information that states this isn't a problem for a naked but surviving human in space? It's easy to throw "It's false!" in my face with no evidence when all I've done is put forth a problem (hands don't have as much insulation as the rest of the body and need warming) and the doubt that a human body would stay warm if unprotected in space with minimal gear to survive (IE the theorized rubber band with an airtank idea). Nov 6 '18 at 8:16

Temperature control in this case depends on 4 factors: generation per kg of body. Amount of kg of body. Surface area to radiate heat off. How well the surface area generates heat radiation.

The ISS does not have a problem heating up. It in fact needs specific area's on the hull where heat is radiated away or the inhabitants would be cooked. In space astronauts wear both undergarments to cool themselves and layers to keep heat in, while the gloves have specific heating elements to keep the hands warm. So I have no idea if humans would lose heat or gain heat in space (if they survived).

These post-humans live in a vacuüm and travel interstellar distances, so they are likely to have a low metabolism and low heat generation. This means they are better off with more mass compared to surface area so they would need to be bigger to accomplish this. Their skin or outer shell would need to be of materials that have little heat radiation. In case of heating up due to sunlight or similar the skin sould have extendable hairs made of heat radiative materials, the hairs having a large surface area when extended and allowing more heat to dissipate.