Does perspiration from the astronauts aboard the ISS stick to the skin, evaporate or somehow float away from the skin?

Is the part of the sweat that sticks to an astronaut's skin kept there until they shower or do astronauts carry towels, so they can wipe it away?

I suppose that it has to be removed somehow, as it may damage hardware by just floating around...


3 Answers 3


They keep the ISS at a pretty comfortable temperature and humidity level, so there's not much sweat accumulation except when they're working out. For that, they use towels.

The sweat that they do produce that evaporates (along with the water vapor they exhale) gets collected as part of the water processing system and recycled into drinkable water.

  • 5
    $\begingroup$ @finnmglas see the schematics in this question space.stackexchange.com/q/26617/6944 and its answers for a visual depiction of the water cycle. $\endgroup$ Sep 9, 2020 at 19:33
  • $\begingroup$ Like that time they found a giant blob of water behind the electrical panel :) $\endgroup$ Sep 12, 2020 at 0:24

According to a COLUMBUS Module engineer I once spoke with, it is common practise to use "silica gel" (the stuff in the small white bags you get buying new shoes or bags or everything) extensively because as you mention humidity is dangerous for everything onboard the ISS.

I made a quick Google search for sources:

Clearing the Air in Space: Improving Life Support on International Space Station and For Deep Space Exploration

The life support system on the space station currently uses a silica gel to remove humidity or water from the air

Performance of Silica Gel in the Role of Residual Air Drying

Silica gel is used as the bulk drying material in the Carbon Dioxide Removal Assembly (CDRA) in operation on ISS.

Besides, the crew have bags of silica gel to put everywhere they find water.

(It would be interesting to know if they have ovens to "recycle" the bags, or if they get new ones as a consumable... could be harder as tough to recycle them in orbit)

  • 2
    $\begingroup$ Recycling of silica gel in space can be as simple as putting the bags outside for a while. Well, you lose the water they contain. Oven probably is worthless - the humidity will go back into the air and back to wherever it tends to condense. $\endgroup$
    – fraxinus
    Sep 10, 2020 at 14:14
  • $\begingroup$ @fraxinus you'd use an oven connected to a condenser. Given mass is a lot more "expensive" than power it's probably done unless there's a particular challenge. $\endgroup$ Sep 10, 2020 at 14:44
  • $\begingroup$ That is the reason, why I said it is probably harder as someone might think... But still a oven with a closed condensator might be more feasible than "putting them outside" $\endgroup$
    – CallMeTom
    Sep 10, 2020 at 14:44
  • $\begingroup$ Some one was seconds faster than me $\endgroup$
    – CallMeTom
    Sep 10, 2020 at 14:45
  • 7
    $\begingroup$ That first link is super misleading (not your fault, it's the NASA writer). Silica gel is only used in the CO2 removal equipment and only serves to dry the air stream going into that equipment. Most of the cabin humidity is removed by the Common Cabin Air Assemblies. ntrs.nasa.gov/citations/20100040659 "The temperature and humidity of the International Space Station (ISS) United States On-orbit Segment (USOS) cabin air is controlled by the Common Cabin Air Assembly (CCAA). " They are condensing heat exchangers and do not use silica gel. $\endgroup$ Sep 10, 2020 at 18:18

Zero gravity does not restrict the evaporation of sweat.

On Earth the evaporation of water is enhanced by air movement like wind.

In zero gravity, there is no air circulation caused by thermal differences but the air in the ISS is circulated with ventilators. So the evaporation could not be reduced by zero air movement. Not to forget the body movement during a workout causing a movement of the skin relative to the air.

Sweat is evaporating in a wide range of temperatures as long as the humidity of the air is low. The temperature and the humidity of the air in the ISS is controlled in a comfortable range, so the astronauts bodies may be cooled by sewating if neccessary. To keep humidity comfortable, water vapor must be removed from the air.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.