Life support systems. On crewed vehicles, there is a lot of equipment to maintain the various fluids that keep the crew alive.

Common subsystems — at a minimum, all crewed space vehicles (including EVA suits) have some version of these:

• Temperature & Humidity Control (THC)
  • Temperature for obvious reasons.
  • Humidity is important for crew comfort, but also water condensation is very bad for spacecraft: water droplets get everywhere and cause electrical shorts in equipment, mold & mildew issues, etc.
  • Water may be dumped overboard, or in fancier vehicles saved & reused for other purposes.
  • Tech typically involves: fans, ducting & valves, condensing or non-condensing heat exchangers with ATCS, desiccant absorbers, Nafion membranes
• Atmosphere Revitalization (ARS)
  • Scrubs harmful compounds out of the crew’s air.
  • Mainly CO2, but also lots of other trace compounds given off by humans and equipment.
  • CO2 may be vented overboard or saved & reused for other purposes.
  • Tech typically involves: fans, ducting & valves, absorber cannisters (LiOH, activated charcoal, etc), Nafion membranes, absorber swing beds for recycling, reactors (similar to automotive catalytic converters)
• Pressure Control (PCS)
  • Maintains total pressure and partial pressure of O2.
  • There is a safe “corridor” of O2 concentration based on total pressure.
  • Too little oxygen causes hypoxia & death, too much increases fire risk, etc.
  • Too little total pressure causes depressurization sickness and ventilation systems lose effectiveness, too much total pressure dumps air overboard & wastes air.
  • Tech typically includes: high-pressure gas tanks, lines & valves including pressure regulator & relief valves.

Fancier vehicles that have longer missions & need to better conserve the limited precious life-giving fluids add these kinds of systems in varying degrees:

• Water Recovery (WRS) & Waste/Hygiene Control (WHC)
  • Collects waste water from various sources like humidity concentration, trash, toilet, shower, etc.
  • Tech involves pipes, valves, tanks & pumps, water recycling pre-treatment chemicals
• Regenerative ECLSS (RECLSS or just “Regen”) — This is a loose umbrella term for all kinds of fluid recycling:
  • Create breathable oxygen and/or hydrogen fuel from water (electrolysis),
  • water from H2 & CO2 (Sabatier process),
  • Recycles & purifies various types of waste water.
  • Tech includes electrolyzers, reactors, distillers, de-ionization beds, etc. Lots of more complicated chemistry and chemical plant-like processes.

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