9.3 Environmental Control and Life Support Systems

Spacecraft need Environmental Control and Life Support Systems (ECLSS) to keep astronauts alive and comfortable in the harsh space environment. ECLSS handles air revitalization, water management, waste handling, and temperature control, ensuring a safe and habitable environment for space travelers.

Long-duration missions pose unique challenges for ECLSS, including limited resources and the need for high reliability. Advanced technologies like bioregenerative systems offer promising solutions, potentially enabling closed-loop recycling and even food production in space, crucial for future deep space exploration.

Environmental Control and Life Support Systems (ECLSS)

Functions of spacecraft ECLSS

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• Air revitalization maintains a safe and comfortable atmosphere for the crew by:
  • Supplying oxygen for breathing (electrolysis, Sabatier reaction)
  • Removing carbon dioxide exhaled by crew (zeolite adsorption, amine absorption)
  • Controlling humidity levels to prevent condensation (heat exchangers, desiccant beds)
  • Filtering trace contaminants and odors (activated carbon, catalytic oxidation)
• Water management ensures a reliable supply of clean water through:
  • Recovering and purifying wastewater and urine (vapor compression distillation, membrane filtration)
  • Storing and distributing potable water to crew and systems
  • Monitoring water quality to meet safety standards (conductivity sensors, total organic carbon analyzers)
• Waste management handles the collection, processing, and storage of:
  • Solid waste from crew activities (compaction, odor control)
  • Urine from crew (vacuum-assisted collection, chemical pretreatment)
• Thermal control regulates the temperature and humidity of the spacecraft by:
  • Maintaining a comfortable environment for crew and equipment
  • Rejecting excess heat generated by systems (heat exchangers, radiators)
  • Circulating coolant to transfer heat (fluid loops)

Processes in space habitat systems

• Air revitalization processes:
  1. Oxygen generation via electrolysis of water or Sabatier reaction of CO2 and H2
  2. Carbon dioxide removal using adsorption (zeolite, molecular sieves) or absorption (amine-based sorbents)
  3. Humidity control with condensing heat exchangers or desiccant beds
  4. Trace contaminant control through activated carbon filters and catalytic oxidizers
• Water recovery processes:
  1. Urine processing using vapor compression distillation or membrane-based filtration
  2. Wastewater processing with multifiltration beds and catalytic oxidation reactors
  3. Water quality monitoring via conductivity sensors and total organic carbon analyzers
• Waste management processes:
  • Solid waste collection and storage involving compaction and odor control
  • Urine collection and transfer using vacuum-assisted systems and chemical pretreatment

Advanced ECLSS Technologies and Challenges

Challenges of long-duration ECLSS

• Designing reliable ECLSS for long-duration missions is challenging due to:
  • Limited space and weight allowances in spacecraft
  • High reliability requirements to ensure crew safety
  • Need for redundancy and fault tolerance to handle failures
  • Complex integration with other spacecraft systems (power, thermal)
• Maintaining ECLSS during extended missions faces difficulties such as:
  • Managing consumables and planning resupply logistics (filters, chemicals)
  • Dealing with component degradation and ensuring spare parts availability
  • Controlling microbial growth and preventing biofilm formation (disinfection)
  • Addressing psychological factors related to crew comfort and sensory stimulation

Potential of advanced life support technologies

• Bioregenerative life support systems offer advantages for long-term space exploration:
  • Enable closed-loop recycling of resources (water, air, waste)
  • Reduce the need for resupply missions
  • Provide psychological benefits through interaction with plants
  • Face challenges related to the complexity and stability of biological processes, mass and energy requirements, and integration with physical-chemical systems
• Potential applications of bioregenerative technologies include:
  • Food production using hydroponic or aeroponic systems and nutrient recycling
  • Air revitalization through algae-based oxygen production and plant-based CO2 removal
  • Waste processing via composting and anaerobic digestion
• Research and development efforts in bioregenerative life support involve:
  • Ground-based analogs and testbeds (Biosphere 2, NASA's Biomass Production Chamber)
  • Space-based experiments (ISS VEGGIE system, ESA's MELiSSA project)