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Spacecraft Water Recycling Systems for Short Duration HumanExploration Missions



Spacecraft Water Recycling Systems forShort-Duration Human ExplorationMissions


NASA issoliciting proposals for water recycling systems for short-durationmissions ranging from days to up to several months. Of primary interestare systems to recover potable water from humidity condensate generatedwithin the spacecraft cabin atmosphere. However, the recovery of otherspacecraft waste streams, including urine, are also of interest. Assuch, proposed design solutions can focus on the recovery of water fromhumidity condensate alone, humidity condensate and urine as separatewaste streams, and/or humidity condensate and urine as a mixed wastestream. Systems should be targeted for early phases of NASA’sMoon-to-Mars campaign and be designed for water recovery applications invehicles associated with the Artemis missions, Gateway, lunar and Marshabitats, landers, and pressurized rovers. The interfaces andinfrastructure to support water recovery on these early-phase vehicleplatforms should be considered minimal. Designs should have an eyetoward systems that can operate standalone, with concepts of operationsthat include system interfaces, fluid transfer, storage, processing, andwaste disposal. Systems capable of being easily integrated late into amission architecture and/or a vehicle design cycle would behighly desirable. The ideal system would be lightweight and lowvolume, have a long storage life, be generally“passive” (consuming little to no power),and requiring minimal crew time to operate. Systems should beable to treat up to a four-person crew load for up to at least one month(see requirements below). Systems should have considerations for how totransition into and out of dormancy that include return to full serviceand generating potable water with minimal effort after being left idlefor periods of up to one year. Consumables should be minimized.Simplicity of design is highly desired and disposable systems areacceptable, provided system mass, including any consumables, can beshown to have a highly favorable trade relative to the mass of waterrecovered.

Someperformance metrics and goals to include or toconsider:

  1. Simplicityof design, low maintenance requirements, minimal need for crewinteraction, and high systemreliability.
  2. Lightweight systems. Equipment mass, including consumables, mustbe no more than a small fraction of the amount of waterrecycled.
  3. Ability toprocess humidity condensate to potable water. (See Ref. 5 forestimates of the major constituents in humiditycondensate.) (See Ref. 3 for spacecraft potable water qualitystandards.)
  4. Ability toprocess human urine wastewater to potable water, (See Ref. 4 forestimates of the major constituents inurine.)
  5. Capable ofprocessing up to 2.5 kg/crewmember-day for humidity condensate and/orapproximately 2.0 kg/crewmember-day of urine, with typical crewsizes of from twoto four persons.
  6. Minimalrequirements for vehicle integration (i.e., would allow foreasy implementation within a vehicle platform withlittle to no vehicle or systemmodification). 
  7. Use oflow-toxicity processes and/or chemicals (e.g., pH > 2 andavoiding use of strong oxidizers, carcinogens,etc.
  8. Systemdata should be provided on expected recovery of processed water and thepurity of the water to be produced. Preferred solutions should meet NASApotable water specifications. This includes meeting microbial limits:Bacterial Counts < 50 CFU/mL, Coliform Counts (CFU/100 ml) -non-detect, and removal of protozoa, as well as chemical limits fororganic and inorganic contaminants, (See Refs. 3 and 4, Appendix1.)
  9. Proposedsystem should consider a concept of operation, including other vehiclesystem interfaces and, if needed, requirements for monitoring andcontrol for both nominal systems use and for strategies for transitioninto and out of dormancy.
  10. Proposalsshould provide estimates of mass, crew time, consumablesand resupply, power, mass, volume, and coolingrequirements.
  11. Systemanalysis should include how the system scales with respect to number ofcrew and or amount of water processed.
  12. Proposedsystems should provide a potential list of planned components, includingmaterials of construction, especially wettedmaterials.
  13. System hazards should be considered and identified and,where appropriate, concepts for proposed mitigation strategiesprovided.

Expected TRL or TRL Range at completion of theProject: 2 to 5

Primary TechnologyTaxonomy:

  • Level 1 06 HumanHealth, Life Support, and HabitationSystems
  • Level 2 06.1 EnvironmentalControl & Life Support Systems (ECLSS) and HabitationSystems

DesiredDeliverables of Phase I and PhaseII:

  • Research
  • Analysis
  • Prototype
  • Hardware

DesiredDeliverables Description:

Phase I Deliverables—Reports demonstrating proof ofconcept, test data from proof-of-concept studies and conceptsand designs for Phase II. Phase I tasks should address criticalquestions focused on reducing development risk prior to entering PhaseII. The final report should include a plan or strategythat explains in detail the approach for providing a solutionfor short-duration, lightweight, water recovery systems forexploration. 

Phase II Deliverables—Delivery of technologically maturecomponents/subsystems that demonstrate performance over the range ofexpected spacecraft conditions. Prototypes must be full scale.Robustness must be demonstrated with long-term operation and withperiods of intermittent dormancy. Systems and chemical agents shouldincorporate safety and design features to provide safe operation upondelivery to a NASA facility. Deliverablesshall include complete documentation, including an operatingmanual, technical data sheets with detailed description and compositionof the material or product, testing methods and test data,design sketches or drawings, and full information on material and/orchemical sourcing. The Phase II deliverables shall also include a finalreport documenting all work accomplished for the Phase II effort andshall not duplicate the Phase II proposal.

State of the Art and CriticalGaps:

State of theArt (SOA) water recovery systems for human spacecraft were specificallydesigned for water recovery from waste streams typical of the operationson the International Space Station (ISS) (Ref. 7). They are large, heavy, andpower intensive. The SOA systems were designed for continuousoperations, have not been proven for use after long periods of dormancy,and were not designed for repairability except by replacement of largeorbital replacement units (ORUs). Future missions are expected to have abroad range of wastewater, have crewed mission increments that arerelatively short in duration, have long periods of dormancy, and havemission elements that lack the infrastructure to support theSOA water recovery systems.  A new class of low-power, mass andvolume water recovery systems are envisioned for short-duration waterrecovery to fit the gap associated with these specific near-term missionprofiles. In addition, these technologies could serve for contingenciesor backup to primary systems for use on longer duration missions withfull recycling.

This technology need addresses severalpotential gaps under the Systems Capability Leadership Team (SCLT)Environmental Control and Life Support (ECLSS) Roadmap for Water andWastewater Processing. including:  STPRT#1011 “Water Recovery System for Surface Missions(lunar and Mars)”, STPRT #984 “Robust Advanced WaterRecovery System” and #867 “Water Recovery Mitigationfor Dormant Periods.”  Fulfillment of these gapswould be considered enhancing or enabling for lunar exploration wherelimited resupply may be tolerated and depending on massconstraints for a specific vehicle element. For lunar missions, however,any mass savings will benefit other mission objectives, includingscience. For Mars exploration, where resupply will be highlyrestrictive, these systems could be potentiallyenabling. If these gaps are not closed, mission requirementsfor water resupply will be considerable and possibly evenmission limiting.

Relevance / ScienceTraceability:

Waterrecovery technologies for short-duration missions will be useful for allphases of NASA’s Moon-to-Mars campaign. Initial missions tothe lunar surface are expected to be approximately 30 days in durationand occur on a yearly basis. These short-duration water recovery systemscould be deployed in the lander, pressurized rover, and habitats. Thesesystems are also relevant to Gateway, which also will initially beinhabited on a short-term basis. These short-duration water recoverytechnologies will also be applicable to surface assets on Mars, givenour initial human missions may have short stays and be supported only byrovers for the early missions. However, these systems couldalso be used for contingencies and backup systems for long-durationhabitats, orbital stations, and transit vehicles.

NASA's Exploration Systems Development Mission Directorate(ESDMD) manages the human exploration system development for lunarorbital, lunar surface, and Mars exploration. Programs in the missiondirectorate include Orion, Space Launch System, Exploration GroundSystems, Gateway, Human Landing System, exploration ExtravehicularActivity (xEVA), and Human Surface Mobility.  Many of thefuture near-term mission campaigns call for short-duration crew stayswith long periods of dormancy, especially as related to Gateway, lunar,and Mars surface missions. Early missions will involve EVAs andhigh crew mobility by way of rovers. Water consumption rates to providecooling and potable water for these systems are very high.  Atthe same time, many of these early mission assets will lack theinterface and/or infrastructure requirements to support the SOA watersystems. A new class of short-duration, low-mass, low-power,and low-volume water recovery systems are warranted to help conservewater supplies, ease the cost and logistics, and to tolerate the longperiods of dormancy associated with these early mission classes.


  1. Howard, David F., Christine M. Stanley, R. Gregory Schunk, PaulKessler, and Tiffany Nickens, "Regenerative Life SupportSystems for Exploration Habitats: Unique Capabilities and Challenges toEnable Long-Duration-Mission Habitats  Beyond Low EarthOrbit", ICES-2022-196, 51st International Conferenceon Environmental Systems 10-14 July 2022.
  2. Technology Readiness Level Definitions.
  3. Spacecraft Water Exposure Guidelines (SWEGs), JSC 63414,NASA Johnson Space Center, July 2017.
  4. Straub II, John E., Debrah K. Plumlee, William T. Wallace, JamesT. Alverson, Mickie J. Benoit, Robert L. Gillispie, David Hunter, MikeKuo, and Jeffrey A. Rutz, "ISS Potable Water Sampling andChemical Analysis Results for 2016", Paper# ICES-2017-337, 47thInternational Conference on Environmental Systems 16-20 July 2017.
  5. Putnam, J. (1971). Composition and Concentrative Properties ofHuman Urine. Prepared by McDonnell Douglas Astronautics Company- Western Division, Huntington Beach, Calif. 92647 for LangleyResearch Center, National Aeronautics and SpaceAdministration, Washington, D. C.
  6. Muirhead, D.M., S.M. Moller, N.A. Adam, and M.R. Callahan."A Review of Baseline Assumptions and Ersatz Waste Streams forPartial Gravity Habitats and Orbiting Microgravity Habitats",Paper # ICES-2022-388, 51st International Conference on EnvironmentalSystems.
  7. Carter, L., J. Pruitt, C. Brown, J. Bazley, D. Gazda, R. Schazler,and L. Bankers. “Status of ISS Water Management andRecovery” Paper # ICES-2016-017, 46th International Conferenceon Environmental Systems, July 2016. https:/

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