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Long-Duration Exploration Portable Life Support System (PLSS)Capabilities

Description:

ScopeTitle:

Long-Duration Exploration Portable LifeSupport System (PLSS) Capabilities

ScopeDescription:

Innovativedesigns for PLSS are sought to enable future long-durationmissions to the Moon and Mars.  

 

1. Non-VentingCO2/H2O Sequestration.

 

For long-duration Exploration PLSSssupporting both long-term lunar and Mars operations, the need to savethe water released from the human operator during an extravehicularactivity (EVA) increases with the EVA count and mission duration aswater is not readily available from the environment. Non-venting carbon dioxide (CO2)/water(H2O) sequestration would seek to mount within thePLSS, sequester CO2/H2O from theventilation loop of the suit, which is closed and circulated by a fankeeping the outlet CO2/H2O levels lowfor subsequent return of the gas to the suit volume.  Uponcompletion of the EVA, the recovered water andCO2 could be regenerated by some mechanism to provideit to the vehicle Environmental Control and Life Support System (ECLSS)for subsequent processing.

Key parameters include:

  • CO2 uptakerates: 2.5 g/min at 1600 BTU/hr and 3.2 g/min at 2000 BTU/hr with outletgas concentration <2.5 mmHg
  • H2O uptakerates: 2 g/min at 1600 BTU/hr to 2.4 g/min at 2000 BTU/hr (this islimited by the usage of a liquid cooling and ventilation garment in thesuit volume) with outlet gas concentration below 50% RH and <45ºF dew point
  • Overall volume constraints withany valve/manifold: W (<10 in.) x H (<8 in.) x D(<5 in.)
  • Overall mass constraints:<12 lbm with goal of <6 lbm
  • Flow rate through system: 6 acfm(170 lpm)
  • Allowable pressure drop:<2 in.-H2O at 4.3 psia, 6 acfm, 60ºF
  • Operating pressure range: 3.5 to23.5 psia
  • Gas inlet temperature range: 50to 90 ºF
  • Working fluids: air or 100%oxygen
  • g-field operations: 1g, 1/6g,3/8g, microgravity (ug)

2. Condensing Heat Exchanger (CHX) WithGravitational Field (g-Field) IndependentSlurper.

For long-duration Exploration PLSSssupporting both long-term lunar and Mars operations, the need to savethe water released from the human operator during an EVA increases withthe EVA count and mission duration as water is not readily availablefrom the environment.  Almost regardless of the selectedCO2 scrubbing option, sequestration, or semi-open loop,a CHX could be used upstream of the CO2scrubber to recover.  Upon completion of the EVA, therecovered water could be removed from the capture reservoir forprocessing by the vehicle water reclamation system.  Keyobjectives for this CHX approach include: no coatings* required on theinternal surfaces for water handling, operation in varied g-fieldincluding microgravity, and passive operation without requirement forsweep gas or differential pressure gradients.

*NOTE: Coatings tend to spall and cause systemreliability issues over time.

Key parameters include:

  • H2O uptakerates: 2 g/min at 1600 BTU/hr to 2.4 g/min at 2000 BTU/hr (this islimited by the usage of a liquid cooling and ventilation garment in thesuit volume) with outlet gas concentration below 50% RH and <45ºF dew point
  • Overall volume constraints withany valve/manifold: W (<10 in.) x H (<8 in.) x D(<5 in.)
  • Overall mass constraints:<2 lbm
  • Flow rate through system: 6 acfm(170 lpm)
  • Allowable pressure drop:<0.75 in.-H2O at 4.3 psia, 6 acfm, 60ºF
  • Operating pressure range: 3.5 to23.5 psia
  • Gas inlet temperature range: 50to 90 ºF
  • Working fluids: air or 100%oxygen
  • g-field operations: 1g, 1/6g,3/8g, ug 

3. Non-Venting Heat Rejection forMars Atmosphere.

For long-duration Exploration PLSSssupporting both long-term lunar and Mars operations, the need tominimize or eliminate the water used for evaporative cooling of thespacesuit during an EVA increases with the EVA count and missionduration as water is not readily available from theenvironment.  The state of the art with respect to spacesuitcooling technologies for the past 60 years has been sublimation offeedwater to vacuum with more recent developments using evaporationacross a membrane of feedwater to a reduced pressure environment such asvacuum.  In both cases, water usage on the order of 5-10+ lbmof feedwater is experienced per EVA to enable the elimination of wasteheat from the crewmember, avionics, and environmentalinleakage.  In order to be more efficient with usage of alimited resource during spacesuit activities, the suit needs to be ableto reject heat using means that do not result in such significant waterusage.

Peak Heat Rejection: 500 W metabolic wasteheat, 100 W avionics waste heat, 100 W inleakage from theenvironment

Interface to transport loop that removes heatfrom the system (crewmember and avionics):

  • Working fluid: water
  • Nominal flow rate: 200 +20/-30pph
  • Allowable pressure drop:<1 psid
  • Outlet temperature: <50°F (10 °C)
  • EVA duration: 8 hr
  • Nominal heat rejection: 460W
  • Ambient pressure: vacuum to 9Torr (CO2)
  • Ambient sink: varied
  • Volume/form factors: The rearsurface of the PLSS is approximately W (23 in.) x H(30 in.) x D (7 in.)
    • The internal volume that couldbe available if replacing the evaporator:
  • Mass limitation: <15lbm
  • Additional consideration giventhe implementation will relate to fall impact loads should the solutionbe mounted to the PLSS and subject to contact with objects during a fallduring an EVA in 1/6g or 3/8g 

 

4. Continuous CO2Removal Capable of Operating in Mars Atmosphere and Vacuum.

For long-duration Exploration PLSSssupporting both long-term lunar and Mars operations, the need toeffectively eliminate CO2 from the ventilation loopwhile operating in a partial atmosphere such as that on Mars is achallenge that needs to be addressed.  This could be done byextending the application of current technologies such as amineswingbeds providing the motive force via thermal swing, mechanicalpumping, or other potential options. The challenge facing all of thesecases includes the extreme limitations on volume, mass, and power that aspacesuit application offers.

Key parameters include:

  • Ambientpressure: < 9 Torr
    • A conceptwith tolerance of pressures up to 1 atm would greatly simplify theintegration and lower the system mass/volume impacts
  • Inputs:
    • Hold theinput <1.5 Torr with 3.2 g/min CO2 + 2.4 g/minH2O continuous at 2000 BTU/hr test condition
    • A conceptwith tolerance of transient pressures up to 23.5 psia would greatlysimplify the integration and lower the system mass/volumeimpacts
  • Electricalinterface: 28 VDC
  • Power:<25W
  • Volume:<50 in3
  • Mass:<4 lbm

Expected TRL or TRL Range at completion of theProject: 2 to 4

Primary TechnologyTaxonomy:

  • Level 1 06 HumanHealth, Life Support, and HabitationSystems
  • Level 2 06.2 ExtravehicularActivitySystems

DesiredDeliverables of Phase I and PhaseII:

  • Research
  • Analysis
  • Prototype
  • Hardware

DesiredDeliverables Description:

Phase I

  • Objective: Feasibility assessment for given technology.
  • Deliverables: Interim and final reports. 

Phase II

  • Objective: Prototype that can be integrated into the ExplorationExtravehicular Mobiliy Unit (xEMU) Design, Verication, and Test (DVT)unit enabling both component and integrated system testing.
  • Deliverables: Interim and final reports along withprototype hardware.

State of the Art and CriticalGaps:

The state-of-the-art PLSS components existin the current Extravehicular Mobility Unit (EMU) that is in operationon the International Space Station. Gaps exist for spacesuit componentsto operate on the lunar surface for extended duration and for operationon Mars. The gaps will be defined in the PLSS Roadmap to be released tothe public at a workshop planned for FY 2024.

Relevance / ScienceTraceability:

This technology is planned forfuture lunar and Mars missions where long-duration stays are required.This work can be traced to the Exploration Systems Development MissionDirectorate (ESDMD) and Space Operations MissionDirectorate (SOMD).  The targeted suit configuration for thissubtopic takes innovation beyond the xEMU that was designed,integrated, and tested in house in the EC5/Crew and Thermal SystemsDivision at the Johnson Space Center.

References:

The PLSSRoadmap—To be published in FY 2024 to the public at aNASA-sponsored workshophttps://www.nasa.gov/extravehicular-activity-and-human-surface-mobility/

The following link will provide access to peer-reviewed paperspublished at the International Conference on Environmental Systems fortechnologies developed for the xEMU PLSS prototype inrelated areas such as the Rapid Cycle AmineCO2 Removal and the Spacesuit Water MembraneEvaporator for heat rejection:

International Conferenceon Environmental Systems (tdl.org)

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