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Advanced Space Suit Portable Life Support System (PLSS)

Description:

Lead Center: JSC

 

NASA plans to continue using the current EMU/spacesuit for the life of ISS. However, with the anticipation of a replacement suit for ISS or other future mission, the plan for an Advanced EMU is underway. Technology gaps remain for the PLSS. The following is a list of technology focus areas specifically for the Advanced PLSS:

 

  • Continuous trace contaminant removal capability - Activated charcoal is the state of the art and provides a logistics impact to future missions. The primary trace contaminants to remove include ammonia (NH3), carbon monoxide (CO), formaldehyde (CH2O), and methanethiol (also known as methyl mercaptan) (CH3SH). The minimum objective would be to remove all of the significant compounds that threaten to exceed the 7-day SMAC2 during an EVA. For continuous removal, the most advantageous integration with the current state of the art CO2/H2O removal system would be integrated such that regeneration or desorption occurs with a pressure swing from 4.3 psia to <1 torr over a ~2min period half-cycle at temperatures in the 60-80° F range. A small amount of heat flux is available from the cross-coupled adsorbing bed; additional heat input requirements from resistance heaters, etc. would negatively impact the system trade the more significant the value becomes.
  • Small, oxygen compatible gas flow meter for suit operations - Small, oxygen compatible gas flow meter for suit operations: The current state of the art for flow measurement on the ISS EMU space suit is a flapper valve attached to a microswitch which is limited to a single set-point. The accurate measurement ranges required for the sensor are 2-8 acfm +/- 1% with a pressure drop of less than 0.68 in-H20 in a 100% oxygen (O2) environment (traces of NH3, H2O, CO2); suit pressure from 3.5-25 psia, temperature from 50-90° F, relative humidity (RH) 0-50%, and CO2 from 0-15mmHg. This flow meter needs to fit within a volume/shape factor of approximately 2.5 in x 1.5in x 3in or less including fluid ports and electrical connectors; if added as an in-line flow, 1 in inlet/outlet porting will be necessary. Operating life objective is 8 years without calibration and 5000 hours of powered operation.
  • Small hermetic micro switch - Current state of the art is 3-5 times larger than needed. Honeywell MicroSwitch HM-1 series is a typical state of the art. Combining Single Pole Double Throw (SPDT) circuits that add additional toggle mechanisms would further grow the size of the switch. Hermetic is defined as leakage <10-8 atm-cc/sec. Switching currents for these switches are signal level at <500mA.
  • Multi-gas monitoring within the suit - Multi-gas monitoring: Advanced suit could benefit from measuring Oxygen (O2), carbon dioxide (CO2), water (H2O), ammonia (NH3), carbon monoxide (CO), formaldehyde (CH2O), methanethiol (also known as methyl mercaptan) (CH3SH), etc. The measurement of trace contaminants becomes even more important if an alternate approach (e.g., pressure or temperature swing adsorption) to the traditional activated charcoal cartridge is used. There is a need to measure the following major constituents and trace contaminants ranges in the gas stream across a total pressure range of 3.5 – 23.5 psia and temperature range of 35-125F: O2 = 20-100%; CO2 = 0-30 torr over 3.5-23.5 psia; H2O = 5-90% RH; NH3 = 0-50 ppm; CO = 0-400 ppm; CH2O = 0-5 ppm; and CH3SH = 0-5 ppm.
  • Power - Current state of the art is lithium-ion batteries with cell level energy densities of 200 W-h/kg but packaged energy densities of ~130W-h/kg after addressing mitigation for thermal runaway. Safe, high-energy density power sources are needed which are rechargeable post-EVA.
  • Heat Transport Improvements - Several improvements are needed in this focus area including:
    • Improvement in the Liquid Cooling and Ventilation Garment (LCVG) state of the art.
    • Improvement in the UA such that warmer water can be used to sink the waste heat from the human and hence reduce the evaporator size.
    • Drastically alter the human-to-cooling loop interfaces such as a fluid-filled suit with directly pumped cooled water.
    • Alter the Thermal Micrometeoroid Garment (TMG) such that the emissivity/absorptivity can be dynamically altered to improve thermal.
  • Human-Machine Interface Improvements - Current state of the art for this focus area includes mechanical switches and a 16 x 2 Liquid Crystal Display (LCD). Low power, wide thermal range, rad tolerant high definition graphics displays that can be integrated with the suit soft goods or hard goods such as heads-displays.

 

These technology gaps were detailed during the 2017 SBIR/STTR Industry Day (https://sbir.nasa.gov/events/sbir-industry-day).

 

Phase I Products - By the end of Phase, it would be beneficial to have a concept design for infusion into the Advanced PLSS. Testing of the concept is desired at this Phase.

 

Phase II Products - By the end of Phase II, a prototype ready for system-level testing in the PLSS or in a representative loop of the PLSS is desired.

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