NASA is developing an Exploration Portable Life Support Subsystem (xPLSS) for next-generation Exploration Extra Vehicular Mobility Units (xEMU) planned to replace existing space suits. NASA has identified technology gaps in current xPLSS due to the amine swing-bed system not being design for the partial atmosphere of Mars. To solve this, NASA is requesting the development of a robust “Boost Compressor” which can pull vacuums down to 0.1 torr and outlet pressure tolerance over 15.2 PSIA to simplify system complexity.
Common pressure swing adsorption (PSA) solutions include dynamic blowers utilizing high impeller speeds to create a differential pressure. Operating up to 100,000 RPM makes them compact and lightweight but the impeller design causes the flow rate to depend on the differential pressure. When pressure is increased, flow diminishes. Here, the blower would be limited to discharge pressures below 5 PSIA, rendering it insufficient to achieve NASA goals.
Another option is positive displacement compressors that handle larger pressure differentials, exhibit minimal flow reduction with an increased pressure differential, and handling larger turndown ratios. These are preferable when a wide range of operating conditions, varying pressures and speeds, and higher reliability are required. Their ability to handle inconsistent conditions ideally suits these for PSA applications. The downside is that they are speed limited by bearing loading, making them less ideal for space applications.
Air Squared is proposing the development of a Spinning Scroll Boost Compressor (SSBC) that merges the strength of both technologies by capturing high-pressure differential without sacrificing high-speed performance. The innovative spinning motion of the scrolls eliminates various centrifugal loads, allowing it to operate at speeds >8,000 RPM, reducing size and weight. This removes the need for a counterbalance, reducing bulk by eliminating counterweights and easing bearing loads.
The SSBC will define next-generation PSA for xPLSS xEMU in Mars and Deep Space exploration. Capable of operating over several different partial atmospheric environments in a compact footprint, the SSBC will provide flexible xPLSS design adaptable to varied NASA missions and provide a foundation for both Lunar Gateway habitation and human exploration of Mars. These innovations will accelerate the SSBC’s adaptability for both the ORION Spacecraft and Human Exploration Research Opportunity (HERO).
Given the improved pressure and flow rate, adaptability as a compressor, vacuum pump, and expander, and reduced complexity of spinning scrolls, several positive displacement solutions would benefit from the development of the SSBC. Qualified spinning scroll machines would upgrade the performance of aerospace environmental control systems, vacuum mass spectrometry, and waste heat recovery.