The Microwave Regenerative Sorbent-based Hydrogen Purifier (MRSHP) is a unique microwave power-based technology demonstrator created for the purification of a hydrogen product stream produced by the Plasma Pyrolysis Assembly (PPA). The MRSHP prototype uses 2.45-GHz microwave power to heat a 13x sorbent bed during a vacuum/thermal contaminant desorption step. By utilizing the well-known high-sorbate-loading capability of conventional physical sorbents coupled with microwave dielectric heating phenomenon, this technology is employed as a regenerative filter for a contaminated hydrogen gas stream.
The efficiency of Air Revitalization (AR) aboard crewed spacecraft becomes increasingly more important as the duration of the mission increases. Several steps are required for efficient recovery of oxygen from carbon dioxide produced by crew respiration. The Carbon dioxide Reduction Assembly (CRA) converts carbon dioxide and hydrogen into water and methane. The water is electrolyzed in the Oxygen Generation Assembly to recover oxygen and a portion of the hydrogen consumed by the CRA. However, half of the hydrogen used by the CRA is used to form methane, a waste product. Much of the hydrogen contained in methane can be recovered using the PPA, a hydrogen recovery (from methane) post-processor that converts the methane predominantly into hydrogen and acetylene.
With the MRSHP operating in sorption mode, contaminated hydrogen gas flow from the PPA enters the top of the sorbent bed through an energized, normally closed solenoid valve. After losing its contaminants by selective physical sorption within the bed, the purified hydrogen then exits the bottom of the bed and passes, via a second energized normally closed solenoid valve, out the effluent line from the prototype. The use of normally closed solenoid valves assures that the sorbent bed remains isolated from unwanted contaminants when the prototype is not in use. A third normally closed solenoid valve, also connected to the top of the sorbent bed, is energized during desorption mode for removal, via an external vacuum source, of the desorbed contaminants driven off by low pressure and microwave heating.
In order to prepare for NASA’s projected manned Mars mission slated for the mid-2030s, several AR system elements must be advanced to fully flight-certified status. Included in this list of AR elements is the PPA and associated hardware, with the hydrogen purification assembly deemed of paramount importance. To support this schedule, a 4-CM scale hydrogen purification device such as the MRSHP, that is capable of integration testing with the advanced third-generation PPA located at Marshall, is required within the next few years.