CLEVELAND (NASA PR) — On long duration deep space missions, providing crew-members with a steady supply of oxygen is a real challenge. Because resupply is not an option and taking huge tanks of oxygen on exploration spacecraft is not practical, oxygen must be recovered from what is produced during normal metabolism.
Astronauts breathe in oxygen and most is turned into carbon dioxide and water vapor. Getting the oxygen from the water is pretty straightforward and can be done with electrolysis alone. The real trick is efficiently getting oxygen from the carbon dioxide.
“There are many methods for doing this but on an en-closed spacecraft with limited power it becomes a real challenge,” says Kevin Kempton, Game Changing’s pro-gram element manager for Affordable Destination Systems and Instruments. “Right now systems on the International Space Station only recover about 50 percent of the oxygen. About half the oxygen is vented as methane, which is a byproduct of the current recovery process.”
To explore the technical possibilities, NASA’s STMD created the Spacecraft Oxygen Recovery (SCOR) project, and a Space Tech REDDI, Game Changing Development Program call for proposals addressing “Advanced Oxygen Recovery for Spacecraft Life Support Systems” was put out as a NASA Research Announcement. NASA uses competitive, collaborative opportunities to complement NASA research initiatives and address specific technology gaps in NASA programs.
In Phase I, four SCOR teams were competitively selected to develop their concepts into engineering development units (EDUs) that could be evaluated for future trade stud-ies. A minimum of 75-percent oxygen recovery was specified as a hard requirement and teams had to predict the “equivalent system mass” of a flight unit so technology comparisons can be made.
NASA received four very different EDUs over the summer for further testing as potential components in the overall Environmental Control and Life Support System (ECLSS) on future spacecraft. All four development teams overcame significant technical challenges to deliver their systems in time. These teams developed new catalysts, new ceramic fabrication techniques, new chemistries, and novel mechanical systems to make their EDUs work. Many of the techniques have great potential for use in terrestrial applications here on Earth.
The four teams were composed of personnel from industry, academia, and NASA:
- UMPQUA Research Company with Continuous Bosch Reactor Technology
- NASA Glenn Research Center/pH Matter LLC with a Solid Oxide Co-Electrolyzer (SOCE) and a Carbon Formation Reactor.
- NASA Glenn Research Center/University of Delaware with an Ion Exchange Electrolysis Unit and a Carbon Formation Reactor.
- University of Texas-Arlington with a Microfluidic Electrochemical Reactor
Kempton explains that SCOR technologies can also play a key role on the surface of Mars where carbon dioxide is readily available in the atmosphere. “Using in situ resources to generate oxygen for propellants and consumables will be a big driver in making a trip to Mars feasible,” he says.
NASA is continuing SCOR technology development with a Phase II effort in 2017. The SCOR team will take what has been learned and advance this key exploration technology closer to flight readiness.
Engineers at UMPQUA Research Company, Myrtle Creek, Oregon, developed a continuous Bosch reactor technology in which oxygen is recovered from carbon dioxide in the form of water using catalysts developed in-house at its research facility. A water electrolysis unit is operated in tandem to provide oxygen to the crew. The continuous Bosch reactor operates at high temperatures to achieve nearly 100-percent recovery of oxygen.
Engineers at NASA’s Glenn Research Center teamed with small business pH Matter, LLC, Columbus, Ohio, in developing an oxygen recovery system comprising a high-temperature solid oxide co-electrolyzer (SOCE) combined with a carbon formation reactor. The SOCE produces oxygen directly from the co-electrolysis of water and carbon dioxide. The carbon formation reactor employs catalyst formulations and preparation techniques to achieve nearly 100-percent recovery of oxygen.
Another group of engineers at NASA’s Glenn Research Center teamed with University of Delaware investigating an approach combining an ion exchange membrane electrolysis unit and a carbon formation reactor. The room-temperature electrolysis unit, developed at University of Delaware, employs an ion exchange membrane in which oxygen is electrolytically produced directly from carbon dioxide, also producing carbon monoxide as a byproduct. The oxygen is provided to the crew and the carbon monoxide is directed to the carbon formation reactor, resulting in nearly 100-percent recovery of oxygen.
The University of Texas-Arlington developed a microfluidic electrochemical reactor designed to recover oxygen from carbon dioxide through carbon dioxide electrolysis. In this approach, oxygen is released directly to the cabin while byproduct hydrocarbons may be discarded or stored for other purposes. Using experiences in electrode development and fabrication, the team is optimizing an electrochemical cell designed to operate at room temperature and pressures and achieve approximately 77-percent recovery of oxygen.