LOx / LCH4: A Unifying Technology for Future Exploration

Reduced mass due to increasing commonality between spacecraft subsystems such as power and propulsion have been identified as critical to enabling human missions to Mars.  This project represents the first ever integrated propulsion and power system testing and lays the foundations for future sounding rocket flight testing, which will yield the first in-space ignition of a LOx / LCH₄ rocket engine.

A brass-board liquid oxygen / liquid methane (LOx / LCH₄) pressure fed propulsion subsystem sized to eventually fit on a sounding rocket will be developed and tested.  The subsystem will feature active helium re-pressurization and integrated main engine and reaction control systems (RCS).  Concurrently, a brass-board fuel cell power system will be developed and tested.  The power system features a Solid-Oxide Fuel Cell (SOFC) manufactured by Delphi capable of producing 1 kW of power from Oxygen and Methane reactants.

Once characterization testing of the propulsion and power subsystems is complete, the subsystems will be integrated and further testing will be performed.  LOx / LCH₄ stored cryogenically in the propulsion subsystem propellant tanks will be used by the SOFC subsystem to produce power which will be used to operate valves, sensors, etc. on the propulsion system.  A flight-like firing profile will be performed featuring both main and RCS engines to provide a space-power profile to the SOFC.

6/1/16 STATUS:

A 1kW Solid Oxide Fuel Cell manufactured by Delphi Automotive was integrated into a test stand at NASA’s Johnson Space Center for space power profile testing. The system was initially run and characterized on pure oxygen and a hydrogen/nitrogen blend. The polarization test indicated a healthy fuel cell with fairly minimal loss of voltage from its previous test in 2009 (about .05V/cell) and also showed an impressive one-pass oxygen utilization rates between 70 – 85%. The SOFC was also run through various current variation profiles to test response time and transient jumps. The SOFC was able to respond to all user inputs, including a maximum increase of 400W. Initial testing was only able to test the fuel cell up to 37A (about 1kW), less than its 60A maximum. A second load bank was added to the system to increase the load demand and test the SOFC at a higher amperage.

Concurrently, a steam methane reformer (SMR) was solicited for and procured through an RFP process. This reformer will be added to the fuel cell power module to reform methane into a hydrogen-rich fuel stream and allow the fuel cell to operate in an integrated fashion with the main propulsion system. JSC expects delivery of the SMR by June ’16 and will begin integration efforts shortly thereafter. 

The propulsion brassboard has been designed, fabricated and is in final assembly whereupon it will hot-fired for checkout prior to integration with the Solid Oxide Fuel Cell.