Production of Lunar Oxygen by Vacuum Pyrolysis

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1 Lunar OXygen Project Production of Lunar Oxygen by Vacuum Pyrolysis Dr. Eric Cardiff, Brian Pomeroy NASA GSFC Lt. John Matchett USAF / GWU

2 Goals Demonstrate the production of oxygen from a lunar simulant by the vacuum pyrolysis technique, including all the subcomponents. Model the system to indicate potential yields. Demonstrate the feasibility of a large solar concentration system (two approaches). Examine the potential for the system to be used to extract other volatiles from the lunar regolith.

3 Vacuum Pyrolysis Overview Vacuum pyrolysis is based on the vaporization reaction of metal oxides that simultaneously reduces the oxide and produces O 2 at temperatures between 2000ºC and 2600ºC. SiO (s) SiO (g) O 2 2(g) The reduced oxide can be condensed out of the low-pressure gas at temperatures below ~500ºC

4 Vacuum Pyrolysis Has a much higher potential efficiency (6.3% - 21%). Requires no imported chemicals. Can potentially produce metallic byproducts from the condensation. First proposed by Steurer and Nerad in The most significant experimental work, Senior, 1991, was a proof-of-principle experiment that showed pressure increase due to gas production (order of µg) from heated minerals. O 2 was not recovered or sampled. Sauerborn, DLR, has done some proof of principle work with a high flux solar furnace at relatively low temperature (1700K).

5 Vacuum Pyrolysis Flowchart Mining Benefication: Pit Scalping (remove large rocks) Crushing Minimal Benefication Solar Energy Condensate Removal Reactor Condensation Slag Discharge Non-vaporized Slag Discharge O 2 Storage Gas Sensor Instrumentation Structural Materials

6 Experimental Approach Two different solar concentrator designs

7 Fresnel System Fresnel Concentrator Coolant Circulator Thermal Condensation System O 2 Storage Window Crucible Radiation Shield Ceramic Support Scroll Pump

8 Fresnel System

9 Prototype System in Testing

10 Concentrator System Window Coolant Circulator Thermal Condensation System Crucible O 2 Storage Mirror Concentrator Mass Spectrometer Scroll Pump

11 3.8m Diameter Reflector System

12 Experiment Status The Fresnel system is complete and operational We have demonstrated run times of over an hour. Limiting factor is the vacuum window. We are currently investigating the failure mechanisms of the window. Condensation occurs within inches of the surface the condensation system is integrated into the vaporization chamber. All of the instrumentation is operational. The reflector system is built. Three techniques were evaluated for mirroring. The combustion chamber for this has been designed and built.

13 Instrumentation Residual Gas Analyzer: gas analysis. Pyrometer: surface temperature (>1600 C). Thermocouple: surface temperature in-situ IR thermometer: chamber and window temps. Scanning Electron Microscope with X-ray analysis: chemical and morphological characterization of the pyrolyzed and condensed surfaces.

14 Current Results

15 Current Experimental Results Mass loss was measured from ilmentite vaporization. Images, SEMs, and temperature data. Mass loss was measured to be several orders of magnitude more than out-gassing of volatiles (tested in vacuum and oven): several grams. A mass loss has also been measured from enstatite It is also significantly more than outgassing. Condensation of enstatite was also studied. It is all within 1.6 inches (4 cm) of the sample. A substantial mass loss was also obtained with MLS-1A.

16 Current Experimental Results The SEM was used to probe the chemistry of the slag. Ilmenite slag shows a relative increase in the amount of titanium present at the vaporized surface, and a relative decrease in the amount of oxygen present at the surface. This indicates the oxygen is in fact leaving the system. The condensate also appears to be reduced by SEM analysis.

17 Current Experimental Results Particles of Ti remain at the surface while the iron has melted and vaporized.

18 Ilmenite Test Picture

19 MLS-1A Test Picture MLS-1A is a lunar simulant.

20 Condensate from Ilmenite Test Picture taken from the chamber wall above the surface of the non-vaporized slag. The material on the walls is reduced oxide material that condensed from the vapors, and splatter from boiling.

21 Current Modeling Results Yield should be ~10% for ilmenite! If we heat the equilibrium to 2500 C and then condense out the remaining oxidized gasses, only the oxygen system is left. The vaporization will shift left for lower pressure.

22 Future Work

23 Pumping Modifications RGA measurements have not been successful because a leak valve had to be used to reduce the chamber pressure. The setup was modified to lower the chamber pressure and integrate the RGA directly into the flow. Flex Hose Leak Valve Flex Hose Turbopump RGA Turbopump RGA Scroll Pump Old Design Scroll Pump New Design

24 Volatile Species Although it is not possible to examine with regolith simulants here on Earth, the same system can be preheated to ~700K to extract many of the volatiles that are present in the lunar regolith. This includes the H 2 and He 3 that is embedded in the lunar regolith by the solar wind, as well as indigenous, or meteoritic, volatile species of scientific interest (Ar, etc.). Analysis has been performed to predict potential yields of these volatile species in the lunar regolith. The in-situ production of volatile materials on the moon will be difficult, but the vacuum pyrolysis technique CAN be used to support scientific studies.

25 The second flight, the demonstration mission, requires further development of those components which were not direct heritage from the instrument flight. The demonstration mission is fully capable of producing oxygen from lunar regolith. Implementation Plan The instrument/volatiles mission will demonstrate some of the key technologies, such as the window and collector. This mission advances the technology to TRL 5. The pilot plant can be modular in design and scaled to meet the desired production rate. The pilot plant serves as a prototype for a future production plant.