The Technology Transfer and Partnerships Office
Regolith Feed Systems for ISRU Reactors
ROxygen I Oxygen Production Plant with an Inclined Auger RFS being Field Tested on Mauna Kea Volcano in Hawaii (2010)

Figure 1. ROxygen I Oxygen Production Plant with an Inclined Auger RFS being Field Tested on Mauna Kea Volcano in Hawaii (2010). (Image credit: Kennedy Space Center / Johnson Space Center)

Various Lunar ISRU O2 production plant prototypes that can extract chemically bound oxygen from the minerals in the lunar regolith are being designed and tested. This work demands that lunar regolith (or simulants) shall be introduced into the O2 production plant from a holding bin or hopper and subsequently removed from the ISRU O2 production plant for disposal. This sub-system is called the Regolith Feed System (RFS) which exists in a variety of configurations depending on the O2 production plant oxygen being used (e.g. Hydrogen Reduction, Carbothermic Reduction, Molten Regolith Electrolysis). Each configuration may use a different technology and in addition it is desirable to have heat recuperation from the spent hot regolith as an integral part of the RFS. The development of these technologies is a partnership comprised of Kennedy Space Center, Johnson Space Center, Glenn Research Center, Honeybee Robotics, ASRC Aerospace Corp., and Team QNA-ESC.


Auger Feed Systems

— 1. ROxygen Phase I This regolith transfer system consists primarily of slightly inclined augers, auger motor/gear reductions, excavator ramps, valves, tubing, a control system, and a 4-sides hopper tapered inward towards the bottom. This hopper is the interface that accepts regolith from an excavation vehicle and delivers it to the auger feed inlet. (Figure 1.)
— 2. PILOT / Carbothermal Reduction Reactor
The Carbothermal Reactor receiving bin has its own auger drive system that transfers the regolith into an internal hopper system, which is isolated by a gate valve system through which the auger is horizontally translated for regolith transfer. Once the internal hopper is full, the auger retracts and the valves are closed (Figure 2).

Auger system for Carbothermal Reactor as part of PILOT

Figure 2. Auger system for Carbothermal Reactor as part of PILOT.

— 3. Counter-flow auger systems
Counter-flow auger systems have been investigated in order to combine regolith transfer with heat recuperation in a simultaneous operation. The results were promising since it was possible to accurately control and measure the regolith flow and heat transfer. The work showed that the counter-flow auger systems repeatedly effectively transferred more than 50% of the heat in the hot exit stream to the incoming cool regolith stream.









ROxygen I Oxygen Production Plant with an Inclined Auger RFS being Field Tested on Mauna Kea Volcano in Hawaii (2010)

Figure 3. Pneumatic feed system supplying the Carbothermal reactor.

Pneumatic Feed Systems
The method of pneumatically conveying lunar regolith becomes a viable option in the case of ISRU oxygen production since a gas exchange/circulation system is already required for the ISRU chemical reactors being considered for oxygen production on the moon. In addition, pneumatic conveyors involve no moving parts during the transfer of regolith particles thus reducing the risk associated with mechanical breakdown. (Figure 3)