264 is found on the Mauna Kea volcano, is a good mineralogica l simulant for lunar regolith. This soil was used  as a feedstock for the two types of ISRU reactors  to produce the water that could subsequently be  electrolyzed to yield oxygen. 

Regolith Feed Systems for ISRU Oxygen Production Plants 

A regolith feed system needs to provide an efficient and reliable mechanism for regolith transfer in order  to serve as an interface between an excavator syst em that collects raw regolit h material, and an ISRU  production plant that extracts useful product materi als, such as water vapor, from the regolith through a  chemical process. Auger and pneumatic regolith c onveying systems are two types of regolith feed  systems that have been field tested and are described below. Each was tested at the Mauna Kea lunar analog field site; the auger system in November 2008 and the pneumatic system in February 2010.    ROxygen is a NASA ISRU project that is concerned with extr acting oxygen from the mineral Ilmenite in  the lunar regolith via a hydrogen reduction process in a fluidized-bed reactor system. The ROxygen  regolith transfer team identified the flow and transfer characteristics of lunar soil simulant to be a concern for lunar oxygen production efforts. It is important to develop hardware designs that have the ability to  flow and transfer a given amount of lunar regolith simul ant to a desired vertical height under lunar gravity  conditions. The first generation of the project (ROxygen I) tested an inclined auger regolith feed system to transfer material approximately 7 ft (2 m) vertically from the ground and into a solids inlet located at the  top of an ISRU reacto r chamber. For RO xygen II, a pneumatic method wa s designed to convey the  regolith vertically which avoided exposing any moving parts to abrasive regolith simulant particles. A  similar “proof of concept” pneumatic regolith transfer  system was built and field tested at Mauna Kea for  the Carbothermal ISRU project, in which oxygen is extracted from metal oxide minerals using a carbothermal reduction process that  utilizes methane. The pneumatically conveyed granular material is  separated from the convey gas usi ng cyclone separator technology.   

Auger Regolith Feed System 

Description

The National Aeronautics & Space Administration (NASA) In-Situ Resour ce Utilization (ISRU) program in  the Exploration Technology Development Program (ETDP) has designed and built oxygen production  plant prototype under the name of ROxygen. The first generation prot otype (ROxygen I) was tested in  November 2008 on Mauna Kea volcano in the Big Is land of Hawaii. The Roxygen I system was a self  contained hydrogen reduction reactor payload that was pa rt of the modular Outpost Precursor Testbed for  ISRU & Modular Architecture (OPTIMA) system. The goals of the OPTIMA test were to demonstrate: (1) an excavation and regolith delivery to/from ISRU plant, (2) oxygen extraction from regolith at the desired  outpost production rate, (3) oxygen storage, and (4) system integration, modularity of modules for swapping, and surface operations.  The ROxygen I regolith simulant feed system was designed to deliver regolith simulant from ground level to the inlet tube located at the top of the ROxy gen I reactor cylinder. The reactor was designed with a  vertical configuration to allow gravity to feed regolith simulant into and out of the reactor cylinder. In addition, the regolith simulant feed sy stem was required to channel the spent regolith from the outlet of  the reactor to a regolith disposal location on the ground for eventual pickup by a spent regolith removal system. The feed system had to be simple, lightweight, reliable, safe and capable of transportation and field assembly. The packaging of the feed system into the overa ll ROxygen I prototype envelope was a  major driver in the generation and selection of variou s concepts. In order to maintain pressure inside the  reactor, the regolith feed system had to be capable of isolating the reactor at the inlet and outlet tubes.  Regolith tolerant valves were researched and devel oped with seals capable of maintaining a desired  pressure even after cold and hot regolith had pass ed through them. Since the energy requirements of an  ISRU reactor can be quite large as the regolith heats to a temperature approaching 1000 degrees Celsius, it was highly desirable to incorporate a heat  recuperation system into the regolith feed system.  NASA/CP-2010-216272