277 Conclusions 

The OPTIMA tests on Mauna Kea, Ha waii in November of 2008 demonstr ated the feasibility of producing  oxygen at rates equivalent to 660 kg/year in a Lunar  Outpost. The enclosed auger regolith feed system  performed well and met all objectives. Batches of 8 kg of tephra were consistently, repeatably and  successfully fed from the input hopper to the reactor and then expell ed to the surface. High temperatures  and abrasive particles were handled well with this sys tem. Lifetime testing is required to determine the  wear rates and ultimate system reliability. The system  proved to be very robust in limited field testing.  Phase II of the ROxygen system design will incorporate the lessons learned and increase the fidelity of the prototype hardware.  As a result of terrestrial and reduced gravity experim ents, we have been able to show that the dense-flow  pneumatic transfer method is able to successfully c onvey lunar regolith simul ants such as NU-LHT-2M  and Tephra to a vertical height of 5 ft (1.5 m), which is not an absolute physical limit but simply a limitation  that was imposed by the available vertical space in the reduced gravity aircraft. Although we have shown  that it is possible to transfer lunar regolith simul ants pneumatically as a dense flow of dusty gas in a  simulated lunar gravity environment, it is also import ant to realize that the re duced gravity aircraft also  undergoes periods of increased gravity as high as 1.8 g, which may cause the granular regolith simulant material to become compacted. The degree to which this effect might influence the pneumatic regolith transfer process can be lessened by keeping the si mulant in a semi-fluidized state throughout the  parabolic flight.  A cyclone separator is an important component of a pneumatic regolith transf er system delivers the  regolith to a desired location, and filters the convey gas sufficiently so that the gas can be reused. It may be possible to design a single cyclone to perform ga s-solids separation provided that a moderate dense  flow of dusty gas is able to yield a sufficient mass  transfer rate by metering the regolith feed at the  eductor. The exhaust gas from any cy clone separator will contain fine part icles that may be detrimental to  the mechanical operation of a compressor intended for reusing the gas. In that case, a second cyclone, known as an electrocyclone, may be designed to re move particles that are even smaller than those  removed by an ordinary cyclone of the same size.    Overall, the reduced gravity flight  experiment and field testing proved that lunar regolith simulant can be  effectively conveyed pneumatically in an ISRU oxygen production plant in order to introduce regolith  simulant into the reactor; fluidize it within the re actor and hopper feed systems; transfer it from outer  reactor annulus zones to an inner reactor cylinder vess el; and subsequently expel it from the reactor for  disposal or use in subsequent resource processing (sili ca, aluminum, titanium, iron, etc.). The results of  this experiment were used to influence the design of the ROxygen second generation oxygen production  system being developed by t he NASA ISRU project, in order to show t hat it is indeed pos sible to produce  a minimum rate of one metric ton of oxygen per year (of lunar operation) from lunar regolith simulants in a reliable, long life and low maintenance system.   Acknowledgements 

The NASA RFS team would like to acknowledge the support of the ETDP, Cx P Lunar Surface Systems  Office and the ISRU project for funding and direct ing technology development and systems integration  work. In particular we would like to thank the ISRU project manager: Mr. William Larson, the deputy ISRU project manager: Mr. Gerald Sanders, the Director of the Innovative Partner ships Program (IPP), Mr.  Douglas Comstock, and the Chief of the Lunar Surfac e Systems (LSS) Office, Mr. Christopher Culbert.   The reduced gravity experiment  was supported by the NASA IPP under a 2009 program known as  Facilitated Access to the Space En vironment for Technology Development and Training (FAST). NASA  IPP also supported the Pacific International Space C enter for Exploration Studies PISCES) analog field  tests on Mauna Kea Hawaii in November 2008, as well as the Carbothermal pneumatic feed system  attachment that will be tested in January 2010 at the PISCES test site, Mauna Kea, Hawaii.  NASA/CP-2010-216272