Ramaswamy Balasubramaniam

Development and Validation of a Model for Hydrogen Reduction of JSC-1A

Hydrogen reduction of lunar regolith has been proposed as a viable technology for oxygen production on the moon. Hydrogen reduces FeO present in the lunar regolith to form metallic iron and water. The water may be electrolyzed to recycle the hydrogen and produce oxygen. Depending upon the regolith composition, FeO may be bound to TiO2 as ilmenite or it may be dispersed in glassy substrates. Some testing of hydrogen reduction has been conducted with Apollo-returned lunar regolith samples. However, due to the restricted amount of lunar material available for testing, detailed understanding and modeling of the reduction process in regolith have not yet been developed. As a step in this direction, hydrogen reduction studies have been carried out in more detail with lunar regolith simulants such as JSC-1A by NASA and other organizations. While JSC-1A has some similarities with lunar regolith, it does not duplicate the wide variety of regolith types on the moon, for example, it contains almost no ilmenite. Nonetheless, it is a good starting point for developing an understanding of the hydrogen reduction process with regolith-like material. In this paper, a model utilizing a shrinking core formulation coupled with the reactor flow is described and validated against experimental data on hydrogen reduction of JSC-1A.

An Extension of Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

The realization of the renewed exploration of the moon presents many technical challenges; among them is the survival of lunar surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an extension of an earlier analysis of performance of thermal wadis based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. The current analysis has been performed for the lunar equatorial region and validates the formerly used one-dimensional model by comparison of predictions to those obtained from two- and three-dimensional computations. It includes the effects of a thin dust layer covering the surface of the wadi, and incorporating either water as a phasechange material or aluminum stakes as a high thermal conductivity material into the regolith. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness.

Component and System Sensitivity Considerations for Design of a Lunar ISRU Oxygen Production Plant

Component and system sensitivities of some design parameters of ISRU system components are analyzed. The differences between terrestrial and lunar excavation are discussed, and a qualitative comparison of large and small excavators is started. The effect of excavator size on the size of the ISRU plant’s regolith hoppers is presented. Optimum operating conditions of both hydrogen and carbothermal reduction reactors are explored using recently developed analytical models. Design parameters such as batch size, conversion fraction, and maximum particle size are considered for a hydrogen reduction reactor while batch size, conversion fraction, number of melt zones, and methane flow rate are considered for a carbothermal reduction reactor. For both reactor types the effect of reactor operation on system energy and regolith delivery requirements is presented.

Thermal Wadis in Support of Lunar Science & Exploration

Challenges associated with the exploration of the Moon include both the high cost of bringing hardware from Earth (perhaps at costs of

Waste Management Options for Long-Duration Space Missions: When to Reject, Reuse, or Recycle

50,000 to

Analysis of Water Extraction From Lunar Regolith

100,000 per kilogram), which therefore places a high economic burden on bringing consumables and technologies from Earth, and providing power and heat for outposts and other systems that must survive the extreme cold of the two-week lunar night. However, it should be possible to develop thermal energy reservoirs using in-situ lunar materials, as systems that can store energy for use during periods of darkness on the Moon. In this paper, we discuss the potential to emplace one or more thermal wadis – engineered sources of heat and power – on the lunar surface in support of lunar science and exploration. These systems can provide a substantial architectural advantage to robotic systems, teleoperated from Earth and/or from a manned lunar outpost.

Enabling Long-Duration Lunar Equatorial Operations with Thermal Wadi Infrastructure

The amount of waste generated on long-duration space missions away from Earth orbit creates the daunting challenge of how to manage the waste through reuse, rejection, or recycle. The option to merely dispose of the solid waste through an airlock to space was studied for both Earth-moon libration point missions and crewed Mars missions. Although the unique dynamic characteristics of an orbit around L2 might allow some discarded waste to intersect the lunar surface before re-impacting the spacecraft, the large amount of waste needed to be managed and potential hazards associated with volatiles recondensing on the spacecraft surfaces make this option problematic. A second option evaluated is to process the waste into useful gases to be either vented to space or used in various propulsion systems. These propellants could then be used to provide the yearly station-keeping needs at an L2 orbit, or if processed into oxygen and methane propellants, could be used to augment science exploration by enabling lunar mini landers to the far side of the moon.

Hydrogen Reduction of Lunar Regolith Simulants for Oxygen Production

Distribution of water concentration on the moon is currently an area of active research. Recent studies suggest the presence of ice particles, and perhaps even ice blocks and icecemented regolith on the moon. Thermal extraction of the in-situ water is an attractive means of satisfying water requirements for a lunar mission. In this paper, a model is presented to analyze the processes occurring during the heat-up of icy regolith and extraction of the evolved water vapor. The wet regolith is assumed to be present in an initially evacuated and sealed cell which is subsequently heated. The first step of the analysis involves calculating the gradual increase of vapor pressure in the closed cell as the temperature is raised. Then, in the second step, the cell is evacuated to low pressure (e.g., vacuum), allowing the water vapor to leave the cell and be captured. The parameters affecting water vapor pressure build-up and evacuation for the purpose of extracting water from lunar regolith are discussed in the paper. Some comparisons with available experimental measurements are also made.

Heating-Rate-Coupled Model for Hydrogen Reduction of JSC-1A

Long duration missions on the moons equator must survive lunar nights. With 350 hours of cryogenic temperatures, lunar nights present a challenge to robotic survival. Insulation is imperfect, so it is not possible to passively contain enough heat to stay warm through the night. Components that enable mobility, environmental sensing and solar power generation must be exposed, and they leak heat. Small, lightweight rovers cannot store enough energy to warm components throughout the night without some external source of heat or power. Thermal wadis, however, can act as external heat sources to keep robots warm through the lunar night. Electrical power can also be provided to rovers during the night from batteries stored in the ground beside wadis. Buried batteries can be warmed by the wadis heat. Results from analysis of the interaction between a rover and a wadi are presented. A detailed three-dimensional thermal model and an easily configurable two- dimensional thermal model are used for analysis.

Analysis of Water Recovery Rate From the Heat Melt Compactor

Abstract Hydrogen reduction of the lunar regolith simulants JSC-1A and LHT-2M is investigated in this paper. Experiments conducted at NASA Johnson Space Center are described and are analyzed utilizing a previously validated model developed by the authors at NASA Glenn Research Center. The effects of regolith sintering and clumping, likely in actual production operations, on the oxygen production rate are studied. Interpretations of the obtained results on the basis of the validated model are provided and linked to increase in the effective particle size and reduction in the intra-particle species diffusion rates. Initial results on the pressure dependence of the oxygen production rate are also presented and discussed. Nomenclature c o molar concentration of hydrogen in regolith bed (moles/m 3 ) D effective gas diffusion coefficient (m 2 /s) F factor defined by Equation (1) (s –1 ) k equilibrium constant L length of regolith bed (m) p gas pressure (Pa) r p regolith particle radius (m) t