Lunar Prospecting Using Thermal Wadis and Compact Rovers

Recent missions have confirmed the existence of water and other volatiles on the Moon, both in permanently-shadowed craters and elsewhere. Non-volatile lunar resources may represent significant additional value as infrastructure or manufacturing feedstock. Characterization of lunar resources in terms of abundance concentrations, distribution, and recoverability is limited to in-situ Apollo samples and the expanding remote-sensing database. This paper introduces an approach to lunar resource prospecting supported by a simple lunar surface infrastructure based on the Thermal Wadi concept of thermal energy storage and using compact rovers equipped with appropriate prospecting sensors and demonstration resource extraction capabilities. Thermal Wadis are engineered sources of heat and power based on the storage and retrieval of solar-thermal energy in modified lunar regolith. Because Thermal Wadis keep compact prospecting rovers warm during periods of lunar darkness, the rovers are able to survive months to years on the lunar surface rather than just weeks without being required to carry the burdensome capability to do so. The resulting lower-cost, long-lived rovers represent a potential paradigm breakthrough in extra-terrestrial prospecting productivity and will enable the production of detailed resource maps. Integrating resource processing and other technology demonstrations that are based on the content of the resource maps will inform engineering economic studies that can define the true resource potential of the Moon. Once this resource potential is understood quantitatively, humans might return to the Moon with an economically sound objective including where to go, what to do upon arrival, and what to bring along

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 analysis of the performance of thermal wadis based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. Analysis has been performed for the lunar equatorial region and for a potential outpost location near the lunar south pole. 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

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 enable the operation of lightweight robotic rovers or other assets in cold, dark environments without incurring potential mass, cost, and risk penalties associated with various onboard sources of thermal energy. Thermal wadi-assisted lunar rovers can conduct a variety of long-duration missions including exploration site surveys; teleoperated, crew-directed, or autonomous scientific expeditions; and logistics support for crewed exploration. This paper describes a thermal analysis of thermal wadi performance based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. Analysis was performed for the lunar equatorial region and for a potential Outpost location near the lunar south pole. The results are presented in some detail in the paper and indicate that thermal wadis can provide the desired thermal energy reserve, with significant margin, for the survival of rovers or other equipment during periods of darkness

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 1-D model by comparison of predictions to those obtained from 2-D and 3-D computations. It includes the effects of a thin dust layer covering the surface of the wadi, and incorporating either water as a phase-change 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

Ferrocyanide safety study

The overall objective of this study is to investigate the potentially rapid reactions between the ferrocyanide-containing salts, present in the SST's, and oxidants, such as nitrate, also present in the SST's. The objective of the energetics subtask is to investigate, on a screening basis, SST operational and compositional parameters which could affect the reaction between nickel cesium ferrocyanide, the expected form of cyanide in the SST, and nitrates and/or the nitrate radiolysis product nitrite. The objective of the large-scale explosion study is to independently confirm the results of the PNL laboratory-scale experiments and to determine the explosive behavior of a large sample of ferrocyanide and oxidant. The objective of the PNL-5441 revision subtask is to revise the complexant stability report, PNL-5441, to provide a current overview of the ferrocyanide safety issue and provide information to permit establishment of guidelines for SST management. 1 fig

Boiling heat transfer enhancement in mini/microtubes via polyhydroxyethylmethacrylate (pHEMA) coatings on inner microtube walls at high mass fluxes

In this experimental study, flow boiling in mini/microtubes was investigated with surface enhancements provided by polyhydroxyethylmethacrylate (pHEMA) coatings (of ~30 nm thickness) on inner microtube walls. Flow boiling heat transfer experiments were conducted on microtubes (with inner diameters of 249 µm, 507 µm and 998 µm) having inner surfaces with pHEMA coatings, which increases heat transfer surface area, enable liquid replenishment upon bubble departure, provide additional nucleation sites, and serve for extending Critical Heat Flux (CHF) and enhancing boiling heat transfer. De-ionized water was utilized as the working fluid in this study. pHEMA nanofilms of thickness ~30 nm on the microtube walls were coated through initiated chemical vapor deposition (iCVD) technique. Experimental results obtained from coated microtubes were compared to their plain surface counterparts at two mass flux values (10,000 kg/m2s and 13,000 kg/m2s). In comparison to the plain surface microtubes, coated surfaces demonstrate an increase up to 24% and 109% in CHF and heat transfer coefficients, respectively. These promising results support the use of pHEMA coated microtubes/channels as a surface enhancement technique for microscale cooling applications