Locating and Identifying Lunar Volatiles using Heat and Mass Transfer

Locating and determining what lunar volatiles exist in the Moon's PSR's an inherent need to Volatile Mining efforts. The ability to find lunar volatiles, characterize icy regolith, map volatile density and determine volatile species is important for future ISRU mining operations. A simple solution is to use the effects of heat and mass transfer incorporated in an in-situ sensor that provides data on ice type, volatile density, and volatile species. Attached to a lander or mobile system, this single sensor removes the need to physically collect samples for analysis and instead collects data In-situ with limited interaction with the environment. This reduces complexity to the hardware, improves mission efficiency (more data), and uses less energy to gain the same data as an excavator/oven system.

A penetrometer is a probe that is mechanically forced into regolith, providing force data. Force curves relate to regolith strength and ice structure type. Relaxation data from the same penetrometer also provides insight into volatile concentrations. However, by modifying a penetrometer more definitive data can be gained. By embedding a thermocouple and a resistor heater into the penetrometer tip, temperature data is collected at various depths. By applying micro-watts of heat energy to the tip of penetrometer, the rate the tip cools correlate to thermal inertia in the icy regolith, providing insights into type of ice and volatile concentrations. Combining data from the penetrometer, thermocouple and the heater provides high confidence in ice type and bulk volatile concentration.

An additional modification and technique provides volatile species and species density. The tip of the penetrometer has a small gas inlet port, the penetrometer shaft is a tube allowing gas to flow to the base of the penetrometer. A mass flow sensor at the base collects data on gas flow out into the PSR vacuum. Once at the desired depth, the heater is warmed at 5 K increments and mass flow data is collected. At each temperature specific volatiles sublimate and the gas flows up through the penetrometer. The permeability of lunar regolith is poor and the pressures created from such small quantities are low, the bulk of the produced gas flow up the penetrometer. For example, Hydrogen Sulfide (H2S) is volatile detected during the LCROSS impact. H2S also sublimates at a lower temperature than water. As the heater warms up, the Hydrogen Sulfide will sublimate through the mass flow sensor before water begins to sublimate. Once a higher temperature is reached water vapor then feeds through the mass flow sensor. Through experiments this affect can be characterized and used to provide data on volatile species and species density.

This payload technology is estimated to weigh less than 10 kg’s. It could be fitted on a rover or lander arm and can be used to quickly assess an area of its volatile concentrations, the strength of the underlying regolith and what specific volatiles are there while also providing an estimated quantity. This could dramatical improve a prospector missions ability to collect more data in a specific amount of time, as this process can be conducted on the scale of minutes. In addition, it doesn’t kick up additional dust or required overly complex mechanisms that need to be thermally maintained in a PSR.

At the Colorado School of Mines, Center for Space Resources (CSR), three ‘dirty’ vacuum chambers are frequently exposed to lunar simulant. Penetrometer experiments are accomplished at CSR as well, specifically focusing on determining ice concentrations in different lunar icy regolith types. The CSR is currently performing experiments on Thermal Mining, producing and performing experiments on Icy Regolith’s. The Center for Space Resources has the unique equipment and expertise to prove this method is viable for Lunar PSR resource prospecting.

This research will support volatile mining efforts. This could dramatical improve a prospector mission's ability to collect more data in a specific amount of time, as this process can be conducted on the scale of minutes. In addition, it doesn't kick up additional dust or required overly complex mechanisms that need to be thermally maintained.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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