Compact, Modular Heat Flow Probe for Future Lunar Missions

Abstract

The Lunar Geophysical Network (LGN) mission is one of the space missions recently recommended to NASA by a panel of scientists assembled by the National Research Council. The LGN mission would deploy a ‘global, long-lived network of geophysical instruments on the Moon’ to collect seismic, heat flow, laser ranging and magnetic data. Our team of scientists and engineers are currently developing a heat flow probe suited for such a mission and the robotic and human missions to the Moon considered by other government agencies and private sectors (e.g., SELENE-2, Resource Prospector, Luna-Glob, Golden Spike). Our heat flow probe is a compact and modular system that can be deployed robotically on a small lander. It weighs less than 2 kg and use only 10 Watts of power. It is designed to reach 3-m below the lunar surface, 0.6 m deeper than reached by the heat flow probes on the Apollo missions. It obtains the heat flow by measuring thermal gradient and thermal conductivity of the depth interval of the regolith penetrated. The probe uses a pneumatic excavation system in deploying its thermal sensors to the subsurface. The deployment mechanism (~0.3 m long) spools out a glass fiber composite stem downward. The stem then forms a hollow cylinder of ~1.5-cm diameter, and subsequently pushes the penetrating cone into the regolith, while gas jets, emitted from the cone tip, blow away loosened materials. Removing material from the bottom of the hole allows the stem to advance with minimum thrust. A short (~1.5-cm), thin (2-mm diameter) thermal probe, attached to the cone tip, measures temperatures and thermal conductivities of the regolith by stopping for 30 minutes at different depths on the way down. During each stop, the system shuts off the gas jet and pushes the needle sensor into the undisturbed bottom-hole regolith. After the cone reaches the targeted depth, the temperature sensors embedded on the fully extended stem monitor long-term stability of the thermal gradient. Lab tests have been conducted in the last 3 years to refine the deployment mechanism and the sensor system. The latest prototype of a fully integrated system was able to penetrate nearly 2 meters into lunar regolith simulant in vacuum chamber. Further improvement is currently being made now to reach the targeted 3-m depth.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015