Experimental investigations of thermal properties of icy lunar regolith and their influence on phase change interface movement

Abstract

Heat and mass transfers occurring on surface and within subsurface of extraterrestrial bodies during natural and future industrial heating processes require knowledge of thermal properties of porous dry and icy materials. This paper investigates thermal properties of icy lunar regolith with various water ice contents and their influence on phase change interface movement. A series of experiments has been employed to simulate borehole heating of icy regolith samples under low vacuum (0.1–1.5 ​Torr) and very low temperatures (>93 ​K) using JSC-1A regolith analogs prepared as “mud-pies” with water contents from 0 to 15 ​wt%. Cylindrical samples were heated via cartridge heater located in the center of the samples. Real-time measurements of temperatures in an array of points and vacuum chamber pressures were recorded. To decipher thermal properties data in this inverse heat equation problem, a 3D finite element method modelling has been used to simulate the behaviour of both the samples and the vacuum chamber. The results provided rough matches with expected thermal properties and the model was used in determination of phase change interface movement in the samples. These results could be applicable to research on properties and composition of other rocky and icy extraterrestrial objects or design of water ice prospecting instruments. Most importantly they should improve our understanding of processes applied in extraterrestrial water mining and visualize engineering challenges of these processes.