Methods for Measurement of Thermophysical Properties of Lunar Simulant

Abstract

Oxygen extraction from the lunar regolith is a key objective of ne ar-term research for lunar exploration. Replacing oxygen from Earth with oxygen obtained from lunar regolith can reduce the weight o f spacecraft at launch by 42%. (Eighty-five percent of the weight of a typical spacecraft at launch is oxygen used to fuel the craft.) We are developing tools to numerically model the minimum power required to bring the lunar regolith to the processing temperature so that oxygen can be extracted using electrolysis methods. At this time, the thermophysical properties of lunar regolith are unknown. In this paper, we describe methods for measuring thermophysical properties of copper and aluminum. We have devised methods to measure thermal conductivity, heat capacity and thermal diffusivity. In testing for these three properties, we would then be able to compare our results with similar tests for lunar regolith. The test rigs for thermal conductivity and heat capacity are modeled from ASTM Standards E1225-04 and D4611-1, respectively. To measure thermal diffusivity, we modify Codastefano’s method for measuring mass diffusivity. Nomenclature M (T) = Thermal conductivity of meter bars (reference materials) as a function of temperature S (T) = Thermal conductivity of specimen T(t) = Temperature of a body at a given time t = Specific heat capacity = Temperature of the surrounding medium = Density of Material = Thermal diffusivity ( /( cp) b = Time constant measured in (1/s); D = Mass diffusivity or diffusion coefficient