Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

Abstract

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.

Enabling Long-Duration Lunar Equatorial Operations with Thermal Wadi Infrastructure

“…Previous analysis of wadi's has shown that 1D, 2D, and 3D models produce similar results (Ref. 6), so we compare the results of the detailed 3D model with those of a simplified 2D model of rover and wadi. Three cases are examined with each model (1) a rover on a wadi with no shield, (2) a rover on a wadi with a shield, and (3) a rover on a wadi with a low emissivity shield.…”

“…This assumption is based on previous analysis showing that results for a 3D wadi are very similar to results for a 1D wadi (Ref. 6). Figure 5 shows three different views of the rover on the wadi.…”

“…5). That analysis showed that a wadi can remain warm through the night when providing 25 W/m 2 of constant heat flux to a rover.…”

Thermal Wadis in Support of Lunar Exploration: Concept Development and Utilization

“…One of the areas where cost effectiveness could be improved is with the use of lunar rovers. Electronic devices, in general, will cease to function at temperatures below -55°C (Ghaffarian 2002), which is problematic because temperatures on the Moon during the lunar night can drop to about -173°C (Balasubramaniam et al 2009). One of the most promising locations of a lunar station would be at the south pole of the moon where the amount of time in sunlight would be maximized (Dale 2006).…”

An Extension of Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

“…3). Our objective was to analyze the extent to which a thermal wadi can provide temperature control for a robotic rover based on several simplified configurations of operational hardware and modifications to the native regolith for creating the wadi thermal mass.…”