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

R. Balasubramaniam, S. Gokoglu, K. Sacksteder, R. Wegeng, N. Suzuki
2011 Journal of thermophysics and heat transfer  
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 supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an analysis of the performance of thermal wadis
more » ... f thermal wadis based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. Analysis has been performed for the lunar equatorial region and for a potential outpost location near the lunar south pole. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness. Nomenclature C p , C 0 p = specific heat of the wadi and regolith, respectively, depth of the regolith layer underlying the wadi, m f, f j = periodic surface heat flux in the medium as a function of time and in a time interval j, W=m 2 k, k 0 = thermal conductivity of the wadi and regolith, respectively, W=m K N, N 0 = scaled depth of the wadi (d= t 0 p ) and the regolith layer [d 0 d= 0 t 0 p ], respectively q = solar flux impinging on the wadi surface, W=m 2 q = q=q max , scaled solar flux q max = peak solar flux, W=m 2 q rov = heat flux supplied to the rover, W=m 2 q rov = q rov = abs q max , scaled rover heat flux T, T 0 = temperature distribution as a function of x and t in the wadi and the underlying regolith layer, K T a = environment temperature, K T a = T a =T ref , scaled environment temperature T i = initial temperature of the wadi, K T ref = reference temperature, abs q max = 0 1=4 , K T s = surface temperature of the wadi, K t = time, s t 0 = one half of the synodic period on the moon (354 h), s x = coordinate in the vertical direction into the wadi and the underlying regolith, m , 0 = thermal diffusivities of the wadi and regolith, respectively, m 2 =s abs = radiative absorptivity of the wadi surface = dimensionless parameter, 1= 2 p k 0 =k = 0 p = radiative emissivity of the wadi surface = = 0 , scaled emissivity of the wadi surface 0 , 1 = daytime and nighttime emissivity, respectively, of the wadi surface , 0 = scaled temperature distribution in the wadi (T=T ref ) and the underlying regolith layer (T 0 =T ref ) = dimensionless parameter, k= t 0 p 0 1=4 abs q max 3=4 = scaled coordinate in the vertical direction, d x=d for 0 x d and x d=d 0 d for d x d 0 , 0 = densities of the wadi and regolith, respectively, kg=m 3 = Stefan-Boltzmann constant, 5:67 10 8 W=m 2 K 4 = scaled time, t=t 0 j = periodic scaled surface heat flux in the medium in the time interval j in Jaeger's method
doi:10.2514/1.49843 fatcat:fydq55rr2ndjde6ibpbtjugvba