Analysis of a technique for thermo-physical characteristics determining of lunar soil under its heating by the sunlight

Аuthors

Alifanov O. M.^*, Dudkin K. K.^**, Netelev A. V.^***, Salosina M. O.^****, Chernova L. M., Chumakov V. A.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: o.alifanov@yandex.ru
**e-mail: lord-konst@mail.ru
***e-mail: netelev@mai.ru
****e-mail: salosina.m@yandex.ru

Abstract

The article presents analysis of a method for determining the lunar soil thermophysical properties with a penetrating probe, which employs solar radiation as a heat source. The probe utilized in the Apollo missions was considered as a prototype. A 3D mathematical model was being employed while simulating physical process of heat conduction. The soil thermal conductivity was being determined by constants for the three layers. This partition is stipulated by the strong dependence of the soil properties on its occurrence depth. The lower, fourth layer was presented as a semi-infinite body. To analyze the developed method for lunar soil thermo-physical properties estimation effectiveness, a model experiment was performed in the ANSYS environment. The finite elements sizes selection in a numerical experiment was preliminarily performed. The heating duration amounted 259200 seconds. Heating was being performed by the surface radiation with the sunlight. Heating was being performed by the surface exposure to the direct sunlight. A zero thermal flow was being set on the semi-infinite layer. Ideal conditions of heat conjugation were being set between the layers. Daily temperature fluctuations were not accounted for. The numerical experiment allowed computing temperatures at the points of measuring thermocouples setting. The lunar soil thermal conductivity at the given heating capacity coefficient was being computed based on this data. The thermal conductivity computing was performed by the local search of discrete values of the coefficients in the solution search area with further detailing in the vicinities of the most prospective values. Matching of computed temperatures in the thermal sensors placing points to temperatures obtained in the simulation experiments was the termination criterion of the iteration cycle for the solutions search. An inference on the weak effectiveness of the method was drawn notwithstanding the fact that the authors managed to obtain exact thermal conductivity value. This decision is stipulated by the fact that a great number of assumptions, associated with the heating modes, and effect of the structure and measuring system, was made to achieve the desired accuracy.

Keywords:

lunar soil thermophysical properties; thermal probe; inverse problems, simulation modeling

References

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