Transient thermal envelope for rovers and sample collecting devices on the Moon

The requirements for the design of rovers and sample collecting devices for the Moon are driven by the harsh and diverse thermal lunar environment. Local lunar surface temperatures are governed by boulders and craters. The present work quantifies the changes in solar and infrared heat fluxes and impinging on a rover or a sample collecting device, on the surface of the Moon, by combining lunar surface models, spacecraft and manipulator models, and transient thermal calculations. The interaction between a rover, boulders, and craters was simulated for three solar elevation angles (θ = 2°, 10°, and 90°), resembling lunar surface temperatures of Treg = 170, 248, and 392 K, respectively. Infrared and solar heat fluxes for paths in the vicinity of a single boulder, a field of five boulders, and a single crater were compared to a path on an unobstructed surface. The same heat fluxes were applied to closed and open sample collecting devices to investigate the temperature development of the transported regolith sample. The results show how total received infrared heat on a rover may increase by up to 331%, over the course of a transit in front of sunlit boulders compared to the same transit over an unobstructed plane. Temporary this leads to a 12-fold increased infrared heat flux at closest distance to the obstacle. A transit through a small bowl shaped crater on the other hand may decrease total received solar heat by as much as 86%. Relative as well as absolute influence of surface features on received heat fluxes increases significantly towards smaller solar elevation angles. The temperature of pristine samples, transported in closed or open sample collecting devices, increase from 120 to 150 K within 1 to 1.3 h if exposed to direct solar illumination and infrared heat. Protection from solar illumination yields in 8-fold and 5-fold increased transport times for closed and open sample devices, respectively. Closed sample transporters dampen short exposure times to solar illumination but also lead to higher sample end temperatures in the same period. The degradation of absorptivity and emissivity, due to coverage with dust or scratches obtained during operation, will significantly alter the sample temperature in a negative manner. The results indicate that transient thermal analyses, that take into account the local lunar environment, are feasible and permit more detailed thermal envelopes for future rover missions to the surface of the Moon.     «

The requirements for the design of rovers and sample collecting devices for the Moon are driven by the harsh and diverse thermal lunar environment. Local lunar surface temperatures are governed by boulders and craters. The present work quantifies the changes in solar and infrared heat fluxes and impinging on a rover or a sample collecting device, on the surface of the Moon, by combining lunar surface models, spacecraft and manipulator models, and transient thermal calculations. The interact...     »