Lunar Portable Life Support System Heat Rejection Study

Performing extravehicular activity at various locations on the lunar surface presents thermal challenges that exceed those that have been experienced in space flight to date. The lunar Portable Life Support System (PLSS) cooling unit must maintain thermal conditions within the spacesuit (SS) and reject heat loads that are generated by both the crew member and the PLSS equipment. The amount of cooling that will be required varies based on lunar location and terrain due to the heat that is transferred between the suit and its surroundings, A study, which assumes three different thermal technology categories, has been completed that studied the resources that are required to provide cooling under various lunar conditions as follows:

1. 1.
   SS water membrane evaporator
2. 2.
   Sub-cooled phase change material (SPCM)
3. 3.
   Radiators with and without heat pumps

Results from this study, which are presented here, show mass and power impacts on the cooling system as a function of the location and terrain on the lunar surface. Resources (i.e., cooling equipment mass and consumables) are greater at the equator and inside sunlit craters due to the additional heat loads that are placed on the cooling system. Whereas radiator and SPCM technologies require minimal consumables, radiators do not reject the required SS heat loads over a significant portion of the lunar surface thermal environments and SPCM comes with significant carry-weight penalties. A wider investigation is recommended to determine whether these penalties and limitations are offset by consumable savings.