Speaker
Description
Spacecraft such as lunar rovers need to control onboard temperatures within an allowable range in response to the large temperature changes between day and night on the lunar surface. The high temperatures during the day require a large enough radiator to dissipate heat from the equipment, which takes a high heat transport capacity. On the other hand, equipment with the same heat transport capacity as daytime would require considerable heater power and battery to keep the equipment warm during the long cryogenic night.
To achieve efficient heat transfer during the hot day and minimize power consumption by a heater at cold night, it is effective to add a heat switch function to the loop heat pipe. The heat switch controls the temperature of equipment by changing the thermal conductance at high and low temperatures.
This workshop presentation will describe three methods of adding heat switch function to loop heat pipes: one is to heat the reservoir, the second is to install a bimetallic passive valve in the vapor line, and the third is an electrohydrodynamic (EHD) active valve in the liquid line. These methods were compared in thermal vacuum tests where the environmental temperature varied significantly. The EHD active valve is a new method proposed by the authors, and thermal vacuum tests confirmed that each method, including the EHD active valve, can control the equipment temperature at low temperatures. In this workshop, we introduce the proposed design of the EHD active valve and report the results of a comparative evaluation of the power consumption and additional pressure loss associated with the installation of each method.
