A Heat Switch for European Mars Rover 2008-01-2153
The future Mars rover thermal design presents a unique challenge to the thermal engineers: the need arises for a thermal control system able to keep rover elements within their operational and non-operational temperature ranges in the face of extreme environmental conditions, characterized by broad day/night temperature excursions, cold biased conditions and long periods in standby modes induced by dust storms.
A thermal device is needed, which allows the removal of excess heat from dissipating units during the Martian day and to keep them above their minimum operational/survival temperature during night. Moreover the scientific goals introduce strict requirements in terms of allowable internal components temperature ranges and thermal stability, which the candidate device has to fulfill against wide-ranging power dissipation modes.
Such a device has been called Variable Thermal Conductance Device, or ‘Heat Switch’. The paper presents a heat switch demonstrator concept, which is based on a Loop Heat Pipe with a temperature-regulating valve.
Heat Switch specifications are reviewed, and the main design characteristics to meet the requirements are explained. The demonstrator has been designed, built and tested for exploring its operational envelope, both versus the Rover functioning modes and the Mars environment.
Test sequence is described in detail, focusing on the methods to characterize the key parameters of the Heat Switch.
Main findings of the demonstrator development activity are summarized, and recommendations for use in an operational mission on Mars are issued.