Paraffin-Actuated Heat Switch for Mars Surface Applications

Missions to the surface of Mars pose unique thermal-control challenges to rover and lander systems. With diurnal temperature changes greater than 100 °C, the presence of a Mars atmosphere, and limited power for night-time heating, the thermal-control engineer is faced with a fundamental problem: how to successfully keep components above their survival or operating temperatures at night while managing higher environmental temperatures and dissipation rates during the day. A report describes such a paraffin-actuated heat switch as part of the thermal-control system for a robotic exploratory vehicle on Mars. Over a predetermined temperature range, the switch heat conductance varies by nearly two orders of magnitude to regulate temperatures. The actuation of the heat switch is entirely mechanical and autonomous, relying on the temperature based expansion and contraction of paraffin contained in a seal boot.