Spacecraft: Surface Operations: Rover

Making sure the rover doesn´t get too hot through the heat rejection system

The "Russian doll" configuration of the spacecraft (where the rover is at the center of many different surrounding structures) makes it difficult to get rid of the excess heat from the rover electronics. During cruise, the rover is nestled inside the lander structure, which, in turn is surrounded by the aeroshell (the structure that protects the lander and rover from the fierce aerodynamic heating during Mars entry). The aeroshell is further attached to the cruise stage, which carries the propulsion and power system for the journey from launch to Mars entry. Because the rover acts as the brains at the heart of the spacecraft, a large amount of power (and heat) is generated within the rover body, or Warm Electronics Box, during cruise. Hence, a mechanically pumped fluid system known as the Heat Rejection System (HRS) was developed.

The heat rejection system is comprised of a pump on the cruise stage and tubing that snakes across the cruise stage, down the lander, and into the rover to pick up the heat (including the battery RHUs, and radiators on the cruise stage) and release the heat out into space. The pump is capable of shuttling 150 watts of rover waste heat. Its working fluid is CFC-12, similar to freon that is used in older automobile air conditioners. This fluid is maintained between -7º and 0º Celsius (19º Fahrenheit and 32º Fahrenheit) throughout cruise, which keeps the electronics and batteries at similarly tight temperature levels.

The cruise stage contains the propulsion system. The propellant lines and tanks and thrusters are maintained at appropriate temperatures by classic approaches: thermal blankets known as multi-layer insulation and thermostatically controlled heaters.

The aeroshell and lander also have critical equipment that must be temperature-controlled. They also use thermal blankets and heaters. In some cases, the heaters are used only to condition (that is, "warm-up") critical equipment such as airbags, gas generators, rocket assisted descent rocket motors, and the transverse impulse rocket system prior to Mars entry.