content long 20-January-2019 21:48:55

Engineering

Thermal Control

As well as getting to Mars, the spacecraft has to provide a benign environment for the instruments and on-board equipment. That means keeping some parts of the spacecraft warm and other parts cold. Two instruments, PFS and OMEGA, have infrared detectors that need to be kept at very low temperatures (about -180°C). The sensors on the camera (HSC) also need to be kept cool. But the rest of the instruments and on-board equipment function best at room temperatures (10-20°C).

The plan is to keep the inside of the spacecraft at 10-20°C by encapsulating the whole thing in thermal blankets and to cool those instruments that need it. The thermal blankets will be made from gold-plated aluminium-tin alloy. "We will design the thermal isolation so that the spacecraft doesn't get warm when the Sun or Mars shines on it, nor cold when it's on its interplanetary cruise. This is a challenging problem for the mission engineers" says Schmidt.

Material not covered by insulation may face temperatures of -100°C in the shade and up to 150°C in sunlight. Such temperature variations can cause material to shrink and expand unacceptably. Major external equipment on Mars Express, such as the solar array and high gain antenna, would require a large amount of power to keep them at room temperature - so they are made from composite materials which can withstand wide temperature variations without significant deformation.

The instruments that need to be kept cold will be attached to radiators that face deep space. Instrument and radiator will be thermally insulated from the rest of the spacecraft. Cooling will be through loss of heat to space which is very cold (about -270°C).


Last Update: 26 October 2017

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