Thermal cycling

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Thermal cycling test
(based on ESA ECSS-Q-ST-70-04)

Space vehicles are exposed to continuous temperature changes e.g. due to changing sun irradiation. For materials to be capable for space applications the performance under changing ambient temperatures in vacuum is an important issue. The thermal-cycling test may be used to assess materials for their space capability.
The test setup used for thermal cycling of samples consists of a heating/cooling plate made of copper which can be temperature controlled in a range between 80K and 500K. Cooling is performed with liquid nitrogen, heating is performed electrically. A maximum temperature-gradient of 8°C/min can be used for thermal cycling.
The temperature of the heating/cooling plate is monitored and adjusted by an Eurotherm® temperature controller. Furthermore, several thermos-couples are implemented in the setup continuously monitoring and recording temperatures on different relevant spots of the setup (pre-defined by customer). All thermo-sensors are calibrated and have accuracy better than ±2°C.
The entire setup is placed in a vacuum chamber capable of pressures down to 10-7 mbar. For thermo-cycling processes a pressure better than 10-5 mbar is required. For pumping a turbo-molecular pump is used. A PC program controls and measures all relevant variables and allows automatically completing complicated temperature profiles.
On customer request additional electrical feedthroughs are available and may be used for in-situ measurement of diverse properties (e.g. electrical resistivity) during the thermal cycling test. The measured values are recorded together with the temperature and vacuum values.
Post examination (SEM-, LO-microscopy, NDT) and testing (e.g. mechanical tests, electrical tests) can be carried out at AAC.

thermal cycling.jpg_1FIG.: Typical temperature and vacuum plots during thermal cycling test

According to different customer requirements a variety of vacuum cambers are available offering different dimensions and different feed-feedthroughs to perform in-situ measurement of various properties (e.g. electrical resistivity) during the thermal cycling test.

Test rig Size of

heating/cooling plate

Temperature range
TVC

Thermal vacuum Chamber

100x70cm, 2 plates -160 to +250°C
LVC

Large Vacuum Chamber

100x70cm, 2 plates

Shroud 100x100x40cm

-160 to +250°C
Outgassing 30cm diameter -180 to +300°C
WRK 50x50cm -180 to +300°C
MiniWRK 35x30cm -180 to +500°C
Thermal Cycling facts:

Temperature range
Tmin -180 °C
Tmax +300 °C

Vacuum
< 10-5 mbar

Typical temperature cycles (if not otherwise specified by customer)
Temperature extremes: -160 °C and +160 °C
Heating and cooling rates: 6 °C /min
Dwell times at temperature extremes: 15 min
Number of cycles: 100