A common hardware used by thermal engineers in spaceflight projects are polyimide (Kapton®) and all-polyimide foil electrical resistance heaters. Typical applications range from thermostat-controlled survival heaters, operational heaters, to test heaters (either to simulate internal or external heat dissipation sources, for example radiators).
Same as with any other aerospace hardware, also heaters can fail, however as the standards for the de-rating of heaters are very strict, this rarely happens in flight model (FM) hardware. It happens more frequently in test heaters. The most common origin of a failure on foil heaters are gas inclusions or local delamination. In the first instance such failures lead to local hot spots. The hot spots are elevations of temperature above the local average temperature of the foil heater.
The present activity, funded by the European Space Agency, aims at start the process of developing a standardized non-destructive test method for the correct integration of foil heaters by the use of IR cameras. The tasks performed covered: literature review of non-destructive inspection methods, IR NDT trade-off and technical assessment of relevant IR camera and measurement set-up parameters, perform relevant tests aiming at identifying a possible threshold for acceptance/rejection of a heater installation.