Global Surface Temperature Measurement for Hypersonic Flight Vehicles

This dissertation describes the use of permanent-change thermal paints as a technique for global surface temperature measurements on short-duration hypersonic flight vehicles. The thermal paints provide an inexpensive, robust and relatively quick way of instrumenting hypersonic flight vehicles to measure in-flight surface temperatures through a single or multiple colour change which is a function of both the soak temperature and exposure time. A lack of quantitative surface temperature measurement for hypersonic flights through the use of this technique was found in the existing literature. The colour-change dependency on the exposed temperature history necessitated the transient calibration of these thermal paints. An experimental rig capable of replicating the time-varying high temperatures encountered during the short-duration hypersonic flights has been designed and developed using an electric-arc based method as a part of this work. This enabled the calibration of the thermal paints for theuse during hypersonic flight tests. Permanent-change thermal paints were used on the USAF/DSTO HIFiRE-0 hypersonic test vehicle as an initial test to measure the heating distribution for a suborbital parabolic flight trajectory. Post-flight recovery of the flight vehicle indicated that the patches of the thermal paints applied on the patch antenna section of the aluminium instrumentation can had undergone a visible colour change due toin-flight heating. The calibration of the same thermal paints was performed using the electric-arc based system which reproduced the predicted surface temperature histories obtained from the numerical conjugate-heat-transfer simulations. The numerical code and methodology used during this work to predict the surface temperature histories of the hypersonic flight vehicles was validated using in-flight data available from the HIFiRE-1 hypersonic flight test. The colour-change of the thermal paints for both the recovered flight and the calibrated samples were quantified andcompared using spectral and image analysis. The comparison provided a good agreement between the two sets of data and a quantitative surface temperature map of the patch antenna at the end of the descent phase of the HIFiRE-0 flight vehicle was deduced using the calibration data. The accuracy and the ambient pressure dependence of the thermal paints have also been discussed in this work