Total temperature probe calibration in supersonic rarefied flows

Shielded thermocouple total temperature probes have been designed with recovery factors very close to unity. However, it has been observed that at very low densities the recovery factor drops off sharply. It was determined experimentally and theoretically that the sharp drop in performance in supersonic rarefied flow regimes is due to the growth of the thermal boundary layer inside of the probe shield and the consequent cooling of the stagnated gas in front of the thermocouple junction. The effect of the slip temperature jump is included in the design calculations.