Off-Line temperature profiling of Mo-based rocket engine combustion chamber using thermal history paint

• Temperature profile in space sector relevant tests is retrieved by nanosensors. • UC-THP performs well at complex geometries exposed to flame heating • The sensitivity of UC-THP is significantly increased on molybdenum-rich substrate. The paper studies application of thermal history technology for rocket engine testing. For that purpose, we have applied upconverting thermal history paint with Gd 2 O 3 : Er 3+ , Yb 3+ , Mg 2+ powder as a maximum temperature sensor. The proposed off-line temperature measurement approach addresses key limitations of conventional on-line methods, such as the limited spatial resolution of thermocouples and the emissivity-related inaccuracies inherent in IR thermography. To address the measurement challenges associated with thermal history technology under short-duration thermal exposure—typical of space propulsion testing—the developed paint is capable of undergoing permanent changes in its luminescence characteristics within seconds . Two calibration procedures were developed: an in-situ method utilizing temperature signals from the experiment, and an ex-situ method based on data collected using a dedicated calibrator. The developed paint was deposited on a flat plate and a combustion chamber of rocket engine and tested on a flame test stand. The samples were exposed to flame heating from the unpainted side, while on-line temperature measurement were taken on the side of sample covered with upconverting paint. Luminesce signal was measured after sample cooled off with use of dedicated setup including photospectrometer and transmit-receive probe mounted on a traversing system. The results show no paint degradation for temperatures up to 1200 °C. Two-dimensional surface temperature profiles were successfully reconstructed off-line, demonstrating good agreement with pyrometric measurements. The developed methodology achieved high spatial resolution (on the order of 1 mm) and temperature measurement uncertainty below 10 K at temperatures above 1000 °C. These results indicate that the proposed approach can serve as a valuable complement to standard temperature measurement techniques in rocket engine testing.