Heat Flux Estimation from Thermocouple Data in a GOX/GCH4 Capacitive Rocket Engine Combustion Chamber

This paper presents the results of an experimental test campaign conducted to evaluate the performance of a GOX/GCH4 capacitive combustion chamber developed within the framework of the Breeze project by The Exploration Company. The thruster is designed for reaction control purposes on Hilal, a space vehicle conceived for lunar missions. During the campaign, the combustion chamber completed 47 hot fire tests under varying operating conditions, including different combustion pressures, mixture ratios, and ignition sequences. The test matrix comprised both short duration burns for ignition characterization and longer burns under nominal conditions to assess thermal behavior. The injector plate design enables gaseous film cooling; however, the chamber's intrinsic heat-sink capability allows long-duration burns even without active cooling. Thermocouple measurements were acquired during the tests to support wall heat flux estimations, which are compared against numerical simulations in this work. Simplified methods for computing wall heat fluxes are described and implemented. The results provide valuable insights for the design and optimization of GOX/GCH4 propulsion systems and contribute to the development of reliable and reusable components for future space missions.