Experimental study on the effect of rocket nozzle wall materials on the stability of methane

Sammanfattning: There has recently been an increased interest in methane as a rocket propellant due to its physical properties as well as the possibility of in-situ resource utilization in places like Mars. As part of ESA’s Future Launcher Preparatory Program, KTH in cooperation with GKN Aerospace has started the MERiT program, which seeks to study the characteristics of methane under conditions found in rocket nozzle cooling channels. In particular, the current work examines the influence of different wall temperatures, fluid flow rates, and fluid residence times on methane pyrolysis due to the catalytic properties of nickel based metals. Pyrolysis is the thermo-catalytic decomposition of methane, which results in the creation of hydrogen and solid carbon in the cooling channels. This can affect the performance of the rocket engine, the cooling channels, as well as the lifespan of the engine, which makes the process important to quantify when designing highly reusable engines. A chemical kinetics computer model has been developed, which has been used to quantify the most important parameters for methane pyrolysis. Based on these results, a small-scale pyrolysis experimental setup has been developed and used to characterise methane pyrolysis for different material temperatures and gas flow rates. The experimental setup has been proven to work and consistently provide pyrolysis at temperatures between 600 ◦C to 700 ◦C, although more work on the data collection side, in particular with regards to a gas chromatograph and a scanning electron microscope, is required to quantify and compare different experiments.