Development of a catalytic hydrogen micro-propulsion system

In the present study, the feasibility of a catalytic hydrogen micro-propulsion system suitable for providing thrust for micro-satellite attitude control and orbit transfer is demonstrated and examined experimentally and numerically. The effects of major design and operational parameters of fuel/air flow rate, equivalence ratio and nozzle contraction ratio on the thruster performance are investigated. For ease of observation and numerical comparison, a platinum catalytic tube with an inner diameter of 500 μm and length 1 cm is used as the reactor and is tightly inserted into a quartz tube with a convergent nozzle made of quartz of different contraction ratios. For most of the cases tested in experiments, catalytic surface reaction occurs near entrance of the platinum tube due to the high diffusivity and high surface reaction rate of hydrogen. With increasing fuel concentration, the transition point from kinetic-controlled reaction to diffusion-controlled reaction moves further downstream. When the fuel velocity is increased, the hydrogen may not be consumed completely because of insufficient residence time. However, the unburned hydrogen has been heated, by upstream surface reactions, such that gas phase autoignition may occur in the recirculation zone just down stream of the platinum tube. The catalytic hydrogen micro-thruster developed in this study can self-sustain and provide a maximum thrust of 7 mN, which is suitable for precision attitude control of micro-and pico-satellites.