Design and experimental research of a sub-Newton N₂O monopropellant thruster with inner-heater

Nitrous oxide (N₂O) is a green propellant with excellent application prospects. A sub-Newton N₂O monopropellant thruster with inner-heater and a N₂O self-pressurization stable supply system with regenerative heat compensation are designed in this paper. The experimental research of the thruster is described, including measurements of preheating power, activation temperature, vacuum thrust, specific impulse, life-span and pulsed operation performance. By inserting the heater into the catalyst-bed, preheating efficiency of the heater is significantly improved compared to the thruster with outer-heater. Thus, the preheating power demand of the thruster is successfully reduced to around 10 W. The mean vacuum thrust of 322 mN is attained and the corresponding specific impulse reaches 162 s at the mass flow rate of 0.2 g/s. Successful activation temperature of 523 K is achieved, and the activation performance of the thruster is affected by the loading factor. A long term hot-firing test longer than 12000 s is attained. The pulsed operation performance of the inner-preheating thruster is also studied by measuring chamber pressure. Impulses with different magnitudes are produced by adjusting the opening duration of the control valve. A minimum impulse of 81 mN∙s is attained. Finally, the performance of the thruster is evaluated by comparison with other thrusters of the same type. The results indicate that the proposed thruster with inner-heater is superior in terms of preheating power, activation temperature and specific impulse performance.