Performance of Gas-Generator-Type Hybrid Thruster Using a Laser Ignition

This paper describes the design and tests of 0.4-N class gas-generator-type hybrid thruster using laser ignition for onboard propulsion systems. Conventional hybrid rocket engines have advantages such as variable thrust and combustion interruption. However, the oxidizer-to-fuel ratio (O/F) is varied from the optimal value during thruster firing because the fuel-grain cavity is enlarged owing to combustion, and this reduces specific impulse. Hence, we propose a gas-generator-type hybrid thruster using laser ignition for onboard propulsion systems. In the thruster, the gas generator produced fuel-rich combustion gas using the oxidizer and solid fuel at a constant mass flow rate to maintain O/F at the optimum value. The semiconductor laser is used to ignite the solid fuel for enabling the multi-start capability. The firing tests showed that the use of hydroxyl terminated polybutadiene/ammonium perchlorate/carbon black=50/50/0.5 wt% allowed the gas generator to produce the fuel-rich combustion gas at the target mass flow rate, and that combustion was interruptible by discontinuing the oxidizer supply.