DEVELOPMENT OF A DIRECT INJECTION GAS-HYBRID ROCKET SYSTEM USING GLYCIDYL AZIDE POLYMER

Abstract

The development of a direct injection gas-hybrid rocket system using glycidyl azide polymer (GAP) as a solid fuel for the thrusters of very small satellites is described. Furthermore, a performance evaluation and the combustion characteristics of the propulsion system are presented. GAP is capable of self-decomposition and generates fuel-rich gas, which makes it viable as a fuel gas-hybrid power source for rockets. GAP also has a higher density compared to other polymers such as hydroxyl-terminated polybutadiene (HTPB), and the high-density specific impulse enables the development of a small thruster system. Gaseous oxygen was used as the oxidizer for the first test of the gas-hybrid rocket. The gas generator was tested using a 60 mm diameter motor with an end-burning GAP grain. The experimental combustion pressure was initially set at 1 MPa, and adjustments to the oxygen flow were made based on the test results of the gas-generator combustion. The resulting ignition smoothness and combustion stability were observed. Excellent characteristic velocity efficiency (90%)—larger than that of a classical hybrid rocket motor-was obtained. Moreover, quenching of the GAP gas generator was achieved after the oxidizer injection was stopped, which implies that this system has the capability of re-ignition.