Hypergolic ignition of liquid fuel and liquid oxidizer in a rocket motor

In a research project carried by TUBITAK SAGE, Turkey's first operational liquid fuelled rocket motor has been designed, manufactured and tested. From the results of the thermochemical calculations, a bipropellant system was found to accomplish the desired thrust levels with acceptable mass flow rates of the fuel and the oxidizer. The feasibility analysis showed that hydrogen peroxide (H/sub 2/O/sub 2/), which can be obtained from the domestic market up to 70% concentration, could be used as the oxidizer. An alcohol based Ex-1 was selected as the fuel. Due to the low specific impulse (Isp) of the 70% H/sub 2/O/sub 2/, a distillation setup was bought and installed to increase the concentration up to 90%, which is also specified as the rocket-grade hydrogen peroxide. The liquid fuelled rocket motor has the following specifications: duration of 1 second, fuel and oxidizer tank pressures of 100 bars, chamber pressure of 70 bars, oxidizer and fuel mass flow rates of 10.3 and 2.6 kg/s, respectively. The liquid fuelled rocket motor is composed of the following parts: integrated combustion chamber and its nozzle, an injector, oxidizer, fuel and nitrogen gas tanks, and feeding systems consisting of pipes, flow and pressure control valves. The high-performance injector was an unlike triple impinging jets type injector with 40 injection ports for the fuel and 80 ports for the oxidizer. From the tests, it was observed that this injector provides well-atomized and well-mixed mixtures of fuel and oxidizer. Type of the ignition system is very critical in such systems. If a pyrotechnic igniter is used, timing becomes the most important factor. If fuel and oxidizer are injected just a few milliseconds before the igniter is activated, the igniter performance can degrade and ignites very late. Such a scenario ends with a detonative explosion and causes catastrophic damages. If the opposite happens, the nozzle exit cover opens before the fuel and oxidizer reach to the motor. In this case longer ignition delay may occur. Therefore usage of traditional igniters is quite dangerous and difficult in liquid fuelled rocket motors. Therefore, hypergolic ignition technique was preferred which means ignition without any extra effort. When some special metal salts and propagators are added to the fuel, ignition starts automatically just after it mixes with the oxidizer. To reach this goal, many metal salts and propagators were tested, and finally the best mixture and proportions were obtained. The best solution was tested in different ways and successful ignition tests were done. In this paper, the tests performed with various metal salts and propagators, laboratory test results, and rocket motor test results are presented.