Selection of the method for determination of ignition delay of hypergolic propellants

Ignition delay is one of the most important parameters characterising hypergolic propellants. This parameter has a strong im-pact on thruster operation, especially during the cold start. Ignition delay influences the intensity of pressure rise and its peak values during the start of a thruster. High-pressure levels cause stress inside the chamber wall, which directly affects durability and safety. One of two measurement techniques is usually chosen to determine the ignition delay: visual and pressure-based methods. Visual methods are based on high-speed imaging and subsequent image analysis. In the pressure-based method, the pressure trace is analysed. In this study, both techniques were used together and compared in terms of ignition delay determination of hypergolic propellants igniting during the drop tests. The advantages and disadvantages of both techniques were indicated and described. In the setup used in the study, the visual method was found to be more accurate and reliable.