Characterization of a Nylon-6/Gaseous Oxygen Hybrid Rocket Performance with Hydrogen versus Methane-Based Torch Igniter System

Hybrid rockets have recently become a more and more desirable method for small satellitepropulsion, due to their lack of safety issues compared to their liquid and solid rocket counterparts. A major reason for this is because the fuel and oxidizer are both separated by distance and state when stored in a hybrid rocket. This also makes it relatively more difficult to ignite and start up the rocket. While many igniter systems have been invented, currently no reliable, self-igniting system has been flown. Recently, a Hydrogen-Oxygen torch was designed, built, and tested in UC Davis’ Energy Research Lab. Methane is typically used in torch igniters for lab-scale testing of hybrid rocket motors. A side-by-side comparison on the same igniter system between Hydrogen and Methane as the igniter fuel was done to investigate which, if any, fuel can exhibit better transient and/or steady state performance. Due to the higher heat of combustion, adiabatic flame temperatures and theoretical characteristic exhaust velocities when reacting with Oxygen, Hydrogen was found to have more reliable and repeatable ignition transients. The solid fuel regression rates were also found to be higher when using Hydrogen despite competition to burn with Oxygen between Hydrogen and the solid Nylon-6 fuel. These performance benefits come at the cost of being less volumetrically efficient than Methane as Hydrogen has a significantly smaller density at a given temperature and pressure.