OPTICAL CHARACTERIZATION OF THE LASER-INDUCED IGNITION SPARK IN A CRYOGENIC ROCKET COMBUSTOR

Abstract

Experiments at the European Research and Technology Test Bench P8, located at the DLR Institute of Space Propulsion, were carried out to validate the feasibility of laser ignition on the research rocket combustor "BKA". Propellant injection in BKA was carried out via 15 coaxial injectors with liquid oxygen as oxidizer and gaseous hydrogen or gaseous methane as fuel. Crucial parameters such as the equivalence ratio between oxidizer and fuel (ROF), plasma temperature, ignition delay time, and breakdown threshold can be determined using appropriate methods for plasma analyses. The research rocket combustion chamber "Brennkammer A" (BKA) was equipped with a laser ignition facility and with the opportunity to evaluate the optical emission of the ignition spark. Furthermore, a laboratory-scale cavity, filled with well-defined samples, was used to analyze the plasma lifetime of gaseous samples of known properties. Thus, the local ROF inside the ignition kernel was derived.