This study demonstrated the successful operation of a new liquid oxygen-gaseous methane rocket engine test facility to characterize the performance of a swirl coaxial injector. In support of safe system functional development, an oxygen compatibility and hazards assessment was completed to identify and minimize operational risks. Facility changes were implemented to create a more fault tolerant system. Major upgrades included initiatives to manage the oxygen risk and mitigate specific oxygen ignition mechanisms. Oxygen compatible materials and facility configuration changes were instituted to achieve safer experimentation. The demonstration testing of the cryogenic propellant system employed the swirl coaxial injector element in an ongoing program to study liquid oxygen-methane injectors. The injector performance was evaluated by experimental determination of combustion efficiency. The combustion efficiency determined for the injector arrangement during the single operational test was 80% with a 95% confidence systematic standard uncertainty estimate of 4%. Random uncertainty estimation must await repeated tests.