One of the most important parts of the engine is the oxidizer supply. It consists of three high pressure tanks containing the liquid nitrous oxide. Every tank can be separately connected with a ball valve. With these 3 tanks different burning times can be achieved and larger engines with higher overall thrust can also be adapted. For redundancy and safety reasons two solenoid valves controll the oxidizer supply to the engine. The volumetric flow is measured with a venturi tube. Complemented with the density of the liquid nitrous oxide the mass flow during a test is calculated. With this setup and some more pressure sensors all relevant parameters of the oxidizer supply, meaning pressure losses over the valves, venturi tube and injector can be determined.