Green impulse for advanced fuels

Rocket propellant from nitrous oxide and hydrocarbons

Hydrazine (N2H4) has been used in the feld of orbital propulsion (such as for satellites, probes and landers) since the 1960s. The use of hydrazine has several advantages: the propellant can be stored for long periods of time, is effcient and can be utilised in simple propulsion systems by using a catalyst. Despite all these benefts, hydrazine has a major drawback: it has adverse health effects meaning that extensive safety measures are required when fuelling a spacecraft, which in turn leads to increased costs.

Several so-called ‘green propellants’ are therefore being investigated worldwide. DLR is examining various propellants consisting of either ammonium dinitramide (ADN), hydrogen peroxide (H2O2) or a mixture of nitrous oxide and hydrocarbons (HyNOx). The latter propellant – a nitrous oxide/hydrocarbon blend – comprises so-called ‘pre-mixed monopropellant’. This means that the oxidiser and propellant are mixed and liquefed under pressure in a tank. However if such a mixture unintentedly ignites, it would be accompanied by a sudden reaction. If the mixture is burned in a rocket engine, there is a danger that a flame flashback happens in the propellant supply line and the tank via the injection system. In a spacecraft, this would have catastrophic consequences for the entire system and must therefore be prevented at all costs. In order to use this propellant safely and reliably, the development and use of optimised flame arresters is essential. DLR scientists are testing and analysing these flame arresters within the exhibited ignition measurement section. Using the knowledge gained, flame arresters will then be designed and used for a DLR model engine.

German Aerospace Center (DLR)
Lukas Werling · E-Mail: ·