Advanced propellants for satellite applications
Satellite propulsions are still operated with liquid fuels, like dinitrogen tetroxide, hydrazine, mono-methyl hydrazine (MMH), asymmetric dimethyl hydrazine (ADMH); they are toxic but storable for extremely long periods and ensure stable propulsion features. The European REACH regulation, in force since 2007, has listed hydrazine as one of the agents that maybe prohibited in the near future throughout Europe, the reason being its harmful effect on human health and the environment.
To compensate for this element we need alternative and progressive new propellants, the so-called “green propellants” enabling the same or even better performance features in propulsion systems. Of course, they should be considerably less harmful for individuals and the environment. There may no longer be a need for full-body protective suits with external air supply and evacuating the facility for refuelling as compared to the current hydrazine use.
Liquid advanced propellants are scrutinized with respect to their rheological flow, vaporisation and combustion properties. Various vaporisation concepts (with different injector types and geometries) are subject to optical measurement to identify their appropriateness so that suitable propellant conditioning methods can be developed for several types of propellants. Research and development activities on effective combustion chamber processes are dedicated to explore combustion and heat development in the combustion chamber. For this purpose, experiment results and semi-empiric models are applied to evaluate, analyse, develop and verify propulsion systems.
For example, the DLR strategy project “Future fuels” focuses on combustibles that may be used in energy supply, traffic and aerospace technology. This projects aims at identifying, analysing, evaluating and testing prospective propellants to replace hydrazine as rocket propellant with a pre-mixed fuel combination of nitrous oxide and ethene.