ENVIRONMENT-FRIENDLY COMPOSITE PROPELLANTS BASED ON AMMONIUM DINITRAMIDE

This paper gives an overview of new composite propellants with environment friendly ingredients investigated at Fraunhofer ICT which is believed to lead to a new generation of high performance halogen free(ammonium perchlorate free) propellants. In particular, two formulations, which can be prepared from commercially available substances, were characterized, tested and compared to the actual state-of-the-art AP/HTPB/Al in a small-scale motor campaign. The HISP project mainly focused in obtaining maximum performance, and this led to an ADN/GAP/Al propellant. It revealed stable combustion and high performance but high burning rates in the order of 24 mm/s at 7 MPa, improvable mechanical properties and some concerns about the shock sensitivity. The aim of GRAIL was to overcome these drawbacks introducing the low burning ammonium nitrate as a second oxidizer accepting some specific impulse losses. The output was an ADN/TILM/PSAN/GAP/Al propellant. The burning rate was reduced to around 9 mm/s at 7 MPa and the shock sensitivity test was passed. The mechanical properties were still poor but can be improved by coated oxidizer particles. The use of a dual-oxidizer let the pressure dependence of the Vieille's law rose till 0.6, which is borderline for a stable function of a rocket motor. Unfortunately, no ballistic modifier exist for ADN propellant up to the present day, but alane as a high-energy metallic fuel is able to adapt ballistic properties and could be a potential propellant ingredient if commercially available.