THE HARD START PHENOMENA IN HYPERGOLIC ENGINES VOLUME III. PHYSICAL AND COMBUSTION CHARACTERISTICS OF ENGINE RESIDUES

摘要

It has been established that the physical characteristics of the engine residues as well as their combustion characteristics are signifi-cant in establishing explosion hazards within these RCS engines. The residue viscosity and surface tension play a major role in the formation of deposits of these materials necessary to constitute explosive systems. After having measured the viscosity and surface tension for hydrazine nitrate solutions in both water and hydrazine, one can then estimate the nature of the deposits under various engine operating conditions.nIt also has been established that hydrazine nitrate does not thermally dissociate sufficiently rapidly below its explosion decomposition limit to provide a means for removal of this material by heating the engine and re¬moving the HN faster than it is being formed. Thin film detonation studies have demonstrated that relatively thin films of HN/H2H4 solutions can be detonated when suitably initiated. Although the detonation of the film per se does not probably destroy an engine, the gas pressure resulting from the explosion can. Impact sensitivity studies indicate that HN is not particularly sensitive. Although it was demonstrated that these films can detonate in situ, it was subsequently shown that the combustible material deposited on the engine walls is explosively burned after removal from the wall by a heterogeneous detonation in the gas-phase. Although the presence of a low velocity detonation in the thin film studies suggested the possi¬bility of cavitationally induced detonation initiation, no evidence was found to indicate that cavitated HN/N2H4 solutions are shock, sensitive.