Rocket plume /N2O4/MMH/ impingement on aluminum surface

Abstract

T combustion of bipropellant motors under high-altitude conditions using dinitrogen tetroxide and hydrazine fuels has been reported to result in the formation of nonvolatile residues. The partial oxidation of the fuel is particularly evident during the pulse mode operation of the motor where high-combustion temperatures are not attained. Two major problems resulting from the use of these restartable space environmental engines are the contamination of vehicle surfaces from bipropellant rocket exhaust products and the occurrence of large transient ignition overpressures, which could have deleterious effects on engine operation. The latter results from the sudden detonation of the combustion residues which had accumulated on the rocket chamber wall. Both problems result from the incomplete combustion of the oxidizer and the fuel. The major product from the partial oxidation of hydrazine type fuels by N204 has been identified as fuel nitrates. Although the chemical nature of the combustion residues has been studied by several investigators, no information is available on the particle size and distribution of residues in the plume. In this study, a polished aluminum bar was placed in the plume of a N2O4-monomethylhydrazine (MMH) bipropellant motor during pulse mode firings under highaltitude conditions to obtain the imprint of residues striking the metal surface at very high velocity.