Boron Combustion Characteristics in Ducted Rockets

Abstract

A test program was performed with the objective of experimentally investigating the boron reaction characteristics in a ducted rocket by systematically varying the primary chamber conditions.

In order to vary the primary chamber conditions a test device was used which burned boron powder and gaseous propellants (hydrogen or carbon monoxide, oxygen and nitrogen) in the primary motor. The reaction characteristics in the secondary chamber were observed by color photography through quartz windows of the secondary chamber. In the tests the following parameters were varied: (1) primary chamber temperature, (2) mixture ratio of the gaseous fuel in the primary chamber from below stoichiometric to above stoichiometric at different primary chamber temperature levels in order to vary the afterburning capability of the gaseous exhaust in the secondary chamber, and (3) secondary chamber pressure.

At primary motor conditions which approximated propellants with high boron and low oxidizer/fuel content the boron particle temperature at the primary nozzle exit was not sufficient to initiate self-sustained boron combustion in the air. In order to farther heat up and cause ignition of the boron particles in the secondary chamber it was necessary to burn additional gaseous fuel in the secondary chamber. It was also demonstrated that the hot (probably reacting, but not ignited) boron particles were necessary for triggering the gaseous fuel ignition in the air.