A laser technology for measurement of solid propellant transient burning rates during rapid depressurization

A laser technique of transient burning rate measurement of solid propellant has been investigated. A photocell detects a laser beam passing through th e propellant strand, and the cross-section of the laser beam is regulated s o that the laser energy varies linearly along the height of the strand. Usi ng a photo-controlled depressurization system, it is desirable to set up th e starting time of depressurization in advance, and the initial rate of dep ressurization can be easily reproduced. Experimental results show that: (1) for a short time after depressurization begins, the burning rate remains u nchanged; (2) during the depressurization process, the burning rate, while continuously decreasing in magnitude, exhibits low frequency oscillations; (3) the amplitude and the frequency of the burning rate oscillations, refer enced to a smooth rate-time curve, increases as the depressurization rate i ncreases: (4) for a short time after depressurization, the transient burnin g rates is higher than the steady state burning rate at the corresponding p ressure, and then the transient burning rates oscillate around the quasi-st eady rate. The experimental dynamic burning rates are compared with those a vailable by microwave and capacitance methods. The discrepancies in the thr ee experimental results have been discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.