Typical Strand Burner

By having a surge tank attached to the strand burner, only a very slight pressure rise occurred as a result of the burning of the strand. Consequently, burning occurred at essentially constant pressure. This method has also been adopted for use with strands which have been cut from sheet proplnt and even strands sliced from sections of cast grains. Fig 1 shows a typical strand burner assembly... 

The burn rates of propellants are determined in a strand burner (Crawford bomb/ acoustic emission technique) at various pressures using an inert gas for pressurization. This data, when fitted in the empirical relation r = a.P" provides the pressure index n and the coefficient a. This technique is highly useful as a first approximation and is extensively used for propellant screening and quality control. The bum rates at different pressures are also determined by static testing in a ballistic evaluation motors (BEMs) and burn rates are typically scaled up from 1-5% for full scale motors. 

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