Study into the Operational Characteristics of a Recoilless Rifle Mounted on Army Helicopters. Volume I. Experimental Investigation into the Effect of Suppressing Recoilless Rifle Back Blast Utilizing a Porous Diffuser and Deflections
Final rept. Oct 1972-Oct 1973
LOCKHEED MISSILES AND SPACE CO INC HUNTSVILLE AL HUNTSVILLE ENGINEERING CENTER
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The study was concerned with developing a method or device to reduce blast overpressure of a 105 mm recoiless rifle to permit its mounting on the outboard bomb shackle of a Cobra helicopter. Two devices were mounted at the nozzle breech of the rifle test weapon. The primary device built was a cylindrical porous wall shroud for which the porosity could be varied. The second device consisted of a pair of parallel flat plates. The flow field generated by a recoilless rifle firing presents a complex time dependent mixed flow problem involving the interaction of two gases with strong shocks. A method was developed using a time-dependent finite difference technique to numerically solve the unsteady inviscid adiabatic flow equations. Also included in the report is a development of a dense gas equilibrium thermochemical analysis program which can be used to predict the post combustion products of high chamber pressure combustion such as occurs in recoilless rifles and other armament. An inviscid flowfield analysis of the 105 mm exhaust plume is also described.