Performance dependency of 120 mm mortar on ambient temperature conditions

In this study, the results from two series of test firings are analyzed to determine the effect of ambient temperature on the overall performance of the 120 mm mortar system, using an instrumented mortar simulator (IMS). The IMS is equipped with pressure transducers at multiple axial and circumferential locations along the tube, and the muzzle velocity of the projectiles is measured with two separate radar systems. A total of 147 firings were conducted at -45, 21, or 63°C with various charge increment and flash tube configurations. Previous flash tube and ignition cartridge component tests conducted by this research team have demonstrated that the venting of flash tube products into the granular propellant bed of the ignition cartridge is highly nonuniform; therefore, about half of the firings were performed with mortar rounds whose ignition cartridge contained a flash tube modified to reduce this nonuniformity. In this way, the impact of the modified flash tube on the overall performance of the mortar system can be studied as well as the initial temperature effect. It was determined that the sensitivity of the muzzle velocity to the initial temperature is essentially constant throughout the range of temperatures tested, though the standard deviation of the muzzle velocities measured for the -46°C firings is approximately double that for the 21 and 63°C firings. The flash tube modification was found to have a significant effect only for the -46°C firings, where it resulted in reduced muzzle velocity and reduced standard deviation of muzzle velocity.