Use Of An Instrumented 120mm Projectile For Obtaining In Bore Gun Dynamics Data

Use of an Instrumented 120MM Projectile for Obtaining In-Bore Gun Dynamics Data

Simulation work undertaken by DERA to investigate the dynamic behaviour of gun systems during firing has predominantly used the existing package of SIMBAD. In-bore behaviour of the projectile has had little experimental data to increase confidence in the modelling predictions. A programme of work was started in 1996 for the UK MoD with the aim of designing, building and firing a number of instrumented projectiles, the final objective being to obtain data with which to validate a model of the Challenger 2 MBT L30 gun system. The UK design consists of a 16 channels data-logger, which captures the information during in-bore motion together with a specially designed battery assembly. Data is stored on board and downloaded once the projectile has been recovered. Instrumentation consists of six accelerometers and six displacement transducers for the purposes of measuring overall projectile motion as well as in-bore balloting of the projectile relative to the barrel. Three projectiles were fired from a smoothbore 120 mm L30 gun system in March 2000 and retrieved using over-water recovery. The last round was fired with a muzzle velocity of 1550 m/s resulting in a peak acceleration of 42,000 g. All data-loggers and accelerometers survived the launch along with a number of the displacement transducers. Although the data gathered proved insufficient for full model validation purposes, important lessons were learnt regarding instrumentation components, particularly battery design and assembly. These lessons are being incorporated into a series of instrumented firings planned for a 90 mm electro-magnetic launcher.

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The Development of a 'Hard-Wire' Technique for Obtaining In-Bore Data

An instrumentation system has been developed which is capable of obtaining high frequency response data from a projectile during gun launch. The system uses a 'hard-wire' technique to provide a direct recording path from an instrumented projectile. The technique has been used many times and has proven to be very reliable. A one-channel, and a two-channel system have been designed and tested which can be used with various projectiles. Data recorded using these systems agrees well with theoretical calculations. (Modified author abstract).