EXPERIMENTAL STUDIES ON LAUNCH DYNAMICS OF SLANT LAUNCHED SURFACE TO AIR FLIGHT VEHICLE

Surface to air flight vehicles are launched at low slant angles to intercept and neutralize low flying attacking enemy aerial targets like fighter aircrafts, helicopters which are on cruise missions. These flight vehicles are generally housed in hollow launch canisters which are used for storage, transportation and launching through mobile launchers. The lateral signature of launch canister is chosen such a way that more number of canisters can be accommodated per one launcher. To accommodate the flight vehicle in launch canister, it is accordingly configured with foldable wings and fins. New designs of flight vehicle, canister and launcher system need to be verified for all the interfaces and the controllability of flight vehicle when it clears the canister. While coming out of canister at low elevation launch angles, the flight vehicle starts deviating from its intended trajectory due to the combination of gravitational force, thrust misalignments, aerodynamic forces, low initial thrust, lateral shift of centre of mass, deployment forces of wing and fin etc. To record actual launch dispersions and to remove any hidden uncertainties in new designs, a live firing with a full scale short duration flight vehicle was undertaken. A propulsion system was specifically designed to function for a small duration simulating the actual thrust time profile of that of the full scale rocket motor system for that initial duration. One short duration rocket motor system was static tested to verify the design parameters and another one was integrated with the rest of the actual flight hardwarethus realizing in to a full scale short duration flight vehicle. The geometry, length, weight and centre of mass, launch shoe interfaces etc of short duration flight vehicle was ensured as that of actual full scale flight vehicle. Actual launcher, actual canister and short duration flight vehicle were appropriately instrumented. Parameters like vibration, shock, accelerations, body rates, pressure, temperature, strain, acoustic etc. were recorded in real time during the live firing. The motion of short duration flight vehicle, its attitude, unfolding of wings, unfolding of fins etc were recorded through high speed video sensors. Variations of parameters recorded in actual dynamic conditions were compared with estimated parameters. Some useful inputs have been obtained for improving the design for low elevation launch angle missions. The effects of these improvements have been subsequently verified through simulations and full scale live flight tests.