New Delhi: A large case-bonded rocket motor of 12 T class was static tested successfully earlier at Advanced Centre for Energetic Materials (ACEM), Nasik.
The composite case rocket motor was designed and realised indigenously and belongs to the Mark III version.
The main objective of the static test was to validate the design for optimised EPDM (Ethylene Propylene Diene Monomer (M-class) rubber) insulation where a reduction of 80 kg was carried out compared to the Mark I version, and to evaluate the augmentation factors. The motor has a submerged nozzle with provision for actuation, which is also realised indigenously.
The 12 T class solid rocket motor is one of the largest rocket motors with EPDM liner in a composite casing being processed in India. The propellant is based on hydroxyl terminated polybutadiene (HTPB)—Ammonium Perchlorate (AP)—Aluminium (Al)-based composition.
The complete process technology for realisation of the solid rocket motor has been developed and matured at ACEM. The processing involves critical steps such as mixing of propellant in multiple-bowl program, viscosity management during the long casting period, confinement based pressure curing without application of inert gas etc. Compliance with stringent quality requirements ensured a defect free propellant grain as revealed by the non-destructive inspection.
The static testing of motor involved data acquisition of 34 channels for temperature, 27 channels for strain, 2 channels for thrust, 4 channels for pressure in addition to instrumentation for displacement, pyro currents, actuator signals and high speed videography. The data were recorded and displayed in real time along with the prediction curve. Pressure-time and thrust-time profiles matched the prediction data.
The motor produced maximum thrust of approx. 500 kN and maximum pressure of 7.25 MPa and the test duration was 74.4 seconds. Strain, temperature and displacements were within the test specifications. Based on the data recorded, the optimised insulation thickness was validated.