Abstract:A high thrust ratio in a single chamber dual thrust motor is required to reach a peak velocity very quickly. To achieve a high thrust ratio in a single chamber dual thrust motor, a composite propellant grain, which acts both as booster and sustainer, based on HTPB/AP/Al (84% solid loading) with low aluminum content and having a burning rate of 25±0.5 mm/s at 7 MPa, was successfully developed. This was studied for viscosity build-up, mechanical and ballistic properties, followed by casting and curing as a single type propellant grain. The high burning surface area was created by making grooves of 3 mm width and 60 mm depth over the surface of the nozzle side of the grain while casting and a prototype, thus obtained, was static tested. The data revealed that a grain with one groove demonstrated a thrust ratio of 8, while two grooves, realized a thrust ratio of 30. The experimental thrust ratio values achieved are also in agreement with the predicted values of the thrust ratio of the same composition.