Design of a Solid Rocket Motor for a Transonic Research Vehicle

Abstract

Hypresearch is a project that has been under development with the collaboration of ATG Europe, TU Delft, TNO for the past 7+ years. The eventual goal of the project is to fly a hypersonic research vehicle at Mach 6 (2 km/s) at an altitude of 42km for a continuous time interval of 360 seconds. Before this goal can be attained, however, several milestones must be achieved, the first of which is the testing of aircraft controls during launch in the transonic phase. The current Hypresearch mission envisions a first-stage separation and second-stage ignition at transonic velocities, hence it is important that all crucial systems function properly in the transonic regime. To achieve this, the Transonic Research Vehicle (TRV) project was set up. The subject of the thesis was the propulsion system of the TRV-1, with the goal of accelerating a glider payload to Mach-2 in vertical launch, and testing the payload separation mechanism while decelerating through the transonic phase. The goal of the thesis project was to design a solid rocket motor for the TRV-1, and to verify its performance through simulations and static motor tests. Firstly, the project goal was broken down into a series of requirements. Main requirements included the velocity (Mach 2) to be attained by the vehicle, the mass (6.25kg) and pre-defined shape of the glider, as well as limitations on the acceleration (40g) and resources in terms of cost, manpower, and materials/facilities accessible to students. The design process started with the preliminary design during which two design concepts were selected based on ballistic performance and trajectory simulations. In the detailed design phase, materials were selected and a detailed manufacturing, assembly, integration, and testing plan was drafted. In order to test the material properties of the selected design on a limited resources budget, a scaled-down test method—the so-called SGM or Single Grain Motor method was developed. Following a series of SGM tests, the final full-scale test configuration was selected, and several defects of the design were eradicated. However, during the SGM test campaigns, and the subsequent full-scale test, it was discovered that the actual performance in terms of total impulse was notably lower than that predicted by the model. Following the test campaigns, an investigation identified the causes of the performance loss to be excess water absorbed by the propellant during the curing process. A manufacturing method to prevent this in the future, as well as a design iteration of the motor to be performed in order to attain the mission goal, was recommended.