Sounding rockets are used in various research applications such as micro-gravity research, re-entry experiments and atmospheric measurements. They provide a low-cost alternative to orbital test platforms. A recent development in the field of sounding rocketry has been the development of steerable upper stages to enhance these capabilities.

To bring this capability to T-Minus Engineering and its miniaturised sounding rocket, the Barracuda, the development of an upper stage for this rocket was commenced. One of the key subsystems of this upper stage is propulsion system. This thesis addressed the design, modelling and mass-optimisation of this upper-stage propulsion system.

Based on previously developed technologies within T-Minus Engineering, a high-test peroxide and gasoline thruster was designed, utilising catalytic decomposition of the peroxide to auto-ignite the propellants while also using the peroxide regeneratively cool the combustion chamber. The outcome of this project will further guide the development of bi-propellant thrusters at T-Minus Engineering.

Solid rocket motors power sounding rockets and their thrust profile are determined mostly by their internal geometry. This study investigates the effect of the changes in internal geometry by changing the aspect ratio, truncation and elongation of grains in multiple BATES grain solid rocket motors. BATES grains are propellant segments in a thick-walled cylinder shape. Longitudinal effects, like erosive burning, augment the burn rate over the motor length changing the thrust profile. As part of the thesis, a model was made accounting for longitudinal variation both in the grain regression and gas flow. This model was validated through data from T-Minus Engineering measuring the pressure at the forward closure. With a sensitivity study, the effect of aspect ratio and length was researched. This resulted in a recommendation for geometry changes of the DART booster of T-Minus Engineering B.V. . Furthermore, additional validation data was acquired of static pressure along the length of the motor, instead of single-point measurements, to provide better validation of one-dimensional models. This was done using a non-invasive and inexpensive method using strain gauges on the chamber.