Abstract
Affordable small satellites need affordable propulsion systems. The primary objective of this research was to investigate cost-effective propulsion system options for small satellites. The research comprised four interrelated goals: Identify key cost drivers for spacecraft hardware. Characterise propulsion technology costs. Characterise propulsion system costs. Evaluate and compare the cost-effectiveness of system options. Each of these goals was attained. Important results and conclusions emerged. To begin with, key spacecraft hardware cost drivers were shown to occur during each phase of a mission—definition, design and acquisition—and a process for resolving them was advanced. Furthermore, propulsion system costs were shown to include far more than performance and price. A new paradigm for understanding the total cost of propulsion systems was defined that encompasses nine dimensions— mass, volume, time, power, system price, integration, logistics, safety and technical risk. This paradigm was used to characterise propulsion technology options. From this effort, hybrid rockets emerged as a promising but underdeveloped technology with great potential for cost-effective application. To evaluate this potential, a dedicated research program was completed during which a hybrid motor was designed, built and tested using 85% hydrogen peroxide as oxidiser and polythene as fuel. The basic concept for a hybrid upper stage was proven. Excellent combustion performance was measured and characterised. Real total costs for future small satellite applications were assessed. This research demonstrated that hybrid rockets offer a safe, reliable upper stage option that is a versatile, cost-effective alternative to solid rocket motors. In addition, despite negative industry bias, hydrogen peroxide proved itself as a safe, effective oxidiser for hybrid and mono-propellant applications. The characterisation of propulsion system costs led to a complete design case study for a minisatellite aimed at the most cost-effective solution. It was shown that by focusing on the key cost drivers and trading among the cost dimensions, a truly versatile, cost-effective system design can be achieved. Finally, an innovative technique was derived to parametrically combine the diverse cost dimensions into a useful, quantifiable figure of merit for mission and research planning. Overall, it was shown that the most cost-effective solution is found by weighing all options along the nine dimensions of the cost paradigm within the context of a specific mission. Overall, the research advances the state of the art of hybrid rocket technology specifically, and satellite engineering in general.