Exploring potential candidates of alternative solid hydrocarbon propellants for cold-gas thrusters

Cold-gas thrusters play a vital role as a subsystem in satellite operations facilitating space maneuvers in numerous missions. Achieving optimal propulsion necessitates not only continuous development of thruster design but also an exploration of novel propellant options to enhance overall performance. While an ideal propellant remains elusive, many studies have identified alternative options to replace commonly used inert gases. Choosing a solid-state propellant offers benefits such as the absence of a pressurised tank and sloshing effect. Hydrocarbon propellants are advantageous due to their non-corrosiveness and abundance as organic compounds on Earth. The sublimation process for manipulating solid propellants typically requires only a few watts, making it suitable for low-power budget missions. This work presents five solid hydrocarbon propellants for cold-gas thrusters, three of which have not yet been experimentally explored. The comparison between various aspects, including mass flow rate, power consumption, and several key performance parameters, is discussed. The measured mass flow rate is a function of the species and temperature, following the trend of the vapour pressure. The power consumption for all propellants only depends on the required heating temperature as they share similar thermal properties. The thrust generated by each propellant is comparable and linearly proportional to the mass flow rate when the flow is choked. Specific impulse remains relatively constant across different mass flow rates due to the strong correlation between thrust and mass flow rate. The thrust-to-power ratio is generally comparable among the propellants, except hexamine, which demands more power at higher operating temperatures due to increased heat loss. Among these alternatives, camphor emerges as the most promising candidate due to its low power consumption, thrust generation, and mass efficiency. On the other hand, naphthalene offers the best in terms of its superior thrust-to-power ratio and cost-per-kilogram advantage.