Conceptual design of a low-pressure micro-resistojet based on a sublimating solid propellant

• A propulsion system, using water stored in frozen state as propellant, is presented.
• The vapor pressure of ice is used as the only propellant feeding method.
• A conceptual design of the system is theoretically and numerically investigated.
• Estimated performance meets the typical requirements of small satellite missions.
• The system characteristics are particularly promising for nano-satellite and cubesat applications.

In the current and future trend towards smaller satellite missions, the development of a simple and reliable propulsion system with performance and characteristics in line with the typical requirements of nano-satellites and CubeSats plays a crucial role for enhancing the capabilities of this type of missions. This paper describes the design of a micro-resistojet using water stored in the frozen state (ice) as propellant, operating under sublimation conditions at low pressure. The low operating pressure allows for using the vapor pressure of ice as the only method of propellant feeding, thereby allowing for extremely low thrust and electric power usage. The results of an extensive set of numerical simulations for optimizing the thruster geometry in terms of power ratio and specific impulse produced are discussed. In addition, the design of the complete propulsion system is described. It makes use of a limited number of moving parts and two power sources, one in the thruster to increase the propellant temperature and one in the tank to maintain the propellant storage conditions. Results show that the proposed design represents an alternative option capable of meeting the typical requirements of small satellite missions by means of an intrinsically green propellant such as water, with the pressure inside the system never exceeding 600 Pa. Optimization results showed an optimum thrust to power ratio in range 0.2–1.2 mN/W for an expansion slot aspect ratio of 2.5.