Cold gas propulsion microthruster for feed gas utilization in micro satellites

Micro spacecraft, which have gained huge popularity in the last decade, are termed as “CubeSats”, a well-known class of small satellites. The fast growing functionality and popularity of CubeSats have helped researchers push technology demonstration towards efficient performance and reliability needed for commercial and governmental applications. Keeping in mind the increasing space debris, dependence of satellite life on fuel, and the use of fossil fuels as propellants, recent efforts are being made to develop a cold gas propellant-based (CGP) micro propulsion system. The CGP system has various merits, namely, non-toxicity, easy to use, and low leakage concerns over other propulsion systems. Liquid propellant-based propulsion requires a liquid feed system, which uses pressurized gas (such as helium, argon and nitrogen) to pressure-feed liquid to the combustion or vaporization chamber so as to produce thrust. But once the liquid propellant is depleted, the pressurized gas is unusable while the system runs out of fuel. Thus, the proposed CGP system being studied, apart from being used as a normal cold gas propulsion system, also offers the advantage of being used as a propulsion system for a liquid fueled system, in the event the liquid fuel runs out. The present work reports on cold gas micro thruster development, utilization of feed gas in a liquid fueled thruster, and the experimental study on the CGP system in simulated vacuum conditions and under a range of pressure conditions. Pressure in the pressure feed gas system for a 1–50 kg category of satellites varies from 4 to 8 bar depending on the mission requirement. The pressure reduces as the liquid propellant gets exhausted. The experimental results are used to validate a computational fluid dynamics model of the system. Thrust values are obtained between the micro to milli-Newton range so as to fulfil the requirements of attitude and station keeping for CubeSats in the 1–50 kg dry mass range. Under vacuum conditions, we obtained thrust values of 0.8 mN at 1 bar feed pressure to 2.24 mN at 4 bar feed pressure. These thrust values are nearly twice those achieved for sea level tests for the corresponding feed pressure. Furthermore, the parameters such as Mach number, velocity vector, pressure, temperature, specific impulse, and nozzle efficiency are studied and reported for atmospheric and vacuum conditions.