Development Status and 1U CubeSat Application of Busek’s 0.5N Green Monopropellant Thruster

The monopropellant community has been pursuing low-toxicity alternatives to hydrazine for the past two decades. One of such “green” monopropellants, known as AF-M315E, has caught attention of many by offering both improved performance and handling safety. A 0.5N-class, AF-M315E micro thruster was recently developed by Busek that can deliver \u3e220sec vacuum Isp. Both steady-state and pulsed firings were demonstrated. The thruster, when cold, requires a small amount of pre-heating power to start which is no more than 12W or an equivalent of 1.6W-Hr energy input. The thruster is complemented by a novel piezoelectric microvalve that needs less than 200mW to operate and weighs a mere 67g. The valve features an all-welded, all-titanium wetted design for long-term propellant compatibility. It is rated for 1200sccm GN2 max flow and 1.5×10-4sccm GN2 leak rate. The valve passed environmental testing before being integrated into the thruster, and together they demonstrated a minimum impulse bit of 0.036N-sec. Busek is currently developing a 1U CubeSat propulsion system centered on the integrated 0.5N thruster and microvalve. The system is designed to be self-contained and fully loaded with propellant, which allows for simple spacecraft integration and reduced operating cost

Development of Busek 0.5N Green Monopropellant Thruster

The monopropellant community has been actively pursuing low toxicity, green monopropellants for the past two decades. Of the large number of formulations developed, AF-M315E has received the most attention in the U.S. In comparison with hydrazine, AF-M315E offers improved Isp and density-Isp while being extremely stable and easy to handle. Despite the potential benefits, development of AF-M315E thrusters has been slow due to the lack of suitable catalysts. Busek is pioneering an alternative catalytic reactor to address such issue. Busek has developed a 0.5N-class AF-M315E thruster that has demonstrated 20+ minutes of cumulative life and consistently performs at a c* efficiency in the range of 89-93%. A piezoelectric microvalve for the 0.5N thruster has also been developed. It is superior to state-of-the-art solenoid valves of similar flow level as it requires only 0.5W of power and weighs a mere 67 gram. Potential commercial applications for the 0.5N thruster are abundant, including but not limited to primary propulsion for NanoSats and ACS propulsion for SmallSats. Scaling up the thruster is feasible and will create more opportunities to compete with legacy hydrazine thruster systems in the future