Low-Cost, High-Efficiency HAN/HEHN-Based Multi-Mode Propulsion System

Launch-on-demand satellites require both high thrust and high specific impulse (Isp). In this project, Ultramet will develop a multi-mode propulsion system that is capable of delivering an Isp of 291 seconds (density Isp of 453 s) in high-thrust mode using HAN/HEHN monopropellant. The propellant will be burned in Ultramet’s radiation-cooled oxide-iridium/rhenium (Ox-Ir/Re) combustion chambers capable of handling the ultrahigh temperature. In high-Isp mode, Busek radio frequency electrothermal thrusters will be employed after propellant decomposition in an American Pacific Corporation (AMPAC) gas generator with an Ultramet Ox-Ir/Re liner. Attitude control will be accomplished by directing generator gases to a small Busek thruster or by using small Ox-Ir/Re thrusters. Such a propulsion system will be able to accommodate many different types of orbital maneuvers, including Hohmann transfers, phase changes, and plane changes. Much of the required hardware has already been developed. Busek thrusters have been tested extensively, and Ultramet’s radiation-cooled combustion chambers have been hot-fired with O2/H2 and HAN/HEHN. The focus of the proposed project will be to further develop a HAN/HEHN catalyst and combine it into an integrated system with AMPAC’s gas generator and Ultramet’s Ox-Ir/Re combustion chamber under AMPAC’s current work.