Development and In-Flight Testing of an Iodine Ion Thruster

The increase in the number of small satellite missions is enabling the development of new mission scenarios, requiring in turn further miniaturization of the systems onboard. An example is the deployment of small satellite constellations, which typically require onboard propulsion to perform phasing, collision avoidance and deorbit maneuvers. In this work we describe the development, testing and first in-space demonstration of a one Cubesat unit standalone iodine-fueled electric propulsion system based on a gridded ion thruster. The propulsion system, called NPT30-I2-1U, has all the subsystems necessary to its operation integrated inside the 1U volume, such as power processing unit, operation controller and iodine propellant storage and management. An inductively coupled RF plasma source is used for propellant ionization and a two-grid assembly for ion acceleration, while the beam neutralization is achieved with a cathode-neutralizer based on thermionic hot filament cathode. The propellant is solid iodine, stored in the internal unpressurized tank and sublimated during the operation. The system can provide up to 5500 Ns of total impulse at a specific impulse up to 2450 s and thrust levels of up to 1.1 mN in the range of input power of 35-65 W. Extreme miniaturization of the system is achieved through several innovations, including pipe-less propellant delivery, custom RF generation technology, a dedicated plasma ignition system and integrated thermal management. The necessary level of robustness and safety is achieved through implementation of reliability engineering approaches: system has built-in self-test and self-tuning algorithms and several layers of security loops. It should be mentioned, that the NPT30-I2-1U is the first iodine-fueled electric propulsion system launched to space and therefore many iodine-related aspects such as a propellant storage configuration, corrosion and sublimation control, iodine plume neutralization etc., have been tested in space for a first time