Development and Test of an High Power RF Plasma Thruster in Project SAPERE-STRONG

The main objective of the project SAPERE/STRONG is the realization of a space tug, coupled to the rocket VEGA, devoted to the transfer of payloads of different sizes from an intermediate orbit to a target orbit. The principal propulsion system of the tug will be an Helicon Plasma Thruster; the University of Padova CISAS “G. Colombo” is the partner responsible for the design, realization and testing of the mentioned thruster. We have developed two prototypes: i) a 200 W motor for preliminary testing with a target thrust of 8 mN for 0.4 mg/s Xe mass flow rate, ii) a 1 kW prototype, whose target thrust is roughly 100 mN, which is the real objective of the project. The principal instrumentation employed for the performances characterization is a thruster balance, developed within the same STRONG project, and a Faraday probe. The testing and optimization campaign is still ongoing at the CISAS facility, the preliminary results presented in this paper are related only to the 200 W prototype. We have described the balance measurement procedure using, as example, a 150 W input power and 0.2 mg/s Xe mass flow rate test: the measured thrust is T = 1.43 ± 0.18 mN. A performance characterization is available in the range: input power from 50 W up to 200 W, and the mass flow rate from 0.05 mg/s up to 0.2 mg/s; the thrust increases with both the input power and the mass flow rate, while the specific impulse decreases with the mass flow rate. A performances characterization in a wider range of input power and mass flow rate, and a performances optimization campaign have been scheduled for the next months.