Experimental Characterization of a Scalable Pulsed Magnetoplasmadynamic Propulsion System

Abstract

A self-contained magnetodynamic Pulsed Plasma Thruster (iMPD) propulsion system for small satellites has been set up at the Institute of Space Systems (IRS) at Stuttgart as part of a three year research project. The system includes a modified version of the iMPD thruster ADD SIMP-LEX of the IRS. This paper presents unit and subsystem level verification tests. The scope of the work included characterization of the system thrust performance at IRS and environmental testing for verification of the overall design at the STG-CT-facility at DLR Göttingen. The goal was to demonstrate operation of the new self-contained propulsion system under relevant environmental conditions, to raise the Technology Readiness Level. The system enables advanced research of pulsed plasma applications, low-cost space-flight for small satellites, ground facility interaction studies and plasma diagnostic standardization. Development work leading up to the setup of the system is included in the analysis of the presented results and referenced for tracing. A redesign of the micro-newton thrust balance operated at IRS was performed to improve isolation from ground and thruster accommodation. Power train and thruster head modifications on the iMPD thruster for integration into the system are described. Scaling performance results of two iMPD setups, original and modified, are compared. For each setup, parameter variation measurements for scaling of pulse energy and capacitance are presented. System tests at 67.6 J yielded an average cold impulse-bit of 1.56 mNs and an effective exhaust velocity of 26.7 km/s, raising the thrust efficiency from 24 % to 31 %. Single pulses have been confirmed to sporadically reach thrust efficiencies above 40 percent, however with poor repeatability. Flight level qualification testing under 10-7 mbar and 4.3 K ambient thermal-vacuum was successfully demonstrated.