PEPL RMFv2 – 5kW Rotating Magnetic Field Thruster

PEPL RMFv2 in operation in the Large Vacuum Test Facility

Approx. Specs.
Ø20 cm x 35 cm, 10 kg
Tested at PEPL
2021 – ongoing

Following the marginal success of the first RMF thruster developed at PEPL, a second RMF thruster version (PEPL RMFv2) was constructed which incorporates several lessons learned from the first prototype. The v2 thruster shares a similar topology to the version one thruster, however, as opposed to the original design the v2 thruster lacks a flux conserving aluminum structure, as this was theoretically shown to reduce thruster performance. Additionally, the v2 thruster features an improvement to the location of neutral propellant injection. Previously, the neutrals were supplied behind the ionization source which led to the high centerline densities. In the new design, the gas feed is located at the exit plane of the thruster with rearward injectors around the circumference. The goal of this is to increase the residence time of the neutral gas and supply higher propellant density at the wall near the RMF coils. A key distinction of the version two design is the inclusion of a new RMF power processing unit from Eagle Harbor Technologies. This new architecture pings an LC oscillator tank formed with the RMF antenna with a 0-600V square wave at the LC resonant frequency. This setup allows for higher RMF frequencies (400-500 kHz), higher sustained rotating fields, and longer pulse times than the former single-capacitor bank discharge.

In January of 2021, the RMFv2 thruster produced a maximum thrust of 8 mN at a 1.5% pulse duty cycle (200us pulses at 75 Hz pulse repetition rate) at 4kW RMF power at 420kHz. This corresponds to an active thrust of over 500 mN, correcting for the low duty cycle.

Selected Publications