Cathode & Electromagnet Qualification Status and Power Processing Unit Development Update for the Ascendant Sub-kW Transcelestial Electric Propulsion System

A review of the component-level flight qualification efforts and power processing unit development status of the Ascendant Sub-kW Transcelestial Electric Propulsion System (ASTRAEUS) program is presented. Component-level qualification efforts were undertaken for the system’s ultra-compact heaterless LaB6 hollow cathode and electromagnets, both of which employ designs bespoke to ASTRAEUS, as they represent the highest failure risks for the thruster. Through parallel long-duration wear and ignition tests, the ASTRAEUS cathode demonstrated invariant discharge performance over more than 5000 h of operation at its maximum operating current of 4 A and demonstrated more than 25,000 ignition cycles. The ASTRAEUS electromagnets completed their environmental qualification through a demonstration of more than 1200 deep thermal cycles with no indication of coil degradation (the test articles previously completed qualification-level vibration and shock testing). ASTRAEUS’s prototype power processing unit has demonstrated more than 92% total power conversion efficiency and class-leading power density & specific power density of 4.5 W/cm3 & 1670 W/kg, respectively. The various power converters found in the ASTRAEUS power processing unit are reviewed with a focus on the methods by which such high performance was achieved

Magnetically Shielded Miniature Hall Thruster: Design Improvement and Performance Analysis

ABSTRACT: Magnetic shielding has been shown to dramatically reduce discharge channel wall erosion of high powered Hall thrusters, thereby increasing their useful lifetimes. However, unique challenges exist for developing a low power magnetically shielded Hall thruster. A previously tested 4 cm magnetically shielded miniature Hall thruster demonstrated low performance of its magnetic circuit, resulting in an asymmetric field topology, low thrust, and low efficiency. A 6 cm magnetically shielded Hall thruster was developed to improve upon the 4 cm design. The 6 cm device, which generated a symmetric and fully shielded field topology, was tested at 30 operating conditions ranging from 160 W to nearly 750 W. Visual observation of the plasma and discharge channel during and after operation was used to assess the level of magnetic shielding that was achieved. Hall2De plasma simulations were also used to offer further evidence of magnetic shielding. Thrust stand measurements provided thrust, anode specific impulse, and anode efficiency data at each operating condition. Pole face erosion, which is believed to be associated with the 6 cm thruster's non-optimized magnetic shielding field topology and strength, identify the near-term challenges to resolve before long lifetimes and high efficiencies can be achieved in low power Hall thrusters

Extended Life Qualification of the Magnetically Shielded Miniature (MaSMi) Hall Thruster

We present an update on the life qualification of the Magnetically Shielded Miniature (MaSMi) Hall thruster (also known as the ASTRAEUS Thruster Element), which was developed at the Jet Propulsion Laboratory and was recently licensed to ExoTerra Resource for flight production (renamed Halo12). In 2020-2021, the thruster successfully completed a 7205-hour wear test at operating powers from 200-1350 W, processing over 100 kg of xenon propellant and producing 1.55 MN-s total impulse with no measurable degradation in performance. The wear test is being extended to further demonstrate the service life capability of the thruster. In separate tests, prot-flight MaSMi hollow cathodes demonstrated \u3e 25000 ignition cycles and \u3e 13000 hours of operation at 4 A discharge current, and a set of three MaSMi electromagnets underwent \u3e 3000 deep thermal cycles (-123 °C to 495 °C). Laser-induced fluorescence (LIF) measurements of ion velocities and plasma modeling with Hall2De, a widely published numerical plasma code, have been carried out to elucidate the physical mechanisms driving pole erosion trends observed in thruster wear testing. Survival probabilities for micrometeoroid impacts and other random failure modes in flight were also analyzed