C4.5 A Review of the High-Isp / High-Voltage Hall Thrusters
Symposium: C4. IAF SPACE PROPULSION SYMPOSIUM
Session: 5. Electric Propulsion (1)
Day: Tuesday 30.09.2025
Time: 15:00 AEST
Room: C3.6
For space missions where transit times is not a major constraint, such as comet chasers (Deep Space 1), asteroid rendezvous missions (Psyche’s spacecraft), and generally interplanetary missions, a high specific impulse (Isp) is crucial. In the near-Earth environment, there are several missions where efficient propulsion systems are also essential from propellant consumption point of view. These include long-term drag compensation in LEO and VLEO (GOCE), long-term formation flight (for space-to-space communications), high-precision missions (LISA Pathfinder), and interferometry missions (LISA). High Isp can also benefit commercial space applications, such as orbit corrections, slow plane change, orbit repositioning for commercial space debris removal (ADRAS-J) and potentially for the upcoming OSAM missions.
Despite Hall Effect Thrusters (HET) having been studied since the 1960s and extensively used since the 2000s, a technological barrier appears to be emerging around 3000 seconds of Isp. Although theoretically, the potential for increasing the Isp in HETs is limitless by raising the discharge voltage or reducing the mass of the propellant species, these adjustments lead to significant impacts on both the thruster (plasma properties) and the system (power supply units capable of handling high voltage levels).
This review offers an exhaustive overview of HETs operating at high-voltage / high-Isp, by covering a relevant set of thrusters developed over the past 10 years (across all TRLs), data results from characterization tests or partial life-span test campaigns, and Safran Spacecraft Propulsion (SSP) own activities. This state-of-the-art analysis describes the technical solutions proposed for optimizing the magnetic field, managing thermal loads, and optimizing the discharge channel geometry using various materials. Drawing on SSP experience, additional topics are addressed, such as the influence of different channel materials, the homogeneity of the anode mass flow-rate, ceramic beveling, and thruster aging on maximum critical discharge voltages.
The review study underscore the need to explore new high-voltage tolerant ceramics for the discharge channel, increase the magnetic field intensity without compromising life-span or plasma stability, optimize the geometry of the discharge channel, design thrusters with better thermal management, and develop robust high-voltage wiring, connectors and electronics at PPU level. SSP is actively engaged in these challenges: several technological building blocks are currently being tested through an improved version of the PPS R 5000, and high-voltage dedicated laboratory models are currently under test. These activities will provide significant insights into the functional triad (performance, stability and life-span) of high voltage HETs and prepare the next steps toward a high-voltage DM thruster.