A year of sustained growth and learning about electric thrusters

By Patrick “Paddy” Neumann|December 2024

The Electric Propulsion Technical Committee works to advance research, development and application of electric propulsion for satellites and spacecraft.

n April, Busek’s BHT-6000 thruster passed environmental qualification, while Aerojet Rocketdyne completed acceptance testing for its 12-kilowatt Hall Effect thrusters, or HETs. Both designs are to propel the Power and Propulsion Element of NASA’s planned Gateway lunar station.

Also in April, NASA completed initial checkout of the HETs aboard its Psyche spacecraft and began cruise operations with the thrusters. As of August, they had operated nominally for some 2,500 hours.

In September, Busek shipped its 250th Busek BHT-350 thruster. As of October, 100 of them were operating in low-Earth orbit aboard OneWeb broadband satellites.

In qualification news, the 1-kW-class Magnetically Shielded Miniature Hall thruster designed by NASA’s Jet Propulsion Laboratory qualified to 8,254 hours in August, while its H10 HET demonstrated thermal steady-state operation up to 15 kW, reaching thrust efficiencies exceeding 70%. As of November, Northrop Grumman’s sub-kilowatt NGHT-1X Hall thruster demonstrated 9,400 hours and 1.5 mega- newton-seconds total impulse. Northrop Grumman has six flight units in production for a 2025 delivery.

In April, Georgia Tech researchers published the results of their study, in which they fired an incoherent laser Thomson scattering system to noninvasively measure electron density, electron temperature and azimuthal electron drift velocity in HETs with high spatial resolution. This experiment provided new details into the physics of HETs, such as detecting nonisothermal magnetic field lines, contradicting traditional models.

In alternate propellant work, researchers at CNES, the French space agency, in March investigated water vaporization in microgravity aboard the AirZeroG aircraft. While water-fueled electric propulsion systems have previously flown, this is the first in-depth study of their performance.

Neumann Space of South Australia operated its ND-15 thrusters aboard the SpIRIT and Skykraft 3 missions over several months, the first time a molybdenum-fueled design was fired on-orbit.

As of June, ENPULSION of Lower Austria sent some 200 Field Emission Electric Propulsion thrusters to orbit, with multiple indium-fueled units accumulating over 1,000 hours of active thrust-operations time.

In January, George Washington University researchers received a DARPA grant to continue development of their thruster that achieves beam neutralization via positive and negative ions derived from low-pressure air. They tested this thruster at various pressure conditions, determining that it is most suitable for 80-100 kilometers altitude.

In January, doctoral students at the Universities of Surrey and Southampton in the United Kingdom validated a new inverted pendulum thrust balance against a well-characterized torsional thrust balance. An external discharge Hall thruster was the test article.

In March, students from the Rose-Hulman Institute of Technology in Indiana presented a paper at the IEEE Aerospace Conference on achieving ignition with a gridded-on thruster, the first of its kind designed and tested by an all-undergraduate team.

In September, the Japan Aerospace Exploration Agency confirmed the completion of a hot-fire test campaign validating a 6-kW-class Hall thruster subsystem and flight-proven Hall thruster subsystem. The components were integrated into the Engineering Test Satellite-9, scheduled to launch in 2025.

Nuclear-electric research and development continued. In May, the Accelerating Space Science with Nuclear Technologies workshop, held in Arizona, brought together leading experts to discuss new capabilities provided by long-life, high-power electric thrusters. Feedback included requirements for reducing spacecraft transit time for outer planet missions and increased maneuvering capability at the destination. As part of NASA’s Space Nuclear Propulsion Project, JPL, Princeton University and NASA’s Glenn Research Center in Ohio continued developing high-power, lithium magnetoplasmadynamic thruster technologies for crewed Mars missions. Current work is focused on testing a 200 kilowatt-electric, steady state, self-field thruster while designing a higher-power, 500-kWe engine.

Contributors: Moe Ahmed, Jack Fisher, Rich Hofer, Wensheng Huang, Akira Kakami, David Krejci, Stephane Mazzouffre, Ishaan Mishra, Alex Nikrant, Kurt Polzin, James Szabo, Anmol Taploo, Mitchell Walker and Hiroki Watanabe