X-37B vehicle

The US Air Force Research Laboratory (AFRL) has partnered with the Space and Missile Systems Center (SMC) and the Rapid Capabilities Office to conduct a Hall thruster experiment onboard the X-37B orbital test vehicle mission 4 (OTV-4).

The Hall thruster being used for the experiment is a modified version of the units that have powered SMC’s first three Advanced Extremely High Frequency (AEHF) military communications spacecraft.

Hall thrusters are a type of electric propulsion device that produce thrust by ionising and accelerating a noble gas, usually xenon. They provide greater specific impulse or fuel economy, and may lead to increased payload carrying capacity and a greater number of on-orbit manoeuvres for a spacecraft using them rather than legacy rocket engines.

The experiment involves collection of telemetry from the Hall thruster operating in the space environment and measurement of the thrust imparted on the vehicle. It aims to enable in-space characterisation of Hall thruster design modifications that seek to improve performance relative to the units onboard AEHF.

"Hall thrusters are a type of electric propulsion device that produces thrust by ionising and accelerating a noble gas."

Data obtained from the test would be used to validate and improve Hall thruster and environmental modelling capabilities, which improves the ability to extrapolate ground test results to actual on-orbit performance.

AFRL commander major general Tom Masiello said: "Space is so vitally important to everything we do.

"Secure comms, airborne intelligence, surveillance, and reconnaissance (ISR), missile warning, weather prediction, precision navigation and timing all rely on it, and the domain is increasingly contested.

"A more efficient on-orbit thruster capability is huge. Less fuel burn lowers the cost to get up there, plus it enhances spacecraft operational flexibility, survivability and longevity."

The X-37B programme is managed by the Rapid Capabilities Office. It performs space experimentation, risk reduction and concept-of-operations development for reusable space vehicle technologies that could become key enablers for future space missions.

To date, the US Air Force has completed three OTV flights, which have accumulated a total of 1367 days of on-orbit experimentation prior to successful landings and recoveries at Vandenberg Air Force Base, California, US.

Image: The X-37B orbital test vehicle taxis on the flightline at Vandenberg Air Force Base, California, US. Photo: courtesy photo.