NASA begins tests on most powerful solar electric propulsion thrusters

The thrusters will play an important role on NASA's Gateway, the outpost orbiting the Moon.
Ameya Paleja
The electric propulsion thruster during qualification testing at NASA Glenn
The electric propulsion thruster during qualification testing at NASA Glenn


Engineers from NASA and Aerojet Rocketdyne have begun the multiyear qualification testing of the most powerful solar electric propulsion (SEP) thrusters, which are expected to radically change propulsion in space, a press release from the space agency said.

For decades, space research has relied on chemical propulsion to generate millions of pounds of thrust and has attempted to make bigger and more powerful rockets to take us further in our space voyages. While this is a standard even with the most advanced methane-powered rocket engines, it is not necessarily the most efficient way to move about in space.

Chemical propulsion requires spacecraft to carry large amounts of propellants onboard, especially if they have to make return journeys back to Earth. However, electric propulsion can drastically reduce the amount of fuel required on spacecraft while also increasing travel speeds, making it critical for future missions.

What is solar electric propulsion?

In an electric propulsion system, electricity is used to ionize inert gases such as Xenon or Krypton. A magnetic or electrostatic field is then used to accelerate these ions and push them out of the thruster to generate high speeds. While this might not appear flamboyant to the eye without all the fireworks we associate with rocket engines, it is still a spectacular sight to behold.

Interestingly, the electricity used to ionize the gases can be derived from sunlight which is abundantly available across the solar system.

Electric propulsion drives will also allow spacecraft to change their speeds and trajectories mid-way through the missions.

SEP on the Gateway

NASA has already experimented with SEP on its Dawn Mission but is now preparing to demonstrate the most-powerful version ever built on the Power and Propulsion Element (PPE) on the Gateway, its outpost that will orbit the Moon.

Gateway is a 60kW-class spacecraft where 50kW will be dedicated to propulsion, NASA said in an older post. Aerojet Rocketdyne has built an electric propulsion system that has been dubbed the Advanced Electric Propulsion System (AEPS).

At 12kW, the AEPS is two times more powerful than the most advanced electric propulsion system built but needs to undergo qualification testing before it can become part of the PPE on the Gateway.

NASA begins tests on most powerful solar electric propulsion thrusters
A view of the electric propulsion system during tests

To do so, NASA and Aerojet have begun yearlong tests of one of the qualification units, which are identical to the thrusters that will fly on the Gateway in 2025. After verifying that the thruster is built correctly, engineers expose it to extreme shock, vibration, and temperatures, simulating conditions during the launch and flight of the Artemis Mission.

Another qualification unit will be made available in 2024 and will undergo tests that mimic orbit raising and transition to lunar orbit maneuvers. All tests are being conducted in massive vacuum chambers at NASA Glenn Research Center.

“This testing campaign is a big deal,” said Rohit Shastry, the lead AEPS engineer. “It’s kind of the final leg before we test the thrusters that will actually fly on Gateway.”

The comprehensive test will include 23,000 hours of operation for the thrusters over a four-year period. The thrusters that will be placed on the PPE of the Gateway will actually be launched prior to the wear tests being completed.

"With NASA missions, launch dates are critical,”  said Clayton Kachele, the AEPS project manager at NASA Glenn, in the press release. “In this case, NASA is trying to expedite the process, and we’re doing it intelligently. We will complete a few thousand hours of wear testing to prove successful operations before PPE launches. We’ll then complete the final 15,000 hours or so to fully qualify AEPS for future customers."

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