Plasma thrusters used on satellites could be much more powerful than previously believed

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Plasma glow from the H9 MUSCLE Hall thruster during testing with Krypton propellant.Credit: Plasma Dynamics and Electric Propulsion Laboratory

Hall thrusters, an efficient type of electric propulsion widely used in orbit, have been thought to have to be large to generate much thrust. Now, new research from the University of Michigan suggests that smaller Hall thrusters can generate much more thrust, making them potential candidates for interplanetary missions.

“Previously, it was thought that only a certain amount of current could flow through the thruster region, which translates directly into the amount of force or thrust that can be produced per unit area.” aerospace engineering Who led the new Hall thruster research to be presented at AIAA Psytech Forum Today at National Harbor, Maryland.

His team pushed the envelope by operating a 9-kilowatt Hall thruster at up to 45-kilowatt while maintaining about 80% of its nominal efficiency. This increased the amount of force generated per unit area by almost a factor of 10.

whether to call plasma thruster or ion drive, electric propulsion But science is at a crossroads. Hall thrusters are a well-proven technology, but an alternative concept known as magnetoplasma dynamic thrusters promises to pack more power into smaller engines. Is not …

Hall thrusters were thought to be uncompetitive because of the way they worked.of propellant,Normally noble gas Like xenon, it travels through a cylindrical channel accelerated by a strong electric field. Proceed backward to generate forward thrust. But before we can accelerate the propellant, we need to lose some electrons to give it a positive charge.

electrons accelerated by magnetic field Running in a ring around the channel, which Jorns called a “buzz saw,” it knocks electrons off propellant atoms, turning them into positively charged ions. However, calculations suggest that as the Hall thruster attempts to drive more propellant through the engine, the thundering electrons within the ring are knocked out of formation, destroying its “buzzsaw” function. I got

“It’s like trying to chew more than you can chew,” Jones said. “Buzz’s saw can’t handle that much material.”

Additionally, the engine gets very hot. Jorns’ team put these beliefs to the test.

“We named the thruster H9 MUSCLE because essentially we took the H9 thruster and cranked it up to ’11’ to create a muscle car. 100,” said Leanne Su, a PhD student in aerospace engineering who is presenting the study.

They tackled the heat problem by cooling with water. This gave us an idea of ​​how big a problem the breakdown Buzz saw could be. Using a conventional propellant, xenon, her H9 MUSCLE operates at a maximum of 37.5 kilowatts and has an overall efficiency of about 49%, not far from his 62% efficiency at 9 kilowatts of design output. .

It ran on krypton, a lighter gas, and took full advantage of its 45-kilowatt power supply. With an overall efficiency of 51%, it reaches a maximum thrust of about 1.8 Newtons, much larger than the 100-kilowatt-class X3 Hall thruster.

Plasma thrusters used on satellites could be much more powerful

PhD student Will Hurley leaves the room where a new Hall Plasma thruster is being tested in the PEPL lab. Credit: Marcin Szczepanski/Michigan Engineering

“It’s kind of a crazy result because krypton usually performs much worse than xenon in hole thrusters. So we see that we can actually improve the performance of krypton compared to xenon by increasing the thrusters. That’s a very cool and interesting way to go. Current densitysaid Sue.

Nested Hall thrusters like the X3 (also partially developed by UM) have been investigated for interplanetary cargo transport, but are much larger and heavier, making it difficult to transport humans. The regular Hall thrusters are now back on the table for manned travel.

Jorns says that when Hall thrusters operate at these high powers, the cooling problem will require a space-consistent solution. Still, he is optimistic that individual thrusters could be arranged in an array that he would operate at 100 to 200 kilowatts and provide megawatts worth of thrust. This could allow him to travel 250 million miles to Mars on a manned mission, even on the far side of the Sun.

The team hopes to pursue cooling issues similar to those in developing both Hall thrusters and magneto-plasmadynamic thrusters on Earth, where few facilities are available to test Mars mission-level thrusters.Amount of propellant ejected from thruster The vacuum pump is too fast to keep the conditions in the test chamber space-like.

For more information:
Leanne L. Su et al, Operation and performance of magnetically shielded Hall thrusters at ultra-high current densities, AIAA SCITECH 2023 Forum (2023). DOI: 10.2514/6.2023-0842

Quote: Plasma thrusters used in satellites could be much more powerful than previously thought (24 Jan 2023).

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