New research calculates the first step toward predicting the lifespan of electric space propulsion systems

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New research calculates the first step toward predicting the lifespan of electric space propulsion systems

Illustration of Hall Thruster plumes affecting carbon surfaces at the atomic level. Credit: University of Illinois at Urbana-Champaign

Electrical propulsion systems in space use energetic atoms to generate thrust. The high-velocity beams of ions strike the graphite surfaces of the propellant, eroding them a little more with each stroke, and are the primary limiting factor for the life of the system. When the ion thrusters are tested in a closed chamber, the carbon particles rebounding from the walls of the graphite chamber can also be re-deposited back onto the thrust surfaces. This changes the measured performance characteristics of the motive.


Researchers at the University of Illinois at Urbana-Champaign used data from low-pressure chamber experiments and large-scale calculations to develop a model to better understand the effects of ionic corrosion on carbon surfaces—the first step in predicting their failure.

“We need to accurately assess the rate of erosion of the ions on the graphite to predict the lifetime of the propellant, but testing facilities have reported varying evaporation rates, which has led to significant uncertainty in the predictions,” said Huy Tran, PhD. Student in the Department of Aeronautical Engineering at UIUC.

It’s hard to replicate the space environment in a lab room, Tran said, because it’s hard to build a room large enough to avoid ionic interactions on the walls of the room. And although graphite is commonly used for accelerator grating and shaft caps in pushers, there is no agreement as to which type of graphite is more wear-resistant, known as spray.

“the Basic problem With the test of the ion impulse in a chamber is that the propellant continuously spits out xenon ions which also impinge on the walls of the chamber which are made of graphite sheets, but there are no chamber walls in space,” Tran said.

“When these xenon ions hit the graphite sheets, they also vanish carbon atoms that re-deposit on accelerator networks. So instead of the web getting thinner and thinner because of motivation Erosion, some people have seen in experiments that the grids get thicker over time because the carbon is coming back up from the walls of the chamber.”

the simulation Resolve limitations and uncertainties experimental data The researchers gained insight into a critical phenomenon.

“Whether it is pyrolytic graphite on homogeneous ion optics, isotropic graphite on column shells, or poco or anisotropic graphite graphite On the room our walls Molecular dynamics simulation showed that the rates and mechanisms of sputtering are identical across all of these different reference structures,” said Hak-Ping Qiu, Tran’s advisor.

He said that the spraying process creates a unique carbon structure during the bombing process.

“When the ions come in and damage the surface, they turn the surface into an amorphous structure no matter what carbon “Hulk,” Zhou said. You end up with a sparse surface that has the same unique structural properties. This is one of the main findings we have observed from our simulations.”

Chiu said they even tried it with diamonds. Regardless of the much lower initial porosity and stiffer bond formation, they obtained the same discontinuous structure.

“The model we developed correlates the results of molecular dynamics simulations with the experimental data,” Chiu said. “The next thing we want to look at is the evolution of surface morphology over time as you put more and more xenon ions into the system. This is closely related to ionic drivers of deep space exploration.”

The paper has been published in the journal carbon.

more information:
Tran et al., Effects of Surface Morphology and Carbon Composition on Spray: Bridging Scales Between Molecular Dynamics Simulations and Experiments, carbon (2023). DOI: 10.1016/j.carbon.2023.01.015

the quote: New Research Calculates First Step Towards Predicting Lifespan Of Electric Space Propulsion Systems (2023, January 31) Retrieved January 31, 2023 from https://phys.org/news/2023-01-lifespan-electric-space-propulsion.html

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