Electric spacecraft propulsion has become a mature technology for main propulsion, station keeping, and attitude control. Due to the overwhelming lack of plume measurements in space, there is incomplete understanding of actual in-space performance of electric propulsion plasma devices. AE Ph.D. student Allison Timm received a National Defense Science and Engineering Graduate Fellowship for her research proposal to minimize or eliminate these knowledge gaps through the development of a payload package.
“The primary objective of the project is to design, develop, and characterize an engineering payload package for the in-space characterization of electric propulsion plasma plumes,” said Timm, who works with AE Professor Joshua Rovey at the University of Illinois Urbana-Champaign.
Timm explained the package will include a Langmuir probe, Faraday probe, emissive probe, and retarding potential analyzer. These probes will be designed, developed, and constructed to be compact, so they can be integrated into a two-unit payload package measuring 10 cm x 10 cm x 20 cm.
The Langmuir probe will measure the electron temperature, electron density, and floating potential. The emissive probe will measure the plasma potential. The Faraday probe will measure the ion current density and the retarding potential analyzer will measure the ion energy distribution.
“The probes are not novel,” Timm said. “Ground-based testing consistently implements them to characterize plasma plumes. Due to the consistent use of these probes on the ground, they will be adapted for in-space payload package implementation to conduct the same measurements in-space as on the ground.” The challenges of this project are the electrical design as well as overall construction due to the size and weight constraints of space flight. Additionally, the space environment introduces the issue of radiation which will be taken into consideration when constructing the payload package.
She said understanding plasma electric propulsion performance in space will make it easier to accurately predict in-space thruster performance, reduce uncertainty, and better understand the differences between in-space and ground-based performance.