Ph.D. Proposal

Muhannad Eladl

Advisor: Prof. Mitchell Walker

"Investigation of the Effect of Composition on the Rate of Wall Interactions in Air-Breathing Inductively Coupled Plasmas"

On

Thursday, June 3 

9:00 a.m. 
Guggenheim 244

 

Abstract
There is a growing interest in operating satellites in very low Earth orbit (VLEO) in the altitude range of 80-400 km. Despite the increase in required number of satellites due to decreasing coverage per satellite, operating in VLEO comes with many advantages, including but not limited to lower power requirements and reduced latency for communication with the satellite, improved imaging resolution, lower collision risk with space debris, easier access to orbit due to decreased cost of launch vehicles, improved geospatial accuracy, and easier deorbiting. However, operating in VLEO poses a unique challenge that has thus far limited the number of satellites in this orbit. The air density is too low for lift-based aircraft to operate, but high enough that the drag acting on the satellite requires non-negligible counteractive propulsion in order to maintain a steady orbit. A large amount of propellant is required to provide this thrust thus decreasing the payload budget and providing a lifetime limit on the mission with current VLEO satellites limited to operating for ~4 years compared to 15+ year lifetime of GEO satellites. 

Air-breathing electric propulsion is a unique concept that offers one potential solution, where electric propulsion (EP) thrusters are operated in VLEO using the gas that naturally exists in the atmosphere as propellant, thus minimizing or completely eliminating the required propellant storage. However, the composition of the air in VLEO constantly changes not just with altitude, but also with time of day, time of year, solar activity, and position over the Earth. As such, ABEP systems must operate on a molecular propellant, that is not only poorly understood compared to conventional neutral gas propellants, but also whose composition and mass flow are constantly changing. Modeling provides an efficient approach for iterating through ABEP designs while working with such a novel propellant. While current models have been capable of reproducing the overall trends in performance of ABEP systems, the actual performance metric outputs are over-estimated in comparison to experimental data due to key limitations in these models. 

The proposed work will attempt to address one of the limitations of these models by using Terahertz Time Domain Spectroscopy (THz TDs), a laser diagnostic, to characterize the radial distribution of the plasma density of an air-breathing RF Inductively coupled plasma (ICP) of varying composition of nitrogen and oxygen. This will be used to gain a better understanding on the effect, if any, that composition has on wall-plasma interactions of air-breathing plasmas. The measurements will also be used to experimentally inform coefficients used by 0D global models to characterize wall-plasma interactions for air-breathing ICPs. Currently these coefficients are assumed to be constant. A modified version of a published air-breathing ICP model will be used to compare the results between the constant and experimentally informed coefficients. 

Committee

• Prof. Mitchell Walker – School of Aerospace Engineering
• Prof. Sedina Tsikata– School of Aerospace Engineering
• Prof. Lukas Graber – School of Electrical and Computer Engineering