This project is an all-undergraduate, student-led effort to create a fully functional Hall-Effect Electric Propulsion Thruster that performs as predicted in a vacuum chamber. I joined the project in August 2024 but recently transitioned to focus on the RDE Propulsion project under the same organization, PURPL. During my time on the project, I primarily contributed to the design and planning of the neutralizer component of the thruster.

In recent times, electric propulsion thrusters have found increasing applications both within and outside of aerospace. This has led to a growing effort by student organizations, including PURPL, to develop their own thrusters. The basic concept behind a Hall-effect electric propulsion engine is to generate thrust using magnetic and electric fields. A neutral gas is injected into the discharge chamber, where it is ionized by a radial magnetic field as its electrons are stripped away by fast-moving electrons within the chamber. The ionized gas is then accelerated out of the thruster by an electric field, expelling it at high velocities.

To prevent the thruster from accumulating an electric charge, the ejected ions must be neutralized. This is accomplished by attaching a neutralizer at the end of the thruster, which releases free electrons into the exhaust plume to neutralize the ions. This ensures a stable exhaust beam and maintains the efficiency of the thruster.

Electric/ion propulsion engines, such as Hall-effect thrusters, have been used in various spacecraft. For example, NASA's Dawn spacecraft utilized ion propulsion to travel long distances beyond Earth's gravitational pull. Despite the high specific impulse of electric propulsion, which uses far less fuel compared to the thrust generated, it has its limitations. The acceleration from electric propulsion is extremely low, meaning it would take a long time for a spacecraft to reach high velocities using this method alone. However, when time is not a critical factor, this high-efficiency propulsion technique offers significant advantages and is gaining widespread adoption in the industry.

As mentioned earlier, my work focused on the neutralizer component of the thruster. Before diving into any work, however, we spent several weeks studying the NASA JPL Fundamentals of Electric Propulsion: Ion and Hall Thrusters paper to develop the necessary understanding to tackle this task. After completing this training, I was assigned to the neutralizer team for the project.

In this role, I was responsible for researching the requirements for properly connecting the neutralizer filament to the power supply unit wire. With guidance from a graduate student here at Purdue, I gained a better understanding of how these connections function. The connector needed to both conduct electricity to the neutralizer filament and withstand the extremely high temperatures generated by the neutralizer.

The filament itself would be composed of thoriated tungsten, operating at 1900 K. However, I learned that the closer the distance along the filament to the wire connector, the greater the temperature fall-off, meaning the wire connector would experience much lower temperatures. With this in mind, I selected a barrel wire connector made of beryllium-copper. The two wires would be screwed into the barrel connector, as shown in the graphics from our preliminary design review below.