Joseph Speakman, who will start his senior year at the Air Force Academy in Colorado Springs this fall, spent some time at the University of Tennessee Space Institute this summer as part of the Cadet Summer Research Program (CSRP). Cadet Speakman explained that cadets have to do two programs in the summer and then get a three-week summer break. The Summer Research Program is a highly competitive program that allows cadets to gain real-world experience in their fields. CSRP sends cadets to Air Force bases all over the country and the cadets can submit a “wish list” of places and projects. Cadet Speakman is majoring in Astronautical Engineering and put Arnold Air Force Base on his wish list of places to go for the Summer Research Program.
UTSI Professor Trevor Moeller is currently working on a project for Arnold Engineering Development Center to develop a new kind of thrust stand to measure the thrust exerted by electric propulsion thrusters, a type of space rocket. Cadet Speakman spent a month researching this project with Moeller at UTSI, from May 20 to June 21. On Earth, electric propulsion thrusters don’t provide much thrust, and would not be able to launch, or even budge, a satellite. However, in the space environment with very little atmosphere, the small amount of thrust that these propellant-efficient thrusters generate is useful for adjusting the attitude of satellites and maintaining their orbit.
In order to test the performance of these thrusters on Earth, experiments must be run inside a vacuum chamber. Cadet Speakman helped Moeller with a series of related experiments to research the performance of a critical component of the new thrust stand he’s developing, using gallium, a non-toxic liquid metal.
To measure the thrust, electricity must be transferred from stationary to moving parts on the thrust stand without bending a wire and introducing unwanted forces. In order to eliminate this solid wire connection, Moeller and Cadet Speakman ran experiments with two pieces of copper wire moving freely in a pool of liquid gallium. It has been thought by some rocket scientists that gallium should not be able to carry more than 15 amps of current, but Moeller’s calculations indicate the liquid metal can handle a higher level of electric current. Moeller said that the successful use of gallium is a critical part of the design of the new thrust stand, and, judging from the results of experiments to this point, it looks like it will work.
Cadet Speakman performed several tests to see how much current could safely pass through the gallium. “I did the experiment inside a vacuum chamber to simulate the actual environment in which the thrust stand will be used, and I found that the gallium can handle at least 50 amps of current for long periods of time,” said Cadet Speakman.
Cadet Speakman is very interested in thrusters since he hopes to work with satellites in the future. In fact, he’ll be building a satellite next year as a senior at the Air Force Academy.
“I had a great experience at UTSI,” said Cadet Speakman. “The experiment I performed in the lab really helped me apply the concepts that I learned in the classroom, and I was able to benefit UTSI and AEDC, as well. Moeller and Research Specialist Doug Warnberg were great mentors, and they helped me solve the problems I encountered and helped to make my project a success.”
Moeller was very pleased with the results of the experiments performed by Cadet Speakman. “Joe did an outstanding job with this experiment, and his hard work has helped support the feasibility of the critical role the gallium electrical pot will serve in the thrust stand that we are developing,” Moeller said.
MEDDLING WITH METALS AT UTSI—Air Force Cadet Joseph Speakman and University of Tennessee Space Institute Professor Trevor Moeller are shown above studying an experiment within a vacuum chamber. Moeller and Cadet Speakman are running an experiment using a liquid metal, called gallium, as part of Moeller’s work to design a new rocket thrust stand for AEDC.
–UTSI Photo by Shanna Relford