AFMC Command News

AEDC, university collaboration yields successful research

  • Published
  • By Shawn Jacobs
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  A collaboration between Arnold Engineering Development Center and graduate students at the University of Tennessee Space Institute resulted in the most recent of three cryo-contamination experiments in AEDC's small ultra high vacuum, or UHV, chamber.

Researchers at both organizations are calling the joint venture a success.

The researchers used a laser to study detection and possible mitigation of ice buildup on a mirror in the UHV. Similar to frost on a windshield, cryo-contamination inside space chambers in a lab or on satellites in space is not a new problem. The cryo-deposits cause the chamber optics to degrade and result in other problems for the chamber's mechanical components.

Dr. Trevor Moeller, an assistant professor at UTSI and a principal investigator, said the research went extremely well.

"We've had people working the experiment that include ATA [Aerospace Testing Alliance], Air Force civilians and UTSI personnel working side by side on the project at various times, and I think it's gone extremely smoothly," he said. "It has allowed us to take some ideas that we've had at UTSI and use ... the UHV chamber over on base to allow us to test some of those capabilities in an environment and for applications that are of interest to the Air Force.

"The initial results that we got from the optical detection system basically confirmed what we got in the second test, and we had a new laser in our optical setup that provides us higher resolution, so that it gives us more details of what we're measuring. Things look very consistent so far even though we haven't completed our analysis, but initially things look very good."

Dr. Heard Lowry, an ATA Technology and Analysis Branch Technical Fellow who oversaw the experiment, agreed.

"They have actual data that will give us information on the deposition versus time -- how much water vapor is accumulating versus time," he said. "The real detail has yet to be pulled out of all the data, but just right away we've ... learned something. We hope to contribute to the literature there as well. I think it's definitely a success."

Dr. Lowry said good data was obtained from the first two tests, but the recent one, completed Jan. 18, 2012, was even more sophisticated.

"[In the] previous tests we had trouble getting the devices we were trying to get the contaminants on as cold as we wanted, but we did get some data," he said. "This test we worked to obtain better cooling to these areas and we got them down another 30 degrees Kelvin. We saw a big difference in how the water attached to the mirror.

"In the first test when the temperature was higher, it was like a very clear thin sheet. It just kept building up. And during the latest test, the cryo-deposits fractured almost immediately, now that this temperature was colder. It looked like the frost on a windshield; you could see strong scattering from the laser light. We're trying to learn more about at what temperature and thickness that happens."

Dr. Moeller said experimentation also involved ways of developing an early warning system of cryo-deposit buildup and attempts to mitigate the problem.

"We had a mitigation technique that we did -- a very preliminary test that utilized electromagnetic fields applied to surfaces to try to prevent or slow the accumulation of these water molecules on critical surfaces," he said. "We're still analyzing all of the results, so I can't say how well that worked but it's a next step in the sequence. You detect the problem, and then the second step is to find out how to prevent it from happening or slow it down."

Dr. Moeller said the same mitigation methodologies used to reduce or remove ice from components in space chambers would be applicable to satellites in space.

Jim Burns, AEDC's Space Chambers Lead, initiated the project with UTSI about two years ago and called the collaboration a "win-win."

"I believe partnering with universities allows us to gain access to specialized expertise when needed and also keeps us connected to the front lines of research," he said. "That lets us tap into much more areas than we could if we tried to do everything in-house. Ultimately one long-term advantage of a partnership would be for UTSI to leverage what we do with their own grant and research applications. Much like making stone soup, none of us has all the resources to do it alone, but together we can."