AEDC and UTSI cryo-contamination research heralded a success

  • Published
  • By Shawn Jacobs
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  A collaboration between Arnold Engineering Development Center (AEDC) and graduate students at the University of Tennessee Space Institute (UTSI) resulted in the most recent of three cryo-contamination experiments in AEDC's small ultra high vacuum (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 were obtained from the first two tests, but the recent one, completed Jan. 18, 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."

Dr. Lowry thinks more research along this line is warranted.

"We had another type of contamination occur that seems to be related to a type of thermal grease that was used in one of the components," he said. "The next testing is really going to be looking at that and seeing how that might migrate from where it is to the surface of the things we're interested in. We want to bear down on that more and try to learn more about it."

Dr. Lowry said he's looking forward to further collaboration with UTSI.

"We have some other goals for the UTSI contract that we need to start working on, so we wanted to go ahead and get this one done and move to the next thing on the list," he said. "Hopefully, we can continue this work relationship with UTSI. We're under contract until the end of the [fiscal] year right now, and we're trying to show how useful this is and maybe we can get money to continue their work next year."

Dr. Moeller said he, too, would like to continue to partner with AEDC on current and future research.

"I think this has been an extremely positive program," he said. "We've learned a lot [and] we have had some very good collaborations, and assuming that there is funding going forward, I think that there's a lot more to be learned and a lot more that we can do together."

UTSI graduate students involved in the research included James Rogers and Billy Ring. Jesse Labello, who participated in the previous experiments, graduated with his Ph.D. and had to move off the project. Other UTSI faculty who participated included Dr. Monty Smith and Dr. Frank Collins, a retired professor emeritus.

"We have multiple papers that are going through [clearance] for public release that will be submitted to journals to show people the work that we have been doing at AEDC," Dr. Moeller said. "We'll also be submitting abstracts to technical conferences to help spread the word about the good work that we're doing together."