Test at AEDC helping determine feasibility of high energy lasers for the warfighter

  • Published
  • By Patrick Ary
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  Successful testing at Arnold Engineering Development Complex (AEDC) is giving the Air Force Research Laboratory (AFRL) valuable data that will help determine the feasibility of high energy lasers for the warfighter.

AFRL's Directed Energy Directorate (AFRL/RDLE) out of Kirtland Air Force Base, N.M., is testing high power lasers (10 of kilowatts) against materials of interest under simulated flight conditions in AEDC's Aerodynamic and Propulsion Test Unit (APTU). Testing began in April and is expected to run through August.

"The bottom line is that directed energy is at a transition point right now," said Robert Ulibarri, program manager for AFRL's Laser Effects Branch. "This kind of testing is going to determine whether high energy lasers are viable or not for the warfighter."

One of AFRL's primary interests is in material removal under airflow when a laser is applied to the material - essentially, whether it enhances the material removal process. This is the first APTU dedicated test series for looking at material responses under flight-representative airflow temperature and pressure conditions, Ulibarri said.

"We've done a lot of testing under static conditions that are under sub-Mach airflow," he said. "We're moving into a regime now where we want to look at the effects during simulated flight, and that's why we're [at AEDC]."

APTU is capable of simulating true temperature and pressure conditions in the Mach 3 to Mach 8 range. Those were test conditions AFRL wanted to test under, but in order to bring the test to AEDC the complex had to modify the APTU to accommodate specific equipment the customer needed to bring - lasers, diagnostic equipment, instrumentation and independent generators to ensure an adequate supply of power to AFRL equipment.

"At the end, you're putting a laser on a target," said AEDC APTU program manager Capt. Alex Hausman. "But there is a lot of upfront infrastructure that came together to do this."

APTU's tunnel was modified with ports installed to accommodate the laser transmission into the test cell while maintaining the test environment (partial vacuum). Shutters were also installed on the windows to protect them from contamination during the facility start-up and shutdown events.

Another major change involved widening the existing 17-inch gap between the nozzle exit and diffuser entrance to 54 inches in order to expose more of the test article and give AFRL/RDLE more flexibility during testing.

"If we couldn't open it up, they would have been limited in target installation, aim points and instrumentation, so we opened up the gap," Hausman said. "It exposed more of the test article and just gave them more flexibility with their objectives."

In order to ensure the flow wouldn't be affected, AEDC engineers simulated it on a computer with a larger gap between the nozzle and diffuser for predictions on how the flow would work.

"We completed CFD (computational fluid dynamics) to make sure that we did not have any spillage into the test cell or anything that would affect the test," said Dusty Vaughn, ATA's APTU project manager.

The work of integrating so much equipment into the tunnel was complex but worked out well, according to Ulibarri.

"I would say it was fairly complex, but it fell together pretty rapidly," he said. "Within the course of a couple of weeks we were up and running."

Preparations for the test involved more than facility modifications. Ulibarri said the program has been in discussions for two years, and AFRL looked at lessons learned from a 2009 test they ran in the von Kármán Gas Dynamics Facility's Tunnel C as well as some risk reduction efforts before coming back to AEDC.

"We kind of knew what risks were coming up, and we learned how to reduce that risk pretty well," he said.

AFRL met with AEDC in August to talk about a plan. The team held a Technical Review Board in October to discuss the test, and APTU workers conducted a series of risk reduction runs in December.

"We went and revisited some things offline from the customer and re-engaged in April," Hausman said. "We did the risk reduction runs in April to everyone's satisfaction, and then we went in with the start date and progressed on to testing. So it wasn't overnight that all these changes were made. It was realized over time."

Meanwhile, preparations were also underway at Kirtland among the organizations that would come from there to AEDC for the test: AFRL, Boeing and Ball Aerospace. Even though three groups were joining together to work with a fourth at AEDC, Ulibarri said the integration couldn't have been much smoother.

"I don't think we could have done it without the support of our ATA guys," he said. "The beauty of it is I think we integrate into a single team. They've been here to support us."

Ulibarri expects a larger matrix of test data than AFRL originally hoped for to come from the testing, and he hopes they will be back at AEDC for more in the future. He said the information they're gathering will go toward finding uses for directed energy in the future.

"There are several AoAs (Analysis of Alternative) coming out," Ulibarri said. "The next-gen fighter is one of them, and directed energy is looking for a spot in that. We'll try and convince the warfighter that directed energy is mature enough to be in the game, and this test is going to help provide some answers to that - to show proof that HEL systems can be ready in time for integration."