Tunnel 9 ushers in new paradigm for evaluation and test

  • Published
  • By Janaé Daniels
  • AEDC/PA
Arnold Air Force Base, Tenn. --  For the past year, engineers at the Hypervelocity Wind Tunnel 9 located at Arnold Engineering Development Center's (AEDC) White Oak location renovated their main tunnel controller. They installed a state-of-the-art digital control room and completed a successful return to service, verifying all aspects of the facility operation.

To validate Tunnel 9 as fully operational required a detailed and demanding process of deliberately increasing the throttle of the facility until full pressure and temperature were achieved according to Dan Marren, Tunnel 9 site director. Marren explained that the final stage for validation would normally involve a standard check model where test cell functionality, data throughput and veracity of information can be verified against benchmark data.

"While running a standard check model is anything but standard in Tunnel 9 - high temperatures and pressures with dynamic angle-of-attack sweep approaching 80 degrees a second - this time it was even more atypical given our enhanced data goals," Marren said. Several high-speed systems under development today will require a more complete understanding of the challenges that are between technology development and fielding.

AEDC management took this opportunity to determine if Tunnel 9, which uniquely provides the test environment necessary for understanding these complex challenges, could be utilized in a new and innovative way. In the year preceding the completion of the control room, engineers readied experiments, methods and instruments to make measurements that can interrogate more fully the physics-based phenomenon required.

"Late last year, a proposal was made to replace the standard sphere cone check model with an actual system configuration representing the most likely Air Force solution to the next generation prompt global strike missile system, HTV-2," Marren said.

The Falcon program is a joint venture by the Defense Advanced Research Projects Agency (DARPA) and the Air Force. The program's objectives are to develop and demonstrate hypersonic technologies that will enable prompt global reach missions. The first flight test is currently scheduled to fly from Vandenberg Air Force Base, Calif., to Kwajalein Atoll, Marshall Islands, later this year.

Marren says this vehicle because of its complex 3-D shape also challenges the understanding of certain critical physics-based phenomenon and fits the return to service goals. Since AEDC's Tunnel 9 provided the pre-flight database, that data can be used as a benchmark for validation of the wind tunnel.

"Having a well characterized data set in Tunnel 9 made it the perfect configuration to tell if all systems were a go," Marren said. "In addition, this next generation vehicle will require more physics-based design information to get through development and Tunnel 9 must be ready for that enhanced requirement."

Moving from just supplying air-on test time for the purpose of building an empirically-based data set to a new approach that seeks to understand the physics driving the most severe design challenges requires the capability to go beyond the standard data approach and perhaps move out of a comfort zone in customer support.

"Success here will require building partnerships with science and technology activities, inventing test techniques and methods tuned to obtaining important hard-to-measure quantities and providing data in a format that feeds the weaknesses in our computational models," Marren said.

The initial quick-look data suggests that all the various technology efforts are producing 100 percent successful results.

"I am amazed at the level of success that has been achieved simultaneously for so many different technologies 'piggy-backed' together," John Lafferty, Tunnel 9's technical director, said. "This level of success is a testament to the quality of our people and the rigorous planning involved. According to Marren, this was an opportunity to try this new approach by reaching out to Tunnel 9 partners with the help of the University of Maryland, Air Force Office of Scientific Research, Air Force Research Laboratory, Test Evaluation/Science & Technology, NASA and Sandia National Laboratories.

The result is enhanced measurement techniques typically seen only in a laboratory environment now applied in a T&E facility to a real-world problem that is milestone driven (in this case by a flight test).

According to Dr. Mark Lewis, chair of the Aerospace Engineering Department at the University of Maryland and former Chief Scientist of the Air Force,

"The hard work in renovating the critical national asset that is Tunnel 9 has clearly paid off on its very first set of runs. "Preliminary results from the early stages of the project are eye-watering, providing marvelous agreement to some of our theoretical models. AEDC has outdone itself in leveraging a shakedown test series to perform no fewer than eight significant experiments at once. I am particularly excited by the fact that our students have been right there in the process, working side by side with AEDC personnel. That is an incredible educational opportunity for those students, but I have also observed that their presence at Tunnel 9 has added an extra spark of vitality for the AEDC staff members as well."

When return to service checks are completed later this month, Tunnel 9 will have an enhanced information capability matched with an accurate and capable controller to once again rise to meet the testing needs of advanced hypersonic systems.