AEDC reaches major milestone with hypersonic engine testing

  • Published
  • By Philip Lorenz III
  • AEDC/PA
Arnold Air Force Base, Tenn. --  A 10-year effort to upgrade a high speed, high temperature, blow-down ground test facility at Arnold Engineering Development Center (AEDC) culminated in a recent hypersonic Mach 6 test run on a state-of-the-art combined-cycle engine demonstrator. 

"This test was significant," said Matthew Bond, test manager of AEDC's Aerodynamic and Propulsion Test Unit (APTU). "The Mach 6 run on June 24 was the first-ever scramjet propulsion test at AEDC. It was an actual test of the Defense Advanced Research Projects Agency Falcon Combined-cycle Engine Technology (FaCET) scramjet using APTU's recently acquired Combustion Air Heater [CAH], Mach 6 nozzle and JP-7 fuel heater." 

Lt. Col. James Colebank, the 718th Test Squadron commander, said the Mach 6 run was more than a first for APTU. 

"This was also a milestone for AEDC because this was the first near-flight scale test of a hypersonic engine here," he said. "There have been earlier experiments conducted on considerably smaller scale engines in our ballistic range, but you'd get only 300 milliseconds of data." 

Both men agreed the availability of high pressure air provided the greatest technical challenge to the Mach 6 run. 

"High pressure air is a scarce commodity, shared among all three test squadrons on base," Colonel Colebank acknowledged. " Scheduling APTU with other testing at AEDC has been, and will continue to be, a significant challenge." 

Chris Smith, the 718th Test Squadron's technical director, said it helps to understand what took place beforehand to bring APTU to its present capability in order to appreciate this milestone. 

"Perhaps the biggest facility upgrade in APTU during the last decade was replacing our old Vitiated Air Heater with the new CAH," he explained. "The CAH increased our capability to generate greater Mach numbers and dynamic pressures while providing greater facility reliability. However, the CAH wasn't part of the original plan. 

"In the 1990s, we acquired the Sudden Expansion [SUE] burner and fixed nozzles from the canceled National Aerospace Plane [NASP] program with the intent to take APTU from a high-supersonic test facility at Mach 4 to a truly hypersonic one up to Mach 8." 

Smith described the SUE burner as "crucial" to providing APTU with the necessary pressures and temperatures to reach hypersonic flight conditions. External funding issues stalled the upgrade. 

"In 2001, we regrouped our efforts and made another push for the upgrade as we knew the nation sorely needed this ground test capability," Smith continued. "One of the reasons the U.S. canceled NASP was the lack of a ground test facility to support development of its propulsion system and buy down risk prior to flight testing. Hypersonic propulsion is the pacing technology hurdle for these types of flight vehicles." 

AEDC initiated a new Military Construction (MILCON) Program in 2002, again with the goal of integrating the SUE burner into the facility and to check out the improved utility systems. 

"However, the SUE burner turned out to be unusable," he recalled. "Limited checkout was conducted in 2004 and the MILCON was closed. That same year, we initiated an AEDC-funded procurement of a SUE burner replacement and also received DOD approval for our 'fly the mission' variable Mach capability under the auspices of the Central Test and Evaluation Investment Program. We took delivery of our CAH in March 2007 and awarded our design contract for a flexible wall nozzle in September of that same year. The rest, as they say, is history."