ARNOLD AIR FORCE BASE, Tenn. -- Several AEDC team members held a brief reunion last month to share memories and reflect on their work in support of the NASA X-43A, also known as the Hyper-X program.
A little more than 15 years ago, NASA’s X-43A Hypersonic Vehicle set a world speed record, setting the Guinness World Record, for an air-breathing hypersonic aircraft.
The X-43A was assembled at the Micro Craft facility in Tullahoma.
“It’s surprising the number of people here at Arnold that supported this project,” said Troy Bisby, Air Force project manager who, at the time, worked as the team lead for Vehicle Assembly, Integration and Systems Test.
The X-43A, part of the NASA Hyper-X program, was an experimental unmanned hypersonic aircraft. The Air Force followed the X-43A project with development of the Boeing X-51 WaveRider, a longer-flying, jet-fueled hypersonic aircraft.
According to Bisby, “NASA had a desire to demonstrate a scramjet-powered flight and working with Boeing, came up with a conceptual design.”
Micro Craft partnered with other contractors to perform the detailed design and build three vehicles. AEDC was also a key player in developmental testing and evaluation.
Many of the people who helped assemble that vehicle have since found a home at Arnold AFB. Dale McKill, now a machinist at Arnold, was the X-43A crew chief. Paul Sullivan, a design drafter at Arnold, supported many of the electrical and mechanical design drawings. Don Wilt and Barry Puckett were responsible for much of the electrical fabrication, while Bob Williams, Casey Crawford, Bradley Rogers, Derrick Burton, Jeff Fulks and Ronnie Long machined and fabricated many of the internal components, as well as the Space Shuttle tiles that were used to protect the vehicle from extreme heat.
John Nichols, a material controller with Acquisitions at Arnold who worked as the manager of contracts and procurement for the X-43A, noted Micro Craft was a small female-owned business when the contract was awarded.
“The contract for this project was one of the largest contracts at that time and a big undertaking,” added Don Thompson, who worked in Quality Assurance at Micro Craft. Thompson now works as a machinist at Arnold.
The Hyper-X program demonstrated hydrogen-fueled, airframe-integrated scramjet propulsion setting a world-record Mach 7 flight on March 27, 2004, and then flew an amazing Mach 9.6, or nearly 7,000 mph, on Nov. 16, 2004. To reach those speeds, the X-43A was placed on the nose of the Pegasus booster rocket, and then drop launched from the wing of a B-52B Stratofortress. When the rocket “stack” reached the proper altitude, speed and position, the X-43A was pushed off the nose of the Pegasus and then flew under its own power. This was the first-ever free-flight of a scramjet powered aircraft.
Thompson mentioned he was one of the people who was able to visit NASA Dryden Flight Research Center in California and witness the free-flight of the X-43A.
“I was fortunate while I worked on the Hyper-X project to travel all over the country and meet some very interesting people,” he said. “Some of the ones that I worked with had literally came out of retirement to work on this project because of their expertise in the field of hypersonics.
“NASA Dryden, located on Edwards Air Base is one of the places where I was able to work. This is where the B-52 was stationed that carried the X-43. There you would see aircraft flying that a few years earlier were models being tested in the wind tunnels. The last time I was there, before the flight of the Mach 10 vehicle, I walked into the hanger where we were working and in the bay next to ours sat a SR-71. They were prepping it for transport to Wright-Patterson for static display. You never knew what you were going to see there.”
Bisby recalled that the Hyper-X was an exciting project to work on, one of very few that actually made it to flight.
“Often, because of funding cuts or a change in government priorities, a program ends before any hardware is built,” he said. “This is one that actually went all the way to record-setting flights. It was a ton of fun and it was truly a team effort.”
AEDC role in the X-43A Hyper-X
Not only were AEDC team members key players for the X-43A, but AEDC test facilities were used for ground testing of the hypersonic vehicle and its parts.
Tunnel B, a wind tunnel at the von Kármán Gas Dynamics facility, was used to examine the aerodynamic forces that occur when separating the X-43A from the booster stack.
“When the stack reaches the proper speed and altitude, the X-43A is pushed off the nose of the Pegasus booster,” Bisby explained. “It is moving incredibly fast in the upper atmosphere and there are a lot of aerodynamic forces that had to be understood to avoid sending the X-43A out of control or colliding with the booster.”
Testing was also performed in AEDC H2 arc heater unit. In 2000, NASA Langley Research Center used H2 to evaluate potential nose leading-edge materials before flight testing the hypersonic air-breathing vehicles. The AEDC test facility was the only facility that could provide the pressure needed to evaluate the materials. Simulating flight conditions in the H2 arc facility convinced the customer that if the materials survived the AEDC tests, they would survive the flight.
The first X-43 vehicles flew at the Mach 7 condition using a silicon carbide-coated carbon/carbon for the horizontal control surfaces and nose leading edge. The materials are designed to withstand maximum temperatures below 3,000 degrees Fahrenheit.
The flight of the third X-43 vehicle was slightly different. Flying at Mach 10 it was exposed to a more severe thermal environment that exceeded the single-use temperature of the Mach 7 leading-edge materials. Therefore, high-temperature coatings were evaluated at H2 in an effort to use passive carbon/carbon material leading edges for the Mach 10 vehicle. Ensuring these materials survived the flight was critical because leading-edge recession could have contaminated the air-breathing engine, as well as affect vehicle control.
Additionally, AEDC Hypersonic Combined Test Force, located at Edwards Air Force Base, California, provided testing coordination for the X-43A. The AEDC unit has long been involved in the testing of cutting-edge, high-speed aircraft, including the renowned X-15 program during the 1960s and, most recently, the X-51 WaveRider.
Some of the unit’s projects are research and development oriented, and teams may spend five to seven years working on a project for one or two test flights. The HCTF partners closely with entities such as NASA, the Air Force Research Laboratory and the Defense Advanced Research Projects Agency.