A key US hypersonic windtunnel is back on line
following a major refurbishment, and it's first occupant is a model of vehicle that is about to make its first flight - DARPA's HTV-2 hypersonic glider
, the last vestige of its once-ambitious Falcon program (pdf
). Graphic: DARPA
Hypervelocity Wind Tunnel 9
is located in White Oak, Maryland, but is operated by the US Air Force's Arnold Engineering Development Center
, which is headquarted in Tennessee. According to site director Dan Marren, Tunnel 9 is the highest-pressure windtunnel in the world, operating at up to 30,000psi and temperatures up to 3,500F. The tunnel has a 5ft-diameter test section and uses electrically heated nitrogen as the working fluid,
One advantage Tunnel 9 offers hypersonics testers is its relatively long run time. While shock tunnels run for milliseconds, Marren says Tunnel 9 can run for up to a second at high pressures and as much as 15sec at low pressures. This allows the model to be moved during a run - for example to do a dynamic angle-of-attack sweep at up to 80deg/sec.Photo: AEDC
The 14-month refurbishment has given Tunnel 9 a fully digital, reconfigurable, control room and a new suite of instrumentation that allows the facility to collect data needed to understand the physics of hypersonic flight. Used for aerodynamic and aerothermal testing, the tunnel's pressure and temperature capability allows it to reproduce the physics of the boundary layer over a hypersonic vehicle.
Understanding boundary-layer behavior, and its transition from laminar to turbulent flow, is critical to designing a hypersonic vehicles, as turbulence greatly increases heating on the airframe. Tunnel 9's new instrumention suite includes temperature-sensitive paint on the model, high-frequency pressure sensors that provide information on boundary-layer behavior and "focused Schlieren" imaging that allows testers to take a close look at the transition point.
For the proving runs after recommissioning, AEDC chose the HTV-2 model, as its complex three-dimensional shape provided a challenging test for the new instrumentation. Tests are being run a speeds from Mach 10 to Mach 14, with the model static and moving. As the HTV-2's exact shape is sensitive, no pictures of the runs have been released, but Tunnel 9 has previously been used to test a full-scale THAAD interceptor:Photo: AEDC