Engineers in Tennessee are contributing to NASA's efforts to understand how air flows over vehicles at hypersonic speeds. That's Mach 5 and above.
A model of an ATK rocket with the NASA Hypersonic Boundary Layer Transition (HyBoLT) experiment mounted on it recently completed wind tunnel tests at the U.S. Air Force's Arnold Engineering Development Center (AEDC) in Tullahoma, Tenn. A full-scale version of the HyBoLT/SOAREX/ALV X-1 ATK launch vehicle is scheduled to fly late this year at NASA's Wallops Flight Facility on Virginia's Eastern Shore.
"The mission of the HyBoLT payload, located on the nose of the launch vehicle, is to obtain unique high-speed flight data for fundamental boundary layer transition flow physics," said James Pittman, the principal investigator for NASA's Hypersonic project.
"Data for atmospheric re-entry technology will be collected on an internally carried payload called SOAREX that will be ejected during the flight," added Pittman.
The objective of the hypersonic test in AEDC's von Kàrmàn Gas Dynamics Facility's Tunnel B was to assess the stability of the HyBoLT/ALV X-1 rocket during the ascent phase of launch. "NASA wants to be sure that this vehicle will have a successful ascent to hypersonic flight test conditions," Paul Jalbert, Aerospace Testing Alliance (ATA) project engineer said. ATA is an aerospace engineering company that works as a contractor for Air Force.
The model was tested at AEDC for only eight hours - four hours at Mach 6 and four hours at Mach 8. The AEDC test was the first of a series of three wind tunnel tests spanning the velocity range from lift-off to Mach 8. The model underwent testing at supersonic speeds at NASA's Langley Research Center in early June and then went to NASA's Ames Research Center for transonic testing.
"The purpose of the three wind tunnel tests is to produce data for an aerodynamic database for the flight control system of the launch vehicle," said Matt Rhode, Langley wind tunnel test lead. "The wind tunnel tests are generating the majority of the data to be used in the aerodynamic database, while Computational Fluid Dynamics predictions are providing scaling from wind tunnel to flight conditions.
The HyBoLT experiment that will fly on the ATK ALV X-1 rocket is looking at research that's relevant to space shuttles and future advanced designs, according to Langley's Chuck Leonard, aerodynamics team lead. One side of the wedged-shape HyBoLT payload model has three rough surfaces, similar to situations encountered by the space shuttle, and the other side has a smooth surface.
"On the shuttle side we included three distinct 'trips,'" said Leonard. "One looks like gap filler. Another looks like a cavity or a shuttle tile that is missing and the third looks like a protruding shuttle tile. We're looking at how those different geometries affect the air flow."
"We're looking for natural transition on the smooth side," added Leonard. "If everything is smooth – what do you see?"
What the researchers see during all the tests may help them address some of the challenges of hypersonic flight, a speed regime that's difficult to simulate and predict.
NASA Langley Research Center