The images were captured during the fourth phase of Air-to-Air Background Oriented Schlieren flights, or AirBOS, which took place at NASA’s Armstrong Flight Research Center in Edwards, California. The flight series saw successful testing of an upgraded imaging system capable of capturing high-quality images of shockwaves, rapid pressure changes which are produced when an aircraft flies faster than the speed of sound, or supersonic. Shockwaves produced by aircraft merge together as they travel through the atmosphere and are responsible for what is heard on the ground as a sonic boom.
“We never dreamt that it would be this clear, this beautiful.”
The system will be used to capture data crucial to confirming the design of the agency’s X-59 Quiet SuperSonic Technology X-plane, or X-59 QueSST, which will fly supersonic, but will produce shockwaves in such a way that, instead of a loud sonic boom, only a quiet rumble may be heard. The ability to fly supersonic without a sonic boom may one day result in lifting current restrictions on supersonic flight over land.
The images feature a pair of T-38s from the U.S. Air Force Test Pilot School at Edwards Air Force Base, flying in formation at supersonic speeds. The T-38s are flying approximately 30 feet away from each other, with the trailing aircraft flying about 10 feet lower than the leading T-38. With exceptional clarity, the flow of the shock waves from both aircraft is seen, and for the first time, the interaction of the shocks can be seen in flight.
“We’re looking at a supersonic flow, which is why we’re getting these shockwaves,” said Neal Smith, a research engineer with AerospaceComputing Inc. at NASA Ames’ fluid mechanics laboratory.
“What’s interesting is, if you look at the rear T-38, you see these shocks kind of interact in a curve,” he said. “This is because the trailing T-38 is flying in the wake of the leading aircraft, so the shocks are going to be shaped differently. This data is really going to help us advance our understanding of how these shocks interact.”
The images were captured from a NASA B-200 King Air, using an upgraded camera system to increase image quality. The upgraded system included the addition of a camera able to capture data with a wider field of view. This improved spatial awareness allowed for more accurate positioning of the aircraft. The system also included a memory upgrade for the cameras, permitting researchers to increase the frame rate to 1400 frames per second, making it easier to capture a larger number of samples. Finally, the system received an upgraded connection to data storage computers, which allowed for a much higher rate of data download. This also contributed to the team being able to capture more data per pass, boosting the quality of the images.
Further reading at NASA; https://www.nasa.gov/centers/armstrong/features/supersonic-shockwave-interaction.html
Credits; NASA images.