The T-38C is a twin-jet aircraft from Northrop Grumman, originally used as a supersonic training jet for US Air Force pilots. But NASA decided to give it an especially fascinating mission: visualizing shock waves.
BOSCO is the friendly sounding method under investigation. It stands for "Background-Oriented Schlieren using Celestial Objects." "A bright light source and/or speckled background -- such as the sun or moon -- is necessary for visualizing aerodynamic flow phenomena generated by aircraft or other objects passing between the observer's camera and the backdrop," NASA notes.
NASA unveiled a series of images yesterday showing a T-38C jet with the shock waves appearing as bent lines radiating from the sides of the plane. A camera on the ground equipped with a special optical filter is pointed upward, and it captures the plane as it flies between the camera and the sun, which appears as a bright, granulated background thanks to the filter.
"Using this naturally speckled background," said NASA engineer Edward Haering, "we could make hundreds of observations of each shock wave, greatly increasing the acuity of the camera system."
NASA developed a code for processing the images, which turned out some pretty spectacular visuals. The results look like the fabric of reality bending in a sci-fi show.
It took some fancy flying to make the images happen. "The pilots had to hand fly the airplane to hit a specific point in the sky to within approximately 300 feet, while travelling faster than the speed of sound," NASA says. They had only a 2-minute window to get this all done.
The new technique will go into rotation for studying supersonic flow patterns. It will help NASA and airplane designers develop what Haering describes as "quiet supersonic overland flight for all."