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Using the schlieren photography technique, NASA was able to capture the first air-to-air images of the interaction of shockwaves from two supersonic aircraft flying in formation. These two U.S. Air Force Test Pilot School T-38 aircraft are flying in formation, approximately 30 feet apart, at supersonic speeds, or faster than the speed of sound, producing shockwaves that are typically heard on the ground as a sonic boom. The images, originally monochromatic and shown here as colorized composite images, were captured during a supersonic flight series flown, in part, to better understand how shocks interact with aircraft plumes, as well as with each other.
The X-59 Quiet SuperSonic Technology X-plane, or QueSST, will test its quiet supersonic technologies by flying over communities in the United States. X-59 is designed so that when flying supersonic, people on the ground will hear nothing more than a quiet sonic thump – if anything at all. The scientifically valid data gathered from these community overflights will be presented to U.S. and international regulators, who will use the information to help them come up with rules based on noise levels that enable new commercial markets for supersonic flight over land.
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.
In classical schlieren photography, the collimated light is focused with a converging optical element (usually a lens or curved mirror), and a knife edge is placed at the focal point, positioned to block about half the light. In flow of uniform density this will simply make the photograph half as bright. However, in flow with density variations the distorted beam focuses imperfectly, and parts that have been focused in an area covered by the knife edge are blocked. The result is a set of lighter and darker patches corresponding to positive and negative fluid density gradients in the direction normal to the knife edge. When a knife edge is used, the system is generally referred to as a schlieren system, which measures the first derivative of density in the direction of the knife edge. If a knife edge is not used, the system is generally referred to as a shadowgraph system, which measures the second derivative of density.
If the fluid flow is uniform, the image will be steady, but any turbulence will cause scintillation, the shimmering effect that can be seen on hot surfaces on a sunny day. To visualise instantaneous density profiles, a short-duration flash (rather than continuous illumination) may be used.
originally posted by: thebozeian
Sometimes I wonder if people actually comprehend what they read? Several people have asked if "this" could be responsible for whats causing booms heard throughout the world. Well "this" is testing a new photographic processing technique, its not an aircraft. Military aircraft carry out supersonic flights all over the world every single day, so no surprises there. Lightning strikes probably cause more supersonic booms around the world in 10 seconds than all the aircraft sonic booms in a year combined. If you somehow misunderstood it and thought this was something to do with the NASA commissioned and Lockheed build X-59 QueSST, well they haven't even finished designing it yet, let alone built it or flown it. And it is specifically being designed to NOT be heard.