For The First Time Ever, NASA Captures Images of Supersonic Shock Waves Merging in Air

Two U.S. Air Force craft were traveling so fast — quicker than the speed of sound — and so close together that the shock waves emanating from the craft began to merge… and NASA was there to capture photographic proof.

The resulting snapshots are the first-ever photos of two supersonic shock waves (pressure waves) interacting in the air. And it's quite a sight: It looks as though the atmosphere folded up into a fresh batch of laundry. [Supersonic! The 10 Fastest Military Airplanes]

As an aircraft travels, it pushes the air in front of it and creates waves, just like a motor boat creates waves as it moves through the water.

But when aircraft travel faster than the speed of sound — or faster than 767 mph (1235 km/h) — it moves faster than the waves it creates. Because air molecules can't keep up with its speed, they begin to compress. This creates a rapid increase in pressure in front of the craft, resulting in a different kind of wave: supersonic shock wave. Though humans can't see these shock waves, we can hear them merging together as they move through the atmosphere as a thunder-like sound called a sonic boom.

In the recent event, NASA's air-to-air schlieren photographic technology captured images of mingling shock waves from two T-38 supersonic U.S. Air Force Test Pilot School airplanes. These craft fly about 30 feet (9 meters) from one another and at a 10-foot (3 m) difference in height, according to a NASA statement.

Snapped by another plane flying at about 2,000 feet (610 m) above the two fast-moving aircraft, the images captured how the shock waves became distorted or curved as they interacted. "We never dreamt that it would be this clear, this beautiful," J.T. Heineck, a physical scientist at NASA's Ames Research Center in California, said in the statement.

They also snapped a photo that they called a "knife-edge" shot of supersonic shock waves created by a single T-38. Shock waves created by a single aircraft look like straight lines emenating like a cone off the tip of the aircraft.