An aircraft tears through the air at tremendous speed. Shock waves, hot gases, and turbulence form around it. A U.S. document proposed looking for these traces to detect and track the aircraft.
Written in 2010 by an intelligence agency within the U.S. Department of Defense, the document concerns aircraft traveling at more than five times the speed of sound. Its idea is simple but surprising: sometimes, you can learn about an aircraft from the air it has disturbed, even if you can’t see it clearly.
The Wake Leaves Clues
When an aircraft travels faster than sound, it pushes hard against the air and creates a shock wave. Its flight also heats the air around it and leaves turbulence in its wake. The document reviews ways to detect these effects and use them to determine where the aircraft is and where it is headed.
For example, a heat-sensing camera might pick up a warm area around the aircraft. Radar sends out radio waves and detects the waves that bounce back. Another method, using laser light, can examine the air around the aircraft. Each trace may offer a different clue about its passage.
Each Method Picks Up Something Different
The document identifies radar and heat-detecting instruments as the most capable tools available for detection at the time it was written. But no single method can detect everything. Radar and heat sensors, for instance, pick up different kinds of traces.
The document therefore proposes combining several methods. Together, they may provide a clearer picture and help track and identify the aircraft, distinguishing it from other things. The review also considers ways to focus on the wake itself, such as examining the heat and gases left behind by the aircraft’s flight.
What Remains Unknown
The document does not describe a particular aircraft or encounter. It reviews existing knowledge and ideas; it does not prove that new methods are already working. The official summary also cautions against treating it as current confirmation of the ideas.
The aircraft moves on. Clues remain in the sky, but who will be able to read them?
