Last fall, NASA released some photographs of its synthetic Schlieren photography that captured the sonic boom of a supersonic jet in flight. Recently, the government decided to classify the high resolution photographs from that release, although low resolution images, such as the ones shown below, can still be found on the internet, for example, here, which includes a short film clip (which has been removed from some other sites recently). We’ve posted several of the still images below that illustrate the shock waves.
The following image shows a supersonic shock wave quite clearly:
Another image illustrates how clearly the aircraft can be photographed using advanced digital photography using the sun as a light source.
We speculate that the rationale for making this technology classified may be to make (if such photography could be implemented on a widespread basis) stealth aircraft and drones potentially identified while in flight by an enemy and targeted and destroyed, or provide warning to move to more secure locations prior to overflight. This is difficult to accomplish against stealth vehicles today.
The question is how advanced such technology could become, and how quickly that could occur. Schlieren photography has been around since the 1860s (yes, about 150 years) and has been commonly used in wind tunnels to detect changes in refraction and therefore shock-wave patterns from a background light source. It is widespread. NASA has upped the game, using telescopes and digital photography, and using the sun as a background light source. Today, we’ve made significant strides in digital photography and image processing, and can “synthetically” create Schlieren images, as NASA has done with GASPS (Ground to Air Schlieren Photography System) that developed these images.
Of course, the timing of the aiming points and photography needed to be very precise, and lots of computer power applied to obtain the results that were shown above. But digital camera technology continues to improve, as shown in this link, and computing power continues on its exponential development curve. Marrying these two could result in a new detection capability – focusing on disturbances in airflow rather than radar that would enable the detection of stealthy aircraft and render those multi-billion dollar investments vulnerable.
There is no way to move an object through air without creating a disturbance in airflow. If a system like this could detect movements using real-time image processing from advanced digital photography over a widespread area, a substitute for radar detection could be at hand, all stemming from a technology originally developed by the German physicist August Toepler way back in 1864.