SCIENTISTS HAVE succeeded in taking what is claimed to be the first clear picture of a sonic boom made by an aircraft in flight.

The technique, pioneered at NASA's Langley Research Center, Virginia, could be a vital tool in the development of a future supersonic high-speed civil transport.

To capture the image, a Northrop T-38 was flown above a small telescope, at an altitude of 10km (5.4nm) and a speed of Mach 1.1, aided by satellite navigation.

The telescope was focused on the Sun, through a narrow slit, which provided a source of illumination. The image of the T-38 was then recorded on 16mm movie-camera film, speed-synchronised to capture the aircraft as it moved through the telescope's field of view.

The turbulent shock waves generated by the aircraft refracted the sunlight according to their density, producing brightness variations on film, which were later computer enhanced.

The shock waves appear as red and green diagonal lines. The main shock waves originate from the nose and the tail of the aircraft, with smaller shock waves from the engine inlets and the wing.

The engine-exhaust plumes appear yellow.

Source: Flight International