Schlieren image captures moment Boom breaks sound barrier
March 4, 2025
Boom Supersonic has immortalised the moment its XB-1 demonstrator passed through the sound barrier on its 13th and final flight on 10 February, co-ordinating with NASA teams on the ground to visualise the supersonic shock waves.
The Schlieren imaging technique – which NASA explains is “used to visualise the flow away from the surface of an object,” in this case capturing the disruption to the adjacent air caused by the sonic boom – is one requiring precise conditions and timing. During XB-1’s final flight, the aircraft’s second pass through the sound barrier was captured in photographic form over the Mojave Desert.
With chief test pilot Tristan ‘Geppetto’ Brandenburg at the controls, XB-1 was positioned “an at exact time in a precise location,” explained Boom, enabling NASA to document the changing air density as XB-1 flew in front of the sun.
Using waypoints computed by NASA, Boom’s flight test team “rapidly developed avionics software to guide the pilot to the specific points in space that XB-1 would have to fly to in order to eclipse the sun,” continued Boom. NASA then used ground telescopes with special filters to capture the resulting image. However, with timings critical, only one Shlieren image run was possible out of three opportunities presented by the flight.
With the subscale demonstrator flight test campaign now complete, learnings gleaned from the XB-1 programme – the first independently-developed US aircraft to break the sound barrier – will now inform the company’s upcoming ‘Overture’ supersonic airliner, while the XB-1 will be immortalised on static display in Boom’s new Denver headquarters.
