NASA is known for its extensive research and development breakthroughs, leading to many inventions that improve our lives on a daily basis – such as Velcro, Teflon and the Biro. Now NASA is looking to improve supersonic flight, and to do so it’s using a technique over half as old as the USA.
Making use of a photography technique developed by German physicist August Toepler in 1864, NASA’s Armstrong Flight Research Center at Edwards Air Force Base, along with Ames Research Center at Moffett Field, are using schlieren imagery to visualise supersonic flow. Using full-scale aircraft in flight, rather than in a wind tunnel, the NASA teams are hoping to gain a clear understanding of the location and strength of shock waves to aid the design of future high-speed commercial planes.
Schlieren imaging reveals shock waves by observing the change in air density around the shock wave, which refracts light in a different way. However, NASA faced challenges taking traditional schlieren techniques out of wind tunnels and model craft photography and applying it to full-scale flying aircraft above the Mojave Desert.
NASA used a modified version of background-oriented schlieren, which relies on a speckled background pattern and a series of images of an object in supersonic flow against that background to deduce light distortion. Here, the camera is strapped to a plane to capture full-scale aircraft in flight, and the technique is dubbed air-to-air background-oriented schlieren, or AirBOS. NASA researchers captured footage of up to Mach 1.09 (768mph at sea level).
“Air-to-air schlieren is an important flight-test technique for locating and characterising – with high spatial resolution – shock waves emanating from supersonic vehicles,” said Dan Banks, the Armstrong Center’s principal investigator on the project. “It allows us to see the shock-wave geometry in the real atmosphere, as the target aircraft flies through temperature and humidity gradients that cannot be duplicated in wind tunnels.”
From there, researchers refined AirBOS tech to use high-resolution cameras and to capture faster aircraft in flight – no easy feat when you’re trying to align two objects above the same patch of land for a photo.
But why go to all this effort? Well, according to Tom Jones, associate project manager for flight at the Commercial Supersonic Technology Project, “the end goal is to facilitate the ability for a new speed regime and open a new commercial market for civil transportation”.
Still, even if NASA doesn’t manage to improve civil aviation, at least it got to take some cool pictures in the process.
Images courtesy of NASA
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