Airborne Schlieren Imaging System (ASIS)
Armstrong researchers are using a schlieren technique to capture images of shock waves emanating from aircraft in supersonic flight. For supersonic flight to ultimately become acceptable, it is necessary to study the shocks and quiet the boom. The ASIS technique captures images of shocks by aligning a supersonic aircraft between a camera-equipped aircraft and the sun, and then watching as the shocks put an apparent ripple on the sun's edge. This technique allows for side-view imaging at operational altitudes where typical supersonic flights are
expected to occur. These images will enable researchers to validate data from supersonic models and wind tunnel tests.
Work to date: The team conducted a proof-of-concept demonstration of the ASIS technique during a February 2014 flight test and is evaluating the results.
Looking ahead: The team will continue to test and mature the technology. The sun-ripple concept and aircraft alignment algorithms developed for ASIS are being considered for use on future projects. The team is working to identify potential research partners.
Innovative: Captures side-view images of shock waves, as opposed to the top-down or mostly bottom-up images captured by other techniques
Accurate: Enables precise sonic boom estimation by validating supersonic models and wind tunnel tests
Supersonic Flight Research
Supersonic flight over land is currently severely restricted because sonic booms created by shock waves disturb people on the ground and can damage private property. Since the maximum loudness of a sonic boom is not specifically defined by the current Federal Aviation Administration (FAA) regulation, innovators at NASA have been researching ways to identify a loudness level that is acceptable to both the FAA and the public and to reduce the noise created by supersonic aircraft. Using cutting-edge testing that builds on previous supersonic research, NASA is exploring low-boom aircraft designs and other strategies that show promise for reducing sonic boom levels.
A variety of factors, from the shape and position of aircraft components to the propulsion system's characteristics, determine the make-up of a supersonic aircraft's sonic boom.