NASA Photos Reveal New Technique for Studying Sonic Booms
NASA has released stunning images of an Air Force fighter jet passing in front of the sun, demonstrating a method for visualizing sonic booms by using the schlieren photography technique. The images were captured as the aircraft went from subsonic to supersonic flight speeds, with the resulting shockwave clearly visible.
The photos were taken at NASA’s Armstrong Flight Research Center, located in California, and feature the Test Pilot School T-38 aircraft.
NASA hopes the information they are now able to capture can help it view sonic booms, assisting in the development of the supersonic X-plane, also known as the Low Boom Flight Demonstration (LBFD) aircraft or Quiet Supersonic Transport (QueSST) according to a report by the Daily Mail.
The aim is to find methods for lowering the resulting “boom” that is created when the X-plane achieves speeds beyond Mach 1. Additionally, the images allow NASA to compare the real shockwaves to their predictions.
Images using the schlieren photography technique use the sun as a backdrop. The approach was previously used in 2016 during a series of flights referred to as Background Oriented Schlieren using Celestial Objects (BOSCO).
BOSCO positioned cameras, aligning with the sun to create the necessary background, and used a special hydrogen alpha filter. Telescopic lenses were used to enlarge the size of the sun in the frame, giving them an opportunity to visualize the shockwaves that were created from supersonic jets passing in front of the sun.
For the X-plane, the method of capturing the images has to be slightly altered. While BOSCO had jets passing the sun approximately 40,000 feet from the camera, the X-plane reaches altitudes of 60,000 feet. This means, instead of using the cameras on the ground, as was done with BOSCO, they will need to be mounted to a chase aircraft.
BOSCO II, a follow-up experiment, adjusted the method for distances of 10,000 feet, mimicking the range that would be required for the air-to-air photographs that the X-plane needs, and used a smaller camera, which could be mountable.
Capturing the images required a substantial amount of accuracy on the part of pilots, even at speeds beyond Mach 1.
“This wasn’t an easy task for our pilots, but they hit the mark,” said Brett Pauer, the Commercial Supersonic Technology Sub-project manager. The images were deemed to achieve a high enough quality to provide needed insights.
NASA hopes to achieve a sonic boom that is 60 dBA lower than current supersonic aircraft technology, such as what was used on the Concorde.
A contract for the X-plane will be awarded by NASA in 2018, and initial plans aim for a test flight of the aircraft in early 2021.