NASA Is Working on Hushing the Sonic Boom of Supersonic Flights

After receiving thousands of claims from Americans against the Air Force due to the chaos caused by supersonic jets, the Federal Aviation Administration (FAA) prohibited overland supersonic flights in 1973. As supersonic aircraft fly faster than the speed of sound, a sonic boom arises, generating massive amounts of sound energy. It occurs as a result of the high air pressure surrounding the aircraft, which hovers through the air at high speeds, causing shock waves. The sonic boom can be heard and felt up to 30 miles away.

Since the ban on supersonic flights is still in effect today, NASA engineers are working on an experimental project to replace the disruptive sonic boom with a lighter thump. This year, NASA plans an inaugural test flight of its Low-Boom Flight Demonstration using its X-59 quiet supersonic aircraft. The agency is now finishing the development of the X-59 at the Skunkworks site, California, in collaboration with Lockheed Martin, an American aerospace company.

Schlieren photography technique

NASA’s aeronautics engineers employed a small model of the X-59 Quiet SuperSonic Technology (QueSST) aircraft in NASA Glenn’s 8 x 6-foot supersonic wind tunnel for boom testing. The deputy manager of the Commercial Supersonic Technology (CST) project, Clayton Meyers, said, “This is the team’s opportunity to get data at the low sound levels produced in the tunnel.” He said that it all came down to their capacity to measure the thump.

A small model of the X-59 inside NASA Glenn’s wind tunnel. Credit: NASA

The one-foot-and-a-half-long model has been put through multiple weeks of testing in the tunnel and has produced shock waves. Intending to visualize NASA’s boom-reducing technology and boom-predicting capability, the engineers used a process of schlieren photography to capture the data sets and shock waves with the help of special cameras placed outside the tunnel and a unique sensor system inside.

The cameras produced schlieren images, which provided the engineers with a visualization of airflow around the aircraft model as well as the positions of the shock waves. Meanwhile, the detailed measurement of the shock waves was derived from the sensor, from which the engineers could determine the strength of the shocks.

Here’s to future X-59 flights

The results of the tests appeared to be good news for the team as the strength and position of the shock waves produced by the model matched those of prior computer models for quiet supersonic flight. Schlieren visualizations and detailed measurements are important in helping NASA compare the data with those from computer-based models.

It will also improve the engineers’ ability to understand and predict sonic thumps for future X-59 missions. Besides, schlieren imagery also helps researchers understand how new aircraft designs, like the X-59, reduce sonic boom noise. John Wolter, the lead researcher of the wind tunnel sonic boom test, said, “With the X-59, we want to demonstrate that we can reduce the annoying sonic booms to something much quieter, referred to as ‘sonic thumps’.”

“The goal is to provide noise and community response data to regulators, which could result in new rules for overland supersonic flight. The test proved that we don’t just have quieter aircraft design, but that we also have the accurate tools needed to predict the noise of future aircraft,” he concluded.

Credit: Lockheed Martin

In March, NASA will ship the model to Tokyo for another wind tunnel verification test with the Japan Aerospace Exploration Agency (JAXA) and Boeing, in which both teamed up for aircraft noise technology reduction last year. If the X-59 experimental aircraft’s test flight goes smoothly, NASA will validate that the aircraft’s quieter supersonic technology works as planned before proceeding to the commercial flight phase.

Though supersonic flights are still prohibited, there are special conditions for approved flights. According to FAA administrator, Steve Dickinson, “The FAA supports the new development of supersonic aircraft as long as safety parameters are followed.” Let alone, NASA’s supersonic flight test aims at testing its noise reduction technology.

Once quieter supersonic flights become a reality, it is also feasible to get travelers from one location to their destinations much faster, while also minimizing the boom’s disruption to the community.

If you are curious to see the fastest manned plane in the world, don’t miss to watch the video embedded just below.