September 22, 2023

This is what happens during a sonic boom

Two United States Air Force F-16 Fighting Falcons

Two United States Air Force F-16 Fighting Falcons.US Air Force photo by Tech. Sergeant Matthijs Lotz

  • A sonic boom is the loud sound created when something breaks the sound barrier.

  • You break the barrier by traveling faster than the speed of sound, which is 768 mph at sea level.

  • Supersonic flights are banned over US cities because they can cause annoying noises and vibrations.

An F-16 raced to intercept an unresponsive plane on Sunday, and the fighter jet generated a sonic boom that was heard in the DC area.

A sonic boom is a loud sound that people on the ground can hear when, for example, an airplane breaks the sound barrier by flying faster than sound.

Supersonic flight is banned in the US without special government permission because of the annoying noises and vibrations it can produce.

This is what happens when an airplane breaks the sound barrier:

When an airplane goes fast enough, it compresses the air it passes through so much that it can change its density, creating cone-shaped shock waves.

These shock waves act much like the wake behind a boat, which happens because it disturbs the water by moving faster than the water waves.

Air pressure at the end of the cone in front of the plane is normal, while the pressure inside the cone is high because the plane is going through it so fast, pushing the air atoms against each other.

Because the plane concentrates the sound wave energy in one spot, you hear it all at once – it produces a “boom” sound rather than the typical sound of a fighter jet flying by.


This T-38C, a US Air Force supersonic training jet.US Air Force

NASA has developed a way to see supersonic shock waves, and the images are beautiful

NASA and the US Air Force have been trying to visualize this effect for years so they can build better supersonic aircraft and go faster than sound.

Until recently, these types of tests were limited to ground-based wind tunnels.

There, researchers used the Schlieren technique, invented by German physicist August Toepler in 1864, to understand more about how air travels around supersonic aircraft.

Schlieren imaging is a way of seeing the differences in air density, using a particular arrangement of lenses and cameras.

Decades later, NASA researchers adapted this method to visualize supersonic aircraft in flight.

Getting the Schlieren method airborne has been challenging, because the plane carrying the imaging equipment has to fly directly above the plane it’s recording and travel just as fast — which is faster than the speed of sound during supersonic imaging.

The T-38C, a US Air Force supersonic training jet imaged by NASA, traveled at a top speed of Mach 1.09 during testing. (Mach 1 is the speed of sound, which is about 768 mph at sea level.)

But the tricky maneuvering was worth it for this beautiful footage, showing the shock wave from the T-38 flying over the Mojave Desert:

the silhouette of an airplane with straight line shock waves emanating from each side

This schlieren image dramatically shows the shock wave from a supersonic fighter jet flying over the Mojave Desert. Researchers used image-processing software developed by NASA to remove the desert background, then combined and computed multiple frames to get a clear picture of the shock waves.NASA

Here’s another Schlieren image that visualizes the supersonic flow of the T-38 jet in flight:

the straight shock waves from an airplane flying faster than the speed of sound

NASA uses a 21st-century version of Schlieren imagery, invented by a German physicist in 1864, to visualize supersonic flow phenomena with full-scale aircraft in flight.NASA

Understanding how supersonic aircraft affect the air around them could help develop ways to make planes quiet enough for commercial travel, making the journey from New York to London a lot faster.

Read the original article on Business Insider

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