Why Is A Sonic Boom So Loud?


What does speed have to do with sound? And
if there’s no wall in the sky, how exactly do you break a sound barrier? Hey guys, Amy here with you on DNews today
talking speed! Fast things. Not drug things. Most of us will probably never go supersonic.
Though the idea of cutting travel times in half is so appealing, it’s not something
likely to become common place anytime soon. But let’s start with a bit of a history
lesson. In the 1880s, Austrian physicist Ernst Mach was studying the supersonic flow of gases
using a shadowgraph when he successfully photographed a bullet traveling faster than the speed of
sound. What his images showed was a bullet with a shock wave in front of it and another
one trailing behind it, clear proof of the phenomenon of compressibility. This research
eventually led to the measurements that bear his name: a Mach number is the ratio of the
speed of an object traveling through a gas to the speed of sound in that gas. Because while we don’t think about it, air
is made up of molecules, and like any other physical substance, those air molecules can
compress, and when they compress they form shock waves. It’s these shock waves that make flying
faster than the speed of sound such a challenge, and in the 1940s, pilots were coming face
to face with this challenge. These shock waves vibrate the air molecules they’re made of,
and when those molecules vibrate they vibrate whatever is compressing them. In the case
of a fast-flying airplane, the shock waves can shake an airplane hard enough to rip it
apart. It was clear to engineers in the 1940s that
the future of aviation lay beyond the sound barrier, so someone would have to build an
airplane solid enough and fast enough to break through that wall. It was the Bell Aircraft corporation working
on a contract with the US Army Air Force that devised the solution. Taking design inspiration
from a bullet, Bell engineers designed the X-1 aircraft specifically to break through
that wall of compressed air in the sky. The advent of supersonic flight opened a whole
new era of aviation, and though higher Mach numbers don’t come with the same “barriers”
every increase in speed is nonetheless a major technological hurdle. The fastest manned flight on record was set
in 1967 with the NASA-Air Force X-15, a rocket-powered dart of an aircraft that hit a top speed of
Mach 6.7, which is about 4,519 mph! But the X-15 was a hypersonics research vehicle. Most
fighter jets today aren’t nearly that fast, though there are supersonic fighters. Air
Force planes like the F-15 Eagle and the F-22 Raptor are both supersonic fighter jets, and
the F-22 can even hit Mach 2 using afterburners. But there’s another challenge associated
with supersonic flight and that’s the sonic boom. The sonic boom is the sound an airplane
makes when it smashes through that wall of compressed air that builds up in front of
it. But the boom doesn’t just come once when the plane goes supersonic; it keeps going
in the wake of that supersonic aircraft. This is exactly why the Concorde, the world’s
only supersonic passenger plane that flew from 1976 to 2003, only ever flew over oceans.
In fact, the Federal Aviation Administration prohibited domestic civil supersonic flight
over land in 1973. But all is not lost! NASA and its aviation partners are looking into
identifying an acceptable loudness level and working on so-called “low boom” aircraft
designs to reduce sonic boom levels and maybe bring back supersonic passenger flights. But
that’s still something to look forward to down the line. And the U.S. Air Force always has its eye
on the future, too, and it’s a big supporter of DNews! The United States Air Force is powered
by Airmen and fueled by innovation. Every day American Airmen go above and beyond to
break barriers both professionally and personally. Whether it’s overcoming poverty to become
a nurse and officer or becoming the first female Thunderbird pilot, these Airmen are
known for doing what was once thought to be impossible. Have any of you flown supersonically? If so,
tell us what it was link in the comments below because I’m dying to know what it’s like!
And if you haven’t, do you want to? Let us know in the comments below and don’t
forget to subscribe for more DNews every day of the week. Have any of you flown supersonically? If so,
tell us what it was link in the comments below because I’m dying to know what it’s like!
And if you haven’t, do you want to? Let us know in the comments below and keep coming
back to Test Tube for more DNews every day of the week. Have any of you flown supersonically? If so,
tell us what it was link in the comments below because I’m dying to know what it’s like!
And if you haven’t, do you want to? Let us know on the Discovery News Facebook page
or on Twitter @DNews. You can also find me @astvintagespace. Thanks for watching!

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