Thanks to Brilliant for  supporting this SciShow video!

As a SciShow viewer, you can keep  building your STEM skills with a 30 day free trial and 20% off an annual premium  subscription at Brilliant.org/SciShow. These days, you have to be an astronaut or a fighter pilot to break the sound barrier.

But a few decades ago, all you  had to do was buy a ticket. Back then, we had the Concorde,  the famous supersonic plane that could get you from NYC to  London in just under 3 hours. But its reign was short-lived.

Beset by concerns over safety, cost,  and emissions, it was retired in 2003. And there was one other problem: the  Concorde could only fly over the ocean. Supersonic planes create sonic booms,  which are annoying.

And disruptive. So disruptive, in fact, that  many countries have passed laws prohibiting non-military aircraft from  flying faster than sound over land. So if we want super-fast flight back, we need to find a way to take the “boom” out of “sonic boom.” Maybe even make it something else  entirely… like a sonic thump.

And that’s what engineers are proposing.  And they think they’re getting close. [♪ INTRO] Meet the X-59, our newest bid  at commercial supersonic flight. This funny-looking bird is  part of NASA’s Quesst program, which stands for Quieter SuperSonic Travel. The X-59 has been in development for a long time, in partnership with Lockheed Martin’s  Skunkworks, a frequent NASA contractor.

At the time we’re making this episode, engineers are very close to a working prototype. Meaning they’ll have the ability to run  real tests over real areas with real people. Which is important, because it will  let them evaluate the most important and difficult part of the design:  how quiet can they make a sonic boom.

So, why do things that go very fast make  very loud noises in the first place? Well our plane is flying through  air, and air is (in this case) also the medium that propagates sound. As a plane flies, it has to  nudge the air out of the way.

And this pressure is effectively also sound, because sound is a pressure  wave that our eardrums detect. Now imagine the plane is going faster  than sound, around 340 meters per second. It's literally going faster than  that pressure wave can move.

This means the pressure  waves build up continuously, creating a big old shock wave  that we hear as a loud crack. It's like the plane is doing a belly  flop into a pool... again and again. Not only is this as loud as a  thunderclap.

It’s extended, too. Supersonic planes carry their booms  across their entire flight path. There’s even a risk of physical damage  down below, like broken windows.

Sound waves are waves of pressure, after all. Hence the current laws against  commercial over-land supersonic flight. And that severely limits the  capabilities of a commuter aircraft.

For example, you could fly  supersonic from New York to London, but not from New York to Los Angeles. And that brings us to sonic thumps. That’s what the engineers of the X-59 call  the aircraft’s new, quieter sonic boom.

It’s predicted to be quieter  than a car door closing. As for what it’ll sound like exactly, I  am not kidding but we reached out to NASA and they basically said they’d  know when they heard it. But joking aside, big thanks to Mark Mangelsdorf and the X-59 team for answering  our questions for this video.

Now predicting a sonic thump and realizing  that prediction are two different beasts. So, how is the team going to make it real? Well basically, they have to figure out a  way to change a belly flop into a swan dive.

Usually, a boom registers  on a pressure-reading device as an N-shaped plot with sharp points. Now Sharp points here, equal loud noise. But if you can figure out how to  smooth out those sharp points, you can lower the volume of the sound.

And the key, just like in diving, is shape. The X-59 isn’t just weird-looking for no reason. For a start, the plane’s 11.5-meter-long  nose pierces through the air, giving the surrounding air molecules  more time to get out of the way.

This keeps air pressure at the front of the plane from building up all at  once, and softens the boom. The X-59 also has no bulky cockpit window. Instead, the pilots use two small mounted cameras and a 4K live display to  see in front of the plane.

And the bottom is super flat, so  air can just flow uninterrupted. Pretty much all protrusions are kept on top, so that the plane can shield the ground  from any boom that they might create. Turns out there’s not a lot of  folks listening from up above.

All very cool ideas, theoretically.  But how do we know it’s going to work? Well, like anything else, we test it. A lot.

The first and most repeated step in  the X-59’s development is 3D modeling. It’s a huge part of plane design,  as it allows engineers to digitally test and retest designs without  having to build a whole plane. Without it, we probably couldn’t  design this kind of plane at all.

Now once researchers have a good idea  of what the plane should look like, they can move on to the wind tunnel. There, they can test a scale model of the plane to actually measure any booms that formed, see how quiet those booms are, and  examine how the plane works in real life. Then, and only then, can engineers  make a full-sized prototype.

Which is what’s up next for the X-59. The engineers had to pass a few hurdles  on their way to real test flights. Obviously, they had to get through  all the bumps in the design process.

But they also needed special approval  from the Federal Aviation Administration to actually do the technically-illegal  flying-over-land bit. As these tests progress, the team  will have to follow certain rules. For example, they can only fly in certain spaces, and they have to give ample warning  to those below before a flyover.

During the tests, the researchers will  be able to study the flyover communities to see how disruptive the  new-and-improved boom really is. Imagine being approached for that questionnaire. Pardon me, but how annoying  was our sonic thump?

Be honest. The team will also make use of  newly-developed shock wave photography to basically take pictures of the  booms, or thumps as the case may be, and study them in unprecedented detail. It’s still going to be a while  before this thing is finished.

And a quiet boom won’t fix everything. After all, High operational costs  and carbon output still exist. But if it can fly over land, and not  just ocean, the X-59 may actually be cost-effective… unlike the Concorde before it.

After all, if you can fly anywhere,  a whole new world opens up. And thank you to Brilliant for  supporting this SciShow video! Brilliant is an online learning  platform with thousands of interactive lessons in math,  science, and computer science.

They even have bonus puzzles in each of those categories, like their Physics Puzzles. These get you thinking about  physics topics like pressure, which we touched on in this video. If you want to learn more about the  mechanics of the wind tunnel experiments I just mentioned or the waves of  pressure that create those booms, this Brilliant course is a fun way  to start exploring those topics.

To try it free for 30 days, you  can visit Brilliant.org/SciShow or click the link in the description down below. That link also gives you 20% off an  annual premium Brilliant subscription. And thank you for watching! [♪ OUTRO]