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Shockwave Shadows in Ultra Slow Motion (Bullet Schlieren) – Smarter Every Day 203

– Hey, it’s me Destin. Welcome back to “Smarter Every Day.” As long as I’ve understood the physics, I’ve wanted to visualize the Shock Wave on the front of a super sonic bullet. But the problem with doing this, is you have to have access to some pretty expensive optical hardware. Which is why I’m pretty excited about this giant 16″ parabolic mirror. Which is going to let us play around with the speed of sound. Let’s go get “Smarter Every Day”. Okay, We’re going to use a Schlieren Setup to get these bullet images. Here’s how it works. So we have the camera right here, right. So this is a Phantom v2511. We have a mirror way over there
and the way we’re doing that is that we have a point source here. So we’re shining that light
and it’s spreading out; and as it spreads out it hits this mirror, and it bounces back
and as it bounces back, it comes down to a point. One point right there and we’re cutting off half of that light. Long story short it comes right here flips back over goes into the lens. If the air is less
dense then light travels through it faster. If air is more dense light
travels through it slower, that causes the light to move or bend, as it goes through different types of air; and then we can detect those shadows using this Schlieren Setup. This is my buddy Coop. He’s gonna shoot through his own shop. We’re not gonna do this, you know (cow mooing) – I’m not shooting at his shop. I think we’re ready. – On target. – Three, Two, One. Fire.
(gunshot) Whoo huhu (gun clicks)
– Weapon Clear. – That’s a big boom. So let’s see if we got it. (laughing) – [Male] Come here Coop – [Destin] Oh Coop, come look at this. (sound wave) – [Male] Oh Cool – [Destin] That’s unbelievable. Okay, so I’m gonna save that. I like to guess where the
shock waves come from. The initial one looks like its
coming off the bullet itself. But then later there
seems to be this weak one that I’m guessing that
reflected from the plywood table that the mirror is sitting on. Not really sure about that. But then there’s this stronger
one that comes after that and my guess for that one is that it’s coming
off the concrete floor, because it’s more of a pure reflection. Then later if you fast forward the video you can see there’s a very
week shock wave coming across, and my guess is that’s coming
from the muzzle itself. I’m not sure on all these. I canna have to extrapolate, but that’s kinda part of the fun. Three, Two, One. Fire.
(gunshot) (laughing) (sound waves) That’s legit man. Okay so we’ve dropped it to
28 thousand frames per second. We’re trying to get a
really good single image. Fire.
(gunshot) (coughing) I actually put air in my lungs. (sound waves) This footage looks amazing. But to understand exactly
what we’re looking at why don’t we build a little bitty model with a bullet and a stick
and talk about it here. So lets imagine that we’ve
got this bullet sitting here and we’ve got circles
emitting from the front. As we move this thing watch what happens. Those circles will stack up in the front and they kind of relax in the
back and they expand, right. So that’s a normal flight. What happens if the velocity
at which we move thing, out runs those circles moving away? Check this out. As we start to out run it, you’ll notice that we this
expansion in the back here and it tapers down and we get this angle. We get this, I don’t know what
you’d want to call it, right. We’ve got a cone here. What happens if we move
forward even faster? (whooshu) That angle that we made there
is even shallower or pointier. That’s called the Mach Angle and people use that to
measure the exact velocity of a bullet traveling through air. There’s a simple equation. The Mach number is equal to
one over sine of that angle and you can figure out
how fast it’s moving. I use the circle illustration because that’s the way I was
taught in my Aerodynamic book. But if you look at the high speed imagery, you can actually see circles being formed at regular intervals. I don’t understand what they
are, but they clearly there. What we’re about to do
is what I’ve wanted to do from the day I understood
what Schlieren Imagery was. We’re going to shoot a Subsonic
and a Supersonic round, and we’re going to compare the
difference in the shock wave. Coop, whatta we have? – [Coop] So this is a 300 blackout. – [Destin] If I understand correctly. The whole point of this particular round is to keep it Subsonic. – Correct. [Destin] This is a heavier bullet. – This is a by 100 grains. Almost twice the weight
of this bullet here, and so this bullet right here you’ll get somewhere
around 1080 feet per second at the muzzle. Whereas this bullet right here will give you somewhere in
the neighborhood of 1500. [Destin] Do you know what
the sound of speed is? – Yeah, it’s like 12 something. [Destin] I don’t know. We’ll put it on the screen, right here. That’s the speed of sound. So this one above the
sound, that one’s below. All this is on purpose because that weapon and that cartridge design
was made specifically because of these physics. – So lets do Supersonic first. – [Coop] Sure. – Okay. Three, Two, One. Fire.
(gunshot) (sound waves) This shock wave looks
very similar to the 50 cal with one major difference. The angle is more Obtuse which
indicates that the bullet is traveling much slower. So he’s chambering a Subsonic round now and so on the Schlieren we should see a drastically different image. Two, One. (gunshot) (sound waves) It looks like, it looks like(laughing) – [Coop] (laughing) I can
make it, I can make it. (sound waves) – [Destin] Alright, so
this is a Subsonic bullet. So why I we seeing these
little flickery things on the side of the bullet? That doesn’t make a lot of sense to me. So this what I always do
in a situation like this. I went looking for expert,
which lead me to Dr. Kanistras. A well respected aerodynamics professor at University of Alabama in Huntsville. One thing we saw on the Subsonic bullet is we see, we didn’t see that shock wave but we saw these weird lines out to the side of the bullet, you know. – [Dr. Kanistras] What is the
speed, when you say Subsonic? – [Destin] It’s about 10 percent less than the speed of sound. – You have Supersonic flow there. It’s a Normal Shock. What you see there. – [Destin] On a Subsonic bullet? – Uh-huh, what is happening
on a commercial aircraft? It goes between point
eight to one point two. Even if you’re flying Subsonic, you have acceleration of the flow. So you’re reaching one point two. – [Destin] What? – Then you going back Subsonic. – [Destin] So what you’re
saying is even though I have, – [Dr. Kanistras] It’s a Normal Shock. – [Destin] I have a Subsonic bullet but the speed of the air
is Supersonic right there, half way up the bullet. So on this Subsonic bullet,
those things I’m seeing, you’re saying that’s Supersonic flow. – That’s right. – [Destin] And it’s because the air has to move out of the
way around the bullet. So it has to accelerate. – That’s right, yeah – [Destin] Really. – So the flow accelerates, and
creates a Normal Shock there. – [Destin] It’s because
this particular bullet is so close to the speed of sound. – It reaches a transsonic speed, which is point eight to one point two. So even if it’s not
supersonic at this point, at some point on the surface
it will become Supersonic. – [Destin] That’s cool. Thank you. (laughs) That’s really cool. Thank you for explaining that. After this we decided to
move closer to the mirror, so we could see what the muzzle blast (gunshot) from the weapon itself look like. (sound waves) After that we moved the
muzzle back about a foot so we could see that transition period (gunshot) where that bullet pierces
through the blast itself. What’s even more impressive is each one of those
tiny grains of propellant had that visible shock wave you could see associated with it. (sound waves) One more thing real quick,
we took video of revolver. It literally leaks shock
waves out of the side. But before I show you that I want to say thank to the
sponsor which is Audible. Audible has been a partner for
“Smarter Every Day” forever, and I’m very grateful because
I enjoy getting smarter by listening to books as I drive. This is like the perfect
Brand match for me. It helps me get smarter everyday. You can get free book by
going to or text in the word “smarter” to 500 500. I’ve a special book to recommend today. It’s called “THEM, Why we hate
each other and how to heal,” and it’s by Senator Ben Sasse. I steer really far away
from politics at all times, but this is not a political book. It’s about the things that are
eroding away at our culture. Things like loneliness and the importance of your
family support structure, and how we need a scape goat; and sometimes we get
angry at other people. when the problem is things
that we are doing in own life. It’s a really good book. So I highly recommend it. I’m not quite done with
it, but up to this point it seems to be apolitical. So check that out. “THEM, why we hate each
other and how to heal.” You ca get that by going
to or texting the word “smarter” to 500 500. It’s about how we can improve ourselves by working on our communities around us. I really like it, and now definitive scientific proof of why your hands should never
leave the grip of a revolver. One.
(gunshot) (sound waves) One.
(gunshot) – Weapons clear. – [Destin] That is the best video I’ve probably ever participated in. (sound waves) Look at that, oh my goodness. Okay, well I’ve a feeling we’re going to be doing something like this again. Can you see us stopping at this? – No. – Okay. – No way. – Yeah , so there you go. Feel free to subscribe
to “Smarter Every Day” if you’re into this kind of thing. If you’re not, I don’t know
what’s wrong with you (laughs). That’s amazing. Alright, cool, thanks.

100 thoughts on “Shockwave Shadows in Ultra Slow Motion (Bullet Schlieren) – Smarter Every Day 203

  1. I dreamt of this day, and here it is. Thank you for doing the video I hoped you would one day do, Destin. So cool 😎

  2. That subsonic bullet hadn't stabilized. Not a good choice for that ROT. Revolvers by design release pressure between the cylinder and forcing cone.

  3. Do bullets therefore experience lift (pulling force) to some degree? Should a bullet in a vacuum maintain muzzle velocity indefinitely or would there be “space effects” to influence that?

  4. Great vid! Thanks so much!

    One regret, I wish you had videoed a bullet at true subsonic, i.e. without the supersonic flow. Certainly not meant to take anything away from the video – it was simply great!

    Thanks for going to all the time and trouble to make it!

  5. Destin Sen. Ben Sasse wrote this book as propaganda to convince good hearted America that its ok to let your county be overrun with cheap labor for his grotesquely wealthy donors like Paul Singer which is the man who in Ben Sasses own state of Nebraska allowed Paul to deflate the economy of Sidney Nebraska ruining the stability of hundreds of families, ( THE BOOK THEM), IS POLITICAL PROPAGANDA

  6. About that blast out the side of the revolver. An episode of Mythbusters showed that it was strong enough to seriously injure one's hands.

  7. Awesome man to see the shock wave of a bullet but I have a question is it possible to have the whole cone of the supersonic bullet completely behind the bullet

  8. what if the object moving supersonic is not pointy (blunt , Square or round) what Shock wave it will produce, and what if we spin a disk supersonic then how air around will behave?

  9. So cool to visualize compressibility on the subsonic round! It’s incredible to think that some 80 years ago or so, the effects of compressibility weren’t full understood, and many pioneer aviators were killed in accidents related to the phenomenon. Now we can make videos of it in our garages at home, and post it online for millions to see. Ok maybe some of us ought not to (ie: if you live in a townhouse 😂), but you get my drift.

  10. How about a .50 Beowulf or a .444 Marlin bullet with a flat nose?
    This was an awesome video I've studied ballistics and velocity since I could read.

  11. I bet the "Circles" are from the bullet "Ringing"…or oscillating… prolly figure out the frequency using the speed of the bullet and the distance from each ring…???

  12. I have a couple of thoughts: IF the secondary and tercary waves were caused by reflection from the plywood and the cement, covering one or the other with, say, felt or carpet, would cause a change or elimination of one or the other.
    Secondly, I'm assuming the 'bubble' trail is vacuum, but is it not possible that there are two levels of vacuum, one being the bubbles and a very wide secondary vacuum causing those rings in the wake? Considering that the primary wave is pressure, there has to be vacuum behind it, or at least low pressure.

  13. I'm so glad there's a SmarterEveryDay video on this subject that's kept me up for the last few hours… trying to imagine a shockwave at the speed of sound

  14. You need to shoot a round closer to 900fps to see the supersonic flow dissappear! The speed is too close to 1100fps if you're seeing supersonic flow.

  15. Those circular waves coming off of the supersonic bullet in the first test may be generated by the rotational movement of the bullet from the barrel rifling. I imagine if you were to isolate the sound it generated, it might sound like a buzzing or zipping sound. Just a little conjecture.

  16. That's Air Water. The Ether you breathe every Day since your birth. As the bullet get through, those tinny bubbles, are Ether. Thank you for your Help. You just Proved the Existence of Ether. Can you imagine what Have You, Discovered ???
    Thank you.
    NDSR Concepts Universes
    875.000 B.C – 2020 A.C

  17. Loves this video Destin, can't read your book suggestion though. Ben Sasse is part of the community furiously building up hatred and death in this country. Ironic he would write such a book. He's a terrible person.

  18. You should make the bullet shape that cancels shockwaves on a 50 Cal bullet. Allowing it to travel supersonic for longer. (It reduces the drag from the secondary shockwaves)

  19. So, you finally dropped that annoying stupid kid? I'll keep checking in once in a while, if he's gone I'll start watching your vids.

  20. Y’all really need to do this again but with tracer rounds to see how tracer rounds actually ignite!!!👍🏼👍🏼

  21. So what would have been very interesting would have been to test various bullet shapes to see how they affect the shockwave. If you used a muzzleloader you could test a roundball and a sabot with spitzer point bullet and by varying the grain load could propel each to both super and subsonic speeds to see the difference.

  22. One thing I don't understand. Why is the bullet emitting sound waves? I understand it for jets (the sound of the engines) or for a siren on the ambulance. But a bullet isn't a source of sound…so where do the waves come from?

  23. I noticed an interesting feature of the turbulence DIRECTLY behind the bullet, the "line" drawn by the path of the bullet.
    If you look carefully, the turbulence is spiral shaped, due to the rifling-induced rotation of the bullet around it's longetudinal axis. The tailing turbulence is actually twisting with the bullet. The twisting is what governs the shape of the turbulence is it dissipates, as well.

  24. Best part(Quote)If your not into this I don’t know what’s wrong with you!…I have always wondered how much power was lost in a revolver due to the open cylinder.Really cool video.

  25. I took your schlieren Imaging. And subjected it to a chromatic light frequency. Realize there's some decapitation going on in the Shockwave that produces Heat. I'm looking for a way to send you these images.

  26. Seeing those supersonic waves forming along the sides of the subsonic round reminds me of a fighter aircraft approaching supersonic and you’d start seeing those same patterns on the surface. Pretty cool! 😁

  27. I was blown away by the fact that the subsonic bullet actually causes air piercing to go fast enough to break sound speed. That was enlightening !!!

  28. Curious if an arrow would even register. Also as a drone pilot, it would be cool to see a P.I.D. loop in action.

  29. I think you will find that the supersonic shock waves on surfaces that are travelling just below the speed of sound is what caused loss of control issues for early attempts at airplanes to go near speed of sound. Also – a tip – you can use a sound gate compressor to lift faint audio to good levels – I do it a lot fo questions from students in my classes and it works well – Totalrecorder does this but all good audio programs have the capability. Thanks Destin for your enthusiasm on science topics

  30. This one time, of your many great videos, I'll partially disagree. The shockwaves along the curved bullet body (at subsonic) is because of its shape and how air accelerates over curved shapes, hence how airplanes fly. "Moving out of the way" is a poor way to describe that effect. This is why subsonic jets fly in the Mach .85 range as around the nose, top of the wings, and other curved surfaces, the air travels more quickly and that faster flow also has to stay subsonic. If that was a straight cylinder you would not see the shockwaves. Also the position of the body shockwaves are at the regions of greatest change of curvature which demonstrates my point. Regards from a lifelong engineer and pilot.

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