How the Warhead on the AIM-9 Sidewinder Works - Smarter Every Day 282 

Fun fact: From the moment I started working on this video the US Military has fired 4 or so AIM-9X's over the continental US. Thanks to everyone who supports on Patreon and lets me do things like buy surplus missile parts! HAHA! I have plans to build a neat demonstration with them. You can support on Patreon here if that's of interest to you: www.patreon.com/smartereveryday Also, I have an email list. If you'd like to get an email when I post a video, you can sign up here: www.smartereveryday.com/email-list Thank you for your support!

Got you fam “The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't.”

That mystery pivot on the rollerons is the secret sauce that makes them so effective. The rolleron is actually a little aileron-like fin, and that pivot point is its hinge. When the missile tries to roll, the little windmill-wheel precesses and causes the rolleron fin to pivot out against the direction of roll. All four rollerons pivot like that in the same way, and so all four act against the roll.

I'm an F-15C pilot. The seeker in the front of the AIM-9 is gimbaled. There is a magnet in the yellow protective cover and there is a pre-flight check to pull the cover off and ensure that the seeker head moves inside the translucent seeker. The seeker is cooled by a little Argon canister that the AMMO guys install and keep pressurized, the heat buildup of air friction would blind the seeker if it did not have active cooling.

Destin, PLEASE, PLEASE, PLEASE feel free to make short videos like this one ANY TIME you discover something that excites you! This format is really fun. God Bless.

The aim-9 LM rollerons can pivot when unlocked or the term is referred to as uncaged. There's a little latch that is on the back that holds the rollerons from pivoting to prevent damage to them during take off and landing. The latch will come undone by the force of the missile launching off the aircraft. I worked on these in the air force for 7 years. Great video!

I was an AO in the Navy for 10 years. I was watching you point at everything and thinking like "is he going to hit on the rollerons? Hey that X has thrust vectoring is he gonna point that out. You came through man. Well done. Do a HARM (AGM-88) next.

"I'm in front of a building that does things" might be the most amazing thing Destin has every said.

Somthing I heard from a Navy guy when I was in the USAF Reserve. One of his ship's aircraft came back from a mission with a North Vietnamese air-to-air missike sticking through the tailfin. It was very carefully removed and taken down to the missile maintenance shop. Several people had noted that it looked a lot like an AIM-9, so the seeker head was carefully removed and put on the AIM-9 test rig. It checked out perfectly! Furthe examination of the missile showed it was "probably" a Russian copy of an early AIM-9!

This feels like old school smarter every day and I love it. It's really cool just to hear you talk about something that you find interesting for a few minutes.

As an ex-navy ordy, it was taught to me that the sidewinder carried some sort of chain as a payload. I never really understood what that meant until you explained it here. And it always bothered me. I don't know why I never looked it up until now. I think of this from time to time. At least once a year. Thank you! You taught the guy who's supposed to know a thing or two. :)

As a former USAF 462, weapons loader, the rolleron is a fasinating peice of engineering. It's fun using an air hose to spin them. I loaded many 9s on 8th TFW, 35th TFS F-16s at Kunsan. I have a scar where I split my forehead on the forward canard- 3 stitches.

My uncle was one of those engineers in the 50's. He never really talked about his work but he always drove amazing cars. :)

I read last week that the AIM-9X uses the entire visible light spectrum to track it's targets, and not just infa-red like the older versions. This means that the missile is EXTREMELY good at ignoring decoy flares etc. It's a beast.

My dad was an engineer on the Sidewinder and other missiles at China Lake NAWS (formerly NWC). One of my earliest memories at age 4 was going to the Sensors and Platforms section of Michaelson Lab to see how the guidance system within that dome at the front of the missile works. It was incredible.

Hi Destin, my former Marine son was an avionics specialist who worked on F18s. I once joined him on a "Tiger Cruise" aboard the USS AMERICA aicraft carrier one of the best experiences of my life! That "rolleron" reminds me of the little paddlewheel speedometers I used to remove from a through-hull fitting on the sailboats I used to crew on. I would pull them out after a race and immediately shove a bung back into the open hole that was gushing water into the bilge.

Reminds me of the old school Smarter Every Day videos. Love it! 👍🏼 Also, Destin may be the only person to have both a Sidewinder Rolleron and a mildly abstract painting of a cow in the same room.

Can confirm, AIM-9X does have thrust vectoring. Other fun fact, the AIM-7 Sparrow missile was upgraded to the AIM-120 Advanced Medium Range Air to Air Missile, or AMRAAM. The Sidewinder upgrade was originally going to be the Advanced Short Range Air to Air Missile, but someone giggled too much, and they changed it to 9X.

My dad actually worked on the AIM-9 (I'm not certain which variant, but I think it was probably the AIM-9X). He even worked at a building that was later bought by the University of North Texas and turned into an engineering college, where I got my degree. As an interesting little quirk, the building had some kind of signal blocking built into it for national security reasons back when they were working on missiles and such that blocks signals from going in or out, so students have to use the school's wi-fi inside the building, since they can't get cell service. Just a weird coincidence, that my dad would work out of that facility developing missiles, and then years later I would go to that same building for college.

Many many years ago I was on my way home from a late shift at work riding my Honda VFR750 motorcycle. It was 1am, and I was the only vehicle on the dual carriageway I was on, so went for bust. I rode this road every day and knew it well, and considered the gentle curve I was approaching as inconsequential, but this time I was doing 140mph as I tried to lay the bike over to take the curve. I got the fright of my life because the bike didn't want to tip in, and I had to use a lot of strength to force it. I later realized this was the gyroscopic effect of the front wheel making it want to maintain its orientation. That memory was bought back by Dustin describing how those tiny stabilizers worked. 100,000rpm! That's amazing.

The AIM-9 L/M missile rolleron is uncaged by the forward momentum of the missile. There is a weighted metal tab at the back of the rolleron that unlocks the rolleron allowing it to pivot on the hinge you indicated. It’s a brilliant design. Early AIM-9P missiles used string that held the rollerons in position. The rocket motor burned the string off at launch, uncaging the rolleron assembly.

Awesome. For over a decade I was a soldier (Redstone Arsenal) then civilian technical advisor/instructor (Ford Aerospace) to foreign militaries who purchased sidewinder (air-to-air) and Chaparral (ground-to-air) missile systems. And the rolleron was always my favorite part for its elegant simplicity. That said, the guidance system is pretty elegant as well. I was fortunate to have worked with the engineer who originally designed it. Those OG engineers solved some incredibly complex problems with very basic tech including intercept (not chase) in 3 dimensional space, how to pivot a guidance fin (very high torque), and of course the rolleron.

This clip gives me much more appreciation for low tech yet genius solutions that engineers of that era came up with.

The guidance system was really clever. You should do a video on how that worked in the early versions of the AIM-9.

The rolleron flywheel helps with unwanted rotation (roll). The pivots allow the rolleron to act as ailerons to help stabilize the pitch and yaw movement…that’s what I remember being taught in the Air Force when I was in as a weapons troop. Rollerons we’re my favorite feature that I learned about any ordinance for my job. I’m glad you get to appreciate them too!

Rollerons are incredible. I saw a video of a guy who had a wing piece with one and he demonstrated it's abilities by blowing air over it from his shop air line. He tried taking the rolleron apart but at a certain point you can't take it apart any further without destroying its housing. It seems like it's a replaceable part rather than a maintainable one. But now that you've gotten one yourself I cannot wait to see some slow motion footage and a more in depth breakdown of the physics involved!

The ir guidance system on there is also genius: because of the technological restriction of the time, it had to be fully analog. What they did for the sideweinder was to place a rotating disc divided into sixteen sections, with one in two section beeing opaque, and one in two being transparent. Behing the disc was the ir sensor. When the ir signature of the airplane moved across the disc, the sensor would output different frequencies, as the the black and tranparent sections were blocking/letting through a diferent amount of light at different frequencies depending of the position of the ir signature. The outut frequencies could then be analyzed and the missile would try and correct until the output frequency matched the one that would mean the target is centered. Pureley genius!!

That was absolutely fascinating. As a kid, I had the first issue of a jet magazine series and I studied the different configurations of the F14 and how the Sparrow, Maverick, Sidewinder, TARPS pod etc. worked. I had no idea about the rear stabilization. You just made my day!

I love to think that Destin just walked up to this place and started poking at rockets and stuff and the people working there were just like "what is this crazy man doing with a camera?" Edit: since people don't seem to realize somehow... My comment was a joke.

I wouldn't mind just having these small 8 minute videos on stuff that destin finds on his adventures. We too find it cool.

Having worked with AIM-9 systems before, I think one of the most fascinating things about this missile is the way in which the system gets "Armed", its a purely mechanical system and is amazingly brilliant.

The gleeful giggle at having a missile fin. Wonderful. From one engineer to another: I love your channel, Destin. Keep them coming!

The most terrifying thing about the sidewinder is its ability, unparalleled in military history, to turn people into paper silhouettes without even being launched!

Another awesome video! Thanks for all the US Navy stuff!! Retired USN aviation mechanic and I love watching your work!!!🇺🇸

Our family, 9, was in China Lake and then Ridgecrest. I heard so many stories about the first Sidewinder. Then I watched the Story of The Sidewinder on UTube and low and behold there was my father holding , his favorite topic, the gyroscope. We are up to the Aim9, amazing!! Love this channel!!

That thrust vectored nozzle on the X is so unbelievably cool

Dustin, your 'random discussions' are more sensible and informative to the public than many RU-vidrs PLANNED and RESEARCHED talks. Thank you for your efforts. You are appreciated.

This is the kind of video that warms my heart. Destin taking us along on one of his adventures.

On the AIM-9M there is a latch on the back of the rolleron that unlocks from the g-forces of launch. Then the gyro part is free to swing from side to side to stabilize the missile. The AIM-9M and X uses the same warhead, rocket motor and active optical target detector (AOTD). The guidance is totally different between them.

The rollerons are cool and all, but the seeker is the headliner. Absolutely genius use of mechanics, optics and electronics, not to mention the simple working concept and design.

I know you’re super busy with life so you should do more of these quicker style videos! Of course the high production value of your regular video is greatly appreciated, but these quick explanation videos without major fancy graphics are super interesting and engaging!

Awesome video, Destin! I enjoy your channel immensely and it LITERALLY makes me smarter every time I watch it. As a military aviation aficionado I found this short video incredibly engaging. I never knew about rollerons! What a clever solution to a very difficult problem that must have really vexed those engineers back in the 1960s before we had accurate gyros and accelerometers that can fit on integrated chips. I also never knew about the expanding rod warhead. The way you described it made sense to me but the animation you provided really brought it home. Just keep doing what you do!

That was awesome!! Thanks so much man! The design problems I try to solve in my day job are really challenging so I really love dead simple, genius mechanical solutions to incredibly complex problems! Really inspires me to keep pushing to find better answers.

From what you said, the rollerons might not stabilise the rocket, but they only stabilise the little fin they are embedded in. But when the little fin is stabilised and the rocket rolls, it creates a surface to deflect air and that in turn stabilises the rocket. Looking at the outtro: excited engineers are always a little scary to the people around them... I am one myself, I would know xD

Sidewinders are awesome missiles! Because of the way the seeker worked in the earlier missiles, it only knows the angle that it's looking, and nothing about range. The optimal way to guide a missile to a target is leading it like you mentioned, but if you don't know the range, you need the seeker to stay at the same orientation in roll (so the guidance can use the angular rates of the seeker). Instead of having a whole inertial navigation system or any complex electronics in there the rollerons let the missile fly lead instead of pure pursuits using only a couple passive parts and the missile's own airspeed! I think the inertia of the flywheels wouldn't be enough compared to the mass of the missile to keep it stable, so instead they're on those hinged pieces that essentially want to stay in the same orientation, so if the missile starts to roll, they kind of stay in the same position and act as mini control surfaces on those aft fins. If I'm not mistaken, this is what gave the sidewinder its name, if you watch old videos of them it kind of wobbles side to side as the rollerons stabilize the missile. The modern AIM-9X is insanely advanced, with a digital seeker head and all kinds of electronics, that combined with the thrust vectoring you spotted and helmet mounted sights used by the pilots, let the missile engage things "high off-boresight," up to 90 degrees away from the direction the missile/plane that is firing it is pointed. There are a few test videos on RU-vid of them being fired against QF-4 target drones at insane angles while completely ignoring all the countermeasures the drones deployed.

Thank you. I was part of a small business restricted prime contract for the forward fin a very long time ago. Enjoyed going to the lake and especially the annual Waswinder party. The story behind the development of the Sidewinder in the late 40s is fascinating. Take care

Thanks Dustin. Love fighter aircraft and their weapons systems. And learnt something new with the rollerons and the explosive steel. Always a good day when you learn something new.

I used to load both these missiles on F-16s during my time as a weapons systems specialist in the USAF. Seeing this video definitely brought me back!

I've been working with the 3 missiles shown for the past 2 years and Thursday was my last day. It was cool to hear you talk about it. It's cool you got parts too! 😎

This video brings me back to my time in engineering school and the discussion of angular velocity. Then teaching us kids the oh-so-fun right-hand rule. Watching people work through problems while checking their right hand as they mimic rotation to confirm the direction of the angular vector will always make me chuckle.

I have one of these landed just outside my house... I wish I could add a picture.. amazing stuff. Thanks for your work! Really enjoy learning more.

Destin, your energy is so captivating. I just wanted to say that I love your longer in depth videos, but I also love a short old-school type video like this one. Basically I'd watch anything you put out. You're the most genuine personality on youtube.

Oh dang, I think I just had one of those inspirations moments you have when figuring something out with those rollerons. So each of the 4 will have an angular momentum vector but the vector will be in the same tangential direction (clockwise as viewed from the back) around the missile (via the right hand rule) so the vector pointing directions are very important. Now it's doubtful conservation of angular momentum of those relatively small pieces alone will be enough to prevent a rocket moving at a high rate of speed from rotating, however as the rocket rotates that little piece on a hinge tries do try to conserve angular momentum so the flaps do move, and they move in the same tangential direction to the rocket's radius this is basically creating flaps which absolutely do create a counter drag to the rotation preventing it from spinning widely out of control. Now if this is common knowledge, I'm sorry, but yeah I just got a very inspirational "OH SHOOT I FIGURED IT OUT!" moment which kind of gave me a little tingly feeling. Thanks for making these videos.

I went to the RAF Museum in London just yesterday and when I saw this missle the rollerons immediately caught my eye,I took tons of pictures of that specific area and i was determined to google and learn what this design was about. I accidentaly stumbled uppon this video and I got an answer for all my questions. Amazing

Back in the day when I was in the Navy I believe the use of an expanding coil like spring was deployed in the sidewinder. Also worked well splashed a lot of aircraft with it.

I love how you have kept your enthusiasm and appreciation for genius engineering and the ability to see it everywhere and share it with your viewers.

Wonder what kind of watch list you get on when you buy missile parts 🤣. Either way, it's fun to watch Destin nerd out on stuff like this, and I completely appreciate when he does. I have the same kind of love for learning new things like this all the time.

1:21 - VERY KUEL! I spent a couple of months at China Lake having fun with MQ-9 Reapers. Took an afternoon off and saw the museum. The Sidewinder was the kuelest thing on the planet!

Destin, the roll motion is stopped by the gyroscopes precessing under roll and thereby deflecting the aerodynamic surfaces to which they are attached. It is not so much the rigidity in space of the gyroscopes doing the work as the deflection of the surfaces.

I like these short-format videos where Destin is just geeking out at some cool tech lol I like the long-format ones too, but peppering these short ones in between is really entertaining 👏

Destin, awesome video, I love to see how excited you get about life and the things we humans create. To answer your question about rollerons, they provide stability primarily with aerodynamics. The gyroscopic stabilization acts on the flight surface more so than the missile as a whole. The cool thing is, it's completely passive. While in flight, as you said, the flywheels spin up and the movable tabs are locked in place to prevent tab movement while the aircraft is maneuvering. When the missile is released, those tabs unlock and become free to move. Because they are held in space by the spinning flywheels, as the missile rolls, those tabs will remain on the axis of the flywheels. Like a trim tab on an aileron, it will aerodynamically counteract any roll induced during the weapon's flight. I hope this helps you understand rollerons better. PS. I can't wait to see you experiment on those newly acquired fins. Hint: Air compressor and hearing protection. 😁

If I'm not mistaken, the rolleron's gyroscopic motion isn't trying to stabilize the whole missile by itself, but rather just that little pivoting section, which acts like (and well IS) a control surface. The control surface is what confers the stability to the fuselage.

When I was in a rocket club, we considered adding hinged fins with rollers. The reason is that when the rocket rolls, the fins will move to oppose the rotation. That's what the sidewinder missile is doing too. It's just a passive way to stop roll.

I absolutely love how giddy you are about everything you do on your channel!

I love this shorter format! Longer is great too, but diving into cool, unique mechanics in smaller lunch-break-sized videos with your insight is wonderful. Keep it up! 👍

... a deep dive video into how these "rollerons" really work would be awsome 😍

I love watching your content. I got excited with you when you showed the parts at the end of the video. You really do make it feel like you’re taking me on an adventure every time I watch your videos!

Loved this video! My uncle Bud Sewell was one of the inventors of the Sidewinder right there at China Lake!

These casual walk up videos are some of my favorite. Please keep doing them.

I have seen a couple videos about how Sidewinders work (shout-out Curious Droid!) but hadn't heard the details of either the rollerons or the expanding circle of "bad-day" steel in the warhead! I can't wait to hear more. Thanks!

Regarding the Rollerons, the angular momentum of the 4 gyros is not enough to be able to stability the roll axis of the missile as a whole, but it is enough angular momentum to hold the little rolleron control surfaces "fixed". As the missile starts to roll, the gyros don't want to roll with the missile and with the ~45 deg angle on the hinge axis causes an angular deflection in the rollerons, which generates an aerodynamic stabilizing roll torque on the missile.

I LOVE THE AIM 9! i love the buzzing it makes when its locking on to something. its great, i love them

This is why I subscribe to your channel. It is so clear and obvious that you just love learning and sharing that learning with others. Anyone else would have gone through google or one of your many contacts to find out exactly what the pivots on the rollerons do before even attempting to make this video, but the vibe this gives off is that you just saw something as you were walking past it and wondered how it works so you made a video. Thank you for all that you do.

I've been fascinated with the gyroscopic effect ever since I got a gyroscope at the Smithsonian gift shop as a kid.

being prior military as an aviation electronics technician, I worked on the F/A-18 platform troubleshooting the weapons systems, such as the AIM-9X on the aircraft and more. This video definitely made me learn more about the fascinating nature of the sidewinder and brought back some good memories. Thank you!

My grandfather, after completing service aboard the SS375 Macabi during WWII, went to work for Ford Philco and eventually participated in the design of this weapons system. He was a life member of the Institute of Electrical and Electronics Engineers (IEEE) and was a member of the Associations of Old Crows (Electronic Warfare Organization), Armed Forces Communications Association, Air Force Association, Association of the United States Army, the American Space Foundation and the US Naval Institute. Thank you Destin for this video. How proud we are of his patriotism in the defense of our country through engineering.

Amazing video! My last duty station in the Navy was at NAWS China Lake and I was attached to VX-31 "Dust Devils". You brought back some fond memories of the old dust bowl. 😆

A bunch of years ago, the local air national guard group had a display at the state fair. They had a Sidewinder missile. I saw the little "spinny thingy" at the rear of the fins. I spun it, studied it a while, found the hinged section and it dawned on me. NO WAY! THAT'S THE COOLEST THING! Easy to implement too. No electronics. Thanks! I love your giddy enthusiasm for this stuff.

Simple solutions are the often require the most genius. Thank you for sharing this.

Pretty cool. Always wondered what the spinning wheels were in the fins.

There is a interesting story about the guy who came up with that idea. He was a newbe in a design team and they were stuck with the problem of instability for months. The new guy was home playing with his son with some toy and he had a light bulb moment and came up with those rolerons. Really cool story.

More simple short videos like this please! Love'em!

Awesome seeing someone cover this. I've personally handled them and loaded them (inert training ones only unfortunately) but my job is awesome when I get to mess with missiles like these.

The last clip is my favorite, I really like your enthusiasm about the rollers, I too think its interesting, looking forward for what you are going to build with it.

I would love more in-depth videos on how missiles work like this one! It's rare for me to see them up close like that, really neat stuff. And I have also loved the idea of the rollerons once I figured out what they were. Assembling models as a kid and seeing pictures in books they looked so weird since no other missile had those rollerons (except the AA-2 Atoll which was just a reverse engineered AIM-9).

SO fun to have you just stop by on something and casually talk about and think about how it works. This video is unlike your others which are a bit more polished but that is ok because it allows me as a fellow engineer to appreciate and relate to how you think about things just in your everyday life.

5:18 - the AIM-9 was one of the first missiles to lead targets with proportional guidance, and it's a cool point. It's also why stabilization is important. The seeker is a simple IR detector (no pixels or built-in direction sensing) and figures target direction with a spinning mirror that makes it continuously scan in a circle in front of the missile. The hottest part of the circle is where the target is, so the missile leads by comparing how much hotter one part of that spinning circle is than the rest. Thing is, if the whole missile (and not just the seeker) spins, then you don’t know if the hot part of the circle is actually still pointing at your target, hence the rollerons to stop roll. This is why the AIM-9X has no rollerons - its seeker is more like a camera, so it can find direction just by seeing which spot is brightest, so roll doesn't matter. Everything's connected!

This is amazing for so many reasons. Keep up the great work!

I love your deep dive series, but I've got a special love for these little videos! Thanks Destin!

Short and authentic is a good look for you, not everybody can pull out the same fun and engaging educator moves after just a couple hours exploring somewhere, plus substantially less editing required! I vote you mix in more of these clips along with your formal productions, plus it'll boost engagement and keep you flush with suggestions and recommendations. And thank you for showing us that clever passive engineering solution.

the whole original sidewinder missile is a pure combination of a bunch of genius tricks. so simple, so amazing.

Awesome video! I'm looking forward to the slow motion of the spinning rollerons responding to a slipstream when the mocked up missile tries to spin!

I'm always blown away by how you seem to know so much about so many different things. Made a bit more sense that you might have just learned about rollerons from the informational plaques around (unless you already knew about them?!) but I'm still blown away by the fact that you noticed the tiny divots and knew what they were and why they were there. Great video, thanks Destin!

Such a random but extremely interesting topic! You don’t learn too much about these types of subject matters usually due to them being classified.

I used to test rocket motors with Royal Ordnance in the UK. I had a rolleron in its housing sat on my desk, and I can recall chatting on the phone spinning the rolleron like a toy. I also cut my fingers on it, the edgs of the disc are very finely machined angles!

always enjoy your talks keep them coming I worked for L3 company for 30 years building ordinance loved my job shaped charges always fascinated me . This would make a good video.

My grandpa worked on the electrical power systems for the sidewinder, he’s no longer with us but any time I see that missile I remember how he taught me to enjoy science, so thank you Destin for bringing that joy to many others

7:26 "No Mr. FBI Agent, I did not give money to this man for missile parts" - Everyone on Patreon

I've loaded MANY Aim 9's and Aim 7's on the F-4 Aircraft. After loading we did a functional check on the weapons system. We removed the nose cover of the AIM-9 and used a flashlight, for heat, to check the guidance system. Yes, the heat of a flashlight, it was that sensitive. You could see its response by it following your movement. Lethal.

I really enjoy your observational videos about things that others may dismiss. I have always tried to understand things around me that we take for granted. Knowing and understanding things makes me feel connected to the world and makes me feel like I can come up with solutions as an engineer by understanding as much as possible. Some people would just look at a missile and say it's a missile. You look at it and see the steering mechanisms and try to understand why. This curiosity is probably why people have gravitated to you over the years.