Creating A Supersonic Trebuchet

August 9, 2026 by Maya Posch 27 Comments

As awesome as trebuchets are, the fact that medieval engineers didn’t create versions capable of launching supersonic projectiles is a bit of a bummer. Fortunately it’s possible to correct this oversight with modern insights and technologies, as [Tom Stanton] demonstrates in a recent video.

While a traditional trebuchet is fairly straightforward, using a heavy weight moving an arm around a pivot that has the projectile attached to the other side, a few tweaks can make it much more lethal. One change is to have the projectile’s rope wound around the arm, forcing an additional pass around the arm to gain velocity. The other is to use a gearing system which uses the dropping weight’s energy more efficiently.

One complication here is that the arm now takes a few rotations to come up to speed, meaning that the release of the payload has to be controlled exactly, with only about an 0.0025 second release window. The solution was both low-tech and effective: since the arm is attached to a drum that the rope is wound onto, the moment enough rope is unwound from the dropping weight, a latch inside the drum is released to launch the projectile.

In a first test with a 10 kg weight, the projectile reached a velocity of around 528 km/h, which definitely was a good start, but also showed just how not aerodynamic the arm was. Some redesigns later of the entire trebuchet, the entire system was tested again with 10 kg and achieved a projectile velocity of 634 km/h. From there it was time to ramp up the weight to the full 40 kg, which theoretically should hit supersonic speeds.

Unfortunately the first attempt hit a mere 1,152 km/h (716 mph), which is just shy of the sound barrier at 1,235 km/h at 39% system efficiency and some components clearly breaking apart. Some more redesigns later and with a lighter projectile at 4 grams, a 40 kg weight achieved an arm speed of 2,342 rpm. The projectile now left the sling with 346.4 m/s, or 1,249 km/h, with an audible snap as the sound barrier got broken.

Even if the era of trebuchets in warfare is well and truly past, they remain fascinating physics demonstrations, with this case in point.

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Mach Cutoff: Bending The Sonic Boom

July 16, 2025 by Zoe Skyforest 28 Comments

Supersonic air travel is great if you want to get somewhere quickly. Indeed, the Concorde could rush you from New York to London in less than three and a half hours, over twice as fast as a conventional modern airliner. Despite the speed, though, supersonic passenger service has never really been sustainable thanks to the noise involved. Disruption from sonic booms has meant that supersonic travel over land is near-universally banned. This strictly limits the available routes for supersonic passenger jets, and thus their economic viability.

Solving this problem has been a hot research topic for some time. Now, it appears there might be a way forward for supersonic air travel over land, using a neat quirk of Earth’s atmosphere.

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Hackaday Links: February 2, 2025

February 2, 2025 by Dan Maloney 8 Comments

All things considered, it was a very bad week for aviation here in the United States. Three separate crashes, two of which involved US military aircraft, have left over 70 people dead. We’ll spare you the details since there are plenty of other places to get news like that, but we did want to touch on one bright spot in this week’s aviation news: the first successful supersonic flight by a US-made civilian aircraft. There are a lot of caveats to that claim, but it’s clear that Boom Supersonic is on a path to commercializing supersonic air transportation for the first time since the Concorde was retired. Their XB-1 “Baby Boom” test aircraft managed three separate supersonic runs during the January 28 test flight over the Mojave test range. As usual, Scott Manley has excellent coverage of the test flight, including a look at how Boom used a Starlink terminal and an iPhone to stream cockpit video.

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Canned Air Is Unexpectedly Supersonic

February 18, 2024 by Donald Papp 18 Comments

How fast is the gas coming out from those little duster tubes of canned air? Perhaps faster than one might think! It’s supersonic (video, embedded below) as [Cylo’s Garage] shows by imaging clear shock diamonds in the flow from those thin little tubes.

Shock diamonds are a clear indicator of supersonic flow.

Shock diamonds, normally seen in things like afterburning jet turbine or rocket engine exhaust streams, are the product of standing wave patterns that indicate supersonic speeds. These are more easily visible in jet plumes, but [Cylo’s Garage] managed to get some great images of the same phenomenon in more everyday things such as the flow of duster gas.

Imaging this is made possible thanks to what looks like a simple but effective Sch lieren imaging setup, which is a method of visualizing normally imperceptible changes in a fluid’s refractive index. Since the refractive index of a gas can change in response to density, pressure, or temperature, it’s a perfect way to see what’s going on when there’s otherwise nothing for one’s eyeballs to latch onto.

Intrigued by this kind of imaging? It requires a careful setup, but nothing particularly complicated or hard to get a hold of. Here’s one such setup, here’s a Schlieren videography project, and here’s a particularly intriguing approach that leverages modern electronics like a smartphone.

Thanks to [Quinor] for the tip!

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1950s Fighter Jet Air Computer Shows What Analog Could Do

February 14, 2023 by Dan Maloney 40 Comments

Imagine you’re a young engineer whose boss drops by one morning with a sheaf of complicated fluid dynamics equations. “We need you to design a system to solve these equations for the latest fighter jet,” bossman intones, and although you groan as you recall the hell of your fluid dynamics courses, you realize that it should be easy enough to whip up a program to do the job. But then you remember that it’s like 1950, and that digital computers — at least ones that can fit in an airplane — haven’t been invented yet, and that you’re going to have to do this the hard way.

The scenario is obviously contrived, but this peek inside the Bendix MG-1 Central Air Data Computer reveals the engineer’s nightmare fuel that was needed to accomplish some pretty complex computations in a severely resource-constrained environment. As [Ken Shirriff] explains, this particular device was used aboard USAF fighter aircraft in the mid-50s, when the complexities of supersonic flight were beginning to outpace the instrumentation needed to safely fly in that regime. Thanks to the way air behaves near the speed of sound, a simple pitot tube system for measuring airspeed was no longer enough; analog computers like the MG-1 were designed to deal with these changes and integrate them into a host of other measurements critical to the pilot.

To be fair, [Ken] doesn’t do a teardown here, at least in the traditional sense. We completely understand that — this machine is literally stuffed full of a mind-boggling number of gears, cams, levers, differentials, shafts, and pneumatics. Taking it apart with the intention of getting it back together again would be a nightmare. But we do get some really beautiful shots of the innards, which reveal a lot about how it worked. Of particular interest are the torque-amplifying servo mechanism used in the pressure transducers, and the warped-plate cams used to finely adjust some of the functions the machine computes.

If it all sounds a bit hard to understand, you’re right — it’s a complex device. But [Ken] does his usual great job of breaking it down into digestible pieces. And luckily, partner-in-crime [CuriousMarc] has a companion video if you need some visual help. You might also want to read up on synchros, since this device uses a ton of them too.

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The supersonic trebuchet being modeled in software

Supersonic Projectile Exceeds Engineers Dreams: The Supersonic Trebuchet

December 1, 2021 by Ryan Flowers 63 Comments

Have you ever sat down and thought “I wonder if a trebuchet could launch a projectile at supersonic speeds?” Neither have we. That’s what separates [David Eade] from the rest of us. He didn’t just ask the question, he answered it! And he documented the entire build in a YouTube video which you can see below the break.

The trebuchet is a type of catapult that was popular for use as a siege engine before gunpowder became a thing. Trebuchets use a long arm to throw projectiles farther than traditional catapults. The focus has typically been on increasing throwing distance for the size of the projectile, or vice versa. But of course you’re here to read about the other thing that trebuchets can be used for: speed.

How fast is fast? How about a whip-cracking, sonic-booming speed in excess of 450 meters per second! How’d he do it? Mostly wood and rubber with some metal bits thrown in for safety’s sake. [David]’s video explains in full all of the engineering that went into his trebuchet, and it’s a lot less than you’d think. There’s a very satisfying montage of full power trebuchet launches that make it audibly clear that the projectile being thrown is going well past the speed of sound, with a report quite similar to that of a small rifle.

[David]’s impressive project and presentation makes it clear that all one has to do to build a supersonic trebuchet is to try. Just be careful, and watch where you shoot that thing before you put somebody’s eye out, ok?

Speaking of things that can go unexpectedly fast, check out these unpowered RC gliders that approach the speed of sound just feet off the ground. And thanks to [Keith] for the awesome Tip!

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The Politics Of Supersonic Flight: The Concord(e)

January 25, 2021 by Jenny List 29 Comments

Every nation has icons of national pride: a sports star, a space mission, or a piece of architecture. Usually they encapsulate a country’s spirit, so citizens can look up from their dreary lives and say “Now there‘s something I can take pride in!” Concorde, the supersonic airliner beloved by the late 20th century elite for their Atlantic crossings, was a genuine bona-fide British engineering icon.

But this icon is unique as symbols of national pride go, because we share it with the French. For every British Airways Concorde that plied the Atlantic from London, there was another doing the same from Paris, and for every British designed or built Concorde component there was another with a French pedigree. This unexpected international collaboration gave us the world’s most successful supersonic airliner, and given the political manoeuverings that surrounded its gestation, the fact that it made it to the skies at all is something of a minor miracle. Continue reading “The Politics Of Supersonic Flight: The Concord(e)” →