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Supersonic Projectile Exceeds Engineers Dreams: The Supersonic Trebuchet:
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 [~1480 feet] per second! How'd he do it? Mostly wood and rubber [bands] 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.
Link to 15m45s YouTube video with demo near the end.
(Score: 3, Insightful) by canopic jug on Thursday December 02 2021, @01:13PM (2 children)
At those G-forces, the model rocket would shear into pieces on a trebuchet. A ballista would provide a more appropriate thrust. As for the ignition, a very short fuse could do the job if they are still for sale anywhere. The timing would be very difficult. It's fine if the engine ignites at or before apogee. However, after that, thrust will make the thing very dangerous by sending it sideways and down. Even if it hits nothing, going sideways with lots of thrust will make it very hard to fetch and recover.
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(Score: 1, Touché) by Anonymous Coward on Thursday December 02 2021, @07:12PM
Nah... sideways is how we get to orbit.
(Score: 2, Informative) by Anonymous Coward on Friday December 03 2021, @08:26AM
An Estes Gnome is listed as 0.29oz. An A10/3T engine is 0.29oz and produces a maximum of 13N thrust. 0.79oz=0.0224kg. This gives us ~60g peak acceleration. At 60g it takes 0.77s to reach 450m/s.
This requires a 172m power stroke, assuming constant acceleration. That is a *very* large ballista.