So i know it could be an alternative to rocket engines for spaceflight but thats how far i am at. How does it work?
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There was a sci-fi project called Project Orion at DARPA that would have used nuclear explosions to generate pulses to propel a spacecraft.
https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion
Detonation engines are not just for rockets, but a wide variety of applications. They are in theory more efficient that what we have today, but also very complicated to model, because fluid dynamics are really complicated.
The important bit about detonation engines is that detonation in the context means a shock wave that expands faster than the speed of sound in the medium. If it goes slower you have a deflagration not a detonation. (They look more or less the same to a layperson looking at something going boom.)
Stuff like pulse detonation engines have been build and tested and rotation detonation engines are a thing people at places like NASA hope to build.
The result would be more efficient rockets and jet-engine with fewer moving parts.
It is not easy though. The math is hard and the margin of error for things that explode is low.
Still it is a nice idea if it can be made to work.
To start off, you need to know the difference between a detonation and a deflagration. Deflagration is basically when the energy released from combustion doesn’t form a shockwave because it’s not burning faster than the speed of sound. A detonation on the other hand creates a shockwave because it’s moving faster than the speed of sound.
A real world example would be dumping gasoline on the ground and lighting it on fire. It doesn’t form a shockwave, and you can see the fire spread over the gasoline. A detonation on the other hand would be like when the Mythbusters exploded a cement truck. You can see a shockwave form.
So what’s the practical difference for rocket engines? Well, a rocket engine’s efficiency is partially determined by how fast it can throw the exhaust out the back. It’s why ion engines are so much more efficient than chemical engines. All chemical engines today use deflagration, and have a slower exhaust speed. Ion engine “exhaust” (the ions being thrown out the back) move insanely fast. A detonation engine by definition would have much faster exhaust, and therefore much more efficiency.
It’s physically impossible to continuously feed a combustion chamber with fuel/oxidizer fast enough to keep up with a detonation. Not to mention that constantly pounding your rocket with repeated high acceleration/no acceleration cycles would likely be detrimental to most payloads, especially humans.
So how do they get it to work? If you look at detonation engines today, you will basically see a ring of nozzles. Typically, 2 opposite nozzles are detonating and the others are recharging fuel/oxidizer or waiting to detonate. They will basically detonate one after the other, circling the ring. This creates basically a constant “wave” of detonations and solves the issue of shaking the rocket and its payload to pieces.
Here’s a brilliant video that dives into it:
Was the WWWII Buzz Bomb used against England basically a detonation engine? It was technically a pulse jet engine but how different would that be from a detonation engine.
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