Product: Weapon: Gun
Explosively confined gun barrel   (+8, -1)  [vote for, against]
Uses well-timed explosive inertial confinement to contain high explosive-produced pressure in a single-use barrel.

<begin vernon-esque spiel>

Bit of a concept- looking- for- an- idea here but here goes. As per my anno on "N-prize" - this consists of a single use explosive device, similar in concept to an EFP. Basically you have a barrel, surrounded by explosive blocks with a carefully calculated timing sequence.

Inside the barrel is a projectile clad in a sacrificial wear - lining, probably something soft that will act as a lubricant. (Poly/UHMWPE anyone?). The propellant charge can basically be the most energetic explosive you can find, eventually perhaps a small nuclear charge could be suitable.

The concept is that you use the explosive blocks surrounding the barrel to exert inwards pressure on the barrel, preventing it from bursting from the rediculous internal pressure at the time of firing. I could see this as a microsecond-timescale dynamic solution whereby the explosive wave propagation and pressures are tuned to provide maximum confinement at the optimal time, along the length of the barrel.

In fact the cladding explosives could be used to perpetuate the extremely high pressure behind the projectile.

With careful planning and design, the action of the cladding and propellant explosives should be to drive the whole device in the forwards direction whilst detonation is happening (or perhaps slightly before). In this way, the cumulative effect is somewhat like a multi-stage rocket whereby forwards momentum is optimised in the projectile.

Basically used whereby efficiency is irrelevant in comparison with the desire for maximum velocity. It would be interesting to see what the theoretical maximum velocity is comparable to an EFP.

A bit of an idea waiting for the mathematics, but I don't have my hands on a dynamic computational package powerful enough to run any numbers here so it's just an idea in my head at this stage. Very much half baked.

and yes, there are non-military applications. Maybe. Hell, I dunno, but it's an interesting idea in the how- fast- can- we- make- stuff- go quest, I thought.

[insert words to the effect that this is mine, an original idea, that I'm posting here for general use. No one should subsequently claim this as their own, profit, etc, yadda yadda yadda].

</end vernon-esque spiel>
-- Custardguts, Feb 25 2008

Any ideas on the category? I put this here as a joke, wasn't sure where to park it.

 - not really where I wanted it, but OK I suppose.
-- Custardguts, Feb 25 2008

I have seen a paper describing a method for generating EMP using an explosively-collapsed TWT, so it would seem that as far as velocity is concerned, c is the limit. [+]
-- coprocephalous, Feb 25 2008

Oh yah, if you're willing to use nuclear explosives, the sky's the limit.
-- Custardguts, Feb 25 2008

//if you're willing to use nuclear explosives//
No, the collapsing used conventional explosives.
-- coprocephalous, Feb 25 2008

//something like 26,000 fps,// Interesting that that speed is only *just* useful orbital velocity.
-- coprocephalous, Feb 25 2008

<begin vernon-esque spiel>
</end vernon-esque spiel>

I like that. Can I borrow it sometime?

:)
-- Vernon, Feb 26 2008

What you're describing is replicating the "squeeze implosion" initiation system used in Pu-based nukes, but transposed into a linear system.

It's technically practical, but possibly pointless. It's relatively easy to make a "barrel" which will withstand stupendous internal pressures. The problem with any gas-expansion projectile system is sustaining the pressure on the base of the projectile as it accelerates down the barrel. The Millipede did it by having multiple pairs of side chambers at ntervals, and the 20mm prototype built by DWM-Auftrag worked acceptably.

Imagine taking a standard WW2-vintage 18-inch naval gun barrel, which were anyway made with loose liners. Machine down something like a 6-inch barrel and slide it inside. Keep going on the "Matrioshka doll" principle until you have a 50mm inner bore. The breech pressures that such a built-up composite barrel could withstand would be quite impressive.

But you still need to maintain the propellant pressure. Side chambers, and composite-burn-speed propellants are part of the answer.

The main objections to the "squeeze" barrel device would be the high unit cost of a single use device, and the danger to personnel in the vicinity; it would make the average recoilless gun look like a kiddie toy. However, it might have an application for an air-dropped autonomous smart mine - a very lightweight single use barrel, capable of firing a heavy projectie at extreme velocity.

[later]

If you use a ripple-firing of segmented charges to collapse the "barrel" behind the projectile, that would certainly maintain the "breech pressure".

Accuracy is going to be a BIG problem ....

[even later}

Since this a stupidly expensive and highly dangerous use of explosives to propell a projectile at ludicrous velocity in an unpredicatble trajectory, [+].
-- 8th of 7, Feb 26 2008

8th, I think you've grasped the idea. the bit that says..

//In fact the cladding explosives could be used to perpetuate the extremely high pressure behind the projectile.//

..was meant to express the combination of collapsing the barrel, and allowing the pressure of the collapsing charges to perpetuate the propelling force.

And yah, I was only ever thinking it would be used as some kind of airborne single-use device. Think "skeets".
-- Custardguts, Feb 26 2008

Hmmm... the control problem is non-trivial.

Depending on the explosive used (one of the crystalline polynitrated aromatics springs to mind) the detonantion wavefront will couple along the cssing faster than the projectile in the initial stages. So tampers will be needed between each "lens ring" to stop shock-propagation while the projectile accelerates from rest.

The answer might be to have a fairly conventional breech and launch charge to get the projectile moving; once it's gone supersonic, this is detected by instrumentation and the rings are fired in succession just after the projectile passes to maintain thrust. This would have the advantage that the rear portion of the "barrel" might even be re-uesable. You could couple the "breech" to the "barrel" with a gap simialr to that between the cylinder and chamber of a revolver (but beware gas venting issues).

Accuarcy is still going to be a huge problem. Any asymmetry in the manufacture of the rings, or imperfections in the barrel, is going to produce enormous laretal forces on the rear of the barrel before the projectile leaves the muzzle. Again, this could possible be overcome by having "segments" of barrel with breaks between them, decoupling the leverage effect.