this post was submitted on 26 May 2024
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Today I Learned (TIL)
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Do they have a solution for the raspberry jam problem?
(Tried to find a link for the term in case someone thinks it's a sexist joke or something, but seems to be surprisingly hard. So I'll just briefly explain that raspberry jam delta v is the acceleration or deceleration rate where the contents of a passenger compartment start to resemble said substance.)
Ooh! Since we're straying so far off topic, I'd like to share a similarly gross story I don't often get to tell.
Back in the oelden days, I was in the Army and was volunteered to test a replacement for the Tow anti-tank missile. The system I was assigned to evaluate - with a squad of my peers - was the Swedish Bill. They wouldn't tell us much about how it worked, but we did know that the missile would detect when it was over a tank at an optimum angle and explode a shaped charge, driving a round (we suspected it was depleted uranium or tungsten) down into the tank. The round was shot with sufficient force to pass through armor (of the day) and out the bottom of the tank. The round was followed by plasma, and what we were told was this: that the effectiveness wasn't that it would blow up the tank, per se - unless it happened to ignite ammunition in the tank - but that the round went so fast that it created a vacuum inside the tank, sucking any soft material that happened to be in the tank out through the 10cm exit hole. So it created high Delta-P conditions in the tank.
When, decades later, the Delta-P crab video made the rounds, it reminded me of that trial.
Delta-V to Delta-P; how's that for a seque?
Pretty gruesome.
Well, you started it, Mr Raspberry Jam... or should I say Prince Jamroll??
Without knowing anything about weaponry, it seems sketchy to claim that a 1atm pressure difference would do that.
It wasn't 1atm of pressure. The round passing through the (enclosed) compartment of the target at high velocity created a vacuum that sucked any soft material out after it. There was also the explosion that happened on the armor, and some sort of plasma that went in after the round that all probably contributed to the effect.
I don't know the technical details, and as I said, they were pretty proprietary with exactly how the thing worked; I was just a grunt assigned to carry out around and fire it. We had some Swedish military guys training us and consulting on the trials, and that's what they told us the effects were. I assume they'd tested the thing with pigs or something; I don't know if it was designed that way or just a happy side-effect.
What I remember most is that it was like playing a video game, and that it really fucked up tanks. We got to look at the results, and while our targets didn't have any animals in them, it did seem to incinerate anything that wasn't bolted down and spray it on the ground under the target.
The wiki article is equally tight-lipped about the exact mechanism of action. I just know it was different from a TOW in that the damage wasn't from a warhead exploding against armor; it was firing a projectile via a shaped charge as it passed over the target. There was much more debris left of the missile than we found from TOWs, although it was still a pretty destructive process for the missile.
Crazy. I believe it. Maybe it's some combination of overpressure and sudden vacuum. Love your description, thanks for the effort.