Basically, I’m cool with what happens after the THOOMP! But what’s going on inside the mortar before the projectile leaves the tube?
I guess my main question is: is the projectile self launching like, say, a rocket? Or is there a mechanism inside the tube that literally throws the shell out? In the later case, could you explain what the mechanism is?
(Pointless aside: I would normally investigate these things myself firsthand, but I learned my lesson about tubular contraptions long ago… when I tried to figure out how a bong works and lifted it upside-down to my eye to get a peak inside. Sploosh…)
Here is the US Army Mortar Gunnery field handbook from 2000, which might answer some of your questions. I haven’t reviewed it, so I’m not sure, though.
“Propellent is a low-order explosive that burns rather than detonates. The mortar fires semifixed ammunition. When the gases from the burning propellent develop enough pressure to overcome projectile weight and initial bore resistance, the projectile begins to move.”
That explains why there’s always a lag between the dropping of the shell into the tube and the time the shell launches, which always perplexed me because if it had the same mechnism as, say, a bullet, the launch would be essentially instantaneous…
I believe with a mortar, there is a precussion-activated explosive charge which propels the explosive. I’ve seen pictures of mortar rounds which suggest they are rocket-propelled, but I don’t think the smaller ones have any propulsion beyond what goes off inside the tube.
From a technical standpoint, I’ve heard that any artillery that fires projectiles greater than 45 degrees is considered a mortar, and anything that fires them LESS than 45 degrees is considered a howitzer. Mortars were useful because you could lob them over walls and hills and stuff. It seems compulsory to have a battle invovling lots of mortar fire in any film involving Vietnam.
Some mortars were rocket-propelled. Here is a rather interesting example-
As I recall it, the mortar shell has powder charges in the base (increments). These are adjusted(pulled) depending on the range of the target, ie if expecting Final Defensive Fire, most of the propellant is removed so the shell only arcs up a minimal distance. When the shell is dropped down the tube, it hits a firing pin at the bottom, which ignites the propellant. The rest works just like a smooth-bore musket. The shell is launched by ignition gases, just like a bullet. Hope this helps.
