A-Team plausibility question

[dvandom]

Spoilers within, regarding the final set piece in the new A-Team movie and the plausibility of one of the elements.

Okay, so in the final set piece, a single shot from a shoulder-launched rocket ends up breaking a cargo ship in half amidships. Yes, there's some secondary explosions from the containers, but it's still just one rocket.

On the other hand, a cargo ship is designed to resist diffuse forces like waves, and maybe deal with running aground. It's not designed to handle anti-armor weaponry, so it's possible that a single shot in the right place would break the keel.

Does anyone with more knowledge of either ships or anti-armor rockets know if that part of the movie is at least plausible? Or would it take several shots in exactly the right places to sink a ship like that?

Oh, and regarding the tank drop: steering certainly plausible. Slowing down...maybe. It's hard to tell how high the terminal velocity really is on just one chute, they might not have really needed to cut that much speed. But repeated firing wouldn't help any more than a single shot at the end, since the firing cycle is long enough to get back up to the new terminal velocity between shots (not that I'd expect people in a falling tank to think of that). But even if they hit softly enough to avoid destroying the tank's systems, I'm pretty sure a completely submerged tank will not drive. Unless this model is designed for limited runs on batteries or something.

Comments

[dewline.livejournal.com]

A bunch of things involved here. Starting with "How old (are we expected to believe) is the age the cargo ship in question?" I remember there was a plot point about single- vs. double-hulled oil-tankers in a West Wing episode, and that might be an issue connected with the age of the cargo ship.

Not speaking as anything even remotely resembling an expert here, though.

[grant-p.livejournal.com]

I haven't seen the movie at all, but air-dropping a small tank is actually very easy, I've seen it done in RL. Of course, you're not expecting anyone to be ON the tank when it's falling, the idea is to drop it on the right area and the troops then run to it, unstrap, and drive off. I saw Pope Air Force Base demonstrate it live, it only took seconds once it hit the ground. Pope takes pride in being able to air-drop an entire brigade if they have to, complete with full equipment, vehicles, and even a mess tent and portable hospital with surgical capabilities. Amazing people.

You can also drive a tank underwater if you attach a snorkel to the intake and exhaust. This was developed for river crossings, as tanks don't float well. You just attach the snorkel, lock down the cockpit, drive in and out, and un-seal. Most tanks are compatible with this as they are made to seal in case of chemical exposure. I've seen this done too, it looks REALLY silly, but it works.

If this is totally not what you meant, sorry! Like I said, I haven't seen this movie.

probably too high

[drewdederer.livejournal.com]

The only way you'd get a back breaking in the scene described is if you had a major explosion in the cargo containers venting down. Given how open a container ship's holds are at the top, that isn't going to happen. Any explosion would vent up, and wouldn't have the energy to destroy the hull girder at the keel.

What usually causes a ship's back to break is an underwater explosion. Not the shock directly onto the keel plate but the induced "whipping" action on the hull. Kinda like how you used to crush the old tin cans by standing on them and tapping their sides.

The Brits did a bunch of experiments post WWII on "shock" effects on ships (D.K. Brown's books on warships are a good disgest for this).

Things that helped deel with shock.

1. Longitudinal framing (the stressed "ribs" run along the ship, not top to bottom.
2. Welding (more flexible than rivets).
3. Flush deck. If the "deck line" is more or less straight, that's good. Many British ships had a one or two deck "drop" somewhere near the middle. That was a weak point (much like the Comet Airliners' square windows), and contributed to a number of "breaks".

A modern container ship would be welded, longitudinally framed and "flush deck". While not built to warship standards, it does carry a LOT of weight distrubuted far fore and far aft, which means a LOT of stress. It'd take more than a LAW or TOW to crack it.

[dpawtows.livejournal.com]

No, the scene is impossible. You'd need a battleship to sink a freighter that fast in one shot.

The way a man-portable anti-armor missile like that typically works is to create a jet of hot gas/plasma on impact. This burns a small hole in the armor, then the remainder of the jet plays around inside like a flamethrower. The idea is to fry everything on the inside of the tank. Once it burns through the armor, the jet expands rapidly and loses it's armor-penetrating power. There are some forms "spaced" armor that try to set off the missile early, and some forms of double-warhead missiles to counter spaced armor. But that's designed to penetrate extra layers separated by a few inches at most. The movie showed the missile blowing clear *through* the entire ship and out the other side. You need warship-sized cannon to do that.
Here's what happens if you fire a missile like that at a freighter hull: It will burn a hole in it, anywhere from a few inches to a foot across. And it'll start a nice fire on the other side. If there's nothing flammable over there, there's not much effect. For a container ship, I imagine it would ignite the paint of the container just inside the impact point. What happens next depends on what's in the container, and how good the crew are at firefighting. Anybody standing inside the ship near the impact spot will be char-broiled.
There's another type of warhead called a "squash-head" that doesn't blow a hole in the armor. It makes a big disk-shaped chunk of armor fly off the inside surface and bounce around the vehicle interior like a buzzsaw. That's rare in a missile, and even less like the movie.
In general, infantry-level anti-tank missiles make poor naval weapons. Most ships have too much non-essential volume; you can riddle them with holes and not hit anything too important. A tank has very little internal space that's not filled with bits that it needs. You can get "golden-BB"-esque shots that disable a ship with one shot, but that's getting really lucky.