wb9omc@ea.ecn.purdue.edu (Duane P Mantick) (08/31/90)
From: wb9omc@ea.ecn.purdue.edu (Duane P Mantick) Let me pose a hypothetical question about chasing and sinking tankers in the Persian Gulf (or elsewhere for that matter). What effect would a 16" shell from the Wisconsin have (aside from the obvious ignition of any combustibles on board) to the ship? Now that may seem like an obvious question with an obvious answer....what I am thinking of is: while there would be a big hole in the thing (assuming for the sake of arguments, holds with NO oil, mostly empty), would it get blown in half with one well placed round? I have seen what 16" HE can do to granite mountains (that is, making lots of little rocks) but I'm curious about what the dynamics of hitting the hull or upper deck and exploding would have on the rest of the structure. Any theories (and yes I *do* know that the 16" round can go through xx inches of Krupp steel used in an armor belt....this is a *slightly* different case :-) )???? Duane [mod.note: The problem when engaging such "soft" targets with large- caliber guns is mostly one of fusing. The fuses of these shells can be set to various delays; the idea being that the fuse activates upon striking the target, and should have enough delay to allow the shell to travel on to the ship's vitals before exploding. The thing is that if the target is armored, you need a longer delay, because the shell loses part of its velocity in penetrating the armor. The thicker the armor, the greater the delay needed. This was a problem in the Battle of Leyte Gulf, where the Japanese shells were fused too long; many of their battleship shells thus completely penetrated the "baby flattops" before exploding after passing through. However, the problem can be solved. I'd feel confident that modern US Naval practice has anticipated this, given that any ship target these guns would now engages would probably be unarmored. Too, during the war, battleship guns did from time to time strike and detonate against targets as small as destroyers. The large beam of a tanker should simplify the problem still further. - Bill ]
terryr@ogicse.ogi.edu (Terry Rooker) (09/04/90)
From: terryr@ogicse.ogi.edu (Terry Rooker) In article <1990Aug31.030327.22986@cbnews.att.com> wb9omc@ea.ecn.purdue.edu (Duane P Mantick) writes: > >What effect would a 16" shell from the Wisconsin have (aside from the >obvious ignition of any combustibles on board) to the ship? Now that >may seem like an obvious question with an obvious answer....what I >am thinking of is: while there would be a big hole in the thing (assuming >for the sake of arguments, holds with NO oil, mostly empty), would >it get blown in half with one well placed round? First, the moderator's note on fusing is most pertinent. It is difficult to get the proper fusing to detonate while the round is still in the ship. There is no obvious combustion effect, not every round that hits a ship starts a fire. Short of a catastrophic explosion caused by detonating a magazine or large storage tank, it is very difficult to have a single round sink a ship (I am not considering progressive damage). About the only way a single round could break a ship in half is to break the keel, which is the effect of many modern anti-ship torpedos. In this case you might want the 16" round to go through the hull and detonate immediately under the hull. To make matters worse, with all their tankage, tankers tend to be very resilient. Look up some references about the Ohio (?) in one of the Malta convoys during WWII. -- Terry Rooker terryr@cse.ogi.edu
timk@xenitec.on.ca (Tim Kuehn) (09/04/90)
From: timk@xenitec.on.ca (Tim Kuehn) In article <1990Aug31.030327.22986@cbnews.att.com> wb9omc@ea.ecn.purdue.edu (Duane P Mantick) writes: > > >From: wb9omc@ea.ecn.purdue.edu (Duane P Mantick) >What effect would a 16" shell from the Wisconsin have (aside from the >obvious ignition of any combustibles on board) to the ship? Now that >may seem like an obvious question with an obvious answer....what I >am thinking of is: while there would be a big hole in the thing (assuming >for the sake of arguments, holds with NO oil, mostly empty), would >it get blown in half with one well placed round? This would depend on the construction of the tanker, where the shell hits in the tanker, how much HE the shell is carrying, and (if you hit one of the tank compartments) what the tank compartment is carrying. Using the assumptions you've provided above, I would guess that the tanker would be relatively safe from being broken in half with *one* lucky hit - more likely you would punch a hole in the tank compartment, maybe blow the top off or make a big hole in the tank compartment cover, and (Depending on where the shell detonates and how the force of the explosive charge is directed) you may put a hole in the bottom of the ship. Doubtless if the shell detonates inside the tank compartment you'll do a lot of damage to the internal support structures, maybe even blow the compartment walls seperating the tank sections out (if the adjacent tanks are also empty). However, if we change the assumptions around a little...(See below) >[mod.note: The problem when engaging such "soft" targets with large- >caliber guns is mostly one of fusing. The fuses of these shells can be >set to various delays; the idea being that the fuse activates upon >striking the target, and should have enough delay to allow the shell >to travel on to the ship's vitals before exploding. > The thing is that if the target is armored, you need a longer >delay, because the shell loses part of its velocity in penetrating the >armor. The thicker the armor, the greater the delay needed. >...rest of mod.note deleted....] The fusing of the shell and the contents of the the tanker holds would have a definite effect on how much damage a 16" HE shell would do to the tanker. Using a number of different assumptions, I'll attempt to speculate on what could happen given different scenarios of a 16" shell vs (1) tanker. Assuming, for simplicities sake, our representative tanker tank section looks like the following: Depth ----- Tank Cover------------+ -2 V -1 +-----------------------+ Top(0) | ^ | 1 <-- other tanks | | | 2 other tanks --> | fluid depth | 3 | | | 4 | v | 5 |<--- tank walls -->| 6 +-----------------------+ Keel Figure 1 If I've gotten my terminology slightly off, please bear with me.. :-) For the following scenarios I'm assuming: a) a non-shaped charge shell with a spherical explosion pattern (ie the force of detonation spreads out equally in all directions) b) the shell comes in perpendicular to the water line (ie straight down). c) It is doubtful the tanker would be under way with completely empty tanks but rather would partially fill them with some kind of ballast to keep the ship reasonably stable while it's under way on the high seas. I'll assume that they are filled a level equal to 5 on the above diagram. Given: I) The shell is fused to detonate at -2. The area directly under the shell would take the hardest part of the explosive force, and would probably react like a piece of sheet metal being hit by a sledgehammer - by buckling. The area at the center of the explosive impact would get pushed down, and the metal at the seam lines would burst and bend up depending on whether the metal pushed inward by the force of the blast stretches or breaks. Depending on how strong the covering plates of the tank are, if it is able to absorb/deflect most of the blast, not much will happen inside the tank. If it fails catastrophically and does not absorb most of the blast, then part of the explosive force will proceed into the tank compartment, possibly rupturing the tank walls and doing further damage to the tank cover when the explosive force reflects off the water/ballast on the bottom of the tank. II) The shell is fused to detonate anywhere from 2-4 This depends highly on the relative strength of the tanker walls, the ship sides, and the tank cover. Pressure inside the tank compartment will increase dramatically when the shell detonates, putting a sudden increase on the loading of the seams and rivits that hold the structure together. Almost certainly the internal supports inside the tanker, designed to handle relatively static or smaller dynamic loads than those created by a shell detonation would become scrap metal. The tank walls may rupture and allow the force of detonation to continue into other tank chambers. Figuring out what happens to the walls of the tanker would involve considering the following view of the tanker looking at it head-on: Depth | |<-- tanker walls 1 | * | 2 waterline------>| |<-------waterline 3 |----ballast----| 4 | level | 5 +---------------+ 6 Figure 2 (*) is the detonation point. Pressure from the detonation would radiate in a spherical pattern in all directions. Part of the blast would be reflected off the ballast due to the change in the force transmission, part of it would continue on and impact the keel of the tanker and the tanker walls. In order for the metal to fail and break, the amount of force applied to it in a given direction would have to exceed it's yield strength in that direction. In other words the following inequality would have to be satisfied: (1) explosive force > metal's yield strength This would be true for the tanker's wall from depth 1-3. Below the waterline the outside seawater would be exerting force on the tank walls. A diagram of this would look like: outside sea water--->| inside the tanker ^ +-- wall of the ship The deeper you go down below the waterline the greater the amount of force of the outside sea water pushing in on the tank wall, and would have to overcome in order to put a hole in the tanker. The inequality would then become: (2) explosive pressure > yield strength + pressure from outside seawater Which would be true for depth = 4. For depth 5-6 in the tanker, we have ballast on the inside pushing out on the sides of the tank, so our inequality there would change once more: (3) explosive pressure + > metal yield strength + pressure from the ballast pressure from seawater This leads to the conclusion, that, at least for an empty tanker, there would be less chance of a below-the-waterline hole resulting from the shell detonating. However, above the waterline there's nothing pressing against the sides of the ship to reinforce it, and hence you'd have a higher probability of actually putting a hole in the ship there and weakening the structure accordingly. Also, since the tank compartment is primarly filled with air, the rate of loading that would be applied to various parts of the tanker structure would be slower since the air is easily compressed and would absorb some of the initial energy from the detonation. Being a gaseous substance, it would relieve the pressure through any of a number of available relief points it may find at a relatively quick rate. This could allow for less damage to the tanker than if it was filled with a fluid. (This is similar to trying to squirt air out of a bottle and then filling it with honey and trying to squirt that out. It'll take a lot more effort - and hence a lot more loading on the bottle to move the same volume of honey as air). ------ Note - in all this, metal has a tensile strength, which, while lower than the yield strength, subjecting the metal to stresses above this point will leave it in a weakened state. [mod.note: Confused terminology here. A metal's yield strength is the force required to deform it; the tensile strength is that required for complete failure. Tensile strength is greater than or equal to yield strength. - Bill ] ------ All of this would depend on how much HE the shell was carrying. If you put enough HE in the shell (possibly by replacing the armor-piercing tip of the shell with something softer and lighter and adding HE to the space left over) you could theoretically blow the sides out of anything. Now, if we changed one of the assumptions above so that we were dealing with a *full* tanker, life gets a lot more interesting. ----- Changing assumption (c) in the previous two examples to c) The tanker is filled with crude oil. III) The shell detonates within the are of 2-4 as shown in Fig. 1. The failure inequalities previously written in 1,2,3 would change since the tanker walls are under load from the fluid cargo. From this we can derive new inequalities that would need to be satisfied in order for the metal to fail: Above the waterline we need: (4) explosive pressure + > metal yield strength. pressure due to the oil cargo As we move down deeper into the tanker (depth 3 in Fig 2) the pressure from the crude would increase, pushing the metal closer to it's failure point, which means that it'd take less effort to get it to fail there. Consequently there'd be a higher chance that we'd have a waterline failure of the tanker walls with it resulting consequences. Proceeding deeper still, (depth 4 in Fig. 2) the pressure on the outside seawater would reinforce the metal walls, but there would also be the increased weight from the cargo pressing out. This would rewrite inequality 3 as: (5) explosive pressure + > metal yield strength + seawater pressure pressure due to the cargo What would make a shelled tanker's life really interesting is that oil is a *lot* less compressible than air is. As a result, the shock wave from the detonation would hit a lot harder in the direction of propogation than a shock wave being carried by air. As a result, there is a lot higher chance of damage being done to a given portion of the tanker if you detonated a HE shell in a full tanker than if you detonated it in an empty one. There's also the increased possibility for the tanker to catch fire and burn, and/or release it's cargo to the enviroment ;-(. A way to demonstrate the amount of damage that can take place as a result of suddenly displacing a volume of incompressible fluid would be to shoot a .22 bullet into a beaker or other glass container. While I've never tried this myself, I've been told that doing so will shatter the sides of the beaker by the shock wave generated by the suddenly displaced water when the bullet impacts. ----- While I know the previous doesn't directly answer the question originally posed, I hope it provides some useful information / ideas to the net.readers of sci.mil at large. ------------------------------------------------------------------------------ Timothy D. Kuehn TDK Consulting Services "Where Quality is Guaranteed" timk@xenitec.on.ca uunet!watmath!maytag!xenitec!timk 119 University Ave. East, Waterloo, Ont., Canada. N2J 2W1 519-888-0766 if no answer 519-742-2036 (w/ans mach) fax: 519-747-0881. Contract services available in Dos/Unix/Xenix - SW & HW. Clipper, Foxbase/Pro, C, Pascal, Fortran, Assembler etc. *Useable* dBase program generator under construction ------------------------------------------------------------------------------
willner@cfa.harvard.edu (Steve Willner, OIR) (09/13/90)
From: willner@cfa.harvard.edu (Steve Willner, OIR) >From article <1990Aug31.030327.22986@cbnews.att.com>, by wb9omc@ea.ecn.purdue.edu (Duane P Mantick): > What effect would a 16" shell from the Wisconsin have (aside from the > obvious ignition of any combustibles on board) to the ship? Now that > may seem like an obvious question with an obvious answer....what I > am thinking of is: while there would be a big hole in the thing (assuming > for the sake of arguments, holds with NO oil, mostly empty), would > it get blown in half with one well placed round? > [mod.note: The problem when engaging such "soft" targets with large- > caliber guns is mostly one of fusing. The fuses of these shells can be Don't forget that the BB's carry high explosive rounds as well as armor piercing. The HE is intended for shore bombardment, but it would be very effective against unarmored ships. (In fact, since the main mission is shore bombardment, the BB's might not even carry AP any more.) The HE shell for the 16 inch guns weighs 1900 lb, if memory serves. I think the fuse has no provision for time delay, and I'm pretty sure that zero delay is at least an option. Depending on compartmentation, at most a few shells should be sufficient to sink even a large tanker. Larger numbers of smaller shells (from other ships) would be equally effective, of course. ------------------------------------------------------------------------- Steve Willner Phone 617-495-7123 Bitnet: willner@cfa Cambridge, MA 02138 USA Internet: willner@cfa.harvard.edu
budden@trout.nosc.mil (Rex A. Buddenberg) (09/13/90)
From: budden@trout.nosc.mil (Rex A. Buddenberg)
Most, if not all (I'm not up on the appropriate international
conventions) tankers carry inerting systems. Commonly, stack gas
is piped into the tank spaces in order to render the atmosphere
incapable of supporting either fire or explosion.
Consequently, an exploding munition will go off, but is highly
unlikely to start a secondary explosion. If it pokes a hole in
the tanker and oil leaks out, then a secondary fire may ensue.
That said, seems to me that this thread started by someone asking
how you handle a tanker that doesn't want to stop -- bulling
through a blockade -- WITHOUT spilling the cargo all over the
ocean. Terry Rooker's SEAL description is apt. We've done
such things in the Coast Guard too, although under slightly
different circumstances.
The best known is case of a mutiny on a tanker bound for
Philadelphia. Denied entry, anchored off Cape May. Officers
locked in spaces (with radio officer able to discreetly use
his gear). CG WMEC lingered in area until mutineers got used to
it being around. Then moored alongside. After carefully
counting noses and getting several folks aboard for parley,
a joint CG/FBI assault party siezed control.
Rules of engagement were to use nightsticks although shotguns
with solid slugs (won't penetrate tank skins) and a few other backup
weapons of similar nature were in reserve. Mutineers were not
exactly a disciplined resistance so they came down pretty quick.
This case is 7-8 years old now, but the whole mess was
videotaped by the lookout of the watch on the cutter. Interesting
to watch. No shots, no injuries. With a couple of interesting legal
twists -- foreign flag tanker (Liberian, I believe), international
waters; law enforcement action, not act of war.
Rex Buddenberg