Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!lll-winken!sun-barr!newstop!sun!amdcad!amdcad!military From: wbt@cbema.att.com (William B Thacker) Newsgroups: sci.military Subject: Re: Torpedoing Battleships Message-ID: <1991May29.010907.6290@amd.com> Date: 24 May 91 19:22:42 GMT Sender: military@amd.com Organization: AT&T Network Systems - Columbus, Ohio Lines: 92 Approved: military@amd.com From: wbt@cbema.att.com (William B Thacker) Tony Buckland writes: >In the debate over whether or not Rodney torpedoed Bismarck, I >note the side issue emerging of whether surface-ship-launched >torpedos did any damage to Bismarck. Are modern torpedos >available in a specialized type for this kind of armor-piercing >role, in the same way that tanks carry rounds specifically >designed to penetrate the armor of other tanks? The short answer is that since there are very few heavily-armored ships around these days, such a torpedo wouldn't be needed. The long answer is that it never was. 8-) A torpedo isn't like an antitank weapon, punching a small hole through an armor plate. Neither is a ship like a tank, filled wall to wall with fragile and/or flammable materials. Ships are subdivided, and have damage control capabilities: make a small hole, and either the crew will plug it somehow or they'll seal off the flooding compartment until the hull can be patched and the water pumped out. Anything really vulnerable, like magazines, will be buried deep within the hull, behind many layers of armor, bulkheads, fuel bunkers, and what have you. A HEAT-type warhead would dissipate long before reaching the magazines, and obviously it would be, er, "unfeasible" to create a high-velocity kinetic torpedo. The whole thing is much cruder than this. The torpedo is designed to explode near (not necessarily in contact with, just "near") the ship's hull. The detonation creates a rapidly-expanding bubble of gas, desparately seeking relief from the water constrains it. Relative to water, which is incompressible, an unarmored ship is like putty; and even a fully armored ship is not much more than caulk, or perhaps spacking compound. Even the most heavily armored ships could not afford to cover the entire hull with armor; in fact, the armored belt typically extended only a meter or so beneath the waterline, leaving most of the outer hull unprotected. It would take such thick armor to defeat a torpedo blast that a ship simply couldn't carry it. As testimony to hydraulics, consider that the most devastating bomb hits against battleships in WWII were usually very near misses, which exploded underwater next to the ship's sides, not those actually hitting the ship. Instead, warship designers use other techniques to foil torpedos. I'm not sure about current practice, but the state of the art in WWII featured a "torpedo defense system" along the hull sides, from the waterline down to the flat bottom. This was composed of an outer shell, forming the watertight boundary of the hull, which would detonate the torpedo. Behind this would be void space, the more the better; sometimes these spaces were used for fuel or water storage, but it was better to leave them air-filled and to provide vents at the tops, to provide relief for the explosion gasses. Next came the torpedo bulkhead, typically 1-3 inches thick; hopefully this would contain the blast. In the event that it didn't, more void spaces (or fluid-filled compartments) backed the torpedo bulkhead, and behind them, when possible, was fitted a thin (about 1") armored "splinter bulkhead", whose job was to stop any fragments (in the event that the torpedo bulkhead was pierced) from flying into the ship's internals, punching holes and reducing the watertight integrity. On battleships in particular, multiple bulkheads of this type were common. The gist of the torpedo defense system is to allow the torpedo to expend its energy battering through a series of steel barriers, all the while bleeding off the pressure topside, until not enough energy remained to damage the ship's vitals. The torpedo defense system itself would flood, of course, but this was relatively harmless. Thus the major factor determining the effectiveness of an anti-torpedo system was depth; how much of the ship's beam (width, for landlubbers) can be used for this purpose? This presents a number of immediate conclusions. First, smaller ships will be more vulnerable, because they are less beamy. In fact, cruisers typically carried only a vestigial anti-torpedo system, while destroyers had none. Second, even battleships must sacrifice the torpedo defense system at the bows and stern when the ship narrows; it was not uncommon for battleships to have the bow or stern virtually blown off by a torpedo blast. Finally, it leads us to... ... what do we do about the ship's bottom ? If an explosion occurs there, there's no place to vent the gases except through the ship. The designer's answer, basically, has been to give up. They use double and even triple bottoms to provide some semblence of protection, but in fact torpedo or mine explosions beneath the ship's flat bottom were and probably remain devastating. In WWII, torpedo detonators were unable to reliable produce such an attack, although mines could; today, I'm sure it can be done routinely. The most likely result of such an attack is a broken keel, which means the ship is very likely to break up (although there are cases of good damage control overcoming even this). -- Bill Thacker AT&T Network Systems - Columbus wbt@cbnews.att.com