Torpedo and Mine Damage History - Part 1

We previously examined torpedoes and their lethality and debunked the “broken back over a bubble of air” myth by examining available experimental data and applying simple logic (see, "Torpedo Lethality Myth").  However, it’s always worth looking at actual operational experience so let’s look at some historical examples of ships subjected to large underwater explosions due to mines and torpedoes and see what we can learn. 

This is the first of a two part post.  In this part, we’ll look at the historical data.  In the second part, we’ll examine an explanation for the historical data.

I’ve tried to pick a cross section of ship types, sizes, eras, and nationalities while working under the constraint of known data.  Many ships suffered mine/torpedo damage but the damage was too poorly documented to analyze.  The following examples are presented in no particular order.

Tirpitz

Tirpitz is one of the most documented and relevant examples.  According to Wiki, X-Craft midget submarines laid four 2 tonne mines on the sea bed under the bottom of the target.

“first exploded abreast of turret Caesar”

“second detonated 45 to 55 m (148 to 180 ft) off the port bow”

“A fuel oil tank was ruptured, shell plating was torn, a large indentation was formed in the bottom of the ship, and bulkheads in the double bottom buckled. Some 1,430 t (1,410 long tons) of water flooded the ship in fuel tanks and void spaces in the double bottom of the port side, which caused a list of one to two degrees, which was balanced by counter-flooding on the starboard side. “

The mines were massive explosions and caused extensive damage but no threat of sinking and no significant permanent structural damage.  In fact, the damage was repaired over the course of a few months.  These mines probably represented a worst case under-the-hull explosion of the type we’re interested in.

In a later attack, RAF Lancaster bombers attacked with 6-short-ton Tallboy bombs with 5200 lb Torpex D1 explosive.  A single hit on the ship's bow penetrated the ship, passed through the keel and exploded on the bottom of the fjord.  A thousand tons of water flooded the bow and caused a serious increase in trim forward but the ship did not sink.

Along with many bomb hits distributed over several aerial attacks which eventually sank the ship, Tirpitz absorbed three massive underwater explosions of the type we’re concerned with.  In fact, the explosions were probably much more powerful than a torpedo and yet they failed to inflict significant structural damage.

Prince of Wales / Repulse

PoW

-          torpedo hit on outer port propeller shaft exit causing extensive flooding and an 11 degree list to port

-          torpedo hit starboard bow

-          torpedo hit starboard alongside B turret

-          torpedo hit starboard alongside Y turret

Repulse

-          Four or more torpedo hits

Note that Repulse lacked anti-torpedo blisters and modern internal compartmentation.

Yamato

The Japanese battleship Yamato was subjected to multiple waves of attack.

First wave:

-          torpedo hit port side, forward which caused little damage

-          two torpedo hits port side near engine and boiler rooms

-          probably torpedo hit near auxiliary steering

Hits cause an initial list which was corrected with counterflooding.  Top speed was only slightly affected.

Second wave:

-          three or four torpedoes hit port side and one to starboard

This attack caused additional listing but did not put the ship at risk of sinking.

Third wave:

-          Three torpedo hits port side concentrated along the engineering spaces

-          Torpedo hit starboard

At this point, the ship began to sink.  In addition to the numerous torpedo hits, many bomb hits caused additional damage.

Musashi

Musashi was a Yamato class battleship that was sunk on 24-Oct-1944.  The ship suffered numerous bomb hits and the following torpedo hits.

-          1 torpedo starboard amidships which caused some flooding

-          3 torpedoes port side

-          4 torpedoes, three of which hit the forward bow

-          3 torpedoes starboard bow

-          11 torpedoes various locations

The ship sank intact.

Belgrano (Brooklyn class light cruiser)

The Argentinean cruiser was a 44 year old pre-WWII ship, poorly maintained, served by an ill-trained crew, and sailing with all watertight doors open when it was hit by three British 21” torpedoes.  The first exploded just forward of the armor belt and damaged the bow but did not threaten the ship’s stability.  The second hit just aft of the armor belt and opened a large hole which caused severe flooding.  Reports suggest that the third torpedo hit but it is uncertain whether it exploded.

None of the torpedoes broke the ship’s back and the first didn’t even hazard the ship.  The second caused flooding beyond the ill-trained crew’s ability to handle and led to the ship sinking.  It is likely that a well maintained ship, sailing at combat readiness (watertight doors closed), and with a trained crew would have been able to contain the damage and save the ship.

Bismarck

Prior to the action that directly resulted in the sinking of the Bismarck, the ship had suffered shellfire damage though the damage appeared to have no direct impact on the ship’s survivability.

On the evening of 24-May-1941, Bismarck suffered a single torpedo hit which caused only superficial damage to her armored belt.  Other reports suggest several torpedoes hit but did no significant damage. (1)

On the evening of 26-May a torpedo struck Bismarck’s port side and jammed her rudder.

On 27-May, British battleships and cruisers eventually wrecked Bismarck’s upper decks with the Bismarck absorbing as many as 500 shell hits. (1)  Torpedoes were launched by the British ships but the number of hits, if any, are unknown.  Two possible hits were reported. (2) 

Dorsetshire fired two 21 inch torpedoes and both hit the starboard side with no appreciable effect observed.  Another torpedo struck the port side, again with no visible effect.

Bismarck settled deeper into the sea and eventually capsized and sank.

In all, Bismarck suffered at least 5 confirmed torpedo hits and possibly 7 or more.  Other than to contribute to the cumulative flooding, the torpedoes caused no catastrophic structural damage.

HMS Belfast (light cruiser)

The cruiser Belfast struck a magnetic mine in November of 1939.  The ship suffered moderate damage and was repaired and returned to service.  Belfast was 613 ft long and around 11,000 tons displacement.

Photos of the ship in drydock suggest that the mine exploded under the hull, slightly offset to one side.  The explosion caused little direct damage to the hull, leaving a small hole, but did cause shock damage and warping of decks and structural members.  The keel was bent upwards by three inches.

The ship was, apparently, in no danger of sinking at any time.

This was a nearly classic example of the torpedo/mine exploding under directly under the hull and should have been a perfect example of the “broken back due to  suspension of the ship over a bubble” if the phenomenon were true.

Lexington (CV-2)

Two torpedoes hit the carrier on the port side but the ship was able to continue flight operations until a series of massive gasoline-sparked explosions occurred which eventually led to the ship being abandoned.  A US destroyer was ordered to sink the carrier and fired five torpedoes at which point the carrier settled into the sea on an even keel.

Princeton (CG-59)

During Desert Storm, Princeton suffered two bottom-moored influence mine explosions, one under the port rudder and the other under the starboard bow.  The explosions caused superstructure cracks and hull deformations along with various piping damage, shaft damage, and rudder damage but the ship’s weapons were back on line in 15 minutes.  The ship was able to leave the minefield under her own power.

Again, this was a near perfect example of the “explosion under the hull” and yet they did not break the ship’s back nor threaten the ship’s survival.  Further, this is a case of an explosion occurring under a modern, weakly built (as compared to a WWII ship of similar size) hull and yet still did not sink the ship.

Tripoli (LPH-10)

During Desert Storm, Tripoli suffered a mine explosion from a sub-surface moored mine which caused a 16x25 ft hole in the hull below the waterline.  The ship continued operations after damage control measures.

Again, this is a near perfect example of the underwater explosion effect and the results were negligible as regards ship survivability or even mission effectiveness.

Tripoli Mine Damage

Samuel B. Roberts (Perry class FFG)

A mine explosion blew a 15 ft hole in the ship and broke the keel triggering flooding and fires on multiple decks.  The mine is believed to have exploded in contact with the ship’s hull.  The explosion occurred on the port side at the forward end of the hangar.  Despite the near fatal damage, the ship was able to maneuver using thrusters at 5 kts and her combat systems and weapons remained operational.  The ship was saved, repaired, and returned to service.  Repairs took 6 months and cost $89M.

This explosion took place a bit to the side as opposed to directly under the ship and came as close to sinking the ship as any of the examples.  This is also the smallest ship in the examples and a modern, weakly built ship.  Despite this, the explosion did not break the ship in two.

_______

The observation that leaps out from an examination of the historical data is that no large ship has ever had its back broken by a mine or torpedo in the popular “suspended over a bubble of air” scenario.  Yes, a sufficiently large number of mines/torpedoes can cause enough cumulative damage (usually cumulative flooding) to eventually sink a large ship but none has ever been broken and sunk with a single mine/torpedo shot which is the commonly cited claim by the “torpedoes are invincible” crowd.  In fact, not only has no large ship ever been sunk by a single torpedo/mine hit but most have absorbed at least several such hits prior to sinking along with, in most cases, many aerial bombs which contributed to the sinkings.

It is also notable and, frankly, a bit surprising, that even smaller ships have been able to absorb surprising amounts of underwater explosion damage.  The 450 ft long, 4200 ton displacement Samuel B. Roberts was an example of such.

It must be noted that WWII torpedoes were not designed as under-the-keel weapons.  Most WWII torpedo hits impacted the side of the target’s hull somewhere in the lower half of the underwater hull depending on the depth setting of the torpedo and the draft of the target’s hull.  As such, these are not direct representatives of a perfectly placed under-the-keel explosion but they are informative data points, nonetheless.

There is also a school of thought that WWII weapons were not as powerful as today’s.  This is nonsense, as least as far as torpedoes and mines are concerned.  Supersonic, heavyweight anti-ship missiles are another issue but that’s a topic for another time.  Mines haven’t appreciably changed in terms of their explosive power.  Yes, fusing mechanisms have gotten more sophisticated but the raw explosive firepower has not.  The same holds true for torpedoes.  For example, the standard US torpedo of WWII was the Mk14 with a warhead weight of 643 lb.  The current standard US torpedo, the Mk48 has a 650 lb warhead.  They’re identical.

We previously disproved the commonly held belief that torpedoes kill by suspending a ship over a bubble of air and breaking its back.  The empirical evidence in this post further proves that the belief is a myth.  In fact, the empirical evidence suggests that ships can absorb far more underwater explosive effects than anticipated and that even destroyer and frigate size ships are capable of absorbing tremendous damage without structurally collapsing and sinking.

This post should not be read as a claim that torpedoes are insignificant - far from it.  They are powerful and damaging.  The smaller the ship, the more damage an underwater explosion will inflict – no great surprise – and, for smaller ships, such damage may well be fatal.  Still, all ships seem to show a surprising inherent resistance to underwater explosions. 

In part 2 of this post, we’ll examine one of the main, but generally unrecognized, factors behind this resistance to underwater explosions.

______________________________

(1)https://www.wired.com/2009/05/dayintech_0527/

(2)http://www.kbismarck.com/bismarck-last-battle.html