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.
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