The sinking of the Austro-Hungarian battleship, SMS Szent István, on June 10th, 1918, is
the only World War I capsizing of a battleship that was ever filmed.
But what sank Szent István was not heavy fire from large caliber naval guns of another
battleship.
It was in fact small Italian motor boats that sent her to the bottom of the Adriatic Sea
… and all it took was two hits … from two lethal torpedoes.
But why a single torpedo can break a ship’s keel in half without even hitting it, and
why submarine-launched torpedoes have a wire attached to them, is Not What You Think!
For battleships, size really mattered; bigger hulls could carry bigger guns which in turn
could deliver more damage.
To protect against these powerful guns, battleships were covered with iron or steel armor plates,
resulting in Ironclads warships which were prominent in the second half of the 19th century.
It seemed like the worst enemy of a battleship … was a bigger battleship.
This progression naturally led to the development of Dreadnoughts by the Royal Navy.
This class of battleships carried an unprecedented number of heavy-caliber guns.
But!
… there were downsides to all this.
Armor plates were heavy, slowing down the battleships.
Large-caliber guns were powerful, but had slow firing rates.
This created a window of opportunity for smaller vessels, which were fast and maneuverable,
to approach battleships while avoiding hits from their guns.
But what could a little boat do to a mighty battleship covered in armor?
Well, it turns out that much attention had been given to protecting battleships above
the waterline, leaving the submerged part of the hull quite vulnerable.
With the invention of self-propelled torpedoes, small boats could finally be equipped with
a weapon that had the power to cripple, or even sink, any battleship.
This is why in the late 19th century, many navies started to build torpedo boats.
These boats could only carry 2 or 3 torpedoes, but because they were relatively inexpensive
to build, they could perform mass attacks on a fleet of larger ships.
Even sinking one capital ship was well worth losing a squadron of torpedo boats over.
But what made torpedoes so lethal wasn’t simply the lack of armor below the ships’
waterline.
It was that underwater explosions would shock the “ship” out of battleships.
When the above-the-water part of a ship receives a direct hit, the resulting explosion could
blow a hole in the ship's hull or deck.
The damage, no matter how severe, is mostly limited to the area of impact, and unlikely
to sink the ship.
But a single underwater explosion hits the ship multiple times and in multiple ways.
When a torpedo hits the side of the hull below the water line, the explosion creates a bubble
of expanding gas underwater.
The walls of this gas bubble expand faster than the speed of sound in water, thus creating
a shockwave.
This shockwave delivers the first punch which can blow a hole in the ship's hull, similar
to an above-the-water hit.
But in shallow waters, the shockwave can hit the seabed and bounce back, creating aftershocks
that will hit the hull again.
In addition, the physical movement of water that is caused by the detonation can violently
rock an already-weakened ship.
But it gets much worse!
An explosion in the air resonates the air molecules, creating changes in air pressure,
which is referred to as a blast.
An underwater detonation is no different, but because water is much more dense than
air, the resonance in water is much more intense.
This can shake the ship dangerously and can result in anything from equipment and crew
being tossed around, to engines being ripped off their beds.
A violent shake could also create hundreds of small leaks all over the ship and eventually
sink it.
This is exactly why full ship shock trials are performed on new warships.
As part of sea trials, an underwater explosive charge is detonated in proximity of the warship.
These tests will shake up the ship, and in fact can sometimes result in damages.
But that’s precisely why shock trials are done in the first place, to validate the operational
survivability of new ships after exposure to underwater shock.
But if shock trials can damage warships, what about the fish, whales and other marine life!
The Navy takes the safety and security of marine mammals seriously, so all testing is
executed in a way that avoids various migration patterns of marine life.
In addition, if marine mammals are detected in proximity, the testing has to be postponed.
But let’s be real … some fish will float to the top!
Wait a second!
The detonation and the subsequent shockwave can be observed almost instantly, but notice
a large column of water shoots high up into the sky.
That is called the Bubble Jet Effect, and even though it doesn't really impact the ships
during shock trials, the bubble jet effect is possibly the most dangerous aspect of torpedo
attacks, especially when detonated below the keel of a ship.
Remember that underwater gas bubble that is generated by the explosion?
Well, that bubble will quickly rise up to the surface and will raise anything in its
way, including the ship’s hull.
The structure of the hull is designed to resist downward pressure, not upward.
This means that the bubble’s upward pressure will cause severe strain on the hull.
Then the bubble collapses, and the hull falls down into the void in the water, creating
a sagging effect.
As if that wasn’t enough, the collapse of the bubble causes the water to shoot up, delivering
a harsh blow to an already weakened hull.
This … is how torpedoes can sink ships.
As it should be evident by now, torpedo boats were a real danger to capital ships, to the
extent that a new class of warships, called torpedo boat destroyers, were created to deal
with them.
The name was later shortened to destroyers!
Ironically, one of the first weapons that destroyers were equipped with, were torpedoes.
In a way, destroyers became the very thing that they were trying to destroy!
Zumwalt, Arleigh Burke, Spruance, Fletcher and the rest of the modern destroyer classes
are all descendents of these smaller and simpler torpedo boat destroyers.
The speed and agility of torpedo boats against battleships is what made them successful.
But in the first half of the 20th century, a new type of attack vessel was designed that
instead of speed, relied on stealth, and no, not the submarines.
It was the human torpedo.
The first practical human torpedo was designed by Italians.
It was a modification of a standard torpedo which could carry two people.
With an overall length of 22 feet and weighing over 1.5 tonnes, the Italian human torpedo
was nicknamed Maiale, meaning “pig” in Italian, because all the guys who’d ever
been inside Maiale would tell you the same thing; She was a pig to maneuver!
Maiale had a simple steering mechanism that used a propeller, hydroplanes and a vertical
rudder, had 4 speeds to go forward and reverse, giving her a range of 15 miles and a cruising
speed of 2 knots.
Maiale not only was quiet, but she could also travel submerged with the help of electric
pumps that emptied or filled up her ballast tanks.
She could approach her target at a depth of 49 feet, minimizing the chances of being spotted.
Most importantly, Maiale could deliver a punch!
Two warheads, each weighing 280 lbs could be stacked in front of the human torpedo,
and were powerful enough to sink a large merchant ship.
But these warheads had no propulsion system, which meant they had to be manually placed
under the keel of the target ship.
This was a 2-person job, which is why Maiale needed two operators, and the way those operators
worked together to place such heavy explosive charges under the ships … was genius!
The operators of the human torpedo carried high pressure air tanks, which allowed them
to breathe underwater for up to 6 hours.
As the manned torpedo closed onto the target, she would submerge, and position itself by
a bilge keel.
One operator would keep the craft there, while the second one ran a cable over and attached
it to the bilge keels on both sides of the hull, effectively creating a zipline.
Each warhead was then detached and carried over the zipline, and was placed directly
underneath the keel of the ship.
The last step was to set the time clocks on each warhead.
The second operator would get back in and the human torpedo would sneak away.
In 1941, Italian human torpedoes successfully attacked and disabled two British battleships,
the Queen Elizbeth and the Valiant, in the Harbor of Alexandria, Egypt.
The Germans developed their own version of the human torpedo, which only had one operator,
and instead of warheads, it actually carried a torpedo.
But the German version was not as successful due to the operator’s poor visibility, and
since the torpedo had to be launched from a distance, it gave away the location of the
operator.
The Japanese also had their own version of the human torpedo, called Kaiten,which only
offered one-way trips, because once the operator was in, the hatches were locked and the operator
could not get out!
As torpedoes became a popular weapon of choice against naval vessels, they were adapted for
different launch platforms, like airplanes, and yes, some issues had to be ironed out!
Torpedoes also became the primary armament for submarines, but did you know that many
modern submarine-launched torpedoes actually have a wire attached to them, which reels
out as the torpedo moves toward its target?
Of course this cable is not by any means a necessary component of the torpedo.
Because the target parameters can be programmed in advance, while the torpedo is still in
the submarine’s launch tube.
But once the torpedo leaves the sub, those parameters cannot be changed.
Wireless communications don't work underwater over long distances, and even if it did, the
signal could give away the location of the torpedo.
But with the command wire attached, there is a live data link so the operators can change
the torpedoes target, depth and other parameters.
In case the data link is lost, the torpedo would still follow its last given command
and close in on its target.
But how long is that cable?
It’s actually as long as the torpedo’s effective range, which you guessed it, is
classified!
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