Over the last couple of weeks, we have done blog stories covering specific times in Naval history dealing with the torpedo. However, when discussed individually, you may not get the whole picture of the evolution of the torpedo and how it went from floating sea mine to today’s strategic weapon. With that in mind, we thought we’d share a brief evolutionary tale of the torpedo. Today’s definition of a torpedo is “a long metal cylinder with an explosive warhead, propelled through the water by an internal combustion engine or batteries. Modern torpedoes are wire-guided: a think wire spooling from the torpedo links it to the submarine’s fire control computer, from which guidance commands in the form of digital electronic signals flow.”[1] How did we get to such a sophisticated piece of machinery?

There is often confusion when looking at the evolutionary tale of torpedoes. This is mainly because, in the 17th and 18th centuries, sea mines were typically called “torpedoes.” However, the two are very different. The torpedo is a descendant of the floating mine. Therefore, when studying the torpedo, one must begin with the floating mine. The earliest reference to floating mines dates back to 1585. The Dutch would pack an entire ship with explosives, keeping them alongside potential victims.  By the Revolutionary War, this method was replaced with floating barrels of gunpowder. When David Bushnell decided to pack kegs with gunpowder, the idea of using floating mines in warfare became a tangible possibility. The problem with these devices was that they were uncontrollable. They could not be anchored and would drift with the current. Despite their problems, these sea mines ushered in a completely new idea of how to attack an enemy ship. Bushnell referred to these mines as “torpedoes.”

Figure 1 An electric ray or torpedo fish

The term torpedo comes from a fish with the same name, which emits an electric discharge that can incapacitate its enemies. Torpedo fish are part of the electric ray family. They can produce electric discharges from 8 to 220 volts. The name comes from the Latin torpere, which means to be stiffened or paralyzed. As Robert Fulton built on Bushnell’s idea, he also used the term “torpedo” for his mines. Fulton, however, did not believe this weapon should be used during wartime, but beforehand as a preventive measure. By rendering an enemy’s fleet as obsolete, maritime battles would disappear. Fulton’s mines could be anchored, solving the problems of mines drifting away from their target. This style of warfare continued throughout the Civil War. Confederate states used mines to counter Union ships, which outnumbered southern vessels. Samuel Colt would perfect the use of an electric current to detonate a mine in 1844. He also created a moored minefield that could be detonated on command through an operator standing on the shore.

It was not until 1866 that Robert Whitehead developed the precursor to the modern torpedo. This self-propelling torpedo is the design that all torpedoes have been based on ever since. The US Navy originally decided not to invest in the Whitehead torpedo. They instead initially developed their own design based on the Whitehead model, in 1869. However, their efforts never left the testing stage and the program was terminated in 1874, at which time the US Navy purchased their first Whitehead torpedo. The first models of the Whitehead torpedo were cold running and operated on compressed air. Later models would improve speed and distance with the addition of heat. The device used a combustion pot to heat the compressed air allowing the torpedo to go faster. The speed and distance could be varied by changing the amount of heat used. With the modification of a gyroscope, directionality could be improved as well. From 1866 to 1922, torpedo development remained relatively unchanged. Modifications to the war nose or detonators were made between 1910 and 1915. These changes allowed the torpedoes to go from direct impact to a “model that would detonate from any direction or glancing blow to the hull using whiskers; four levers which actually extended from the warhead. Upon any slight jolt of a glancing blow, the whiskers would release the shear pin and allow the firing pin to impact the percussion cap, detonating the warhead.”[2] In 1920, the first air-dropped torpedo was tested.

Figure 2http://pwencycl.kgbudge.com/U/s/US_Mark_14_torpedo.htm mk14 torpedo

In pre-WWII, the MK 14 was developed and later became the standard submarine anti-ship torpedo in WWII. This torpedo is responsible for sinking tons of Japanese vessels and giving them devastating blows. By 1942, the development of the electric torpedo was complete and the MK 18 joined the submarine service. This type of torpedo had a battery compartment instead of the typical air flask. The engine was replaced by an electric motor. The first electric torpedoes were more efficient than their predecessors. However, due to their usage of a lead acid battery, they required maintenance often. This was a problem for the submarine force since hydrogen would be expelled during the maintenance process. This was a safety concern on these diesel fleets. This would mean that purchasing of the torpedo room had to be done on a regular basis. Electric options had its advantages despite these maintenance issues. They could not be detected through the water, leaving no answer as to the location it came from or even that it was coming at all.

After WWII and the beginning of the 1950’s, torpedo development switched its focus onto anti-submarine warfare. At the end of the war, the US had seven torpedoes in service and had 24 more in development. Advancements in sonar technology allowed submarines to be detected from a further distance away. The need arose for strong torpedoes that were more efficient. Testing began on homing torpedoes that would attack based on sound. This proved difficult since newer submarines and propellers were becoming quieter. The MK 27 was the first torpedo to leave its tube under its own power and not by compressed air. As nuclear-powered submarines entered Navy fleets, the need for a faster, more capable submarine arose yet again. The MK 45 was delivered in 1963. It had speeds of 40 knots and a range of 11,000 to 15,000 years. It featured a sea-water activated battery and a detonation command via wire guidance.  In 1976, the MK 45 was replaced with the non-nuclear MK 48. The MK 48 is the primary active service torpedo in today’s submarine fleet.  The latest generation is the MK 48 ADCAP which was produced in 1989. This model can operate with or without wire guidance.  These models can act on their own active or passive sensors to reach their desired target and can even readjust if a target is missed. The MK 48 is 19 feet and 21 inches long and weighs 3,450 pounds. It has a range of 20 miles at a speed of 55 knots, which is four times the range and speed of its predecessor, the MK 37.

Figure 3 Mk-48 ADCAP torpedo was loaded into USS Oklahoma City – Polaris Point, Guam – November 2012 http://www.seaforces.org/wpnsys/SUBMARINE/Mk-48-torpedo.htm

Torpedoes have come a long way from the days of Bushnell and Fulton. The sea mines of the 1700’s have developed their own path and are still used today in Naval warfare. However, their predecessors that were once called “torpedoes” gave way to the improved innovation and conception of today’s modern-day torpedo defense system.

[1] http://americanhistory.si.edu/subs/weapons/armament/torpedoes/index.html

[2] https://www.history.navy.mil/museums/keyport/History_of_the_Torpedo_and_the_Relevance_to_Todays_Navy.pdf