Bliss-Leavitt Mark 8 torpedo

Bliss-Leavitt Mark 8 torpedo
Bliss-Leavitt Mark 8 Torpedo sitting on the deck of PT 21
Type	Anti-surface ship torpedo
Place of origin	United States
Service history
In service	1911–1945
Used by	United States Navy Royal Navy
Wars	World War II
Production history
Designer	Frank McDowell Leavitt
Designed	1911
Manufacturer	Naval Torpedo Station Naval Gun Factory
Variants	Mod 1 Mod 2 Mod 2A Mod 2B Mod 3 Mod 3A Mod 3B Mod 3C Mod 3D Mod 5 Mod 6 Mod 8
Specifications
Mass	2,600 pounds
Length	256.3 inches
Diameter	21 inches
Effective firing range	16,000 yards
Warhead	TNT, Mk 8 Mod 4
Warhead weight	466 pounds
Detonation mechanism	Mk 3 Mod 2, contact
Engine	Turbine
Propellant	Air (2800 psi, 23.4 cuft) Water (90 pints) Alcohol (49 pints)
Maximum speed	36 knots
Guidance system	gyroscope
Launch platform	Destroyers and PT boats

The Bliss-Leavitt Mark 8 torpedo was the United States Navy's first 21-inch by 21-foot torpedo and was widely used in its torpedo boat force at the beginning of World War II. The torpedo was originally designed in 1911 by Frank McDowell Leavitt of the E. W. Bliss Company and entered full mass production in 1913 at the Naval Torpedo Station in Newport, Rhode Island. Under the Lend-Lease Act, about 600 Mark 8 torpedoes were issued to the United Kingdom for use with 50 destroyers it received under the same program.

Design

The design was originally intended to be used on destroyers in an anti-surface ship role. When it was first released, it was a highly advanced torpedo, but when it was actually deployed into service during World War II it was showing its age and unable to compete with the modern torpedo technology. The low speed of the torpedo was one of the complaints; its Japanese counterpart, the Type 93 torpedo, was significantly faster and more difficult to spot in the water.

Deployment difficulties

The Mark 8 had many technical difficulties with its design that would be a bane to the torpedo men who would use them. The first issue came with the process of simply launching the torpedo, which was fraught with its own set of difficulties. The gyro in the torpedo was sensitive when it was first launched and it would need to be launched from an even keel, otherwise the torpedo would lose stability when it hit the water. The other issue concerned the launching mechanism. The initial system was set with a black powder charge to push the torpedo out of the tube. The problem with this in the humid climate of the South Pacific would cause these charges to misfire, sometimes not putting enough force behind the torpedo to fully eject it from the tube. One other risk of these misfires was what is called "hot running", where the torpedo would run in its tube. Though the warhead could not detonate, the motor would overheat and explode without water to cool it, sending shrapnel across the deck. Another issue was that the tubes were heavily lubricated with oil and grease to insure that the torpedo was launched from the tube correctly. The problem became that sometimes during the launching, the charge would ignite the grease and oil in the tube causing a fire that would emit a dark black smoke that would immediately give up the location of the torpedo boat, reveal the point where the torpedo was coming from and allow the enemy to take action to avoid it.

The torpedo also lacked the explosive power of newer models. It carried less than 500 pounds of TNT-based explosive which was far from a guaranteed ship kill on strike. This would frustrate many captains who, when lucky enough to hit an enemy dead on, would have the warhead go off but not do enough damage to sink the target, and allowed many of them to limp back home.

Further reading

• PT Boat Armament PT103.com
• History of Mark VIII PT-king.gdinc.com
• The User manual for the Torpedo Historic Naval Ships Association
• Indexed data Naval History
• Excerpt from MOTOR TORPEDO BOATS TACTICAL ORDERS AND DOCTRINE, July 1942