ASM-A-1 Tarzon
Encyclopedia
The ASM-A-1 Tarzon, also known as VB-13, was a guided bomb
developed by the United States Army Air Forces
during the late 1940s. Mating the guidance system of the earlier Razon radio-controlled weapon with a British Tallboy 12000 pounds (5,443.1 kg) bomb, the ASM-A-1 saw brief operational service in the Korean War
before, as a result of safety and cost issues, being withdrawn from service in 1951.
being awarded a contract by the United States Army Air Forces
for the development of a very large guided bomb. The VB-13 was a combination of a radio-command guidance system as used on the smaller VB-3 Razon ('Range And azimuth only') guided bomb with the British-developed Tallboy 12000 pounds (5,443.1 kg) "earthquake" bomb, known to the USAAF as M112. The 'Tarzon' name was a portmanteau, combining Tallboy, range and azimuth only, describing the weapon and guidance system.
The VB-13, redesignated ASM-A-1 in 1948, was developed under the project code MX-674. It had an annular wing around the mid-section of its body, mounted near the weapon's center of gravity
. At the rear of the bomb was an octagonal tail surface containing the Razon control surfaces. Intended to be carryed by the Boeing B-29 Superfortress medium bomber, the Tarzon bomb used a combination of AN/ARW-38 and AN/URW-2 radio control devices to provide manual command guidance
of range and azimuth, based on visual tracking of the bomb's course, aided by use of a flare
mounted in the tail of the weapon. Gyroscope
s on board the ASM-A-1 aided in stabilisation, while a pneumatic system drove the bomb's control surfaces. The guidance system was considered effective; Tarzon proved in testing to have an accuracy
of 280 feet (85.3 m).
In addition to the 12000 pounds (5,443.1 kg) nominal weight of the Tallboy it was based on, the annular wing and control sufaces boosted the weight of Tarzon by an additional 1100 pounds (499 kg). As a result, the size and weight of the ASM-A-1 were such that the weapon would not fit inside the bomb bay of a Superfortress; instead, the weapon was carried in a semi-recessed mounting, half the weapon being exposed to the airstream. This increased drag on the carrying aircraft, in addition to causing turbulent airflow
that could affect the handling of the B-29.
, it avoided being cancelled, proceeding as a low-priority project. Limited testing was conducted during 1948 and 1949; additional testing at Alamagordo, New Mexico in 1950 led to the Tarzon being approved for operational service in the Korean War
.
Tarzon saw its first combat use in December 1950, the ASM-A-1 replacing the Razon in operational service; the smaller weapon had been determined to be too small for effective use against bridges and other hardened targets. Used solely by the 19th Bomb Group, which had previously conducted the Razon's combat missions, the first Tarzon drop in combat took place on December 14, 1950.
The largest bomb used in combat during the war, Tarzon was used in strikes against North Korea
n bridges and other hardened targets, the Tarzon's improved accuracy over conventional 'dumb bombs' led to the confirmed destruction of at least six high-priority targets during approximately six months of combat use; these included a hydroelectric plant, proving the effectiveness of guided weapons against conventional targets as well as bridges.
Thirty Tarzon missions were flown between December 1950 and March 1951; the weapon's success led to a contract for the production of 1,000 additional ASM-A-1 missiles. On March 29, 1951, however, a Tarzon strike against Sinuiju
went awry; the group commander's aircraft was destroyed as a result of the premature detonation of the bomb when, the aircraft suffering mechanical difficulties, the weapon was jettisoned in preparation for ditching. The thirtieth, and as it proved final, mission, three weeks following the Sinuiju mission, also suffered an unintentional detonation of a jettisoned, "safed" bomb, although this time without the loss of the aircraft.
An investigation proved that the fault lay in the construction of the bomb's tail; breaking up on impact, a 'safed' bomb would have its arming wire removed, rendering it 'unsafe' and detonating the weapon. Modifications were made to solve the problem, but the damage had been done; the safety issues, increased maintenance costs compared to conventional bombs, the fact that the bomb's guidance system required clear-day use only, rendering the bombers vulnerable to enemy fighters, and required that the weapon be released at a prime altitude for the aircraft to be in danger from enemy flak. These combined with the weapon's poor reliability – only six of twenty-eight bombs dropped successfully destroyed their targets – to result in the production order being canceled by the USAF; following this, the Tarzon program as a whole was terminated in August 1951.
Guided bomb
A guided bomb is a precision-guided munition intended to precisely hit a specific target, and to minimize damage to things other than the target....
developed by the United States Army Air Forces
United States Army Air Forces
The United States Army Air Forces was the military aviation arm of the United States of America during and immediately after World War II, and the direct predecessor of the United States Air Force....
during the late 1940s. Mating the guidance system of the earlier Razon radio-controlled weapon with a British Tallboy 12000 pounds (5,443.1 kg) bomb, the ASM-A-1 saw brief operational service in the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
before, as a result of safety and cost issues, being withdrawn from service in 1951.
Design and development
Development of the VB-13 Tarzon began in February 1945, with Bell AircraftBell Aircraft
The Bell Aircraft Corporation was an aircraft manufacturer of the United States, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many important civilian and military helicopters...
being awarded a contract by the United States Army Air Forces
United States Army Air Forces
The United States Army Air Forces was the military aviation arm of the United States of America during and immediately after World War II, and the direct predecessor of the United States Air Force....
for the development of a very large guided bomb. The VB-13 was a combination of a radio-command guidance system as used on the smaller VB-3 Razon ('Range And azimuth only') guided bomb with the British-developed Tallboy 12000 pounds (5,443.1 kg) "earthquake" bomb, known to the USAAF as M112. The 'Tarzon' name was a portmanteau, combining Tallboy, range and azimuth only, describing the weapon and guidance system.
The VB-13, redesignated ASM-A-1 in 1948, was developed under the project code MX-674. It had an annular wing around the mid-section of its body, mounted near the weapon's center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
. At the rear of the bomb was an octagonal tail surface containing the Razon control surfaces. Intended to be carryed by the Boeing B-29 Superfortress medium bomber, the Tarzon bomb used a combination of AN/ARW-38 and AN/URW-2 radio control devices to provide manual command guidance
MCLOS
MCLOS is a first-generation method for guiding guided missiles.With an MCLOS missile, the operator must track the missile and the target simultaneously and guide the missile to the target. Typically the missile is steered with a joystick, and its path is observed through a periscope-type...
of range and azimuth, based on visual tracking of the bomb's course, aided by use of a flare
Flare
-In culture and the arts:*Flare , an acrobatic move employed in b-boying, commonly known as breakdance, and gymnastics*Flare , a female hero who is a member of the League of Champions...
mounted in the tail of the weapon. Gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
s on board the ASM-A-1 aided in stabilisation, while a pneumatic system drove the bomb's control surfaces. The guidance system was considered effective; Tarzon proved in testing to have an accuracy
Circular error probable
In the military science of ballistics, circular error probable is an intuitive measure of a weapon system's precision...
of 280 feet (85.3 m).
In addition to the 12000 pounds (5,443.1 kg) nominal weight of the Tallboy it was based on, the annular wing and control sufaces boosted the weight of Tarzon by an additional 1100 pounds (499 kg). As a result, the size and weight of the ASM-A-1 were such that the weapon would not fit inside the bomb bay of a Superfortress; instead, the weapon was carried in a semi-recessed mounting, half the weapon being exposed to the airstream. This increased drag on the carrying aircraft, in addition to causing turbulent airflow
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
that could affect the handling of the B-29.
Operational history
Although the VB-13 project had not reached the testing stage by the end of World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, it avoided being cancelled, proceeding as a low-priority project. Limited testing was conducted during 1948 and 1949; additional testing at Alamagordo, New Mexico in 1950 led to the Tarzon being approved for operational service in the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
.
Tarzon saw its first combat use in December 1950, the ASM-A-1 replacing the Razon in operational service; the smaller weapon had been determined to be too small for effective use against bridges and other hardened targets. Used solely by the 19th Bomb Group, which had previously conducted the Razon's combat missions, the first Tarzon drop in combat took place on December 14, 1950.
The largest bomb used in combat during the war, Tarzon was used in strikes against North Korea
North Korea
The Democratic People’s Republic of Korea , , is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea...
n bridges and other hardened targets, the Tarzon's improved accuracy over conventional 'dumb bombs' led to the confirmed destruction of at least six high-priority targets during approximately six months of combat use; these included a hydroelectric plant, proving the effectiveness of guided weapons against conventional targets as well as bridges.
Thirty Tarzon missions were flown between December 1950 and March 1951; the weapon's success led to a contract for the production of 1,000 additional ASM-A-1 missiles. On March 29, 1951, however, a Tarzon strike against Sinuiju
Sinuiju
Sinŭiju is a city in North Korea, neighboring with Dandong City, China via international border and is the capital of North P'yŏngan Province...
went awry; the group commander's aircraft was destroyed as a result of the premature detonation of the bomb when, the aircraft suffering mechanical difficulties, the weapon was jettisoned in preparation for ditching. The thirtieth, and as it proved final, mission, three weeks following the Sinuiju mission, also suffered an unintentional detonation of a jettisoned, "safed" bomb, although this time without the loss of the aircraft.
An investigation proved that the fault lay in the construction of the bomb's tail; breaking up on impact, a 'safed' bomb would have its arming wire removed, rendering it 'unsafe' and detonating the weapon. Modifications were made to solve the problem, but the damage had been done; the safety issues, increased maintenance costs compared to conventional bombs, the fact that the bomb's guidance system required clear-day use only, rendering the bombers vulnerable to enemy fighters, and required that the weapon be released at a prime altitude for the aircraft to be in danger from enemy flak. These combined with the weapon's poor reliability – only six of twenty-eight bombs dropped successfully destroyed their targets – to result in the production order being canceled by the USAF; following this, the Tarzon program as a whole was terminated in August 1951.
See also
- AzonAzonAZON was one of the world's first smart bombs, deployed by the Allies and contemporary with the German Fritz X.Officially designated VB-1 , it was invented by Major Henry J. Rand and Thomas J...
- Bat (guided bomb)Bat (guided bomb)-External links:*...
- Fritz XFritz XFritz X was the most common name for a German guided anti-ship glide bomb used during World War II. Fritz X was a nickname used both by Allied and Luftwaffe personnel. Alternate names include Ruhrstahl SD 1400 X, Kramer X-1, PC 1400X or FX 1400...
- Grand Slam (bomb)