The ASM-A-1 Tarzon, also known as VB-13, was a

guided bomb A guided bomb (also known as a smart bomb, guided bomb unit, or GBU) is a precision-guided munition designed to achieve a smaller circular error probable (CEP). The creation of precision-guided munitions resulted in the retroactive renaming of ...

developed by the

United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

during the late 1940s. Mating the guidance system of the earlier

Razon Razon is a Spanish surname, meaning "reason". Notable people with the surname include: * Alfredo Fernando Razon Gonzalez (born 1978), Filipino footballer *Avelino Razon (born 1952), Filipino police officer and politician *Daniel Razon (born 1967), t ...

radio-controlled weapon with a British Tallboy bomb, the ASM-A-1 saw brief operational service in the

Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...

before being withdrawn from service in 1951.

Design and development

Development of the VB-13 Tarzon began in February 1945, with

Bell Aircraft The Bell Aircraft Corporation was an American aircraft manufacturer, 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 ...

being awarded a contract by the

for the development of a very large guided bomb.Parsch 2003Stumpf 1998, p.13. 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 "earthquake" bomb,Schmitt 2002, p.45. known to the USAAF as M112.Gillespie 2006, p.54. The 'Tarzon' name was a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordsNMUSAF Fact Sheet: VB-13 Tarzon Bomb and was pronounced similarly to that of "

Tarzan Tarzan (John Clayton II, Viscount Greystoke) is a fictional character, an archetypal feral child raised in the African jungle by the Mangani great apes; he later experiences civilization, only to reject it and return to the wild as a heroic adv ...

", the popular "ape-man" fictional character. The VB-13, redesignated ASM-A-1 in 1948, was developed under the project code MX-674.Dorr 2003, p.31. It had an

annular wing A closed wing is a wing that effectively has two main planes which merge at their ends so that there are no conventional wing tips. Closed wing designs include the annular wing (commonly known as the cylindrical or ring wing), the joined wing, ...

around the midsection of its body, mounted near the weapon's

center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...

. At the rear of the bomb was an octagonal tail surface containing the Razon control surfaces. Intended to be carried by the

Boeing B-29 Superfortress The Boeing B-29 Superfortress is an American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the B-17 Fl ...

bomber, the Tarzon bomb used the combination of AN/ARW-38 oint Army Navy, Piloted Aircraft, Radio, Automatic Flight or Remote Controlcommand link transmitter on the B-29 and an AN/URW-2 oint Army Navy, Utility, Radio, Automatic Flight or Remote Controlreceiver on the Tarzon to provide manual command guidance of range and

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

. This was done with visual tracking of the bomb's course, aided by a

flare A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, ...

mounted in the tail of the weapon.

Gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...

s on board the ASM-A-1 aided in stabilisation, while a

pneumatic Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...

system drove the bomb's control surfaces. The guidance system was considered effective; Tarzon proved in testing to have an

accuracy Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value'', while ''precision'' is how close the measurements are to each other ...

of . In addition to the nominal weight of the Tallboy it was based on, the annular wing and control surfaces boosted the weight of Tarzon by an additional . This made the ASM-A-1 too large and heavy to 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, and caused turbulent airflow 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 II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, it avoided being cancelled, proceeding as a low-priority project. Limited testing was conducted during 1948 and 1949; additional testing at

Alamogordo, New Mexico Alamogordo () is the seat of Otero County, New Mexico, United States. A city in the Tularosa Basin of the Chihuahuan Desert, it is bordered on the east by the Sacramento Mountains and to the west by Holloman Air Force Base. The population was ...

in 1950 led to the Tarzon being approved for operational service in the

.Schmitt 2002, p.46. 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.Gillespie 2006, p.58. Used solely by the

19th Bomb Group The 19th Operations Group (19 OG) is the operational flying component of the United States Air Force 19th Airlift Wing, stationed at Little Rock Air Force Base, Arkansas. Equipped with the Lockheed C-130 Hercules, the group provides part of Ai ...

, 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, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korea, Korean Peninsula and shares borders with China and Russia to the north, at the Yalu River, Y ...

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 Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...

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.Gillespie 2006, p.59. On March 29, 1951, however, a Tarzon strike against

Sinuiju Sinŭiju (''Sinŭiju-si'', ; known before 1925 in English as Yeng Byen City) is a city in North Korea which faces Dandong, Liaoning, China across the international border of the Yalu River. It is the capital of North P'yŏngan province. Part of ...

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 In aviation, a water landing is, in the broadest sense, an Landing, aircraft landing on a body of water. Seaplanes, such as floatplanes and flying boats, land on water as a normal operation. Ditching is a controlled emergency landing on the ...

.''Steadfast and Courageous'', pp.33–34. 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,Gillespie 2006, p.60. 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 Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...

. 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.

References

;Notes ;Citations ;Bibliography * * * * * * * * *

External links

{{Authority control Weapons and ammunition introduced in 1949 Guided bombs of the United States Bell aircraft

Design and development

Operational history

See also

References

External links