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The Mark 21 nuclear bomb was a United States thermonuclear gravity bomb first produced in 1955. It was based on the TX 21 "Shrimp" prototype that had been detonated during the Castle Bravo test in March 1954. While most of the Operation Castle tests were intended to evaluate weapons intended for immediate stockpile, or which were already available for use as part of the Emergency Capability Program, Castle Bravo was intended to test a design which would drastically reduce the size and costs of the first generation of air-droppable atomic weapons (the Mk 14, Mk 17 & Mk 24).

Mark 21
Type	Thermonuclear weapon
Service history
Used by	United States
Production history
Produced	December 1955 to July 1956
No. built	275 weapons produced in Y1 variant.
Variants	2
Specifications
Mass	17,600 pounds (8,000 kg)
Length	12 feet 4.37 inches (3.7686 m)
Diameter	58.48 inches (148.5 cm)
Blast yield	18 megatons (USAF claim, although never tested[1]).

Design

At 12 feet 4.37 inches (3.77 m) long, 58.48 inches (1.49 m) in diameter, a 80.9 inches (2.05 m) span over the fins, and weighing 17,600 pounds (8,000 kg), the Mk 21 was half the length and less than half the weight of the Mk 17/24 weapons it replaced. The Mk 21 Y1 had a yield of 18 to 19 megatons. The "clean" Mk 21 Y2 (later designated Mk 26) was tested at 4.5 megatons. All 275 Mk 21 weapons stockpiled were the Y1 version.[2][3]

Quantity production of the Mk 21 started in December 1955 and ran until July 1956. Starting in June 1957 all Mk 21 bombs were converted to the more advanced Mk 36, which was removed from service in 1962.[4]

Delivery system

The Mark 21 could only be delivered by bomber; it was carried by the B-36 and B-47. Weapon was carried in a sling apparatus. Aircraft speed at release was limited to 400 knots (740 km/h), so as to not exceed an opening shock of 6,000 gees on the parachute harness. The bomb was equipped with a two-stage deployment system, including a 24 feet (7.3 m) main ribbon canopy which provided up to 108 seconds of retardation.

To carry the Mk 21, the B-47 required the installation of special fin recesses in the bomb bay doors.

Tests

The Mk 21 (Mk 21 Y1, the version in the stockpile) was never tested. The Mk 21C (Mk 21 Y2) was proof tested as the Operation Redwing Navajo shot, with a yield of 4.5 megatons.

Specifications

• Length: 12.3 feet (3.7 m)
• Diameter: 4.8 feet (1.5 m)
• Weight: 17,600 pounds (7,983 kg)
• Fuzing: airburst—Contact burst was also available.
• Yield: 18 to 19 megatons
• Thermonuclear weapon

Users

• United States Air Force

See also

• List of nuclear weapons

References

• Hansen, Chuck. U.S. Nuclear Weapons," Arlington, Texas, Areofax, Inc., 1988. ISBN 0-517-56740-7.
• O'Keefe, Bernard J. "Nuclear Hostages," Boston, Houghton Mifflin Company, 1983, ISBN 0-395-34072-1.
• Goetz, Peter. "A Technical History of America's Nuclear Arms Volume 1," 2020, ISBN 9781719831963

На других языках

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- [en] Mark 21 nuclear bomb

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[it] Bomba termonucleare Mark 21

La bomba termonucleare Mark 21 era una bomba nucleare prodotta dagli Stati Uniti per la prima volta nel 1955. Si basava sul prototipo TX-21 "Shrimp" che era stato detonato durante il test Castle Bravo nel marzo del 1954. Mentre la maggior parte dei test dell'Operazione Castle aveva come scopo quello di valutare armi intese per l'immediata costruzione e immagazzinamento, oppure che erano già disponibili per l'utilizzo come parte dell'"Emergency Capability Program", Castle Bravo era un progetto di bombe avio-lanciabili a gravità, che avrebbe provato un disegno che avrebbe ridotto drasticamente le dimensioni e i costi della prima generazione di armi nucleari sganciabili dall'aria (le varie Mk 14, Mk 17 e Mk 24). Lunga 3,81 m, con 142 cm di diametro e un peso di 6800 kg – meno della metà delle armi Mk-17/24 – la Mk-21 era significativamente più piccola rispetto ai suoi predecessori. La sua potenza esplosiva minima era specificata a 4 megatoni.

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