Mark 21 nuclear bomb

The Mark 21 nuclear bomb was a nuclear gravity bomb first produced in 1955, based on the results of Operation Castle. While most of the shots of the Castle series were intended to test weapons intended for immediate stockpile, or which were already available for use as part of the Emergency Capability program, the first shot, Bravo was to test a design which would drastically reduce the size and costs of weapons of the first generation (Mk 14, Mk 17 & Mk 24). This device was known as "Shrimp" and the Castle Bravo shot produced a yield much beyond expectations. When the military characteristics of the new bomb, the TX-21 were specified, they included a required minimum yield. Quantity production of the Mk-21 started in December 1955 and ran until July 1956. The Mk-21C was proof tested as the Redwing Navajo shot with a yield of 4.5 megatons. At 12 feet, six inches long, and only 56 inches in diameter and weighing less than half what the Mk-17/24 weapons did the Mk-21 was a significant improvement over its predecessors. Starting in June of 1957 all Mk-21 bombs were converted to Mk.-39Y1 bombs.

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.