Mark 21 nuclear bomb
The Mark 21 nuclear bomb was a United States nuclear 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). At long, in diameter, and weighing , the Mk-21 was half the length and one-third the weight of the Mk-17/24 weapons it replaced. Its minimum yield was specified at four megatons.
Ebeye Island
Some of the residents of Ebeye are refugees or descendants of refugees from the effects of the 15- Castle Bravo nuclear test at Bikini Atoll on 1 March 1954. The detonation unexpectedly rained nuclear fallout and two inches (50 mm) of radioactive snow on nearby Rongelap Atoll, which had not been evacuated as had Bikini. The 1954 American authorities then evacuated Rongelap and were returned in 1957 with extensive medical surveillance. In 1985, Greenpeace evacuated the inhabitants of Rongelap to Mejato (island in Kwajalein atoll). Ebeye was the final destination for many of them.