The Mark 24 nuclear bomb was an American thermonuclear bomb design, based on the third American thermonuclear bomb test, Castle Yankee. The Mark 24 bomb was tied as the largest weight and size nuclear bomb ever deployed by the United States, with the same size and weight as the Mark 17 nuclear bomb which used a very similar design concept but unenriched lithium. The Castle Yankee thermonuclear test was the first bomb to use lithium enriched with the lithium-6 isotope, up to perhaps 40% enrichment (the earlier Castle Bravo test had used the same enriched lithium combination but was not weaponised i.e. was not built as a deployable bomb). The device tested was called the Runt II design; it was reportedly very similar to the Runt design tested in Castle Romeo, other than the enrichment level. Castle Yankee had a demonstrated yield of 13.5 megatons. The yield for the weaponized Mark 24 was predicted to be 10–15 megatons. The EC24 bomb was a limited production run of the Castle Yankee test device, with 10 produced and stockpiled through 1954. The EC24 was 61 by and weighed 39600 lb. The EC24 was a purely free-fall bomb design.

Design

The production model Mark 24 nuclear bomb was 61.4 by long, with a weight between 41000 and 42000 lb. It was in service between 1954 and 1956, with a total of 105 units produced. The Mark 24 included a 64 ft parachute to slow its descent. The bomb used manual in-flight insertion (IFI) that required a crewmember to crank a handle that was inserted into a hole in the nose of the bomb. This process inserted the weapon's pit into the implosion assembly.

Survivors

A Mark 24 casing is on display in the Castle Air Museum in Atwater, CA.