Download coordinates as: Operation Castle was a United States series of high-yield (high-energy) nuclear tests by Joint Task Force 7 (JTF-7) at Bikini Atoll beginning in March 1954.

Conducted as a joint venture between the Atomic Energy Commission (AEC) and the Department of Defense (DoD), the ultimate objective of the operation was to test designs for an aircraft-deliverable thermonuclear weapon.

[1] Operation Castle was considered by government officials to be a success as it proved the feasibility of deployable "dry" fuel designs for thermonuclear weapons.

Since then, American nuclear weapons testing had moved to the Enewetak Atoll to take advantage of generally larger islands and deeper water.

The extremely high yields of the Castle weapons caused concern within the AEC that potential damage to the limited infrastructure already established at Enewetak would delay other operations.

The complex dewar mechanisms needed to store the liquid deuterium at cryogenic temperatures made the device three stories tall and 82 tons in total weight, far too heavy and bulky to be a usable weapon.

A solid at room temperature, LiD, if it worked, would be far more practical than the cryogenic liquid deuterium fuel in the Ivy Mike device.

Even though they were much less practical because of the logistical problems dealing with the transport, handling, and storage of a cryogenic device, the Cold War arms race drove the demand for a viable fusion weapon.

The "Ramrod" and "Jughead" devices were liquid fuel designs greatly reduced in size and weight from their so-called "Sausage" predecessor.

The "Jughead" device was eventually weaponized, and it saw limited fielding by the U.S. Air Force until the "dry" fuel H-bombs became common.

Although the U-238 isotope of uranium will not sustain a chain reaction, it still fissions when irradiated by the intense fast neutron flux of a fusion explosion.

Yet J. Carson Mark, the head of the Los Alamos Theoretical Design Division, had speculated that Bravo could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated.

[7] As the fallout spread downwind to the east, more atolls were contaminated by radioactive calcium ash from the incinerated underwater coral banks.

Most of the Castle dry fuel devices eventually appeared in the inventory and ultimately grandfathered the majority of thermonuclear configurations.

Using natural lithium and a heavily modified Teller-Ulam configuration, the test produced only 110 kilotons of an expected 1.5 megaton yield.

While engineers at the Radiation Laboratory had hoped it would lead to a promising new field of weapons, it was eventually determined that the design allowed premature heating of the lithium fuel, thereby disrupting the delicate fusion conditions.