They differed from Crossroads in that they were conducted by the Atomic Energy Commission, with the armed forces having only a supporting role.

A great deal of work remained to improve ease of assembly, safety, reliability and storage before they were ready for production.

Norris Bradbury, who replaced Robert Oppenheimer as director at Los Alamos, felt that "we had, to put it bluntly, lousy bombs.

In theory they could produce 0.91 grams (0.032 oz) of plutonium per megawatt-day, or about 20 kilograms (44 lb) per month.

Plutonium production fell off during 1946 due to swelling of the reactors' graphite neutron moderators.

[4] These reactors were also required for the production (by irradiation of bismuth-209) of polonium-210, which was used in the initiators, a critical component of the nuclear weapons.

[5] Uranium-235 was derived from enrichment of natural uranium at the Y-12 plant and K-25 site in Oak Ridge, Tennessee.

Improvements in the processes and procedures of the electromagnetic and gaseous isotope separation between October 1945 and June 1946 led to an increase in production to around 69 kilograms (152 lb) of uranium-235 per month, which was only enough for one of the very wasteful Little Boys.

In order for this to work outside the laboratory, the wires had to be strong enough to withstand being dropped from an aircraft, but thin enough to not disturb the spherical symmetry of the implosion.

On the other hand, the slower reaction of uranium-235 permits the assembly of super-critical masses, making it theoretically possible to produce weapons with high yields.

The Atomic Energy Commission's Director of Military Applications, Brigadier General James McCormack and his deputy, Captain James S. Russell, met with Bradbury and John Henry Manley at Los Alamos on July 9 to make arrangements for the tests.

The cost of the tests, around $20 million, was divided between the Department of Defense and the Atomic Energy Commission.

Edgerton, Germeshausen, and Grier were contractors hired to design and install the timing and firing systems.

[21] Seven experimental weapon assemblies and six cores were delivered to San Pedro, California, and loaded on the weapon assembly ship USS Curtiss, in February 1948, but the Atomic Energy Commission only gave permission for the expenditure of three cores in the tests.

Source: Berkhouse et al, Operation Sandstone, p. 40 In September 1947, Hull, Russell, who was designated test director on October 14, and Joint Task Force 7's scientific director, Darol K. Froman from the Los Alamos Laboratories, set out with a group of scientists and military officers to examine various proposed test sites in the Pacific.

It also had ocean currents and trade winds that would carry fallout out to sea, an important consideration in view of what had happened at Bikini Atoll during Operation Crossroads.

[24] An LST and four Douglas C-54 Skymaster aircraft were placed on standby to evacuate Ujelan in case it was affected by fallout, but were not required.

Hull opposed making any announcement until after the series was completed, but the AEC commissioners felt that the news would leak out, and the United States would look secretive.

On 18 May, after the series was over, Hull held a press conference in Hawaii, but only permitted the media to quote from written statements.

The detonations were ordered so that later test areas would suffer minimal fallout from the earlier shots.

The gamma ray measurement experiments required darkness, but the Boeing B-17 Flying Fortress drones that would sample the clouds needed daylight to control them.

[30] The detonations in the United States' Sandstone series are listed below: The X-Ray nuclear device used a levitated composite core.

[38] The observers saw a similar flash and felt the same heat as the X-Ray blast, but the 6-nautical-mile (11 km; 6.9 mi) wide condensation cloud was larger, and the sound of the explosion more forceful.

[38] They were correct: its yield of 49 kilotons made it the largest nuclear detonation up to that time,[36] but it was considered inefficient and wasteful of the fissile material.

The Los Alamos personnel assigned to remove the filters from the B-17 drones had apparently carried out the procedure on X-Ray and Yoke without problems, but this time three of them suffered radiation burns on their hands serious enough to be hospitalized and need skin grafting.

[45] The Chief of the Armed Forces Special Weapons Project, Major General Kenneth D. Nichols, saw clearly that the era of scarcity was over.