4.3 OPERATION SANDSTONE. Conducted at the Enewetak Atoll in 1948, Operation SANDSTONE consisted of three tower shots, all detonated at a height of 200 feet (5: 1): Event Date X-RAY 15 April Tower 37 YOKE 1 May Tower 49 15 May Tower 18 ZEBRA 4.3.1 Type Yield (kilotons) Background and Objectives of Operation SANDSTONE. Operation SANDSTONE was the second test series carried out in the Marshall Islands. It differed from the first, CROSSROADS, in that it was primarily a scientific series conducted by the Atomic Energy Commission. The AEC was activated on 1 January 1947 to assume the responsibilities formerly held by the Manhattan Engineer District, dissolved at the end of 1946. The Armed Forces had a supporting role in SANDSTONZ, whereas they had assumed a lead role in CROSSROADS (5: 1). SANDSTONE was a proof-test of second-generation nuclear devices. The two weapons detonated at CROSSROADS were the same type of weapon dropped on Nagasaki. On 3 April 1947, the General Advisory Committee to the AEC recommended development and testing of new weapons. When the President approved the preliminary SANDSTONE test program on 27 June 1947, the U.S. apparently had only 13 nuclear weapons in its stockpile. One year later, despite heavy emphasis on increased production of fissionable material, the number of weapons was only about 50, far short of the number that military planners calculated would be required in a war with the Soviet Union. The great expansion in the U.S. stockpile evident by the end of 1949 was the direct result of the higher production rates of fissionable material and the more efficient weapons designs proof-tested at SANDSTONE (5: 17,18). 78