USS LSM-60
Encyclopedia
USS LSM-60 was a World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
era landing ship, medium (LSM) amphibious assault ship
Amphibious assault ship
An amphibious assault ship is a type of amphibious warfare ship employed to land and support ground forces on enemy territory by an amphibious assault...
of the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
. It was notable for being used as the float to suspend a fission bomb underwater during the Operation Crossroads
Operation Crossroads
Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. It was the first test of a nuclear weapon after the Trinity nuclear test in July 1945...
BAKER test, becoming the first naval vessel to use a nuclear weapon.
World War II Service
LSM-60s keel was laid on 7 July 1944 and she was launched on 29 July. She was commissioned on 25 August, LT. William W. Doar, USNR, commanding.LSM-60 participated in the assault landings at Iwo Jima
Battle of Iwo Jima
The Battle of Iwo Jima , or Operation Detachment, was a major battle in which the United States fought for and captured the island of Iwo Jima from the Empire of Japan. The U.S...
, where she earned one battle star.
Operation Crossroads "ground" zero
In 1946, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
conducted the first nuclear weapon tests designed to measure weapons effects, Operation Crossroads. The second shot of this test, BAKER, was designed to test the effects of an underwater nuclear blast on surface ships and submarines.
LSM-60 was modified with a well through the cargo deck and hull, a derrick to lower the bomb through the well, and a large antenna to receive the detonation signal. On 25 July, a standard Mk. 3A "Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...
" type atomic bomb, nicknamed Helen of Bikini, placed in a watertight casing, was suspended 90 feet below LSM-60 in the lagoon of Bikini Atoll
Bikini Atoll
Bikini Atoll is an atoll, listed as a World Heritage Site, in the Micronesian Islands of the Pacific Ocean, part of Republic of the Marshall Islands....
in the Marshall Islands
Marshall Islands
The Republic of the Marshall Islands , , is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator. As of July 2011 the population was 67,182...
. At 0835 local time the bomb was detonated, destroying LSM-60 and eight target ships, including . A seaman present claimed that "there was not one identifiable piece of the LSM-60 ever located", however a British naval constructor present reports he saw a 3 inches (7.6 cm) square piece of LSM-60 on the deck of a target ship afterward.