USS LSM-60 was a World War II era landing ship, medium (LSM) amphibious assault ship of the United States Navy. It was notable for being used as the float to suspend a fission bomb underwater during the Operation Crossroads BAKER test, becoming the first naval vessel to deploy a nuclear weapon.[1]

LSM-60 with modifications for the Baker Test, Bikini Atoll
United States
Name: USS LSM-60
Builder: Brown Shipbuilding, Houston, Texas
Laid down: 7 July 1944
Launched: 29 July 1944
Commissioned: 25 August 1944
Honors and
1 battle star (World War II)
Fate: Destroyed during "Operation Crossroads" Test Baker, 25 July 1946
General characteristics
Class and type: LSM-1 class Landing Ship Medium
  • 520 long tons (528 t) light
  • 743 long tons (755 t) landing
  • 1,095 long tons (1,113 t) full load
Length: 203 ft 6 in (62.03 m) o/a
Beam: 34 ft 6 in (10.52 m)
  • 3 ft 6 in (1.07 m) forward
  • 7 ft 8 in (2.34 m) aft
  • Fully loaded :
  • 6 ft 4 in (1.93 m) forward
  • 8 ft 3 in (2.51 m) aft
Propulsion: 2 × Fairbanks-Morse (model 38D81/8X10, reversible with hydraulic clutch) diesels. Direct drive with 1,440 bhp (1,074 kW) each @ 720 rpm, twin screws
Speed: 13.2 knots (15.2 mph; 24.4 km/h)
Range: 4,900 nmi (9,100 km) at 12 kn (22 km/h)
Capacity: 5 medium or 3 heavy tanks, or 6 LVT's, or 9 DUKW's
Troops: 2 officers, 46 enlisted
Complement: 5 officers, 54 enlisted
Armament: 6 × 20 mm AA gun mounts
Armour: 10-lb. STS splinter shield to gun mounts, pilot house and conning station

World War II Service

LSM-60's keel was laid on 7 July 1944 and she was launched on 29 July.[2] She was commissioned on 25 August, LT. William W. Doar, USNR, commanding.[3]

LSM-60 participated in the assault landings at Iwo Jima, where she earned one battle star.[3]

Operation Crossroads "ground" zero

In 1946, the United States conducted the first nuclear weapon tests designed to measure nuclear explosion effects on ships, 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" 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 in the Marshall Islands.[4] At 0835 local time the bomb was detonated, destroying LSM-60 and eight target ships, including USS Saratoga (CV-3).[5] A seaman present claimed that "there was not one identifiable piece of the LSM-60 ever located",[4] however a British naval constructor present reports he saw a 3-inch (7.6 cm) square piece of LSM-60 on the deck of a target ship afterward.[6]


  1. The ill-fated USS Indianapolis (CA-35) was the first to carry a nuclear weapon.
  2. "LSM-60". Retrieved 26 December 2006.
  3. "NavSource Online: Amphibious Photo Archive LSM-60". Retrieved 26 December 2006.
  4. "Operation Crossroads". Retrieved 26 December 2006.
  5. "Operation Crossroads 1946". Retrieved 26 December 2006.
  6. Daniel, R. J. (2003). The End of an Era. Periscope Publishing Ltd. p. 83. ISBN 978-1-904381-18-1. Retrieved 2 December 2009.
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