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Operation Sailor Hat

In the 1960s the  Navy found that testing was needed to determine the survivability of ships to large explosions.  A series of tests were conducted at off San Clemente Island in 1964 and then Kaho’olawe Island, Hawaii, in 1965. The centerpiece of the tests was the former light cruiser USS Atlanta IX-304 which was the main test ship.  For each test she would be moved closer to the explosion, a 500 ton explosive stacked in a dome at the shoreline.  USS Atlanta was configured with various superstructures and equipment types to test each. The crew were also left on board to experience the shock. Other ships were present at the tests, including for one of the tests, USS England DLG-22. 

Operation Sailor Hat involved using conventional explosives to simulate nuclear blasts. Delta, the last Sailor Hat test in the ship evaluation program, was conducted to study seismological data, underwater acoustics, radio communications, cratering, air blast effects, cloud growth, fire ball generation, and electromagnetic data. The cost of each 500 ton charge was about $1,000,000.

USS Atlanta was decommissioned on 1 July 1949 and placed in the Pacific Reserve Fleet. Her name was struck from the Navy list on 1 October 1962, and she was earmarked for disposal. However, she underwent an extensive modification at the San Francisco Naval Shipyard. Reinstated on the Navy list as IX-304 on 15 May 1964, the vessel was converted to a target ship for studies of the effects of high energy air explosions on naval ships. The changes included cutting her hull down to the main deck level and erecting various experimental superstructures designed for guided missile frigates and guided missile destroyers on her deck. In these configurations, she was subjected to explosions to determine whether or not the experimental structures could satisfactorily combine essential lightness with equally essential strength and blast resistance. She participated in all three three Operation Sailor Hat tests and others off San Clemente Island. During the tests, Atlanta was damaged, but not sunk. After Sailor Hat she was laid up at Stockton, Calif. later in 1965. Her name was again struck from the Navy list on 1 April 1970, and the former light cruiser was sunk during an explosive test off San Clemente Island, Calif. on 1 October 1970.

USS Atlanta IX304.  Note the numerous radars and similarities of one of the
 structures and its superstructure to DLG-22 and that there is what looks to be a 
bridge aft! All of this was placed on board her to determine how well these 
structures would hold up to the blasts. 

Note the conical stacking of the material and USS Atlanta off the coast.

William Wood, who served on both USS Atlanta and USS England, on 
Kaho’olawe Island as part of the team stacking the explosives 
- Photo courtesy of William Wood GMMC U.S.N. (retired).

"Sailor Hat" Shot "Bravo"'s 500 tons of high explosive are detonated 
on Kahoolawe Island, Hawaii, 6 February 1965, with the test 
ship Atlanta (IX-304) moored nearby. Note smoke or dust around the 
ship's foremast, and the shock wave perimeter expanding 
on the water beyond the ship.

The first test, called Bravo, occurred on February 6, 1965 with USS Atlanta, the guided-missile destroyer Cochrane DDG-21 and the Canadian Navy's escort destroyer HMCS Fraser in the test range.  USS Atlanta returned to Peal Harbor for repairs and modification. The crater resulting from the first detonation was subsequently backfilled and is no longer visible.

Detonation of the 500-ton TNT explosive charge for Shot "Bravo", first of a series of 
three test explosions on the southwestern tip of Kahoolawe Island, Hawaii, 6 February 
1965. Weapons effects test ship Atlanta (IX-304) is moored in the left center. 
Note the shock wave spreading over the water just beyond the ship, and the shock condensation 
cloud lifting overhead.

Damage to USS Atlanta from rocks sent airborne by  a blast - Photos courtesy of 
William Wood GMMC U.S.N. (retired) who served on USS Atlanta and USS England.


Thee second test, called Charlie, occurred on April 16, 1965 with US Atlanta, USS England DLG-22,  Benjamin Stoddert (DDG-22) and HMCS Fraser in the test area.. The last was test Delta on June 19, 1965 with USS Atlanta, USS Dale DLG-19 and guided missile destroyer USS Towers DDG-9 in the test area.

The 500-ton TNT explosive charge for Shot "Charlie", second of a series of three test 
explosions, ready for detonation on the southwestern tip of Kahoolawe Island, Hawaii, 
April 1965. USS Atlanta (IX-304) is moored in the background, with her bow facing 
left. A large SPS-37/SPS-43A type radar antenna is mounted on a pedestal on her 
foredeck, immediately in front of an ASROC launcher. An SPS-30 type radar antenna 
is on the pedestal at her extreme bow. Both of these antennas were relocated after the 
February 1965 Shot "Bravo".

500-ton TNT explosive charge is detonated in Shot "Charlie", April 1965. This was 
the second of three Operation "Sailor Hat" test explosions conducted on Kahoolawe 
Island, Hawaii, in February-June 1965. USS Atlanta (IX-304) is moored to the left 
of the blast, with her bow pointing to the left.
USS England on the left and USS Atlanta on the right during the second Sailor Hat test.

William Wood's Operation Sailor Hat certificate.

The second and third detonations were conducted at the same site; the result
 is the present "Sailor's Hat" crater. Sailor's Hat crater has formed an 
aquatic ecosystem which has become habitat for two endemic species of 
shrimp: Halocaridina rubra and Metabataeus lohena. 

I WAS ON ATLANTA by John Gannon

I was attached to USS Atlanta IX 304 (CL 104) as a BT3 and to the best of my knowledge can tell you how she was prepared for "SAILOR HAT" and what it was like on board in the first tests off San Clemente. However no pictures that I may have taken have survived. My part of course is just from my point of view and I'm sure that there was much more done that I had not knowledge or no recollection of. It is a little strange how things in the Navy work out for 'Lifers" Atlanta was the third ship in my first hitch and I was attached to England over 10 years later as the next to last ship that I served on.

Atlanta was brought out of mothballs and converted at NSY Hunters point in San Francisco. Her main deck was virtually stripped of the WW II Light Cruiser appearance and refitted with a working DLG/CG Bridge facing FWD and a DDG Bridge facing AFT. An unusual appearance to be sure. :-) There were several different types of gun mounts and stuff such as ASROC launchers; hedge hog launchers and various Radar arrays mounted all over her. All things that had been used since Korea and prior to a full fledged VN involvement. The Cruiser had a 6 or 8 inch thick armored deck at the 2nd or 3rd deck running the full length above the engineering spaces and a armored hull around the Engineering spaces. Each Engine Room and Boiler room had a hydraulic hatch that secured the space at the armored deck level and an escape trunk that ran upward to the main deck level. Along that deck were steel beam braces mounted athartships (cross ways) about 2 ft high and every bulkhead had a submarine type hatch mounted in it replacing the normal WTD opening. It was like running low hurdles to get from place to place and then squeeze thru the sub style hatches. I have dents in my shin bones to this day from that! :-)) Every space that was manned had handles mounted on the bulkheads for the crew to hang on to in order to brace for shock waves..

Only the Fwd Fireroom and Engine Room was used for propulsion as I remember. The others were configured with hi speed cameras to record the effects of the blast shock wave, etc.

The first 2 blast tests were done off SOCAL at San Clemente Island. I believe it was something like 10K lbs of TNT at 1/4 mile and then 20K lbs of TNT at 1/8 mile. (I maybe wrong but you know how scuttlebutt distorts things and then add in old timers....You get my drift ;-)) )The crew was trained and drilled on all aspects of what was to be expected. We were anchored but steaming auxiliary at condition 1 (Z) as in real life and the ship was fully manned. I was in the fireroom as 2JV talker. When the explosions went off it sounded as if the ship had been hit by a large hammer and when the shock wave hit us, the ship moved dramatically to the side and even though we were braced in the old knees bent fashion the deck moved out from under our feet, came back up and slapped us. At the instant of the shock wave the paint on the insulation on the piping and bulkheads flaked off and it appeared to be snowing in the fireroom. It was very interesting to say the least.

John Gannon served on both USS Atlanta and USS England

I WAS ON ATLANTA by GMMC William Wood (USN retired)

Originally there were 2 CL's assigned to Operation Sailor Hat, the U.S.S. Vicksburg (CL-87) and Atlanta (CL-86), (I was originally assigned to Vicksburg) but funding had to combine both ships to Atlanta.

John Gannons' recollection is pretty accurate, (although I believe we had a ships crew of about 120). The 10 and 20K blasts off San Clemente, were underwater charges. We went out in the motor whale boat and brought aboard red snapper up to 50 lbs that were killed by the blast an floated to the surface.

Each TNT block weighed 33 1/3 lbs, thus there were 3 Million blocks on the "igloo". There were over 500 high speed cameras mounted around the ship, with 100 computers gathering data. All electronic equipment was "shock mounted". We used cris- crossed bungee cords above and below the equipment, so it was suspended in mid air.

The SPS-30 radar you point out on the bow, was blown off by the shock wave.

GMMC William Wood served on both USS Atlanta and USS England


I WAS ON ENGLAND by Joe Heller

As for Operation Sailor Hat, I was there. And it wasn't much. Have you ever lived near a quarry and been home when they blast. You feel a vibration and then you hear the blast. Operation Sailor Hat was a little stronger than that but I don't recall hearing much of an explosion but being inside at GQ station probably had a lot to do with that. As far as the vibration, you know how the ship bounced when in heavy seas and it straddled a trough in the swells, well the test came nowhere near that. As far as damage was concerned, all I remember hearing about was some cracked fiberglass raydomes. I'm pretty certain that we had no equipment damage in Operations. I recall the general consensus was "That was it?"

The thing that I remember most was the Navy being worried about the shock wave from the blast carrying over to Honolulu and having to wait a few days for the right weather conditions. As a result, we had opportunities for swim call. But when they decided that it would be best if they put the motor whale boat in the water with the gunnies with loaded weapons for shark watch, I decided that discretion was the better part of valor.

I WAS ON ENGLAND by Hugh Roberts

I was onboard the USS England during Operation Sailor Hat. We were on our way back from a six month Westpac trip to Vietnam. For the test I was placed in the passageway outside of the ship's sick bay. There was a count down to the explosion and when it happened it moved the ship a significant amount----if I remember correctly the ship seemed to move at least 4-feet side to side. Once the test was concluded we were allowed to go outside and I remember the most damage I saw was a huge dent in the ship deck around amidships where a bolder had hit the ship----it traveled a significant distance from the blast site on the island. We were one of the ships anchored the furthest from the explosion. Other ships in closer experienced much more damage. Also, if I remember correctly a Canadian Destroyer participated in the test. After the test we proceeded back to stateside.

A closer look at the Sailor Hat crater on Kaho’olawe Island, Hawaii.

There is some video for the Sailor Hat tests. It is incorporated with Swordfish and a SUBROC test. Swordfish  was a low-yield nuclear weapon test (less than 20 kilotons) of an antisubmarine rocket (ASROC) delivery system conducted in the Pacific. The underwater test produced a spectacular eruption on the ocean surface.  There is dramatic video footage of the effects of the Sailor Hat simulated nuclear blasts on the test ships. There is footage of a depth bomb deployment from an aircraft. At water entry, the parachute is jettisoned. A ship-fired, ASROC-delivered Mark 45 torpedo was parachute deployed before entering the water and searching for and finding the submarine target. The torpedo, moving at 40 knots until reaching the proper depth in the water, then began a horizontal movement toward the target. Once in place, the warhead detonated. A submarine rocket (SUBROC) is shown ejecting from a nuclear submarine’s torpedo tube, coming out of the water, flying up to 25 miles, reentering the water, and finally finding its target. A 39-inch long Mark 55 thermonuclear warhead, weighing approximately 460 pounds, was then detonated.

Composite No. 1 -Swordfish, Sailor Hat (Conventional Test), ASROC, SUBROC - Various dates - 17:45 - Color - This video is a composite of several delivery systems and nuclear and non-nuclear Navy tests.