happy Independence Day 2023 / SSK submarines

For readers in the USA, I wish all a happy Independence Day, our nation’s 247th year.

In the US Navy, a warship launched or commissioned on the 4th of July is a special honor. Below is the WWII Gato class submarine USS Angler (SS-240) being launched by Electric Boat Company at Groton, CT on 4 July 1943.

USS Angler survived WWII and during 1952, was selected for conversion into SSK configuration to become USS Angler (SSK-240).

The SSK project came about from two legacies of the defeated Kriegsmarine: the GHG sonar array removed off the surrendered cruiser Prinz Eugen; and two surrendered Type XXI u-boats: U-3008 and U-2513, which the US Navy operated until 1949. The sleek, quiet, deep-diving Type XXIs were considered emblematic of the undersea threats of future decades; meanwhile pairing a lower-frequency directional sonar array with a submarine seemed like an ideal way to destroy other advanced submarines.

(USS Angler’s WWII sister-ship USS Flying Fish (SS-229) with Prinz Eugen’s sonar array reinstalled around the conning tower in 1951.)

During 1949 General Dynamics began concept work on a “hunter-killer submarine” (SSK). This would pair a Type XXI-like hull with new lower-frequency passive sonars. The new SSK hull designation stressed that hunter-killers would have a different mission portfolio than patrol submarines (SS).

(SSK concept artwork by General Dynamics)

However these new post-WWII submarines would only commission one or two a year starting in the early-to-mid 1950s. To more rapidly increase the number of SSKs in the fleet, an interim conversion of WWII submarines was decided upon, with the two projects to run concurrently.

Seven Gato class submarines were selected of which USS Angler was one. The Gato class was selected to preserve availability of WWII Balao and Tench class submarines for the more extensive GUPPY rebuild project.

(USS Angler after conversion.)

The core of the conversion was a AN/BQR-4A sonar. This was a 58-unit set of 10’7″ hydrophones in the bow behind a sound-transparent housing. The improvement was great; during WWII American submarine sonars like the Type JT had passive ranges between 4,000 yds to 4¾ NM. With AN/BQR-4A, USS Angler could regularly make detections out to 11 – 13 NM and in certain situations, as far as 20 – 30 NM.

The array was housed at the extreme upper bow, replacing the bullnose and a free-flood area of the original design. Its size required eliminating the upper two of the six forward torpedo tubes. One of the four diesel engines was eliminated to make room for the processors.

Other changes were eliminating the WWII deck gun, streamlining the conning tower, and other minor alterations.

The SSK concept did not really pan out. Of the new construction, only three of the planned five Barracuda hunter-killers were built in 1951 – 1952. They were successful, as were the seven WWII-vintage conversions, however technology was already overtaking them.

Between 1958 – 1960 the US Navy perfected the AN/BQQ-1 sonar, the first in a lineage of large cylindrical or spherical array systems. Meanwhile from 1959 onwards, all American submarines were atomic-powered (SSN). The SSN concept merged the roles of the patrol and hunter-killer designations.

In 1963 USS Angler was renumbered AGSS-240, this being “general-purpose auxiliary submarine”. USS Angler supported the enlisted submarine school at New London, CT and did midshipman cruises for the US Naval Academy.

(photo via navsource website)

USS Angler decommissioned on 1 April 1968. This submarine, which was “born on the 4th of July” during WWII, was scrapped in 1974.