Throughout the 1960s, the United States Navy (USN) committed to building a new fleet of nuclear-powered fast attack submarines through the "Thresher-class". Fourteen boats were completed and the series was characterized by their angled torpedo tubes (at midships) as well as a spherical bow containing the sonar fit (BQQ-2/BQQ-5 low-frequency sonar sphere). When lead-ship USS Thresher (SSN-593) was lost with all hands aboard (129) during deep diving tests off the coast of Cape Cod on April 10th, 1963, the group was renamed to "Permit-class" (after the second ship-of-the-class). USS Greenling was one of three boats chosen for the "Improved Thresher-class" upgrade (joining USS Flasher and USS Gato).
The Permit-class succeeded the outgoing Skipjack-class and was itself followed by the Sturgeon-class boats.
The contract to build USS Greenling (SSN-614) was awarded to General Dynamics Electric Boat of Groton, Connecticut on June 9th, 1960. Her keel was laid down on August 15th, 1961 and the boat was put to sea on April 4th, 1964. Formal commissioning took place on November 3rd, 1967 and the vessel was given the fighting motto of "Steel True and Blade Straight".
The boat's design was consistent with the class's standard: the sail was positioned towards the bow, which itself was rounded to cut through the water. The sail contained the usual scopes, sensors, and communications masts as well as the dive planes. The hull tapered towards the stern and featured a cruciform tailplane arrangement for control.
Dimensions of the boat included a length of 292.2 feet, a beam of 31.7 feet, and a draught of 24 feet. Displacement reached 3,800 tons. The aforementioned "Improved Thresher-class" program added nearly 14 feet to her length which, in turn, allowed for more internal volume to be had. As such, work and living spaces were able to be enlarged accordingly.
Aboard was a crew numbering 114 officers and enlisted. The armament suite involved 4 x 21" (533mm) torpedo tubes and these tubes resided near midships, angled outwards to clear the hull when fired. twelve to eighteen reloads of the Mk 37 torpedo family were initially carried. Later support arrived for the UUM-44 SUBROC anti-submarine missile and UGN-84 anti-ship missile.
Power came from a single S5W (S = Submarine; 5 = 5th Generation; W = Westinghouse) Pressurized Water Reactor (PWR). This same powerplant fueled the Skipjack-class up until the Los Angeles-class boats introduced the 6th Generation S6G series during the 1970s. USS Greenling could reach speeds of 30+ knots, making her an ideal candidate for fast hit-and-run attacks against Soviet shipping and unsuspecting warships. Due to the nature of nuclear energy, the vessel was given essentially unlimited range and excellent performance under water.
Commissioned in November of 1967, USS Greenling made her home out of New London, Connecticut, giving her clear access to the Atlantic Ocean. She was assigned to SUBRON 10 (SUBmarine squadRON #10) for a bulk of her service life. Her one notable action arrived in May of 1968 in response to the loss of USS Scorpion (SSN-589) - which had mysteriously gone silent. USS Scorpion, a Skipjack-class boat commissioned in July of 1960, went down in the Atlantic Ocean on may 22nd, 1968 with her crew of 99 men. No cause was ever found for the loss of the boat which was eventually located 400 nautical miles SW of the Azores. Greenling did what it could but all was eventually labeled a loss.
Greenling continued in USN service until April 18th, 1994 when she was officially decommissioned from service. Her name was struck that same year and she quickly entered the Ship-Submarine Recycling Program to properly dispose of her reactor set. Only some components of her control room were spared the scrapman's torch and these put on display at the Naval Undersea Museum of Keyport, Washington.
The Thresher-/Permit-class continued in active service, as a whole, up until 1996 when the last boat (USS Gato (SSN-615)) was decommissioned (April 25th, 1996). The Sturgeon-class succeeded the fleet and 37 of the design were built for the USN. These, operating until 2004, were supplanted by the Los Angeles-class.