Few of the U.S. Navy’s post-World War II submarines had such an unusual career as the USS Grayback. It went from carrying some of the United States’ first strategic missiles to stealthily delivering naval special forces to the coast of North Vietnam during the war in Southeast Asia. It was truly a fascinating and bizarrely-shaped boat whose multiple lives underscored how she was able to change along with a morphing Cold War. Here’s her story.
Laid down on July 1, 1954, at Mare Island Naval Shipyard in San Francisco Bay, California, the first of the Grayback-class missile submarines was, like its sister, the USS Growler, built as a conventionally powered submarine that would have a primary armament of cruise missiles. The pair were the first submarines to be designed around an armament of subsonic Vought SSM-N-8 Regulus I strategic missiles. Four of these nuclear-armed, turbojet-powered weapons were carried in a pair of huge cylindrical hangars located above the bow.
The second submarine to carry the name, the USS Grayback was launched on July 2, 1957, and commissioned on March 7, 1958, as SSG-574. Ultimately, the submarine was one of five equipped to launch the Regulus I that were in service by 1960. To launch the airplane-sized missile, the submarine first had to surface, before the rear of the hangar was opened, and the Regulus I disgorged onto a trainable ramp that was recessed into the top of the hull, forward of the sail. The ramp was then turned sideways, and the missile blasted off under the power of a pair of solid-fuel rockets before the Allison J33 turbojet kicked in. The missile had a range of around 575 miles.
The USS Grayback made history as the first submarine to carry Vought’s next-generation SSM-N-9 Regulus II and undertook trials with this Mach-2-capable weapon off the U.S. West Coast. Two of these weapons could be carried, compared to four of the previous Regulus Is and the first successful launch of the missile took place on September 16, 1958, while the Grayback was operating out of Naval Base Ventura County, California. However, the Regulus II was canceled later the same year, by which point the concept of the submarine-launched cruise missile had been overtaken by the development of the Polaris submarine-launched ballistic missile, which promised much greater range, speed, and reliability.
On February 9, 1959, the USS Grayback departed Mare Island for Pearl Harbor in Hawaii, arriving at what would become its permanent home base on March 7. Between September and November of 1959, the submarine completed the first of nine deterrent missions, patrolling the Pacific with an armament of Regulus I missiles. In the course of these patrols, the Grayback spent more than 20 months at sea and logged well over 130,000 miles.
The USS Grayback served in its strategic missile role until it was decommissioned on May 25, 1964, as the cruise-missile submarines divested their deterrence duties to the new Polaris boats.
A new lease of life then began when the USS Grayback was converted as a submarine transport, initially under the pennant number APSS-574. The ability of submarines to transport personnel and materiel, as well as launch raiding parties ashore, while using its inherent capabilities to help avoid detection, was well established by the end of World War II, and would continue into the Cold War and beyond. It is a fascinating subset of underwater warfare that you can read all about in this previous War Zone article.
The conversion work for the new role was authorized in 1967 and was undertaken at the Mare Island Naval Shipyard between November 1967 and May 1969. This included removing the Regulus equipment and lengthening the hull from 322 feet 4 inches to 334 feet. Mess and sleeping quarters now provided accommodation for up to 67 troops. The missile hangars were converted to carry six swimmer delivery vehicles (SDVs) and a diver’s decompression chamber. The SDVs and scuba-equipped divers could be launched and recovered while the submarine submerged. The height of the sail was increased by around 10 feet and a Sperry BQG-4 Passive Underwater Fire Control Feasibility System (PUFFS) was fitted.
The role of the “new” USS Grayback was carrying commando and other covert forces on special missions against targets that required a stealthy approach from the sea. Members of the U.S. Navy’s SEAL teams and Naval Underwater Demolition Teams (UDT) were certainly carried onboard the submarine, as were, in all likelihood, U.S. Army Green Berets. UDTs would be used for example, for undertaking reconnaissance of possible landing zones ahead of an amphibious assault, or to clear the approaches to a beach.
As well as its amphibious role, the USS Grayback could also perform similar duties as an attack submarine, for which it was armed with the thermal-powered Mk 14 anti-ship torpedo of World War II vintage and the electric-powered Mk 37 anti-submarine torpedo. These were operated using the Mk 106 Model 12 torpedo fire-control system.
From August 1968 the submarine’s designation was changed again, to LPSS, indicating an amphibious transport submarine, and the new-look USS Grayback was commissioned for a second time on May 9, 1969. Thereafter, it was operated by the Pacific Fleet and based at Subic Bay in the Philippines.
By the time of the Vietnam War, the Navy was using specially configured submarines to support special operations, the USS Grayback and the Gato class USS Tunny working along the coast of North Vietnam, and also helping gather intelligence.
The submarine’s most dramatic — and secretive — mission took place in June 1972, during the conflict in Southeast Asia. This was Operation Thunderhead, an attempt to rescue U.S. prisoners of war that were planning to escape from North Vietnam’s notorious “Hanoi Hilton” prison. The two PoWs, both aviators, planned to steal a boat and make their escape by river to the Gulf of Tonkin, where they would be picked up by elite troops from the U.S. Navy’s SEAL Team One, Platoon A, and Underwater Demolition Team 11 (UDT-11). Exactly how communications were run between PoWs and rescuers while planning this daring mission has not been explained.
The USS Grayback departed Subic Bay to transport the special forces into the coastal waters off North Vietnam, where plans called for one or more Mk 7 SDVs to be launched under cover of darkness. Piloted by two operators from UDT-11, each SDV would deliver four SEALs from Platoon A to an island at the mouth of the Red River, which flowed into the Gulf of Tonkin. The Grayback was on station around 4,000 yards from the mouth of the river and at a depth of around 65 feet.
A first attempt to launch a reconnaissance mission on June 3, 1972, ended in failure after the four-man team became lost, struggling with navigation errors and tidal currents that were much stronger than expected. Unable to relocate the USS Grayback, the team had to abandon their SDV after the vehicles’ batteries ran out. After eight hours they were rescued by a helicopter around 10 miles south of the submarine’s position and were then flown to the nuclear-powered guided-missile cruiser USS Long Beach, which was stationed approximately 15 miles offshore, serving as the command ship for the mission. You can read all about that particular warship here.
Two days later, the team was to be returned to the submarine by helicopter, with the aim of dropping them into the water alongside the USS Grayback, at night. Again, however, the submarine proved hard to find. Once it seemed the infrared locator beacon had been found, the operators jumped from the helicopter, but the chopper was flying too high and too fast for a safe jump and was downwind, meaning the jumpers hit the water with even much greater velocity. Lieutenant Melvin “Spence” Dry was killed immediately, and one other member of the team was seriously injured.
Meanwhile, the USS Grayback had launched another SDV, but this mission was abandoned too after its crew ran out of air. The second team came to the surface and it was their locator beacon that the first team had inadvertently found. The two teams rendezvoused before both were picked up by helicopter and returned to the USS Long Beach. After the United States began sowing mines in North Vietnamese ports and rivers, the chances of mission success were further reduced, and it was decided to abandon the PoW escape effort altogether.
Operation Thunderhead remained classified for many years and it was not until 2008 that Lieutenant Dry’s death was finally acknowledged as a combat loss, and he was posthumously awarded the Bronze Star for Valor.
From 1975 the USS Grayback was reclassified yet again, this time as an attack submarine, or SS, for administrative reasons, to ensure continued funding from the U.S. Congress for what was now a true niche capability.
Exactly what, if any covert missions, the USS Grayback was involved in during the years that followed is not known, but the Navy undoubtedly appreciated the submarine’s utility and it remained in service until decommissioned for a second and final time at Subic Bay on June 16, 1984.
Befitting a boat with a less-than-conventional history, the USS Grayback received a bright orange paint scheme to increase its conspicuity before it was sunk as a target near Subic Bay on April 13, 1986. It brought to an end the story of a unique submarine — a guided-missile pioneer and a covert amphibious transport with a harrowing Vietnam combat record.
Today, the legacy of the little-known amphibious transport submarines is kept alive by the Navy’s four Ohio class nuclear-powered guided-missile submarines. They traded their strategic nuclear missile armament and now carry diverse cargoes ranging from Tomahawk cruise missiles to Navy SEALs. In this way, they continue the tradition of the USS Grayback, with capabilities befitting the demands of 21st-century warfare.
Contact the author: thomas@thedrive.com