Thresher (SSN-593)

Thresher (SSN-593)
Ship name	Thresher (SSN-593)
Caption	USS Thresher (SSN-593) underway, date unknown
Ship class	Permit-class submarine
Displacement	3,000 tons (surfaced)
Builder	Portsmouth Naval Shipyard
Laid down	14 May 1958
Launched	9 July 1960
Commissioned	3 August 1961
Fate	Lost 10 April 1963

Thresher (SSN-593) was a Permit-class nuclear-powered attack submarine of the United States Navy lost during deep-diving tests on 10 April 1963. The boat's sinking during the Cold War provoked major investigations involving the Department of Defense, President John F. Kennedy, and naval engineering authorities, and led to sweeping changes in United States Navy submarine safety programs and shipyard practices.

Design and Construction

Thresher was designed as part of the Permit-class program developed by the United States Navy Bureau of Ships with construction contracted to Portsmouth Naval Shipyard and participation from Electric Boat and design influence from earlier classes such as the Skipjack-class submarine and technologies proven on USS Nautilus (SSN-571), USS Skate (SSN-578), and designs inspired by concepts from the Naval Reactors program under Admiral Hyman G. Rickover. The hull, pressure hull frames, and submarine systems incorporated advances in high-strength steel metallurgy, hydraulic and electrical components, and the S5W reactor plant, with oversight from the Atomic Energy Commission and coordination with contractors including General Dynamics, Westinghouse, and industrial suppliers operating under Navy standards. Keel and pressure hull fabrication at Portsmouth Naval Shipyard followed specifications set during coordination meetings involving Secretary of the Navy John B. Connally staff, naval architects from Bureau of Ships, and testing protocols aligned with Submarine Development Program objectives.

Operational History

After commissioning on 3 August 1961, Thresher operated in the Atlantic and along the New England coast, conducting trials coordinated with the Office of Naval Research, deep-diving tests tracked by the United States Atlantic Fleet and participating in exercises with units from Fleet Ballistic Missile support vessels and carrier groups. The submarine executed shakedown cruises, sonar evaluations with systems from Navy Electronics Laboratory affiliates and acoustic work related to the SOSUS network, while interacting with platforms such as USS Enterprise (CVN-65), USS Albany (CG-10), and NATO units including elements from the Royal Navy and Canadian Forces during allied antisubmarine warfare exercises. Operational readiness reporting went through channels to Commander, Submarine Force Atlantic Fleet and the Chief of Naval Operations.

Loss and Casualties

On 10 April 1963, Thresher was declared overdue during a deep-dive test off the coast of New England near Nantucket Shoals, prompting search and rescue coordination among the United States Coast Guard, US Navy, and private salvage contractors. The accident resulted in the loss of all hands aboard; the crew complement included officers and enlisted personnel assigned under commands of the Submarine Force, United States Atlantic Fleet and represented families notified through the Navy Personnel Command casualty assistance process. Casualty reports were managed at the highest levels of the Department of Defense and relayed to the White House and congressional oversight committees including the Senate Armed Services Committee.

Investigation and Causes

Investigations were conducted by boards convened under the Chief of Naval Operations with technical input from Admiral Hyman G. Rickover's Naval Reactors office, the Bureau of Ships, metallurgists from the American Society for Testing and Materials, and independent experts from institutions such as Massachusetts Institute of Technology and Naval Postgraduate School. The formal inquiry examined potential causes including hull fracture, reactor scram sequences involving the S5W reactor, seawater ingress through piping or sea valves, coolant system failures, and failures of emergency ballast systems influenced by welding and construction practices at Portsmouth Naval Shipyard and vendor quality assurance by firms like Electric Boat. Findings led investigators to emphasize probable flooding through an improperly secured joint or piping fitting and subsequent loss of propulsion and buoyancy during an emergency ballast blow, with contributory factors including material fatigue, maintenance practices, and emergency procedure limitations as reviewed by panels that included representatives from the National Bureau of Standards.

Aftermath and Influence on Submarine Safety

The loss of Thresher prompted the United States Navy to establish the SUBSAFE program, a comprehensive certification and quality assurance regime overseen by the Chief of Naval Operations and implemented across shipyards such as Portsmouth Naval Shipyard, Newport News Shipbuilding, and naval industrial partners including General Dynamics Electric Boat. SUBSAFE mandated design reviews, material traceability, welding standards enforced by organizations like the American Welding Society, and procedural reforms involving the Naval Sea Systems Command and Naval Reactors office. The program's effects were reflected in subsequent classes including Sturgeon-class submarine, Los Angeles-class submarine, Seawolf-class submarine, and policies scrutinized by congressional hearings in the House Armed Services Committee, leading to enduring changes in Navy procurement, quality assurance, and accident investigation protocols.

Memorials and Legacy

Memorials honoring the crew of Thresher were established by veteran and families' organizations, including monuments near Portsmouth, New Hampshire, commemorations at the Navy Memorial in Washington, D.C., and plaques maintained by the Submarine Force Library and Museum and local veterans groups in Kittery, Maine and Boston, Massachusetts. The tragedy influenced cultural portrayals in media reporting by outlets such as the New York Times and scholarly examinations at institutions including Naval War College and Massachusetts Institute of Technology, while remembrance ceremonies involve representatives from the United States Navy, families, and elected officials from New Hampshire and Massachusetts to honor those lost and to underscore the safety reforms that followed.

Category:United States Navy submarines Category:Shipwrecks in the Atlantic Ocean