On April 10, 1963, the American nuclear submarine USS Thresher (SSN-593) died during sea trials after repairs. In the course of investigating the causes of this disaster, multiple problems of various kinds were identified, which in one way or another could contribute to the death of the ship. As a result, the SUBSAFE submarine security program was proposed, developed and adopted for implementation.
For technical reasons
On December 17, 1917, the submarine USS F-1 (SS-20) collided with the submarine USS F-3 and sank. This was the first loss among modern American submarines – and far from the last. Until the beginning of the sixties, a total of 14 submarines of different classes and types sank in a non-combat situation. The most common causes of boat deaths were collisions with other ships and design flaws, including manufacturing defects.
April 10, 1963 nuclear submarine USS Thresher, the lead ship of the project of the same name, was tested after repair. On this day, the task of the submariners was to dive to the maximum design depth. At a depth of more than 300 m, the boat unsuccessfully tried to blow through the ballast tanks, however, due to malfunctions, the dive continued. After that, the submarine sank to 730 m, where a solid hull was destroyed.
“Thrasher” in the sea
Further investigation identified the most likely causes of the disaster. During the dive, an increase in seawater pressure led to the destruction of the brazed joint of one of the pipes of the ballast tank. Through the crack, water began to flow into the aft compartments, flooding electrical equipment. An attempt to blow through the ballast tanks and float up failed: due to high air humidity, the corresponding mechanisms froze and did not work. The specifics of the layout of the compartments did not allow the submariners to get to the damaged units and save the ship.
Admiral Hyman Rikover, “the father of the US nuclear submarine fleet”, noted during the investigation that the death of the Thrasher was not the result of just one defective compound. He believed that the preconditions for the accident were the wrong approaches to the design, construction and operation of submarines. Accordingly, in order to exclude such incidents in the future, it was required to take certain measures.
Already in June 1963, before the investigation was completed, the Submarine Safety Program (SUBSAFE) was developed. In December, it was approved and accepted for implementation. After that, the Navy specialists had to check the actual projects for engineering and technological errors or “weak points”.
The SUBSAFE program was aimed at maximizing the strength, survivability and stability of the structure. It is curious that the measures of the program affected only the durable hull and ship systems, experiencing seawater pressure. Power plants and means of propulsion, information and control systems and weapons were developed in accordance with the requirements of other programs and protocols. However, on a typical nuclear submarine there are a lot of systems and assemblies, in one way or another, related to the issues of the strength and tightness of the hull.
The program is divided into four areas. Certificates of conformity are issued for projects as a whole and their individual components related to strength. Also materials and assemblies used in construction are certified. SUBSAFE checks are carried out during ship construction and during testing. All documents are kept for the entire duration of the submarine’s service – this simplifies the investigation of various incidents.
After the completion of the sea trials, the submarine receives a final certificate allowing it to be used in the combat composition of the Navy. Since the mid-sixties, all newly built American submarines have such a document. Older ships, built before the introduction of the program, continued to serve, but gradually gave way to new ones.
Deformed pipe lifted from the deceased USS Thresher
SUBSAFE also touched on diving training methods. Sailors and officers in the course of training comprehensively study past accidents, incl. death of USS Thresher (SSN-593). They are introduced to the technical and organizational prerequisites, the course of incidents and the consequences. In addition, submariners can draw conclusions about the progress of recent decades – and assess how shipbuilders have improved their safety.
Consequences of the program
In 1963-64. The US Navy launched the SUBSAFE program. Current submarine designs have undergone additional checks for technical or other errors. It turned out that projects of strategic importance have a lot of shortcomings. Fortunately, they were discovered and fixed in time.
Inspections at shipyards and supplying plants ended with similar results. Not all materials used in the construction of new boats met the requirements. Incorrect assembly techniques and violations of approved processes have also occurred. However, the timely detection of problems made it possible to get rid of them in the shortest possible time and prevent accidents in the future.
USS Scorpion, the last US Navy nuclear submarine killed
The need for additional checks at different stages led to some delays in construction. In addition, all the proposed certification measures were supposed to increase the development and construction time of new submarines, and could also lead to an increase in cost. However, this was considered an acceptable price to pay for the increase in the reliability and safety of submariners.
By the end of the sixties, the US Navy was able to collect sufficient statistics and draw conclusions. On the whole, the SUBSAFE program has paid off. It significantly increased the reliability of the newly built submarines and reduced the number of accidents. In addition, the breakdowns often did not have serious consequences. The security program was recognized as successful, and it is still being implemented.
However, the introduction of SUBSAFE measures did not rule out an accident and tragedy. So, on June 30, 1968, a submarine USS Scorpion (SSN-589) of the Skipjack type sank in the Atlantic Ocean. It was not possible to establish the exact reasons for the incident; several versions were considered. At the same time, the death of the Scorpion confirmed the need for inspections and certification: the Skipjack project was completed before the introduction of a new security program.
Submarine USS San-Francisco in dry dock on about. Guam, January 27, 2005
In the language of numbers
Until 1963, the US Navy lost 14 submarines for non-combat reasons, mostly early designs. The USS Thresher ranked 15th on this sad list. The next – and, to the delight of the fleet, the last – was the USS Scorpion. Since 1968, the American submarine forces have not lost a single combat unit in accidents.
There were many emergency situations and accidents, incl. with the most serious consequences. However, in all cases, the crews were able to organize damage control, take the necessary measures and return to base for repairs.
In this context, the incident on January 8, 2005 is indicative of the Los Angeles-class submarine USS San Francisco (SSN-711), moving at a depth of 160 m at a maximum speed, crashed into a seamount. Serious damage to the bow assemblies has occurred; 89 out of 127 submariners received various injuries, one later died. Nevertheless, the ship traveled more than 360 miles to about. Guam. There, in the dry dock, a temporary nose cone was installed on the submarine, with the help of which she was able to get to the shipyard in Brementon, pcs. Washington.
San Francisco with temporary fairing, May 8, 2005
After a full renovation, the San Francisco returned to service. Subsequently, the command of the Navy noted that without the measures provided for by the SUBSAFE program, the submarine could not even reach Guam. Thus, the measures proposed back in the sixties are still saving submariners.
Death and salvation
The US Navy has faced the problem of submarine accidents since the founding of the submarine forces. As a result of investigations into such incidents, various measures were taken. In general, this helped to prevent possible accidents, but did not completely exclude them. Only in 1963, after the first loss of the nuclear submarine, it was decided to draw up and implement a full-scale quality control program and ensure the safety of submarines.
The creation and implementation of SUBSAFE was not quick and easy, and also led to increased costs at various stages. However, these measures fully justified themselves. The submarine safety program is still ongoing – and its results are well known. The US Navy has no reason to abandon it. And divers can be calm. In the event of an accident, they will be able to save themselves and the ship from destruction.