April 8, 2019 - Lessons from the Loss of the USS Thresher (SSN 593)

What tragedies teach us, as both ship designers and builders.

“This is how we’ve always done it.”

“That’s what I was told.”

“Don’t reinvent the wheel.”

In recent weeks there have been many news articles regarding the Boeing 737 MAX and the crashes of Lion Air Flight 610 and Ethiopian Airlines Flight 302. These tragedies have taken the lives of 346 passengers and crew members. While the root cause of these accidents has not been disclosed, the consensus is it involves the latest version of the plane’s fly-by-wire software and how it actuates the control surfaces.

One of the main struggles facing investigators is the fact that many of the key design parameters have their origins in the baseline 737 design, approved in 1968. Since then, various improvements have been made including larger engines, strengthening of the wings, modernization of the cockpit electronics, and many associated software changes. Each of these improvements was required to meet new regulations implemented subsequent to the initial design. However, legacy design parameters are “grandfathered” and do not receive the same scrutiny and review as the improvements. The combined effect of these small changes, no matter how innocuous each individual change may seem, as an aggregate may be key contributors to the recent tragedies.

Much like the aerospace industry, the submarine industry often leverages past successful processes and designs when creating new products. The VIRGINIA Payload Module and COLUMBIA Class design efforts both utilize a significant amount of technology from VIRGINIA, SEAWOLF, LOS ANGELES, and OHIO Classes. Furthermore, alterations and improvements for existing classes of submarine are integrated into systems and components using technology dating back as early as the 1970’s. All of this work is accomplished using modern technical requirements, with a significant utilization of commercial standards by our vendors (both EB first tier and subsequent sub-tier vendors).

The development and construction of the US Navy PERMIT Class nuclear submarine share similarities with the Boeing 737 MAX. Portsmouth Naval Shipyard, the design agent for this class, had a proven history of successful designs. They built 134 submarines for the US Navy prior to the PERMIT Class, including 2 nuclear submarines, USS SWORDFISH (SSN-579) and USS SEADRAGON (SSN-584). This history of success did not preclude a major accident from occurring aboard the lead ship for the class, USS THRESHER (SSN 593).

On the morning of April 10, 1963 at approximately 9:18 am, following three distress transmissions, the USS THRESHER was lost with all 129 crew and civilian riders. This pivotal point in US Navy submarine history marks the event that sparked the development of the Submarine Safety (SUBSAFE) program to prevent future tragic loss of life. To those whose families experienced this tragedy, it was a life-impacting event that will stay with them forever. To this day, despite the Navy’s rigorous investigation, the exact cause of this tragedy is unknown; however, the following is the widely accepted sequence of events:

One or more silver-braze piping joints in sea water systems failed, resulting in engine room flooding.
Due to the ship’s design and system arrangements, the crew was unable to access vital equipment to control the flooding.
Saltwater spray on electrical components caused electrical panels to short circuit, the reactor plant to shut down, and loss of propulsion power.
The emergency main ballast tank blow system failed to operate properly. Restrictions in the piping system, coupled with excessive moisture in the air, led to ice formation in the piping. This, in turn, resulted in an inadequate blow rate. Consequently, the submarine was unable to overcome the increasing weight of water rushing into the engine room.

Today, we are all challenged with the duty to keep this event alive as a never fading reminder of the importance of the quality and rigor we apply to our jobs, and to be aware of “why we do what we do” at Electric Boat. April 10, 1963 predates the birth of the majority of our current ship designers and builders. While we have a well-respected history of quality, no amount of success completely eliminates the potential of another tragedy aboard a submarine. Today, we must apply the same passion, perseverance, and perspective that ship builders and designers did in the days following the THRESHER. This attitude and rigor is the only thing that can truly ensure our products are SUBSAFE.

Multiple issues contributed to the loss of the 129 lives: construction issues, testing issues, and design issues. At Electric Boat, we design and build submarines that take a nuclear reactor and her crew into an environment that does not otherwise support human life. At depth, the ocean is constantly looking for any way to exploit and overcome potential weaknesses in our design and workmanship on these highly complex platforms. Our processes and procedures, quality systems, and the SUBSAFE, DSS-SOC and FBW SCS Programs have been developed based on many lessons learned, including some at the cost of human life.

The ship designers and builders of Electric Boat are the first line of defense for our sailors. Every day we must use a questioning attitude, challenge complacency, and ensure arrogance does not compromise our ability to provide maximum reasonable assurance. No metric is more important than this one: the number of submergences must equal the number surfaces at the end of a submarine’s life. Much like an equal number of takeoffs and landings, this metric ensures over 120 sailors per ship return home safely to their families and loved ones. Additionally, the reliability of our submarine platforms plays a key role in the defense of our nation. The USS THRESHER serves as our symbol, our tragic reminder of this great responsibility.

Stephen C. Kirkup
Director, Quality Assurance and
Special Emphasis Programs

Following are images that can serve as daily reminders.

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