The sinking of Indonesian submarine 502 on April 21, 2021 and the breakup of the vessel and death of 53 crewmembers highlights the hazards of operating in the oceans. The 502 sinking brings back memories of the sinking and destruction of the USS Thresher on April 10, 1963 off the New England coast with the loss of 129 men.
A Navy inquiry determined most likely there was flooding in the engine room possibly from faulty piping causing coolant pumps to slow or stop and trigger a reactor shutdown with a loss of power. Subsequently the Navy implemented the SUBSAFE program for quality assurance and certification for submarines.
Additionally, the Navy implemented a safe testing program, which ensured all submarine testing would be conducted in accordance with stringent testing parameters.