It was on January 8, 2005, when the USS San Francisco, a Los Angeles-class nuclear-powered attack submarine serving in the U.S. Navy, cruising at more than thirty knots, was situated roughly three hundred sixty miles southeast of Guam.
All appeared to be going well—but there was indeed an unseen danger close ahead. The navigational charts that were often utilized by San Francisco’s crew failed to reveal a seamount—or an undersea mountain—that was, in fact, protruding from the floor of the ocean.
It wasn’t long before the submarine crashed into it.
“The ship’s crew were thrown about, some over distances of twenty feet, and the majority of the one hundred thirty-seven-member crew suffered one injury or another—including one that would later prove fatal,” defense writer Kyle Mizokami wrote for Popular Mechanics.
“Further inspection would explain what happened, and reveal that the submarine’s bow looked like a crushed soda can. USS San Francisco had run into an undersea mountain,” he added.
Despite the head-on crash at a depth of more than five hundred feet and at a speed of more than thirty miles an hour, “the San Francisco didn’t sink, nor did it experience a reactor malfunction.”
The author continued: “Even more incredibly, the submarine was able to move under its own power back to port on the island of Guam. All of that is directly attributable to safety actions the U.S. Navy had taken four decades earlier.”
Those “safety actions” were initiated back in 1963, when the nuclear submarine USS Thresher was deemed to be lost during tests in the Atlantic Ocean. What became clear during the investigation was that the ballast-blowing measures meant to surface the submarine in an emergency had failed.
“Within two months, the Navy had created the SUBSAFE program. The goal was to ensure that, no matter what the emergency, a U.S. Navy submarine’s hull would maintain structural integrity under pressure and the sub would at least be able to surface,” Mizokami wrote.
“Meanwhile, the Navy’s Nuclear Propulsion Program emphasized safe nuclear reactors and reactor handling above all else. If the hull, ballast systems, and reactor all worked properly a crew had a fighting chance of survival,” he continued.
As for the USS San Francisco, even after the devastating collision, “the rest of the hull held pressure, preventing it from sinking. The ballast systems still worked, allowing it to surface, and the nuclear reactor still worked after the crash, allowing the ship to move under its own power.”
“In 2013, an admiral with the Navy’s Naval Sea systems command was quoted as saying that were it not for SUBSAFE decades earlier, USS San Francisco might have been lost,” Mizokami added.
Ethen Kim Lieser is a Washington state-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.