Dramatic pictures from Japanese media show the Japan Maritime Self-Defense Force (MSDF) submarine Soryu on the surface with a damaged conning tower and her starboard diving plane mangled. The Soryu is believed to have surfaced beneath a 50,000-ton Chinese Freighter named the Ocean Artemis which had set sail from Japan on Friday with a load of iron ore. Three minor injuries to the crew of the submarine have been reported.

When the Soryu surfaced she appeared to have had her communications antenna deployed from the conning tower (also called the Sail) which was carried away in the collision. According to a statement released by the Japanese Minister of Defense Kishi Nobuo, the resulting damage to the comms antenna required the vessel’s crew to contact Naval Headquarters using a cell phone three hours after the accident, presumably when in cell phone range to the shore.

The damage to the freighter is believed to be negligible and the government of Japan has issued a statement expressing regret to Communist China. The MSDF of Japan operates 11 submarines of this type in its fleet. The Soryu (SS-501) had her keel laid down in March 2005, was launched in December 2007, and commissioned in March of 2009. The name “Soryu” means green (or blue) Dragon; it was also the name of an Empire of Japan fleet carrier in WWII.

(Photo: Japanese Coast Guard)

This type of submarine is rather unique in that it uses a combination of a diesel engine and a large bank of lithium-ion batteries rather than the traditional lead-acid type. These batteries, while very expensive, are believed to allow the Soryu to remain submerged for up to 30 days and run at a top speed of 20 knots. These batteries also have a reputation for catching fire when they overheat, so the Japanese Navy must have mitigated that risk with very good fire suppression systems.

Collisions between submarines and surface vessels are fairly common. The U.S. Navy has seen nearly 50 collisions between surface vessels and submarines since 1983. In 2009, the Los Angeles class Attack Submarine San Francisco even managed to collide with an entire submerged mountain at 25 knots. In virtually all cases involving a submerged submarine running into another vessel, the submarine is generally found to be at fault. Under the rules of maritime navigation, a submarine below the surface is considered the “burdened” vessel, and the surface ship the “privileged vessel” in terms of the Right of Way. A submerged sub is not visible visually or on the radar which blinds the surface vessel to its presence and intentions. This means that the submarine’s crew has the responsibility to avoid colliding with the “privileged” vessel.

Before any submerged sub surfaces, there is a series of procedures it must follow to ensure that no other vessels are near it. The normal precautions would include: not surfacing in the midst of well-traveled sea lanes leading into or out of a port; having a precise plot of any sonar contacts before surfacing; and finally stopping at periscope depth to have a 360-degree look at the surrounding waters before you surface. Reports indicate that the Ocean Artemis was visible in the telescope as the Soryu came to the surface, which suggests that the submarine did not have an accurate sonar plot of it prior to the event.

The loss of this submarine to extensive repair and overhaul could not come at a worse time for Japan’s fleet. Recently the Chinese Navy has begun cranking up the pressure on Japan in the East China Sea over possession of the Senkaku/Diaoyu Islands which both countries have laid claim to. China has maintained a near-continuous naval presence in the islands’ waters for the last 17 months. The Communist Chinese have in the last month authorized their Coast Guard to use gunfire against any vessel intruding on the area. At some point, this will bring an armed Chinese vessel and an armed Japanese vessel into conflict.

For the MSDF, submarines like the Soryu act as invisible picket boats watching and reporting on Chinese Communist naval activities in the waters near Japan. The loss of the Soryu for repairs will make that job harder.