64TH ANNIVERSARY OF THE PEARL HARBOR ATTACK
Decades of silt obscure wreckage of midget sub
Researchers recently peered inside but could see very little
Although more than six decades have passed since the first shot of the Pacific War, researchers are still having a hard time cracking the mystery 1,200 feet deep off the mouth of Pearl Harbor.
Scientists recently attempted to peer inside the Imperial Japanese Navy "midget" submarine sunk on Dec. 7, 1941, and rediscovered by the Hawaii Undersea Research Laboratory in August 2002.
What did they see? Not much.
The submarine, sunk by patrolling destroyer USS Ward more than an hour before the surprise aerial attack, is sitting on the bottom, perfectly intact except for a shell hole in the conning tower and a coating of marine growth.
"Even though we've made a couple of dozen dives on the site, we still didn't know what condition it was inside, what happened to the shell that was fired at it -- there's no visible exit hole -- or if there are any remains of the crew," said Terry Kerby, HURL submarine pilot.
In a series of dives sponsored by the National Oceanic and Atmospheric Administration's Marine Sanctuary Program, HURL scientists attached a video camera to a rod that was gingerly fed into the sub's interior via the shell hole. Kerby said they had to wait for perfect conditions -- no current that would shove HURL's Pisces sub against the fragile 80-foot wreck. Pisces' bumper bars were outfitted with foam rubber padding to lessen any impact.
The scientists also measured potential corrosion of the submarine's hull, charted possible external threats to the site, completed a detailed series of external images and retrieved data from an environmental probe buried nearby.
The camera inserted into the submarine through the shell hole "is an interesting little gadget purchased from Canada," said Hans Van Tilburg, a shipwreck expert from the National Marine Sanctuaries Program. "It can pan back and forth, and it has a light ring attached to the lens, like a medical camera."
When the camera was inserted into the hole, some damage to the internal structure was observed. Kerby speculated that the shell ricocheted off the conning tower bracing and exited out the submarine's hull bottom, which would have caused it to sink quickly.
According to USS Ward ammunition handler Will Lehner, in town this week to help commemorate the anniversary of the attack, the Ward's artillery shells didn't travel far enough to fuse themselves.
"That sub went right by us and we had to aim down at it," he said. "Those four-inch shells we used had to travel a bit before they became explosive. We just punched a hole right through her."
Kerby said that the camera was difficult to maneuver, and Van Tilburg said they need to "create more of an endoscope approach" to inserting small cameras into wrecks. The 3-1/2 inch rod containing the camera was unable to be inserted straight into the hole, so Kerby tilted it at the same angle the shell was fired from USS Ward, and the rod slipped cleanly into the submarine.
They were unable to peer much forward inside the craft, and what little movement they created kicked up a snow cloud of particles inside the enclosed space.
They were able to tell that the interior is heavily silted, obscuring detail and hiding the deck.
"We saw just a bit of the control space," said Van Tilberg. "Interestingly, there is a fair amount of biologic activity inside, with sponges growing all over. That shows there's some oxygen and interior water movement -- and that the interior is not fouled with leaking battery acid."
There were no obvious signs of remains, which are likely hidden beneath the silt on the deck.
The site is the focus of a growing government effort involving NOAA's National Marine Sanctuary Program, HURL, the National Park Service and the Naval Historical Center to mark the sunken craft as a National Historic Landmark. In February 2004, the Japanese government declared the submarine was U.S. property.
HURL and NOAA scientists are developing a proposal to map all historic wrecks in the Pearl Harbor area in a "Deepwater Maritime Heritage Resources Database."