Japanese Type A Kō-Hyōteki Mini Submarine (HA-16)
Background
The Japanese Type A Kō-hyōteki miniature (mini or midget) submarines were built from 1940 to 1943 in Japan. These mini submarines had an overall length of 23.9 meters, a beam of 1.8 meters, a displacement of 46 tons submerged, and a test depth of 30 meters. They were equipped with two 450 millimeter torpedoes loaded into two tubes on the bow and one 140 kilogram scuttling charge.
This particular mini submarine was identified as HA-16, one of five that took part in the Japanese attack on Pearl Harbor on December 7, 1941, and one of two believed to have entered Pearl Harbor and fired their torpedoes at battleship row. In 1951, the U.S. Navy located the submarine believed to be HA-16 in shallow water off the entrance to Pearl Harbor. It had been damaged from a scuttling charge. It was then raised, taken out to sea, and dumped in deep water.
Exploration
The Hawaiʻi Undersea Research Laboratory found and explored the three pieces of the HA-16 mini submarine south of Pearl Harbor during submersible dives in 1992, 2000, and 2001 (the stern section, midsection, and bow, respectively). On December 7, 2016, NOAA Ocean Exploration and NOAA’s Office of National Marine Sanctuaries explored HA-16 on the 75th anniversary of the attack on Pearl Harbor during a shakedown expedition aboard NOAA Ship Okeanos Explorer. Remotely operated vehicle (ROV) Deep Discoverer — equipped with an Insite Pacific Zeus Plus camera capable of collecting high-definition footage — was used to document the site, which is at a depth of approximately 500 meters.
Modeling
This model of HA-16 is based on the ROV dive footage from timestamps 21:20 to 22:00 for the midship section, 22:15 to 22:50 for the stern section, and 23:15 to 23:55 for the bow section. This footage was exported into 2,321 images using VLC Player. The footage collected during exploration of HA-16 was not intended for photogrammetry. So, to address alignment issues, three individual models were made and then stitched together in Rhinoceros 8 and uploaded to Construkted Reality.
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Photogrammetry model of the Japanese Type A Kō-Hyōteki Miniature Submarine (HA-16) developed by Raymond Phipps, NOAA Ocean Exploration explorer-in-training, July 6, 2023. Model courtesy of NOAA Ocean Exploration, Shakedown, Calibration, and Testing in the Main Hawaiian Islands.
Published October 17, 2024