Akagi 赤城

Background

Akagi 赤城 was a Japanese aircraft carrier that was in service from 1927 to 1942. It was originally designed as an Amagi-Class battlecruiser, but construction as such was not finished due to the 1922 signing of the Washington Naval Treaty. In 1927, the incomplete hull of Akagi was repurposed and used to build a larger and faster aircraft carrier.

Akagi had an overall length of 261 meters, a beam of 31 meters, a draft of 8 meters, a maximum speed of 31.5 knots, and a range of 12,000 miles at 16 knots. It had a complement of 1,630 personnel and 88 aircraft.

Akagi was Japan’s flagship for the Kidō Butai or “Mobile Force” in the Pacific Theater. It took part in several operations during World War II, including the attack on Pearl Harbor on December 7, 1941, the Battle of Rabaul (New Guinea) on January 20, 1942, the Indian Ocean raid from March 31-April 10, 1942, and the Battle of Midway from June 4-7, 1942. During the Battle of Midway, three Douglas SBD Dauntlesses from USS Enterprise targeted Akagi. One of these was piloted by Lieutenant Commander Dick Best, who struck Akagi with a 1,000 pound bomb at the middle elevator for the upper hangar deck, causing a chain of explosions. Akagi soon became inoperable, and on June 5, 1942, Admiral Isoroku Yamamoto ordered the carrier to be scuttled. Destroyers Arashi, Hagikaze, Maikaze, and Nowaki each fired torpedoes into Akagi, sinking the carrier.

Akagi at sea during the Summer of 1941, with three Mitsubishi A6M Zero fighters parked forward.
Akagi at sea during the Summer of 1941, with three Mitsubishi A6M Zero fighters parked forward. Image courtesy of Naval History and Heritage Command. Download largest version (jpg, 1.53 MB).

Exploration

In 2019, Akagi was located during a mapping survey of the Battle of Midway site conducted by Vulcan Inc. in partnership with the U.S. Navy History and Heritage Command. On September 10, 2023, Ocean Exploration Trust and partners conducted the first visual survey of Akagi with remotely operated vehicle (ROV) Atalanta during the Ala ‘Aumoana Kai Uli expedition on Exploration Vessel Nautilus, which was funded by NOAA Ocean Exploration via the NOAA Ocean Exploration Cooperative Institute. At the time, Akagi was intact, but severely disarticulated, and embedded in seafloor sediment. A large section aft of amidships was damaged, likely caused by bomb damage and a subsequent chain of explosions. The deck on the starboard side slopes downward, indicative of where the exhaust port would have been.

Akagi within Papahānaumokuākea Marine National Monument, where it sank during the Battle of Midway in 1942.
Akagi within Papahānaumokuākea Marine National Monument, where it sank during the Battle of Midway in 1942. Image courtesy of NOAA Ocean Exploration/Ocean Exploration Trust, Ala ʻAumoana Kai Uli. Download largest version (jpg, 1 MB).

Modeling

Ocean Exploration Trust collected 18 hours of ROV dive footage of Akagi. The video was processed into still images and color corrected using Adobe Photoshop 2024. The footage was exported into 9,097 still images using VLC Player and color corrected in Photoshop. Seventeen individual models were made: starboard side (5), portions of the port side (2), deck structures (3), stern (3), bow (1), and debris field along the port side of the site (3). Due to distortion of some of the models and quality issues, only 10 of these models were stitched together in Rhinoceros 8 and uploaded to Construkted Reality.

Photogrammetry model of Akagi developed by Raymond Phipps, NOAA Ocean Exploration explorer-in-training, Apri 21, 2024. Model courtesy of NOAA Ocean Exploration/Ocean Exploration Trust, Ala ‘Aumoana Kai Uli expedition.

Site Data
Site Name Akagi
Type UCH
UCH Vessel Date Built March 25, 1927
UCH Vessel Date Sank June 5, 1942
Hull Material Steel
Official Number N/A
Location Hawai‘i
Depth 5 kilometers
Length 261.21 meters
Width 31 meters
Dive Data
Expedition Number NA154
Expedition Name Ala 'Aumoana Kai Uli
ROV Dive Number T1002
ROV Dive Date September 10, 2023
ROV Used Atalanta
Camera Information Insite Pacific Mini-Zeus HD
Video or Stills Video
Model Data
Software Agisoft Metashape Professional Version 2.1.0, Rhinoceros 8
Number of Images Used/Format 9,097/JPG
Image Alignment Percentage 86%
Number of Tie Points 1,152,584
Time to Complete 64 hours
Orthomosaic Views Available No
Images Available Yes
Animations Available Yes
Available File Exports/Location/POC archaeology.oceanexploration@noaa.gov

Published October 17, 2024