
Japan and the nations the English-speaking RocketNews24 team hail from are on good terms these days, but just a few generations ago things weren’t so friendly. While the greatest scientific minds of Japan today focus on putting solar panels on the moon or turning algae into fuel, during the 1930s and 40s weapons development was a much bigger growth area than green energy.
Recently, the wreckage of one of the Japanese Imperial Navy’s most advanced pieces of equipment from World War II was discovered off the coast of Hawaii. What exactly was it? A submarine, or maybe an aircraft carrier?
It was both.
Researchers from the University of Hawaii recently came across an unusual bit of wreckage while scouring the sea floor. Initially discovered last August, both the US and Japanese government have now officially recognized the sunken hull as being that of the I-400, the very first completed vessel from the I-400 submarine line.
At the time of its completion in the shipyards of Hiroshima Prefecture’s city of Kure, the I-400 was the world’s largest submarine. At 122 meters (400 feet) long and with a displacement of 6,560 tons, it was the size of a destroyer, and capable of circling the globe one and a half times on a single fueling.
Aside from their impressive range, the recently found I-400, I-401 (also located off the coast of Hawaii in 2005), and I-402 (scuttled in the East China Sea following the war) all shared another unique characteristic: they were in fact submersible aircraft carriers.
▼ The hangar entrance of an I-400-class submarine/carrier
The I-400 was able to store three Aichi M6A Seiran dive bombers in its aircraft bay. The planes’ wings and tail could both fold for more compact storage, and a catapult was used to launch them from the sub after surfacing, eliminating the need for a full-sized flight deck.
At the end of World War II the US military took custody of the Imperial Navy’s fleet, and the I-400 was brought to Hawaii for analysis. Once researchers were finished examining the vessel, it was used for live fire target practice, eventually being sunk in 1946, after which it wasn’t seen again until the recent discovery of its remains.
Even today, the I-400 still stands as an engineering marvel, and its technological aspects are all the more compelling with the luxury of being able to observe them 67 years removed from their initial intent.
Source: Gadget Sokuho
Insert images: Wikipedia



Japanese-language Chinese news site predicts future of aircraft carriers, uses sci-fi images
Studio Ghibli unveils new interactive stationery dioramas that bring anime movies to life on your desk
7-Eleven Japan brings back best-selling flat croissant that became a hit on social media
Studio Ghibli composer Jo Hisaishi just set three Guinness Records
Pokémon and Polaroid reveal collaboration with adorable Pikachu and Eeveelution camera and film
Universal Studios Japan partners with manga horror master Junji Ito’s Tomie
Starbucks Japan releases two new seasonal drinks that blur the line between summer and autumn
New Shinkansen Supreme Class private cabins get try-before-you-ride displays at Tokyo, other stations
Tokyo pub prohibits talking or keeping your phone out, only lets you drink in morning on weekends
Japanese workers reveal their top five mysterious rules they wish would disappear【Survey】
Japanese convenience store sunglasses just became our newest Convenience Wear obsession
12-year-old British girl who went missing in Tokyo found safe after visiting anime sites around Yokohama
Study finds hundreds of people in Indonesia legally named after Naruto, Inuyasha, other anime stars
12-year-old foreign tourist missing in Japan, police asking for help finding her [Video]
Japan’s Rabbit Island in danger of becoming Boar Island, tourists asked to follow feeding rules
Japanese gacha machine in Shibuya now sells tiny capsule terrariums
Stay at a hotel with a bed for your plushie in Japan
The Japanese city where ordering grilled chicken doesn’t guarantee you’ll actually get chicken
Japanese airlines set to cut fuel surcharges for international flights in September and October
Studio Ghibli adds new Jiji’s baby plush toy to its anime merchandise range in Japan
Tokyo subway installing new ticket gates that don’t accept payment through Suica or other IC cards
New Shinkansen luggage drop-off system begins in Japan, making train travel even easier
Air-conditioned dress shirts arrive in Japan to save working professionals from sweltering heat
Japanese Shinkansen becomes an overnight hotel for three nights this summer
Pokémon Center Online designates first Pokémon items that will require Japanese ID card to buy
Japanese toilet aims to attract foreign tourists but not everybody is happy about it
99-year-old woman rescued while attempting to climb Mt. Fuji
Tokyo’s newest viral dessert is like a Japanese parfait inside a bread bun [Taste test]
New Japanese vending machine at Shinkansen station sells cups of ice on platform
Japan announces sudden 400-percent increase in visa fees for foreigners entering the country
Japan’s human washing machines will go on sale to general public, demos to be held in Tokyo
Studio Ghibli has a new anime out, and there’s only one place in the world where you can see it
Starbucks Japan releases new drinkware and goods for Valentine’s Day
Starbucks Japan releases new sakura goods and drinkware for cherry blossom season 2026
Japan’s newest Shinkansen has no seats…or passengers [Video]
Japanese ninja certification exam attracts 131 candidates from Japan and abroad
Salomon releases Japan-exclusive Mt. Fuji hiking gear that doubles as an amazing souvenir
Put sesame oil in your coffee? Japanese maker says it’s the best way to start your day【Taste test】