Although few people may be aware of it, Japan’s modern-day rocket and automobile industries have their roots in the ingenuity of the engineers who developed radial engines for the Zero fighter in the late 1930s.
Particularly notable among the engineers with links from the Zero to today’s state-of-the-art technology are Ryoichi Nakagawa, chief of the team of Nakajima Aircraft Co. engineers that developed the Zero’s Sakae-21 engine, and Yasuakira Toda, a physicist from Hokkaido University.
Toda, who joined Nakajima Aircraft in 1937, later helped another scientist, Hideo Itokawa, another Nakajima engineer. Itokawa was known as “the father of Japan’s space development program,” which began with the launch of 29 Pencil rockets in 1955.
During the war, Itokawa designed the Hayabusa (Peregrine Falcon) and Shoki (Japanese Defense God) fighters.
“Dr. Toda had improved the Zero fighter’s engine by working with Mr. Nakagawa,” said Yuji Sakakibara, one of only a few Nakajima engineers still alive.
“What is most crucial to produce good engines is to devise excellent combustion and cooling mechanisms, and Dr. Toda recommended some good solutions to meet these challenges, while proving his proposed solutions could work based on a series of experiments,” Sakakibara said.
The more gasoline and air supplied to a cylinder, the more thrust an engine produces. But a large supply of gasoline tends to have the side effect of raising cylinder head temperatures to excessively high levels, thereby damaging pistons and cylinders.
So, how to cool the engine was a key question.
“Mr. Nakagawa designed the Zero fighter’s engine based on Dr. Toda’s proposals concerning how to improve the cooling mechanism,” Sakakibara said.
The Zero outperformed all U.S. fighters at Pearl Harbor and throughout the Pacific until October 1943, when the U.S. pitted the Grumman F-6F Hellcat against the Zero in the skies over Wake Island, according to historian and former Chiba University professor Ikuhiko Hata.
The 1942 edition of Jane’s All the World’s Aircraft notes the Zero provided a maximum speed of 550 kph. The Hellcat outran it at 594 kph. After the battle for Wake, the Zero lost its two-year mastery of the Pacific skies to the Hellcat.
Toda, who joined the postwar Nissan Motor Co. along with Nakagawa, is the same physicist who led the team of engineers at Nissan’s aerospace division.
The team developed the engine systems that powered a series of Japanese rockets, named the Pencil, Kappa, Lambda and Mu, according to Yasunori Matogawa, a senior official of the Japan Aerospace Exploration Agency.
“Dr. Toda aided Japan’s rocket programs by devising igniters for rocket fuel and developing the material for, and the shape of, a nozzle through which a rocket emits a jet of burned fuel,” Matogawa said. “The Kappa rockets of Dr. Toda were really excellent.”
In July 1960, a Kappa-8 reached an altitude of 190 km, entering the ionosphere. The rocket technology later evolved into today’s H-IIA rockets.
Many of the engineers who developed engines for carmakers Honda Motor Co., Nissan and Fuji Heavy Industries Ltd. after Japan’s 1945 surrender to the Allied Forces were those who had lost jobs at Nakajima Aircraft, according to Kazutada Okamoto, a former researcher at the Imperial army’s aviation technology institute.
Okamoto, who worked with Nakagawa’s engineering team at Nakajima Aircraft during the war, joined Fuji Precision Machine Co., the predecessor of Prince Motor Co., to develop 33 engine models for use in sedans, including the Nissan Skyline and Gloria.
Takanori Maema, a former jet-propulsion engineer at Ishikawajima-Harima Heavy Industries Co., in his book quoted Nakagawa, a former Nissan senior managing director, as saying: “Honda Motor employed approximately 10 former Nakajima engineers. Consequently, Nakajima’s technologies were handed on through these people.”
Fuji Heavy Industries, known for its Subaru brand cars, hired such key Nakajima engineers as Shinroku Momose, while Toyota Motor Corp. acquired Tatsuo Hasegawa of Tachikawa Aircraft Co., who later led the team of engineers who developed the Corolla sedan.
In 1945, Gen. Douglas MacArthur, supreme commander of the Allied Powers, barred Japanese from aircraft manufacturing and disbanded 12 aircraft fuselage makers and seven engine makers.
That year, the Japanese government renamed the 250,000-employee Nakajima as Fuji Sangyo Co. It was split up into 15 companies, including Fuji Precision, where Nakagawa led a team of former aero engineers to produce goods from spoons to fishing boat engines.
Fuji Precision later tied up with Tama Motors Co., where 200 ex-Tachikawa Aircraft engineers were producing electric vehicles. The tieup enabled the pair to complete a car with a 1.5-liter gasoline engine modeled after the 1.2-liter engine of the Peugeot 203.
In 1952, Prince Motor took the wraps off the 1.9-liter Prince sedan, while debuting the first in a series of sporty Skyline models in 1956. Prince merged with Nissan in 1966.
Shinichiro Sakurai, who developed various automobile components for the Skyline series under the tutorage of Nakagawa, said: “I found aircraft engineers’ mind-sets are very different from engineers in other industrial sectors . . . their attitude toward technological innovation is incomparably more serious.
“Should a single aircraft bolt become loose and drop, that aircraft could crash,” Sakurai said. “For aero engineers, it was crucial to develop fighters capable of making agile turns and chasing enemy fighters as fast as possible — even by a single second.
“The extremely meticulous and scrupulous care taken to ensure the most accurate construction” of all components in a mechanism is the most important lesson prewar aircraft engineers gave to the postwar Japanese auto industry, thus ensuring its global success, he said.