Sasaki Tatsujiro and others at the No. 2 Science Department at Tokyo Imperial University’s Aeronautical Research Institute in 1942 prototyped the country’s first differential analyzer as a joint research project with the Showa Kookuu-Keiki Research Department. The differential analyzer was a large mechanical analog computer used to solve ordinary differential equations with integrators and other components. James Thomson first described the principle by which a differential equation could be solved by combining integrators in 1887, and Vannevar Bush at MIT built the first practical differential analyzer in 1927.
The Aeronautical Research Institute’s differential analyzer consisted of four integrators, one multiplier, three input consoles, and one output console and was capable of solving fourth-order differential equations. Later, work on the second prototype that would solve eighth-order differential equations began, but it was destroyed in the war just prior to completion. The first prototype machine was installed at University of Tokyo’s Institute of Industrial Science, which was established in 1949, and was used for research there. Using this prototype as a reference, Watanabe Masaru, Miida Junichi, and others developed a very accurate differential analyzer with eight integrators, three input consoles (two of which were automatic tracking devices), and one output console. This machine was built by Tokyo Keisokuki Seisakusho and others.
Tokyo University of Science’s Science and Technology Museum now holds a machine that is very similar in construction to the Aeronautical Research Institute’s original differential analyzer. Because it bears the nameplate of SHOWA KOOKUU-KEIKI, the machine is thought to have been built by Showa Kookuu-Keiki and others almost at the same time as the Aviation Laboratory’s machine. There are reports that Tatsujiro Shimizu at Osaka University’s Department of Science possessed and used a differential analyzer in 1947, and because he later moved to the Tokyo University of Science via Kobe University and the University of Osaka Prefecture, it is said the differential analyzer at Osaka University was brought to the Tokyo University of Science. The differential analyzer at the Science and Technology Museum consists of three integrators, one input console, and one output console.