CDR Tomonaga, one of the two Japanese officers who committed suicide on U-234 when Germany surrendered and who decided they could not fall into American hands. Tomonaga was the inventor of two unique submarine technologies.

In the AUTOMATIC HANGING DEVICE, a sensor was used to measure the weight of the submarine relative to the weight of the water; and the inflow and the outflow of the water into or out of the ballast tanks were automatically controlled through the use of compressed air, enabling the submarine to maintain a predetermined depth without turning its propellers.

In the fuel oil leakage prevention device, a small pump was installed in the fuel tank, creating negative pressure, so that oil might not escape even if the tank was ruptured. Japanese submarines used them very successfully.”