system performed substantially worse than designed. In particular, very poor jointing between the upper-belt and lower-belt armor created a rupture-prone seam just below the waterline. When combined with the relatively shallow system depth and the lack of liquid loading, this caused the class to be susceptible to torpedoes. Joint failures have been attributed to the considerable damage inflicted upon Yamato from a single torpedo impact in 1943, and to the sinking of Shinano from four hits in 1944. Propulsion The Yamato class was fitted with 12 Kampon boilers, which powered quadruple steam turbines, with an indicated horsepower of 147,948 (). These, in turn, drove four propellers. This powerplant enabled the Yamato class to achieve a top speed of . With this speed, the Yamato class' ability to function alongside fast carriers was limited. In addition, the fuel consumption rate of both battleships was very high. As a result, neither battleship was used in combat during the Solomon Islands Campaign or the minor battles during the "island hopping" period of 1943 and early 1944. The propulsion system of Shinano was slightly improved, allowing the carrier to achieve a top speed of . "Super Yamato"-class battleships Two battleships of an entirely new and larger design were planned as a part of the 1942 fleet replenishment program. Designated as Design A-150 and initially named Warship Number 178 and Warship Number 179, plans for the ships began soon after the design of the Yamato class was finished, probably in 1938–39. Everything was "essentially completed" sometime in 1941, but with war on the horizon, work on the battleships was halted to fill a need for additional warships, such as aircraft carriers and cruisers, to replace war losses of those vital ships. The Japanese loss in the Battle of Midway, where four carriers were sunk (out of ten, to date, in the entire navy), made it certain that work on the ships would never begin. In the third volume of their Battleships series, Axis and Neutral Battleships in World War II, the authors William H. Garzke and Robert O. Dulin asserted that these ships would have been the "most powerful battleships in history" because of their massive main battery and extensive anti-aircraft weaponry. Similar to the fate of papers relating to the Yamato class, most papers and all plans relating to the class were destroyed to prevent capture at the end of the war. It is