Also please note that a Missouri was supposed to be able to hit 27kts with only 1/2 of it's boilers lit. AND more compact which means less armor.Īs far as speed goes please not that although there were other improvements the extra 4-5 knots that a Missouri had over a South Dakota were bought with most of the 10,000 ton and 200ft differences between the ships. Throw in double reduction gear sets between the turbines and the props and the weight per HP of an early 1930s steam plant was waaaay lower than even a 1916/7 steam plant of the same power. Together with the oil fuel it meant one big boiler could do the work of 3-4 smaller ones but be lighter and require much less crew. Other big changes were small tube boilers (less weight per ton of water turned to steam), Higher pressures and lots more super heat (some navies carried it too far) which also reduced the boiler weight per pound of steam. Battle ships also have much heavier armor over the machinery spaces so an increase in power plant size causes a disproportionate increase in armor weight which causes the hull to be bigger to "float" the armor which requires more power for the same speed.Īs with many other things, technological advances came in fairly short order so comparing a 1950s ship to a 1930s ship (or engine) doesn't tell us much. More decks and more armor have to be removed to get major power plant pieces into and out of the ship once it is built. Reliability for combat operations and durability because it is a much bigger project to replace battleship power plants. The Diesels need more foot print or volume per horsepower than steam turbines and battleship power plants were built "heavier" than cruiser power plants for both reliability and durability. Even with Steam turbines there is a limit as to how much power you can put through each shaft (or through each propeller?). The difference between 28 and 30 or 30 and 32 knots. Battleships could need 20-30,000 more hp for an extra TWO knots.
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