I suspect that many of you readers (yes, all three of you) will go “well, duh!” about this, but it was only last week that I figured out the significance of nuclear submarines. It’s the oxygen.
Diesel-powered submarines use combustion engines to provide power and charge the sub’s batteries. And just like every other combustion engine, they use a mixture of fuel and oxygen to run. Diesel fuel is stored on board, as is a certain amount of oxygen. But the crew on board use oxygen, too, and the engines use it up quickly. As a result, diesel subs have to surface regularly to refresh their air–both for the crew and for the engines.
Nuclear subs run on nuclear-powered engines. These engines use the heat of nuclear fission to drive steam turbines, which in turn charge the batteries. But this process doesn’t “burn” any fuel, and so doesn’t consume any (or much) oxygen. Which means that the oxygen stores on board can be used purely for for the crew. So a nuclear sub can stay underwater much longer than a conventional sub with the same amount of oxygen on board.
There’s also a matter of nuclear fuel being more compact than diesel, and nuclear engines being more efficient in their power output than diesel engines, but the real key is their ability to go stay under for longer. This provides a real strategic and tactical operational advantage. In the amazing book Body of Secrets, James Bamford describes how the USS Halfbeak, while on a spying mission off the northern coast of Russia, was forced to stay under water for just a matter of days:
“Eventually the oily air began turning thin and rancid. The captain passed the word to break out the carbon dioxide absorbent–cans of powder would be spread on bunks to help draw the deadly gas from the air. Nevertheless, the sub’s doctor warned that the oxygen levels were becoming dangerously low. Sailors, including Cassidy, passed out and had to be revived. Two large oxygen cannisters were placed in the central part of the sub, and it was suggested that those who felt faint should take a few deep breaths from the masks attached.”
Nuclear submarines can stay submerged for weeks rather than days.
Bamford’s book is a eye-popping must-read, and I’m only half-way through. I’ll write more about it once I’ve finished it.
Patrick Robinson has written a book called Barracuda 945, it plays out an interesting scenario which highlights the threat of nuclear submarines if they were to get into the hands of terrorists. It is not a great book, the characters lack a bit of substance, but is worth a read.