Diesel-Electric Submarine (SSK)

A diesel-electric submarine, NATO hull symbol SSK, runs surfaced or snorkeling on diesel generators that charge a battery, then runs submerged on the battery driving an electric motor. The diesels need atmospheric oxygen, so the boat must snorkel periodically, the main detection vulnerability. SSKs are quieter than nuclear boats when on battery and far cheaper, making them effective in littoral and chokepoint defense. Many modern SSKs add air-independent propulsion to stretch the dived endurance. Examples include the German Type 212, Russian Kilo, French Scorpene, and Australian Collins classes.