text: When I talk about Anti-Submarine Warfare , it wouldn’t be a complete description without explaining about the submarines which are being hunted. So I’ll explain in depth about Diesel-Electric submarines in this post.
  As their name suggests, Diesel-Electric submarines run on diesel and electricity. They have a large network of batteries which are charged by the diesel generator. These submarines have to come up to the surface in order to charge their batteries . They snorkel, which means, travelling just below the surface of the water with the periscope and the diesel generator exhaust pipe above the water surface. Once they charge their batteries, they dive into the ocean and run silently on battery power with the diesel generators shut down. After running for a few days underwater, the battery gets drained and these submarines have to surface again to recharge their batteries. Diesel-Electric submarines are also extensively referred to as SSK (Sub Surface Killer) or popularly called as diesels.
  - Produce very less noise compared to their nuclear counterparts
  - Small and agile which makes them deadly in shallow water regions
  - Can shut down/switch on engines whenever needed unlike nuclear boats which have reactor running 24×7
  - Relatively easy to procure, train crew and operate
  - Modern SSKs have Land Attack capability like SSNs
  Diesels were considered noisy and slow earlier, but modern sound suppression systems, improved designs have resulted in the diesels being considered the deadliest submarines in littoral warfare especially because of their ability to shut down their generators and produce almost ZERO noise. They can just stay dead in the water to avoid detection. Modern technology like Air Independent Propulsion System (AIPS) have enabled the diesels to do stay underwater for a period of almost a week compared to the 1-2 days underwater endurance of the non-AIPS equipped subs. Typically diesels can dive to a depth of 150-300 m and have an underwater speed of 15-20 knots.
  Modern navies have started to incline towards nuclear submarines, but some navies like Russia, China and India operate a large number of Diesels along with their nuclear subs. The advantages offered by these submarines cannot be matched by nuclear ones. Diesel subs are comparatively cheap and even small navies can acquire and operate them. Submarines like Type 212, Improved Kilo, Scorpene and Soryu are some of the most modern diesels. The Type 212 is famous for being very small and quiet and has a tiny crew complement of around 30 men. The improved Kilo class is quieter and has additional firepower. It can also fire the 300 km range Klub Anti-Ship missile from its torpedo tubes. Soryu class is comparatively large and has a better endurance compared to smaller subs. However despite all their advantages, they have drawbacks as well.
  - Top speed when submerged is around 15-20 knots and makes it impossible for them to outrun torpedoes or ASW ships
  - Diving depth is limited to 150-300m which makes them vulnerable in deep water regions where they cant use depth for concealment
  - Underwater endurace is limited and ranges from a few hours to a week if AIP is used
  - Small weapons complement of 12-20 torpedoes/missiles (exceptions like Soryu exist)
  - Generally very cramped which makes long deployments very unpleasant
  Now you know that modern diesels are extremely quiet and can stay underwater for a week. Add the ability to fire cruise missiles and torpedoes to them, now they become extremely dangerous in combat, especially in shallow water regions. That’s why they must be detected as early as possible in a conflict and destroyed using adequate techniques and assets which has been covered in my next article here
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