Question

Which of the following statements with regard to 'Air Independent' propulsion technology used in submarines is/are not correct?

1. Using this technology, the submarine generates its own oxygen so it works independently of atmospheric oxygen for its entire life.
2. It ensures the low acoustic signatures (sound emissions) for submarines.
3. The technology can be retrofitted into existing submarine hulls by inserting an additional hull section.

Select the correct answer using the options given below.
(a) 1 only
(b) 2 only
(c) 1 and 3 only
(d) 2 and 3 only​

Answer 1

Option A - 1 Only

■ Explanation :-

• The DRDO recently tested a land-based prototype of an Air Independent Propulsion (AIP) submarine.

• Submarines are essentially of two types :- conventional and nuclear.

☆ Conventional submarines use a diesel-electric engine, and must surface daily for oxygen for fuel combustion. They are optimised for stealth, and their weapons and sensors provide for effective operations close to the shore. Because diesel-electric submarines require to come to the surface frequently to charge their batteries, their underwater endurance time is less.

• Air-independent’ propulsion technology helps to make the diesel generator less dependent on surface air. If fitted with an Air Independent Propulsion (AIP) system, the submarine needs to take in oxygen only once a week. Hence option (a) is not correct.

• In a fuel cell AIP, an electrolytic fuel cell releases energy by combining hydrogen and oxygen, with only water as the waste product. The cells are highly efficient, and do not have moving parts, thus ensuring that the submarine has a low acoustic signature. Hence option (b) is correct.

• It also enhances the submerged endurance of diesel-electric submarines several times, thus having a multiplier effect on its lethality. This technology can be ìnstalled on existing older generation submarines by inserting a new hull section during a retrofit. Hence option (c) is correct.

• Although nuclear submarines offer far better endurance and speeds, they are unsuitable for the shallow littoral waters and most navies cannot afford to build and maintain them as they are very expensive. Also diesel submarines possess the advantage of being able to switch off their engines completely and lie in wait unlike nuclear submarines whose reactors cannot be switched off at will.

• Even though Fuel Cell AIP has many advantages, it is extremely expensive to procure and maintain them. Other limitation is submarines which use AIP need to sail at speeds of less than 10 kts in order to achieve exceptional endurance of 14-18 days as advertised. In comparison, a nuclear powered sub can travel for an unlimited distance at 30-35 kts without sacrificing endurance. So AIP equipped submarines cannot replace nuclear submarines when it comes to blue water or extended period operations.

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