Indian Navy News & Discussion - 03 July 2018

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Austin
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Austin » 03 Nov 2019 11:21

There's a Case for Diesels , By Ensigns Michael Walker and Austin Krusz, U.S. Navy
https://www.usni.org/magazines/proceedi ... se-diesels

The ability of AIP was demonstrated in 2005, when HMS Gotland, a Swedish AIP submarine, “sank” many U.S. nuclear fast-attack subs, destroyers, frigates, cruisers, and even the USS Ronald Reagan (CVN-76) aircraft carrier in joint exercises.11

arvin
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Re: Indian Navy News & Discussion - 03 July 2018

Postby arvin » 03 Nov 2019 11:57

Austin wrote:
Another thing is it is not a good idea to add AIP post submarine construction as they will have to cut the submarine and insert an AIP module which is a big task in itself and adding additional module impact the Submarine acoustic capability and speed because additional few meter plug would come with its own complication. (flow noise , quitening ,drag )



Agree on this. Is there a precedent of a plug like this added on a working vessel?

Replacing lead acid battery with Li ion should give some good endurance boost. Sindhurakshak could have been used as a test bed to work out the proof of concept.

Austin
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Austin » 03 Nov 2019 12:28

Ofcourse they can add that if they qualify DRDO AIP for Sub Based deployment after due testing.

But adding any module post construction is not a good idea because it has impact on submarine performance , An more practical and easier approach would have been to use the proven French MESMA AIP and built a sub with scratch around that AIP that way they can consider this from design stage and optimise the design for the sub rather than be an after thought.

Aditya_V
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Aditya_V » 03 Nov 2019 15:11

I think the IN evaluated the MESMA AIP and did not find it too its liking, from day 1 the Scorpenes were planned for AIP, it has taken DRDO longer than expected. The last 3 IN boats were given a separate class since it was expected the Fuel cell based AIP would have been ready before they were launched. So can't say this is an afterthought.

Manish_Sharma
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Manish_Sharma » 03 Nov 2019 18:42

Porkistani agosta's mesma system came cropper, Nausena evaluation of MESMA also failed to impress, at the most it'd have been a decorative piece. Our own research will better as it's done according to our needs. French have no need to make mesma sophisticated as they only operate nuke submarines.

Aditya_V
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Aditya_V » 03 Nov 2019 18:57

Article regarding AIP

https://nationalinterest.org/blog/the-buzz/air-independent-propulsion-submarines-stealth-cheap-the-24245

https://defencyclopedia.com/2016/07/06/explained-how-air-independent-propulsion-aip-works/

The types of AIP systems are

Closed Cycle Diesel Engines
Closed Cycle Steam Turbines
Sterling Cycle Engines
Fuel Cells


The French MESMA (Module d’Energie Sous-Marine Autonome / Autonomous Submarine Energy Module ) is the only such system available and it makes use of ethanol and oxygen as energy sources. The combustion of ethanol and oxygen under high pressure is used to generate steam. The steam generated is the working fluid and is used to run the turbine. The high pressure combustion allows the exhaust carbon dioxide to be expelled outside into the sea at any depth without making use of a compressor.
The advantage of MESMA is it’s higher power output when compared to the alternatives which allows higher underwater speeds but it’s major drawback is it’s lower efficiency. Also the rate of oxygen consumption is said to be very high and these systems are very complex. These drawbacks make several navies opt for sterling cycle and fuel cell alternatives.


Fuel cells are the most advanced and preferred AIP technology today. This is because of the major advantages they offer in stealthiness and power generation. They contribute to the stealthiness of the sub as Fuel Cells have almost no moving parts, which significantly reduces the acoustic signature of the sub. Fuel Cells can achieve an efficiency of over 80% under certain circumstances. They can also be scaled easily into large or small sizes depending on the displacement of the submarine. This is easier than developing different systems for each submarine class. Hydrogen Fuel Cells are also very environment friendly as they generate no exhaust fumes, which in turn eliminates the need to have special exhaust scrubbing and disposal machinery. The only drawback is that they are expensive and complex.



This completly makes sense, Navy and DRDO are working on something which is really cutting edge hence obviously there would have been unforseen challenges, looks like we are over the major hurdles and we are onto something good here.

Looks like Navy/ DRDO went for fuel amoung advantages it can be scaled up for Project 75 and also reasonably quickly.

And for those wanting why not Saryu- notice Japs use Stirling AIP

As of 2016, the following countries have developed their own AIP systems to be fitted on submarines.
Germany – Fuel Cell
Sweden – Stirling
Japan – Stirling
France – MESMA
Spain – Fuel Cell
India – Fuel Cell
Russia – Fuel Cell
People’s Republic of China – Stirling


LIMITATIONS OF AIP

Other than Fuel Cells, the 3 remaining technologies have a lot of moving parts which generate noise. This is not desirable as quietness is very essential for all submarines. So by using Stirling, MESMA and CCD AIP systems, submarines will be sacrificing some of their stealthiness for additional endurance.
Even though Fuel Cell AIP has many advantages, it is extremely expensive to procure and maintain them.
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.


But given our Arabian Sea shelf depth and unlike USA/USSR which dont have defend home bases, we probably need a green water Navy component, so we need SSP/SSN combo and can't go for pure SSN force.

Aditya_V
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Re: Indian Navy News & Discussion - 03 July 2018

Postby Aditya_V » 03 Nov 2019 19:14

And FInally this scenario I really like, No one will venture from Karachi and Gwadar with the PN Surface and underwater fleet sunk

he advantage offered by increased underwater endurance can be used for ‘ambushing’ an approaching fleet. In one such scenario, an AIP equipped submarine can roam near a strait, waiting for its target to approach. The sub will be running at ultra-quiet speeds of 2-4 knots for several weeks and then attack the target when it appears, using its torpedoes. Even though a non-AIP equipped sub can do the same thing, it’s waiting period, which is very essential for an underwater ambush, is significantly lesser.

In another scenario, an AIP equipped sub can roam near enemy territory for far longer compared to a non-AIP sub. Thus in this situation where intelligence is gathered and spy missions are performed, AIP gives these quiet diesel subs an advantage by allowing them to loiter for weeks without the need to surface.

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Re: Indian Navy News & Discussion - 03 July 2018

Postby Philip » 05 Nov 2019 17:48

What we also need are long endurance UUVs some which could have limited armament.These are perfect for sanitising the chokepoints and guarding approaches to major naval bases and ports.They would relieve manned subs from such mindane tasks enabling them to perform more offensive missions in far- off waters.

However, even the best AIP sub cannot compare with the performance of a nuclear sub which apart from greater UW endurance and speed, carries greater weaponry, decoys, etc.
The lease of a second Akula announced a year ago was good news, but given the needs of the day, the lease of 2 more Akulas would give us a total of 4, which can arrive by 2025+ , of which two would be available at any time of crisis.These SSGNs would be the perfect complement to our desi- built 6 SSNs which going by the Arihant experience will when the first arrives hopefully in the middle of the next decade, be built at the rate of one every 18 to 24 months . 10 SSGN/SSNs would be ideal as the SSNs would have extra duties to protect our SSBNs when required.

What the IN must not succumb to is to try and design/ acquire a large expensive conventional boat which is the equivalent of a " pretender" to a nuclear boat which Oz is trying to do with the French. A former admiral said that the only true AIP sub was a nuclear powered boat. We also need given the huge numbers of PLAN subs in service and being built- as well as 8 AIP Yuans for Pak, large numbers of cost- effective conv. boats like our existing very silent
Kilo class, built quickly at low cost with a v.high capability that even today armed with Klub/ Kalibir missiles seen in action in Syria, are giving western navies nightmares.Kalibir equipped boats with a 2500km range could also in a crisis carry N- tipped warheads, complicating the task of our enemies in locating our second- strike strategic deterrent.


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