Team-BHP > Commercial Vehicles


Reply
  Search this Thread
259,885 views
Old 18th January 2023, 14:36   #331
Distinguished - BHPian
 
Join Date: Aug 2014
Location: Delhi-NCR
Posts: 4,042
Thanked: 63,675 Times
Re: The Indian Navy - Combat Fleet

ASW Shallow Water Corvette

One part of our Anti-Submarine Warfare {ASW}spectrum which needs cover is our ability to patrol our coastal waters around major ports/naval bases. By definition a submarine of the opposing forces would like to lurk around these places with abundant targets to fish for. Defensive ASW patrol in shallow waters is a combination of ASW patrol aircraft and many small {and cheap} ASW patrol crafts which one can risk the loss of. Waters around most Indian ports are relatively shallow especially on the Western, Southern & Bengal seaboards.

The Anti-Submarine Warfare Shallow Water Craft corvettes, are a class of small coastal anti-submarine warfare vessels currently being built for the Indian Navy, by Cochin Shipyard, Garden Reach Shipbuilders & Engineers (GRSE) and Larsen &Toubro. They were conceived as a replacement for the now retired Abhay-class corvettes of the Indian Navy, and are designed to undertake defensive anti-submarine warfare duties – including subsurface surveillance in littoral-waters, search-and-attack missions and coordinated anti-submarine warfare operations with naval aircraft. They were also designed to provide secondary duties – including minelaying and general harbour defense patrol.

A total of 16 vessels are being built for the Indian Navy and the Navy plans to have all 16 vessels in active service by 2026. Unusually while the weapons package is identical there are two separate designs by Cochin Shipyard and GRSE with 8 of each being built. L&T is acting as a sub-contractor to GRSE. Not sure why this was pursued other than to encourage shipyard’s own inhouse design teams.

The two primary ASW weapons are the RBU 6000 rocket launchers and the 324mm light weight torpedo tubes. Secondary armament is provided by the indigenous 30mm CRN91 gun and small craft defense by two remotely controlled 12.7mm heavy machine guns. The corvettes can also be used as mine layers to seed anti-submarine mines.

Quote:
Displacement: 900 tonnes
Speed: 25 knots; Range: 1800 nautical miles at 14 knots {official data; likely to be more}
Powerplant: diesels driving waterjets. These will be the largest water jet powered crafts in the IN. Waterjets improve manoeuverability and shallow water operations.
Armament:
RBU 6000 x 1
324mm torpedo tubes x 6
CRN91 30mm cannon
12.7mm remote controlled, stabilized machine guns x 2
Mines
The Indian Navy - Combat Fleet-1280pxins_trikand_f51image49.jpg
RBU 6000 – 12 barrel rocket launcher that ripple fires ASW rockets that explode at a pre-determined depth. Very effective as a cheap, unguided, repeat use ASW weapon. The IN has found this weapon very effective. A classic example of ingenious soviet design thinking.

The Indian Navy - Combat Fleet-1280pxcrn91_on_icgs_shaunak.jpg
CRN91 – a self-defense 30mm dual purpose cannon for anti-small surface craft and helicopter use. Developed from the 30mm cannon & turret of the Army’s Sarthak Infantry Fighting Vehicle. Rate of fire 300 rounds/minute. Range 4000 metres. Fire control by electro-optical unit developed by BEL, India. While at first glance the design seems a patch work and a little dumpy the IN and Coastguard are happy with it. It has been installed in over 11 classes of warships.

Name:  Arnala_class_ASW_corvette_during_launch_by_GRSE.jpg
Views: 463
Size:  52.9 KB
INS Arnala being launched in December 2022 at L&T's yard in Chennai.

Last edited by V.Narayan : 18th January 2023 at 14:39.
V.Narayan is offline   (7) Thanks
Old 18th January 2023, 15:57   #332
Distinguished - BHPian
 
Join Date: Oct 2012
Location: Delhi
Posts: 8,035
Thanked: 49,754 Times
Re: The Indian Navy - Combat Fleet

Interesting choice going for the waterjets. I am not so sure about the claim it provides better manoevrebillity. Shallow water operation might be a thing. Depends where the jets and water inlets are positioned obviously.

Water jet are not known for their efficiency, but I guess for coastal waters fuel efficiency and range are less important.

Waterjets perform
Most efficiently at high power settings. The slower you run them the worse they get.

Jeroen

Last edited by Jeroen : 18th January 2023 at 16:00.
Jeroen is offline   (2) Thanks
Old 18th January 2023, 17:37   #333
Distinguished - BHPian
 
Join Date: Aug 2014
Location: Delhi-NCR
Posts: 4,042
Thanked: 63,675 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by Jeroen View Post
Interesting choice going for the waterjets. I am not so sure about the claim it provides better manoevrebillity. Shallow water operation might be a thing. Depends where the jets and water inlets are positioned obviously.Water jet are not known for their efficiency, but I guess for coastal waters fuel efficiency and range are less important.
People typically associate water jets with leisure craft and small fast pleasure boats. To best of my knowledge based on conversations with folks who have sailed/commanded such vessels {200 to 400 tonne range} water jets help in shallow water operations and with steerable nozzles help with turning the ship almost on its own axis and in manoeuverability in general. They seem to work well in our waters as the Indian Coast Guard and Navy use it on 10 locally designed boats ranging in size from 40 to 400 tonnes.

Last edited by V.Narayan : 18th January 2023 at 17:47.
V.Narayan is offline   (1) Thanks
Old 18th January 2023, 18:18   #334
BHPian
 
Join Date: Mar 2018
Location: Bengaluru
Posts: 183
Thanked: 558 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by V.Narayan View Post
People typically associate water jets with leisure craft and small fast pleasure boats. To best of my knowledge based on conversations with folks who have sailed/commanded such vessels {200 to 400 tonne range} water jets help in shallow water operations and with steerable nozzles help with turning the ship almost on its own axis and in manoeuverability in general. They seem to work well in our waters as the Indian Coast Guard and Navy use it on 10 locally designed boats ranging in size from 40 to 400 tonnes.
Just to help with the discussion, here is video from Destin of YouTube's Smartereveryday channel showing how the jet drives enable the US Coast Guard's RBM boats perform amazing maneuvers. The video starts at the point where the jet drive is explained but I suggest going through the whole video. Its very informative.
arijitkanrar is online now   (5) Thanks
Old 18th January 2023, 18:48   #335
BHPian
 
Join Date: Aug 2017
Location: Leeds
Posts: 930
Thanked: 2,248 Times
Re: The Indian Navy - Combat Fleet

Interesting that there's two differing designs from two different yards. Any idea why? I initially thought it could be to have a Western fleet variant out of a Arabian sea yard and an Eastern fleet variant out of a Bay of Bengal yard but seems both manufacturers are on the eastern seaboard, thus ruling out that hypothesis.

You said they have the same weapons load out, what then are the differences? Superstructure? Subsystems? Propulsion?

Good to see a domestic system being utilised from a land based platform in the CRN91. Are there any other instances where something like this has been done? Seems rather prudent.

Again just out of curiosity, will 16 such littoral vessels be sufficient for the near shore ASW requirement?

What sort of unit costs do these have?

Thanks
ads11 is offline   (1) Thanks
Old 18th January 2023, 19:38   #336
Distinguished - BHPian
 
Join Date: Aug 2014
Location: Delhi-NCR
Posts: 4,042
Thanked: 63,675 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by ads11 View Post
You said they have the same weapons load out, what then are the differences? Superstructure? Subsystems? Propulsion?
Hull, auxiliary systems, IR, radar & noise signature suppression. I think there will be a follow on class as budgets permit.
Quote:
Again just out of curiosity, will 16 such littoral vessels be sufficient for the near shore ASW requirement? e
I'm no expert at force planning but I'd say 30 would have been a more appropriate number for coastal ASW and harbour defence.
Quote:
What sort of unit costs do these have?
Rs 800 crores a piece at 2019-2020 budget levels. Say Rs 900 crores with the likely budget over runs that happen. Still very cheap at a little over $100 million.
V.Narayan is offline   (2) Thanks
Old 18th January 2023, 19:44   #337
Distinguished - BHPian
 
Join Date: Oct 2012
Location: Delhi
Posts: 8,035
Thanked: 49,754 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by V.Narayan View Post
People typically associate water jets with leisure craft and small fast pleasure boats. To best of my knowledge based on conversations with folks who have sailed/commanded such vessels {200 to 400 tonne range} water jets help in shallow water operations and with steerable nozzles help with turning the ship almost on its own axis and in manoeuverability in general. They seem to work well in our waters as the Indian Coast Guard and Navy use it on 10 locally designed boats ranging in size from 40 to 400 tonnes.
Thanks. Waterjets can be found on quite large ships too. In fact I have sailed on the Stena Discovery many times. At the time the larges waterjet propelled ferry in the world. She was a 10000 Tonnes Catamaran power by 2 waterjets, and 4 gas turbines. Capable of 40-50 knots!

We have quite a few pilot boats here in the Netherlands and Belgium that have water jets.

There are also some even larger navy vessels with waterjets about. The “more manoeuvrability" is just how you want to compare. Compared to a conventional propellor and rudder the waterjet wins hands down . But at the same time, modern harbour tug or tractor with a Z-drive or similar is far more manoeuvrable than the best water jet based vessel. But it does tend to come at the expense of more draft, obviously.

Being able to work in shallow waters, without the risk of damaging a propellor blade is a huge advantage of course. But in general you will find water jet on vessel that need to sail at speeds well over 30 knots. As a very rough rule of thumb below 25-30 knots water jets become very inefficient.

From the internet:

The stand alone waterjet itself, essentially a pump, has a high efficiency of approx 90%, compared to say about 72% for propellors. However, you need to take a look at the total installation.

Such as:

Intake losses
Outlet diffuser losses
Internal skin friction
Pump efficiency
Change in elevation (outlet is higher than inlet)
Velocity ratio

The largest factor in waterjet efficiency is the ratio of velocity at the jet outlet to the inlet. This velocity ratio strongly influences the total efficiency because waterjets depend on high flowrates for efficient operation. Without any water acceleration, the jet fails to produce thrust. But if we force too much acceleration, the efficiency drops off fast.

The Indian Navy - Combat Fleet-screenshot-20230118-2.56.50-pm.png

A higher velocity ratio meant more acceleration and more thrust from a single jet, but at the cost of lower efficiency. The figure showed that changing the velocity ratio also impacted the range of efficient operation. A higher velocity ratio allowed the jet to maintain its efficiency across a wider range of ship speeds, but at the cost of lower peak efficiency. This variation in capabilities drove waterjet manufacturers to supply different models, targeted towards different speed ranges and power requirements.

In fairness to waterjets, we also need to remember the other drag elements required for propeller propulsion:

Propeller shaft drag
Propeller bracket drag
Rudder appendages
The waterjet sits flush inside the hull, with just one outlet. At speed, the exit nozzles completely clear the water. This reduces the total resistance on the vessel. We have no propeller shaft or shaft brackets to drag through the water. Another element removed: the rudder. Waterjets don’t need a rudder, because they direct the thrust through changing the direction of the outlet stream. Removing these elements already gives the waterjet an edge over propellers.

The Indian Navy - Combat Fleet-screenshot-20230118-2.57.10-pm.png

Waterjets might give you good maneuvering control and promise much higher efficiency at high speeds. But that flexibility comes with the price of more subtle limits on performance. Efficiency rapidly drops off if you install the wrong waterjet or use it at the wrong ship speed. Used incorrectly, waterjets perform worse than propellers. The critical speeds of 25 – 30 knots are the transition from propellers to waterjets.

So the dimensioning of the water jet is absolutely critical to get the best efficiency across a range of speeds. Do you happen to know who will be providing the diesel engine and water jets?

Jeroen

Last edited by Jeroen : 18th January 2023 at 19:54.
Jeroen is offline   (4) Thanks
Old 18th January 2023, 20:01   #338
Distinguished - BHPian
 
Join Date: Aug 2014
Location: Delhi-NCR
Posts: 4,042
Thanked: 63,675 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by Jeroen View Post
Do you happen to know who will be providing the diesel engine and water jets?
Thank you for this treatise on water jets. I agree they are not the most efficient and are selected for other properties. In case of the Indian Navy and Coast Guard all diesels mated to water jets are from MTU and the water jets are Rolls Royce Kamewa. I presume it will be so for this class too.
V.Narayan is offline  
Old 18th January 2023, 20:17   #339
Distinguished - BHPian
 
Join Date: Oct 2012
Location: Delhi
Posts: 8,035
Thanked: 49,754 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by V.Narayan View Post
In case of the Indian Navy and Coast Guard all diesels mated to water jets are from MTU and the water jets are Rolls Royce Kamewa. I presume it will be so for this class too.
Can’t go wrong with either I guess! You know of course Rahat Kamewa was purchased by the British Vickers PLC and subsequently acquired by RR. Which subsequently got bought by Kongsberg Maritime Sweden.

So the Kamewa Waternets never left Sweden I guess. The waterjets made today are still known and marketed as Kamewa I believe.

Jeroen
Jeroen is offline   (2) Thanks
Old 18th January 2023, 20:37   #340
Team-BHP Support
 
Gannu_1's Avatar
 
Join Date: Apr 2013
Location: Madras
Posts: 7,169
Thanked: 20,185 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by V.Narayan View Post
In case of the Indian Navy and Coast Guard all diesels mated to water jets are from MTU and the water jets are Rolls Royce Kamewa. I presume it will be so for this class too.
For the 54 Coast Guard IBs we had built, the first 6 boats had Caterpillar engines and the rest had MTU engines. All the waterjets were supplied by MJP. Just FYI.

I am not involved in the ASWSWC projects but let me find out who’s the supplier for the propulsion equipment.
Gannu_1 is offline   (5) Thanks
Old 21st February 2023, 11:55   #341
Distinguished - BHPian
 
Join Date: May 2010
Location: Bangalore
Posts: 1,886
Thanked: 11,831 Times
Re: The Indian Navy - Combat Fleet

Saw the INS Vikrant in the steel last week!

Was at Fort Kochi and watched the carrier move past, full length. Was an awesome sight and felt proud that my country made something this obviously well-engineered. How on earth do fighter pilots take-off and land on that short runway?! Real skill.

At first I didn't realize it was the Vikrant because of the pennants that resembled the Japanese flag (red circle on white). Thought there must be some Naval exercise involving Japanese ships in the area. Then I checked and realized those pennants show the Pennant number R11, the red circle on white indicating '1'.

Also, there didn't seem to be much of a wake or wash/wave being generated as it went past. There was a small boat ahead, and two more behind, could those have been tugs?

Last edited by am1m : 21st February 2023 at 11:57.
am1m is offline   (1) Thanks
Old 22nd February 2023, 11:01   #342
BHPian
 
adi.mariner's Avatar
 
Join Date: Mar 2019
Location: Pune
Posts: 522
Thanked: 1,276 Times
Re: The Indian Navy - Combat Fleet

A couple of warships at Mumbai Anchorage.
Attached Thumbnails
The Indian Navy - Combat Fleet-img_20230221_130739.jpg  

The Indian Navy - Combat Fleet-img_20230218_111736.jpg  

adi.mariner is offline   (4) Thanks
Old 23rd April 2023, 12:51   #343
BHPian
 
dragracer567's Avatar
 
Join Date: Aug 2019
Location: Bahrain
Posts: 932
Thanked: 4,965 Times
Re: The Indian Navy - Combat Fleet

Just out of curiosity, is there any update on the Nilgiri class frigates? The first ship INS Nilgiri was supposed to have been commissioned in 2022 but got pushed to 2023 (IIRC) - but there is no news about sea trials et al. as was the case with the Visakhapatnam class destroyers.

Given these ships were destined for the Eastern Naval Command (again, IIRC), these will likely be the most potent ships in that fleet surpassing even the destroyers in that fleet - key for keeping the Chinese in check in the IOR.
dragracer567 is offline   (1) Thanks
Old 25th April 2023, 15:29   #344
BHPian
 
dragracer567's Avatar
 
Join Date: Aug 2019
Location: Bahrain
Posts: 932
Thanked: 4,965 Times
Re: The Indian Navy - Combat Fleet

INS Sumedha - a 2,200 tonne Saryu class patrol vessel has reached Port Sudan and is evacuating 500 Indians from Sudan who were transported to the Port Sudan by the embassy across very long distances consisting of potentially hostile territory (Khartoum where most foreigners were based is 850 km from Port Sudan). Evacuations are in full swing with Saudi Arabia, US, UK, UAE and EU all having evacuated their staff in ‘challenging missions’ with the French evacuation taking fire and rumours of a Saudia A330 actually being set on fire. India also has two C130J Hercules on standby at the Red Sea port city of Jeddah in Saudi Arabia. If I get time, I’ll post more on the air evacuations by other countries as well.

The Indian Navy - Combat Fleet-497861110fdd4b6e85c7370fc3e24978.jpeg

Could someone please explain why the ship is also flying a Sudan flag?

The Indian Navy - Combat Fleet-46613ac91b7e4859982a8752b536a60d.jpeg

Last edited by libranof1987 : 25th April 2023 at 17:48. Reason: Minor typo
dragracer567 is offline   (4) Thanks
Old 25th April 2023, 17:17   #345
BHPian
 
Join Date: Aug 2017
Location: Leeds
Posts: 930
Thanked: 2,248 Times
Re: The Indian Navy - Combat Fleet

Quote:
Originally Posted by dragracer567 View Post
INS Sumedha - a 2,200 tonne Saryu class patrol vessel has reached Port Sudan and is evacuating 500 Indians from Sudan who were transported to the Port Sudan
Credit where credit is due. Really heartening to see how proactive the Indian govt has been with rescue and repatriation efforts of Indian nationals in a number of recent crises. The logistics and skills involved to coordinate such an endeavour is no less rigorous than any wartime exercise so this is a good indicator for the armed forces as well in their ability to rapidly deploy assets.

What I've heard from friends & folks on the ground in Khartoum is that it's truly gnarly, so it can't have been easy for any of the forces exfiltrating their nationals from the mess unfolding in Sudan.

Quote:
Could something please explain why the ship is also flying a Sudan flag?
I wager it must be tied to naval tradition somehow. Is it like a courtesy thing? I'll wait for the more knowledgeable members to chip in though.

Last edited by libranof1987 : 25th April 2023 at 17:49. Reason: Trimming quoted post
ads11 is offline   (5) Thanks
Reply

Most Viewed
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Copyright ©2000 - 2024, Team-BHP.com
Proudly powered by E2E Networks