[Jeroen]

Originally Posted by Ameya Janvekar

I think the noise component of nuc boats, alongwith the expansion & passage of steam, is also of the pumps which are used to circulate the coolant in the reactor unit.



Had read somewhere that to minimise this noise & harmonic during close quarter manuvers, newer design reactors use a coolant system when during low power setting, the coolant circulates naturally ( forgot the actual tech name for this phenomenon ).



Also if I am not wrong, these pumps etc need to be mounted on mounts / isolators / dampers to prevent the transmission of the same to the hull.



Even if the sub is purely drifting, the reactor coolant pumps will be running & this will always make a minimum noise whereas for a Diesel-Electric sub, once the motor is stopped, there will be no mechanical hamonics / vibrations etc.



Would recommend if possible & if you enjoy the topic of subs, to read a superb novel titled THE HUNT FOR RED OCTOBER by Tom Clancy. It has superb detailing as for the equipment, tactic etc used by & againt subs. Yes the technology & tactics have since evolved, but a gripping tale till the end.

Yes, the pumps do make some noise and at low power settings most if not all mechanical things are shut down and everything relies on natural circulation one way or the other. But the steam flows at very high speeds and expands at the turbine and then condense into water in the condenser. That is much more difficult to completely eliminate.

I have read the book and seen the movie, both are quite good. Although a bit dated I would imagine. Im not sure how much Russia. (Nuclear) sub design has moved on during the last decade. The US certainly did, apparently.

Jeroen

[Jeroen]

Originally Posted by Jeroen

Yes, the pumps do make some noise and at low power settings most if not all mechanical things are shut down and everything relies on natural circulation one way or the other. But the steam flows at very high speeds and expands at the turbine and then condense into water in the condenser. That is much more difficult to completely eliminate.

My thesis during my last year at naval college was on "prediction and prevention of vibration during design". Vibration and noise are not the same, but they are closely related of course. Mind you, I graduated in the late seventies, so my knowledge is pretty dated to say the least.

The easiest bits and pieces of ship machinery to design vibration free are all rotating machinery, excluding combustion engines. They present some additional challenges, including exhaust gasses that can certainly produce a lot of noise and vibration.

The masterpiece of my thesis was a computer simulation program. It gave a ship designer some rudimentary insights into what vibration to expect and to quantify the effects of certain insulation techniques. When I say rudimentary, it was very very basic. Our college did not have its own computer. We were allowed so many minutes per student on some other university computer. Also, we had to program in Basic/Fortran using punch cards! Anybody ever had to program by means of punch cards? It's no fun and very tedious.

I would love to see some of the very advanced design tools they use for subs these days. Virtually no chance I would guess. From all military services the submarines are probably the most protected in terms of the design and performance of their weaponry the world over.

Jeroen

[V.Narayan]

In addition to raft mounted machinery discussed in posts above submarines today are covered with anechoic tiles made of synthetic polymer containing thousands of tiny voids (holes). They serve two functions - (1) To absorb the sound waves of active sonar (from the enemy) thus reducing and distorting the return signal and thereby reducing its effective range. (2) To reduce the sounds emitted from within the boat, typically its engines and auxiliary machinery, to reduce the range at which the submarine herself can be detected by passive sonar.The modern materials consist of a number of layers and many different sized voids, each targeted at a specific sound frequency range at different depths. Different materials are sometimes used in different areas of the submarine to better absorb specific frequencies associated with machinery at that location inside the hull. The Soviets were the first to deploy this as a standard practice in the early 1970s and shocked the Americans with its effectiveness. The British and the US Navy adopted it in 1980. Today most but not all submarines are layered with anechoic tiles. Challenges remain with the adhesives which at times give way causing the tile to fall off underwater. As with many things to do with submarines this was invented by the Germans in WW2 but the adhesive problem proved too difficult to solve practically. Photo below is a close up of a British sub revealing its tiles and a few from the front of the fin having fallen off.

[Jeroen]

Here's something I never quite understood about these anechoic tiles. I get the fact that they absorb sonar waves and even the sounds coming from within.

But when I look at pictures of subs with these tiles it never looks like a particular smooth surface. It looks like a, well, frankly tiled surface! Doesn't that create problems and create sounds (even maybe cavitation) as the sub moves through the water? At slow speeds it would probably not matter much, but these tiled subs don't look like very smooth shapes anymore.

Any thought?

[V.Narayan]

INS Arihant - Nuclear powered Ballistic missile Submarine -India's first

http://www.financialexpress.com/indi...o-know/422327/
http://www.firstpost.com/india/ins-a...e-3058412.html
http://thediplomat.com/2016/10/india...deadliest-sub/

News reports indicate that the Indian Navy has quietly put into operations its first nuclear powered ballistic missile submarine INS Arihant (Arihant in Sanskrit means Slayer of Enemies). The Indian Navy has remained tight lipped. The lead vessel of the class, INS Arihant was launched in 2009 and after extensive sea trials, was confirmed as ready for operations in February 2016. Arihant is the first ballistic missile submarine to have been built by a country other than one of the five permanent members of the United Nations Security Council.

The submarine has four launch tubes that and can carry up to 12 K-15 Sagarika missiles with one warhead each (with a range of 750 km) or 4 K-4 missiles (with a range of 3,500 km). The true enabler for the Arihant to carry out a full deterrence mission vis-à-vis China will be the K-4 SLBM being developed by DRDO with a range capability of ~3500 km. The K-4 would allow the Arihant to undertake patrol missions from the Bay of Bengal far from the fulcrum of China’s anti-submarine warfare capability.

Approximate details in the public domain are:

Displacement, dived: ~6000 tonnes
Length: ~110 metres
Propulsion: pressurized water cooled nuclear steam turbines
Torpedo tubes: 6
Missile silos: 12 shorter ranged K-15 or 4 longer ranged K-4
Speed diving depth are not known and can only be guessed at.

INS Arihant represents successful development of 3 disparate technologies and mating them into one weapon system - ballistic missiles, nuclear power and a large submarine hull. It is believed the Russians assisted us with the miniaturiztion of the nuclear plant to fit into the confines of the hull. A second vessel of this class is also under construction, INS Aridhaman.

Nuclear power and ballistic missiles are topics that can have many divergent points of view. For now I am not getting into a debate

Let us salute the men & women who designed and built INS Arihant and the naval officers & sailors who will sail her for the next 25 odd years. Jai Hind

PS: No official photo has been released. The news articles on the net show all kinds of other submarines as INS Arihant!! Below is an artists rendition and is purely indicative

[akshay380]

A good family friend worked on this project from 1989 but never told even his wife about this. Even his Russia trips were disguised as visit to Vizag. On the day this was unveiled last year, he called and told me about his role. Lucky guy.

[V.Narayan]

Second Kalvari class submarine launched today

Today Mazagon Docks launched the Indian Navy's second Scorpene class submarine INS Khanderi. This follows the first INS Kalvari which was launched in October 2015 and is currently undergoing sea trials and final fit out and expected to join the fleet in March 2017. The last time India built submarines was 25 years ago in the late 80s- early 90s time frame to an excellent German design. Sadly lack of funds, the country's economic woes, accusations against HDW etc saw that programme end in a whimper and a loss of skill and competency building for the nation and our Navy.

The Scorpene is a modern and very successful French design being built in India under license. The current license is for 6 boats.

A Scorpene submarine displaces ~1800 tonnes submerged and can cruise underwater on a single battery charge for 550 nautical miles (~1000kms) at 5 knots (~9 kmph). While the top speed is publicly stated to be 20 knots it is not so important for a submarine which is the original stealth weapon. How long it can cruise silently ie at or below 5 knots is the key for a submarine. And the Scorpene is said to be very very silent. Of course this is the 'official' figure and the real capability will be greater. Quite possible that she can loiter at 3 to 4 knots for 10 to 15 days or more. It is stated that on diesels she can run 6500 nautical miles (12,000 kms) at 8 knots. These figures are usually understated in an understated way!. Our Foxtrot subs of 50 years ago could sail 20,000 nautical miles (37,000 kms) on their diesels!!

The vessel is equipped with 18 long range 533mm torpedoes that can be used against either submarines or ships. It can also carry Exocet SM.39 anti-ship missiles which are launched from underwater (thus keeping the submarine safer than it would be on the surface). The Exocet SM.39 can attack a ship at ranges upto 110 kms after being fired underwater through the torpedo tube. She is also equipped for other key tasks such as laying mines, inserting commando teams ashore, gathering radio intelligence off enemy coasts amongst others.

I am glad to see the Navy making steady progress as a ship builders Navy. Jai Hind.


INS Khanderi, the second Scorpene class submarine launched today at Mazagon Docks



INS Khanderi on a pontoon, ready for launch. She is named for an island fort built by Maharaj Shivaji 20 kms south of Mumbai



INS Kalvari, the first of the class at sea trials. To be commissioned into the fleet later this year



Underwater launch of a Exocet anti-ship sea skimming missile. The last photo on the right shows the missile breaking away from the torpedo casing



Model of a Exocet within its torpedo casing needed for launch from underwater


http://indianexpress.com/article/ind...umbai-4470239/

[V.Narayan]

Navy says INS Kalvari will commission in July-August this year. Weapon Trials successful.
It will be the first conventional submarine built in India to commission in a quarter century


http://timesofindia.indiatimes.com/i...w/58930934.cms
http://www.hindustantimes.com/india-...qg3LgDxsJ.html

INS Kalvari India's first Scorpene class submarine has completed its weapon trials according to press releases. It is attribute to the men and women of Mazagon Docks who have built this boat. The welding and metallurgy of a submarine hull is of a uniquely complex standard and mastering it is an art.

The fact that we had to wait a quarter century to once again be building our own diesel-electric subs is a function of the short sightedness of the then Governments who tossed out our long term contract with HDW, Germany over unproven allegations. The politicians indulged in the corruption while the Submarine Arm bore its consequences.

This year in December the Indian Naval Submarine Arm completes 50 fine years. A big post on that will follow at that time

INS Kalvari

[n.devdath]

Originally Posted by V.Narayan

The fact that we had to wait a quarter century to once again be building our own diesel-electric subs is a function of the short sightedness of the then Governments who tossed out our long term contract with HDW, Germany over unproven allegations.

Very well put. In fact, it is high time we had nuclear powered subs with us by now but with the kind of speeds we maintain to build and commission diesel-electric vessels, a nuclear powered sub would take half a century.

All the best to the officers and sailors though....!!!

[Shreyans_Jain]

Originally Posted by n.devdath

Very well put. In fact, it is high time we had nuclear powered subs with us by now but with the kind of speeds we maintain to build and commission diesel-electric vessels, a nuclear powered sub would take half a century.

All the best to the officers and sailors though....!!!

We have a nuclear powered sub: INS Arihant

One sub is built. I believe 3 more are to be made.

[V.Narayan]

Originally Posted by n.devdath

Very well put. In fact, it is high time we had nuclear powered subs with us by now

We have built one INS Arihant and are building a second INS Ardhiman. We have one on long term lease from Russia INS Chakra. Given that a nuclear submarine is a strategic stealth weapon of deterrence a handful is more than enough.

but with the kind of speeds we maintain to build and commission diesel-electric vessels, a nuclear powered sub would take half a century.

With the Scorpene building programme we should have six new modern boats in over the next 8 years.

On a separate note - building nuclear boats is as we know is a complex project requiring many difficult to produce parts and difficult to source metals. So even countries like France and UK have concluded they cannot build more than on submarine every two or three years.

[V.Narayan]

Originally Posted by V.Narayan

Navy says INS Kalvari will commission in July-August this year. Weapon Trials successful.
It will be the first conventional submarine built in India to commission in a quarter century

http://www.business-standard.com/art...1700746_1.html
First Scorpene ready, PM Modi to commission INS Kalvari next month
The Navy will invite Prime Minister Narendra Modi to formally commission the vessel.....more on the sub when the commissioning happens.

[V.Narayan]

Indian Navy kick-starts process to build 6 nuclear powered attack submarines

Naval Chief Sunil Lanba's press quote below. For those who need to know a nuclear powered attack submarine is a large fast boat designed to hunt and kill ships and other submarines. Most these days will also carry a few cruise missiles to attack land targets with. Their unlimited endurance enables them to hide in the depths of the oceans below acoustic and thermal layers virtually invisible to active sonars.

India kick-started the process to build six nuclear-powered attack submarines which will significantly boost the Navy’s overall strike capabilities in the face of China’s growing military maneuvering in the Indo- Pacific region.

“It has kicked off and I will leave it at that. It is a classified project. The process has started,” Navy Chief Admiral Sunil Lanba said on Friday.

He said the Navy will play its role in the Indo-Pacific region when the much talked about quadrilateral coalition among India, Australia, Japan and the US takes shape, reflecting the Navy’s readiness to play a much assertive role in the critical sea lanes.

In a major move, officials of the four countries earlier this month had set the ball rolling to pursue their common interests in the strategically important Indo-Pacific region where China has been aggressively expanding its military presence.

“We are all aware of the prevailing security scenario in our maritime domain. The continued presence of both traditional and non-traditional threats in the maritime domain demand constant attention and robust mitigating measures,” he told a press conference.

On Chinese presence in the strategically-important Gwadar port in Pakistan, he said it may be a security challenge for India in future.

“It will be a security challenge. We will have to look at it and mitigate,” he said.

http://www.hindustantimes.com/india-...M5zhoCvIM.html

[Sutripta]

Any insights into the Chakra accident?

Regards
Sutripta

[V.Narayan]

Originally Posted by Sutripta

Any insights into the Chakra accident?

Regards
Sutripta

Regret I cant offer much as news releases, quite understandably, have been sparse. While there is media speculation as to where it occurred and how it occurred all of it is only speculation.

Having said this the main sonar in Russian and British submarines is usually in the chin position up in the forward ie the bottom half of the bow. The Americans and Japanese install it in the nose or tip of the bow - just different operational doctrines. A submarines could scrap the bottom of the sea bed in waters less than 2000 feet of depth simply because that is where the boat operates. Different layers of sea water have slightly varying saline densities. As a sub cruises from one layer/patch and into another the boat's buoyancy will suddenly alter due to change in density causing it to pitch up or down in a second before she can be trimmed back again. A 0.5% variation in density could mean a 40 to 50 tonne variation in buoyancy in an instant for a sub this size.

If the damage is restricted to a sonar dome then it is not structural and to that extent less of a challenge. The sonar dome is a relatively fragile part made of softer materials transparent to sound. There is media speculation by arm chair admirals about entering a harbour etc but all that is unknown. Hope this helps - just my two paisa from an arm chair midshipman.