[V.Narayan]

Originally Posted by AlphaKilo

Why do we expect only 1 or 2 in sea and not 3 - 4 out in deep waters out of the 5 (assuming we have 5 commissioned)?

Valid question which I'm sure is on the minds of others too. A SSBN would normally want to patrol in deep waters within range of its intended targets. That for our SSBNs will be the South China Sea, East China Sea, Yellow Sea {I'm ignoring the Arabian Sea for the moment}. An Indian SSBN would typically patrol for 60 to 70 days and take another 20 to 30 days to transit to the patrol zone and back. These zones described above are on an average 4000 nautical miles i.e. ~7400 kms away from our Eastern coast. Also submarines have deep, complex & time consuming maintenance needs and crews have training needs. The experience of the French Navy has been -> 1 always, sometimes 2 in the patrol area + 1 in transit either way + 1 either being readied to go or recovering from a patrol, undergoing safety checks etc + 1 in training/rest/minor or medium repairs + 1 in long refit i.e. deep repairs. This sequence is considered by experienced navies to be the best sustained tempo with two crews per SSBN. The Americans have a larger fleet of 14 but the tempo is similar with 3 maybe 4 on patrol at a time. The British have only 4 and they go to extraordinary lengths to keep one at sea on patrol at all times. The Russians on paper have 12 SSBNs of which they ensure that 1 sometimes 2 are out. Their sailing tempo is rather poor now.

[Sutripta]

Submarine launched cruise missiles - are these sea skimmers? How do these navigate? What accuracy?

Sutripta

[Jeroen]

Originally Posted by Sutripta

Submarine launched cruise missiles - are these sea skimmers? How do these navigate? What accuracy?

Other members might have much more insight into this, but I have done a bit of reading on the navigation systems for these.

In essence they use four different systems
IGS - Inertial Guidance System
Tercom - Terrain Contour Matching
GPS - Global Positioning System
DSMAC - Digital Scene Matching Area Correlation

Where the basics of all these systems is fairly well understood I am not sure how much detail is available in the public domain on how they are integrated. But based on the known characteristics some basic assumptions can be made.

On nearly all (commercial/military) planes you will find a combination of at least inertial guidance system and GPS. GPS as used by the military gives phenomenal high accuracies. IGS is much less accurate, you need a high accuracy position to start with and over time/range the accuracy gets less, due to drift.

GPS and IGS typically work in tandem. IGS big advantage over GPS is it has no external inputs. Once set to go and aligned it will keep going, albeit at decreasing accuracy.

Cruise missile fly according to different profile depending on what segment in the flight they are. The Tercom system is based on a 3D database which it compares to the terrain it is overflying. It checks the 3D database against its radar imagery. It gets programmed with the area/segment the missile will be flying over. It has the ability to correlate 3D images to its position. Its what is used for the terrain hugging. Not much use when flying over water, very useful when flying over difficult terrain.

At some point into the flight the missile starts focussing on its point of impact. That could be a GPS coordinate that has been pre-programmed. Or it could use DSMAC to home in on a specific object.

Above is probably a bit dated. I know there are additional navigational system that are being added to missiles/automous planes. (E.g PTAN)

Jeroen

[V.Narayan]

Originally Posted by Sutripta

Submarine launched cruise missiles - are these sea skimmers? How do these navigate? What accuracy?

Sutripta

Jeroen has explained very well how they navigate. They are not sea skimmers in the manner of a Harpoon or Exocet anti ship missile but they fly close enough to the surface to be hard to spot. Most today use Inertial Navigation and GPS to get to the target and terrain matching to fly low and with less chance of detection. GPS and DSMAC is used for the final homing. But understandably the information in the public domain is limited. Accuracy for the Western ones -Tomahawk, SCALP, is within 10 metres CEP ie 50% of the missiles will hit within 10 metres of the target. Often it is claimed to be within 5 metres. Given that the target is usually much bigger than 10 metres it can be said their accuracy is outstanding. In trials the Tomahawk has demonstrated the ability to home in on an aircraft on the ground.

[Sutripta]

My mistake in not making my question clear. Wanted to know the difference in navigation technology used between land based and sea launched cruise missiles.

A lot of technologies came together to give a working cruise missile, the two main ones being the propulsion unit (Williams mfgd. turbine) and the navigation system.

Inertial guidance is not accurate enough for this use case.
GPS is vulnerable to jamming, and spoofing.
Terrain contour matching (for the transport leg) and digital scene matching (for the final stages) were the two enabling and gamechanging technologies.

The ocean surface is featureless. So terrain contour matching does not work.

Even during the Iraq war, cruise missiles were often programmed to follow a circuitous path. Essentially preferring mountainous terrain to plains.

Sutripta

[Jeroen]

Originally Posted by Sutripta

My mistake in not making my question clear. Wanted to know the difference in navigation technology used between land based and sea launched cruise missiles.

Inertial guidance is not accurate enough for this use case.
GPS is vulnerable to jamming, and spoofing.
Terrain contour matching (for the transport leg) and digital scene matching (for the final stages) were the two enabling and gamechanging technologies.

I practice some of these system work jointly. It is not necessarily one or the other. Most commercial pilots have the wrong notion of how their IRS and GPS work. The way it is shown in operating manuals tend to be a simplified way, usually depicting an on/off situation based on (expected/calculated) accuracy and or errors. Good enough for operating it and making choices as to what system to use. In nearly all cases the actual position used for navigation is a “calculated” position from multiple sources, combining data from multiple sources through some clever logic/filters.

If you dig a bit deeper you might find that for instance the main guidance system for most of the flight is the IGS, but it gets updated by GPS as long as the GPS accuracy is good enough. I believe these sort of missiles might also be equipped with GPS anti-jamming/spoofing systems. I have no idea how effective they are.

Commercial IRS platforms as used in commercial planes have a drift of better than 0,4nm/hour. Military ones probably better. For most of a missile flight above terrain that should be more than accurate.

Another advantage is that IRS also gives you an altitude. Usually much more reliable than GPS. Commercial planes still use essentially actual or normalised barometric pressure for their altitudes. Not sure what these missiles use? Probably a combination of various sources, just like position. I don’t think terrain matching would be able to give you a very accurate altitude, although of course in theory it can. You would need to be able to very accurately measure objects, contour lines and compared to an image from a known altitude. For lateral navigation that is quite the challenge already, but vertical navigation? Obviously the errors vertical are at least an order of magnitude larger. So they are likely to use something else for altitude I would think?

Jeroen

[Sutripta]

So no difference between land launched and sea launched cruise missiles as far as navigation systems go?

Sutripta

[Jeroen]

Originally Posted by Sutripta

So no difference between land launched and sea launched cruise missiles as far as navigation systems go?

Far from an expert, but I would not think so. It would not make sense. These four systems all interact/work together to get the missile from launch point to point of impact as far as I can tell / think. How much of the navigation is done primarily by one over the other is likely to be different sea versus land as discussed.

I was wondering about launching a missile from a moving ship. As you know Inertial guidance is just an advanced way of dead reckoning, based on measuring acceleration and time. So you need to provide any Inertial system a reference to start from (reference position or datum).

On commercial aircraft that could be the position of a gate at the airport. (known position in the FMS database). Or the threshold of a runway. (Some Commercial Inertial system, reference a datum as you push the TOGA button on take off.

But if your launch position is moving (possible rolling and heaving) that needs compensating for. Because it would cause a huge error very quickly. So apart from the obvious visual difference between a land and sea launch, the alignment of the Inertial system must be far more elaborate. (but probably all automated, push of a button stuff I imagine).

Actually the same applies for any plane taking of from a carrier. If they have some IRS it needs to be adjusted for speed, direction, roll rates etc. Never heard how that is done?

Edited: There must be something out there. I googled a bit and a patent pops up:

https://patents.google.com/patent/EP1162431A1/en

Next to nothing on Wiki; so this is all black magic stuff

https://en.wikipedia.org/wiki/Transfer_alignment

Not sure if war ships need to adjust their speed (or direction to minimise roll) in order to launch missiles effectively due to the above?

Jeroen

[V.Narayan]

Myanmar acquires first diesel-electric Sindhughosh Kilo class submarine INS Sindhuvir S58 from India

https://www.navyrecognition.com/inde...rom-india.html

On October 17, 2020, Myanmar acquired its first diesel-electric submarine from India - INS Sindhuvir (S58) Sindhughosh-class submarine that was in service with the Indian Navy. This is a strategic move by India to stymie China’s attempts to get inroads into Myanmar and establish basing rights with that country. A sensible and strong message to China. Earlier Bangladesh, in 2017, acquired two Type 035G 2100-tonne Ming class boats from China upsetting our equilibrium in the sensitive Bay of Bengal area. These were followed by delivery of several other surface vessels including 8 frigates/light frigates and 4 more on order! This increased dependence of the BD Navy on China gives more excuse for Chinese Naval advisors to be posted in Chittagong to help maintain these naval ships and submarines. Clearly something we do not need.

The INS Sindhuvir submarine is diesel-powered Kilo class boat which has a total of six motors including two 3,650 hp (2,720 kW) diesel-electric motors, one 5,900 hp (4,400 kW) motor, two 204 hp (152 kW) auxiliary motors for manoeuvering in confined waters or close to the sea bed , and one 130 hp (97 kW) creep patrol motor. Officially it can reach a surface speed of 17 knots (31 km/h) in submerged mode. It has six 533mm torpedo tubes and carries 18 heavyweight torpedoes (six in the tubes and 12 on the racks), with an automatic rapid loader.

File photo of a IN Kilo-class boat

[V.Narayan]

Fifth Scorpene class submarine, INS Vagir, launched, today, at Maz Docks, Mumbai

https://timesofindia.indiatimes.com/...w/79185652.cms

The 5th Scorpene class submarine, built at MazDocks under license was launched earlier today. The Scorpene's in IN service are referred to as the Kalvari class. She is expected to commission in December 2022 after fit out and extensive sea trials. The 6th and final boat in the squadron, INS Vagsheer is under construction. The 3rd of the series, INS Vela will formally commission, next month, in December 2020 after having successfully completed all its sea and diving trials.

The first Vagsheer was a Foxtrot class, 2475 tonne, 91-metre long diesel electric submarine that served in the IN from 1974 to 1997.

The IN's long stagnant submarine arm is gradually coming back to life with new hulls and modernization of existing ones.

File photo of a Kalvari class boat.

[V.Narayan]

Second SSBN, INS Arighat, to complete sea trials and commission in early 2021.


https://theprint.in/defence/ballisti...y-2021/567869/

India's second SSBN - nuclear powered ballistic missile submarine is scheduled to be commissioned into the Indian Navy in early 2021. Like INS Arihant she will carry the K-15 short range nuclear armed submarine launched ballistic missiles. Two more of the class are under construction and will carry 8 missile launch tubes instead of 4. The Navy, DRDO and L&T have come a long way with successful indigenous development by going step by step. Tejas, Arjun and the nuclear submarine project all started in the early-1980s at a concept stage. Arjun started a little earlier. The Navy said, let's see what we can make and what we cannot let's buy or copy. Let's not aim for the most superlative parameters but settle for what's doable and get it done. Sadly the other two projects did not follow this policy. My late father was closely involved with our Naval nuclear submarine effort and this divergence of approach and that it may lead to nought was evident to the outsider with common sense even in 1989.

Soon we shall have three nuclear powered subs proudly flying the Indian naval ensign. Keeping politics aside the credit for this foresight goes to Mrs. Indira Gandhi.

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Originally Posted by V.Narayan

The Navy said, let's see what we can make and what we cannot let's buy or copy. Let's not aim for the most superlative parameters but settle for what's doable and get it done.

Soon we shall have three nuclear powered subs proudly flying the Indian naval ensign. Keeping politics aside the credit for this foresight goes to Mrs. Indira Gandhi.

I just had to bold the above statement. I honestly sometimes wonder whether it's worth getting that framed in a large banner and post it to the Ministry of Defence so that they can have that above the door to remind them. And while we're at it, I'd absolutely chisel that statement onto the entrance at HAL. There's another Indian agency frequently guilty of biting off more than they can chew.

I hope there's some sort of nod to her on either of the two boats. It was, in India's case at least, a rare but remarkable bit of prescience on her part to get the ball rolling on a programme of such strategic importance.

Speaking of submarines, something that caught my attention recently:

Plans for a purported Indian littoral submarine

Source: http://www.hisutton.com/Indian-Navy-...Submarine.html

A short video shared on Twitter by user Amiet R. Kashyap appears to show a new indigenous submarine design for the Indian Navy. The presentation is from Indian engineering company Larsen Toubro (L&T) who are involved in submarine and special forces diver transport projects. The submarine is generally smaller than the Type-209/1500 Sindhughosh class and Pr. 877EKM KILO (Sindhughosh class) boats. It is however larger than the X-Craft used by the Pakistan Navy, especially their newest class.

However its small size places it in the category of coastal submarines, at the large end of 'midget submarines'. This puts it in company with the North Korean Sang-O class and Iranian Fateh Class). Significantly the Indian design can carry two swimmer delivery vehicles (SDVs) for special forces. In the compromise it only has two torpedo tubes with no reloads. This arrangement is actually most similar to the Pakistan Navy's MG-110 X-Craft, although the Indian design is much larger.

It's an interesting piece of news really. I mean just as India's undersea capability is steadily getting the attention it desperately needed, and the conventional boat fleet is revamped, this would be quite an ambitious next step. Anyway I felt I had to share, especially as you mentioned how far L&T have come - to stumble across this bold plan by L&T, reaffirms your point. More images in the attached article - seems this model isn't a recent thing, L&T have been showing it since 2018. From the language this seems like an independent exploratory project by L&T.

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New milestone for domestic AIP by DRDO

H I Sutton with the undersea news once again (Source).



Excerpts below, emphasis mine:

According to Naval News, India's Defence Research and Development Organisation (DRDO)'s land-based test plant has reached an important milestone. It has been "operated in endurance mode and max power mode as per the user requirements."
Work has been underway for several years at DRDO’s own Naval Materials Research Laboratory (NMRL). Engineering firm Larsen & Toubro is also involved.
The system should soon be ready for installation aboard Indian Navy submarines. The current Kalvari class boats are expected to receive it during a major upgrade. This should happen six to seven years after commissioning, so starting in 2023-24.
The refit will include lengthening the hull to fit in the new module. This is a similar approach to how Sweden added AIP to its submarines. The locally designed system is expected to extend the endurance of the submarines by two weeks. This will greatly increase the potency of these non-nuclear submarines.

REF:http://www.hisutton.com/Indian-Navy-...ubmarines.html



This is a critical programme for the IN, considering the fact that the PN already has AIP boats (albeit older models) commissioned, with additional orders for newer Stirling engine AIP equipped Chinese boats. Not to mention the potential for PLAN conventional AIP equipped boats venturing out into the IOR, given the plethora of friendly basing options they have now. Let's hope DRDO and L&T can stick to that 2023 timeline.

Update: Tweet from DRDO itself
https://twitter.com/DRDO_India/statu...968822793?s=20

[V.Narayan]

INS Karanj, 3rd Scorpene class SSK submarine joins the fleet

https://zeenews.india.com/india/ins-...y-2346872.html

INS Karanj, India’s third Scorpene-class diesel-electric submarine, was commissioned into the Indian Navy in Mumbai on Wednesday. Two submarines of this class, INS Kalvari and INS Khanderi, have already been commissioned into the Navy. A fourth of the class, INS Vela, has been undergoing trials at sea. Two more are under construction/sea trials.

The commissioning of these new quiet French designed boats are a much needed boost to our Submarine Arm. Our submarine fleet as of today stands at 2 SSBNs, 1 SSN, 15 SSKs. A total fleet of 18. This brings us back after 3 decades to the peak fleet strength of 18 boats that we achieved briefly in c. 1990-1992. With 5 boats under construction on home turf we should in the next few years get to a strength of 20 to 21 as newer ones commission and older boats (the early Kilos and the first two Type 1500s) de-commission.

A famous British Admiral once rightfully stated that you cannot buy a Navy, you can only build one for yourself. Today 40 out of 42 vessels being built for the IN are being built in India.

[Jeroen]

Very interesting reading about these AIP developments

Just wondering about this bit:

the current Kalvari class boats are expected to receive it during a major upgrade.

So they are going to retro-fit existing subs with this? I am somewhat surprised. Looking at these images that means opening up the hull or not>

Whereas on merchant ships that is a fairly straightforward procedure to get bit pieces of machinery in and out of the engine room, I was not aware it was used on submarines. I always had this idea that once the hull is done, they will never ever open it up. The hull is effectively built around whatever machinery and otherwise needs to be inside. Any replacement need to come through the normal man holes / existing openings in the hull. Making carrying our major overhaul on subs a very tedious process.

Do they really need to open up the hulls of these submarines for this retrofit?

Thanks
Jeroen