INS Arihant (4 vertical missile tubes) is acting as a missile testbed for some missiles that INS Aridhaman (8 tubes) will eventually deploy (Graphic courtesy DRDO, H I Sutton and The Diplomat via several publications, eg. the Dhaka Tribune).
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MAINLY GHALIB'S COMMENTS
The imminent (symbolic "soft"[2]) launch of INS Aridhaman has been a strong rumor since April 2017 at least (not surprising considering the construction work since 2011). Ghalib would wager that the 'proper' ["hard"] launch is likely in early 2018, then sea trials by early 2020, with commissioning by late 2021.
Nuclear Tipped Missiles
Nuclear Tipped Missiles
Ghalib hopes India retains the 8 vertical launch tube format for the 3,500 km range, 17t, 12m longK-4 SLBMlayout. [Pete estimates the K-15 "Sagarika" may be used on Aridhaman for several years (to 2025?) before the K-4 is a mature missile system.] But the K-15 has many deficiencies including a short 800km range useless [against the city of Islamabad and China] with a light (up to 800kg) warhead. [Pete - Even India's Nirbhay cruise missile has a longer range of 1,500km.] Ghalib hears that the current concept of the K-5 SLBM might have 3 MIRVs per missile [3]. [Pete - However some doubt India is trying to develop MIRVs at thiis stage][4] Initially the K-4 missiles might carry a single warhead only (like a Pu boosted fission device) [Pete - or 2 stage mainly fusion?].
Submarine Reactor Development
Submarine Reactor Development
Russia's VM-5 [5] reactor (used on Russia's one and only Project 661 class test SSN (K-222) formed the on land (at Kalpakkam near Chennai) testbed for Ariahant's 83 MWt reactor. Russian assistance allegedly stopped in 2015-16. The VM-5 design probably formed the basis for some Indian submarine reactor improvements resulting in Aridhaman's reactor being uprated to 100 MWt.
Ghalib comments - according to Indian scientists more than 'Know-how' it was Russian 'Show-how' [of a submarine reactor and other nuclear submarine technology] that was more useful. I think thats the key here. To be 'shown how' makes for the actual breakthrough. See Page 135 of this book talks of Russia and Arihant's 83 MWt reactor:
[1] Information on Indian SSBNs and SLBMs are on pages 130 to 138 of Peter Lobner’s “60 Years of Marine Nuclear Power: 1955-2015 – Part 4 – Other Nuclear Marine Nations”, dated August 2015, large PDF (around 20MB) http://www.lynceans.org/wp-content/uploads/2015/09/Part-4_UK-France-Others-60-yrs-of-marine-nuc-power.pdf
[2] A
A well documented example of a soft launch was when HMAS Collins was launched into the water on August 28, 1993 to meet a political schedule. When launched Collins was incomplete with the design not even finalised. At “launch” on August 28, 1993 important internal pipes and fittings were not installed, the components of the combat system had yet to be delivered, and some hull sections were actually sheets of timber painted black so the submarine would appear complete in photographs of the launching ceremony. Within weeks of the “launch”, Collins was removed from the water, and it was not until June 1994 that the submarine was completed then really “hard” launched.]
[3]If the K-5 is closely based on the Agni V then the K-5 may eventually have 3 to 10 MIRVs per missile. Also the follow-on K-6 may have 10 MIRVs (See Agni VI wiki and right sidebar).
[4]Hans M. Kristensen and Robert S. Norris “Indian nuclear forces” in Bulletin Of The Atomic Scientists, 2017 Vol. 73, No. 4 http://www.tandfonline.com/doi/pdf/10.1080/00963402.2017.1337998 page 5 (208) argue that India has to prioritise given the limited payloads/range of Agno V and VI missiles. India may prefer to at least be capable of hitting distant targets (read targets in northeast China eg. Beijing) with a single warhead per missile rather than having MIRVs which would prevent Agni V/VI's hitting Beijing.
[5] Pete is puzzled the right sidebar for K-222's VM-5m records:
"2 × VM-5m type pressurised water reactors, 177.4 MW (237,897 hp)
2 × steam turbines, 2 shafts
80,000 shp (60 MW)"
How can that data be converted to one reactor of 100 MWt?
[6] Verghese Koithara, Managing India's Nuclear Forces, link.
[7] Arihant: How Russia helped deliver India’s baby boomer” Russia & India Report, 26 October 2015 https://in.rbth.com/blogs/stranger_than_fiction/2015/10/26/arihant-how-rusia-helped-deliver-indias-baby-boomer_533849“As India’s first nuclear powered submarine prepares for its maiden missile launch, a look at the extent of Russian assistance in the Arihant project.”
Ghalib Kabir, Pete and the Authors cited