Following India's 6 Future Alpha SSNs - SSBN Protectorsof April 7, 2021 came the blessing of a veritable avalanche of good comments from Anonymous, GhalibKabir, Gessler and Arpit Kanodia. Rather than attempt to summarise each comment (obscuring meaning and context). Or try to respond point by point (which would fill 10 pages/5 articles) I'll republish the comments. I'll also add some lengthened weapon designations, comments in [...] brackets and extra links.
I'll start combining GhalibKabir’s comments of Apr 8, 2021:
“Pete, I think we discussed this way back in 2019, similar to the Chinese Type 091 (NATO (Chinese Dynasty) reporting name "Han" class) SSN. The future Indian Project 75 Alpha SSN will likely (initially) use a slightly uprated Arihant 40% HEU PWR (uprated from 83 MWt to 100 MWt) implying electrical power uprates to 16.7 MWe from a maximum of 13.8 MW presently) (the rule of 1/6 for naval reactors vs 1/3 for land based).
Peter Lobner got it right with his 100 MWt prediction I think. [See Peter Lobner "Marine Nuclear Power 1939-2018: Part 5, China, India, Japan & other nations" (July, 2018) page 159 (Table) and page 163 at https://lynceans.org/wp-content/uploads/2018/07/Marine-Nuclear-Power-1939-2018_Part-5_China-India-Japan-Others.pdf about 50 MB, 294 pages]
The S-5 class future full size Indian SSBN could see a single Soviet/Russian OK-650 reactor [which India may have designated the CLWR-B2 Compact LWR - see right sidebar] derivative as the bigger SSBN will need 25 MWe or more capacity to be available implying a 160-170 MWt OK-650 [even 190 MW and see also ] class reactor.
However, SSN reactor dynamics are likely to be different as the rapid 'power up power down' variation demand on the SSN reactor for 'sprint chases' will be much higher than an SSBN. The Arihant class' or even the S-5's likely speed requirements could stay between 22-24 knots while the Alpha SSN will need burst speed capability of 35 knots and the ability to do 28-30 knots frequently and consistently... (like China's current Type 093 Shang class SSN for instance).
Also I think INS Chakra IIelements with Arihant base is the most likely in SSN Alpha and not Barracuda or the Alvero Alberto [aka "SN-BR"] Brazilian Scorpene SSN (though some learnings will cross over in welding, silencing, reduction gear design etc.) [Also the future Chakra III might influence the Alpha SSN. "India and Russia, March 7, 2019, signed $3Billion deal to lease another Akula SSN, dubbed Chakra III, should be delivered to Indian Navy 2025].
I do hope India is able to leverage [France's] Thales and [Israel's] Rafael under water suites expertise to equip the SSN with good sonar suites and combat capabilities."
[The Russia-India lease deal means] INS Chakra II cannot be used in offensive war. It cannot be armed with any missile ranging > 290 km i.e. original MTCR restrictions apply (unless I am gravely mistaken)...it can help in case of open war, but will be limited to defending with torpedoes and such short range missiles as to be of very limited utility indeed....plus the sonars and combat suites are very old as well....
I think a vertical launch system (VLS) [on the Alpha SSN? Within a 6,000 tonne (submeged) displacement limit?] combo with Horizontal launch capability could be better... 24 Tri-packed Nirbhay sub-sonic SLCMs in 8 VLS with 20+ combination of Varunastra Torpedoes and BrahMos SLCMs are the most likely combos..
Also while a propulsor pumpjet is desirable and is being tried, I think a conventional 7 blade screw is likely for the first 2 Alpha SSNs at least. Like the Chinese Typo 091 SSN in 1975, the focus first should be to get a couple of Alphas out and test them. Then we can see and make real progress, instead of an unhealthy obsession with 'perfect profile' product launches.
The Type 091 used a 60 MWt inefficient PWR that delivered 8 MWe and was very radiation leak prone. The key difference being the PWR was a LEU (thanks to the Soviets screwing the Chinese over [Soviets were worried Mao was prepared to risk dragging the Soviets into nuclear war against US and Taiwan]. China was left with minimal uranium supplies and also a loss of nuclear and submarine expertise after China's Cultural Revolution). India has been a HEU navy.
Good that [India's Chief of Defence Staff, General] Bipin Rawat, Doval and co were able to prevail on the SSNs after 3 years of wrangle at North Block" [ie. wrangling at the Ministry of Finance, New Delhi].