You’re right, they Pakistan will have to pick something off the shelf (slightly modified) as it can’t put in much funding into R&D. There is speculation that China is developing a nuclear battery plug for SSKs, so Pakistan could be the another beneficiary of this technology, after the PLAN. Not a reactor, but a limited life battery, that could have to be swapped out every 15-20 years, going based on similar technology being developed in the US. Perhaps for the foreseeable future, Pakistan could go for a version of the Type 032 (so it can carry longer range missiles), if equipped with such batteries, to ensure it can allow these subs to operate for months at depth and operating very quietly. The Type 032 is not a small submarine, so it would need to be either packed fully with large conventional batteries or have at least a couple of these nuclear batteries. I speculate that Pakistan is with for Chinese tech to mature in this regard and to get feed back after operating the Hangors class subs for some time.
Btw, an enlarged attack boat with 8-12 VLS tubes and one nuclear battery could also be built, for the PLAN, and then an export approved version for Pakistan. It would be similar in weight as the new South Korean KSS-3 Block 2 (4000 tons), which has 10 VLS tubes of 0.9 meter diameter and 10 meter length.
China has a need to field SSKs that are even quieter, can replace all pre-Type 039B SSKs, and deal with a growing fleet among the coalition of nations looking to contain China and its SLOCs.
en.wikipedia.org
See the propulsion at 12:34 onwards.
Information regarding China's submarine program, especially its nuclear submarine development methods, is highly classified. Currently, almost all the information we have comes from speculation by military enthusiasts or foreign media. Therefore, we should not delve into too many details (there is insufficient credible evidence to support various viewpoints, which could easily lead to unnecessary disputes).
Regarding current submarine diving records from various countries, China's current records are:
Nuclear submarine: Type 091 (#403) nuclear-powered submarine, submerged for 90 days.
Conventional submarine: Type 32 conventional-powered submarine, submerged for 30 days.
From an engineering perspective, achieving longer underwater endurance isn't too difficult. However, it's physiologically and psychologically unsustainable for humans. Therefore, for a long time, people haven't pursued longer underwater endurance. Now, developed countries in this field have begun developing unmanned underwater vehicles, which don't face this problem.
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Back to the topic.
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According to the China-Pakistan agreement, the last four Hangor Class Submarine submarines will be completed in Pakistan.
Therefore, we can conclude that the pressure hull manufacturing technology for this class of submarines will also be transferred to Pakistan. This is one of the key construction technologies for submarines.
We are unsure whether the cooperation agreement includes technology for submarine-specific steel. That is, we cannot determine whether the steel used in the Hangor Class Submarines built in Pakistan will come from China or be sourced domestically. This is also a core technology.
As for the submarine's subsystem technologies (power engines, detection equipment, attack equipment, etc.), I believe this is not currently a priority for Pakistan.
Pakistan itself has a relatively weak technological foundation in related fields and lacks a mature industrial chain to support it. Its economic foundation also makes it difficult to support the substantial costs of independent research and development.
Pakistan has a wide range of options in the international diplomatic arena. It does not have the need or desire to independently develop related subsystems.
However, if Pakistan fully masters the technology for independently building submarine platforms and continues to evolve it, it will be a remarkable achievement in itself.
Special Note: Attack submarines (used for naval warfare) and ballistic missile submarines (used for nuclear counterattack) are completely different things. The latter can be extensively modified to become the former, but the former cannot become the latter.
Hangor-class submarines are typical attack submarines; it is meaningless to draw deep connections between them and ballistic missile submarines used for nuclear counterattack.
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