In late 2011 an internet rumor spread about Pakistan's development of nuclear submarines and in early 2012, we have heard major news networks in Pakistan announce the development of Pakistan's nuclear submarines "in 5-8 years". The earliest news of Pakistan's nuclear submarine project was in 2006 when General Musharraf announced that Pakistan now has the technology to build nuclear submarines.
The first point to ponder is that Pakistan, unlike certain other countries, prefers to develop weapon systems quietly. If this kind of announcements are coming out, it all probability Pakistan already has a nuclear submarine, or at minimum critical components, well underway. The most critical component is the nuclear power plant, and the news thus points to the development of a miniature power plant.
RUMINT suggests that Pakistan's nuclear submarine is likely to be based on the Qing Class Chinese SSK, which Pakistan is believed to receive 6 units of. Given the giant size of the Qing Class (5,000-6,000 tons), the submarine is ideally suited as the basis for a Pakistani SSN / SSBN. RUMINT also suggests that Pakistan is seeking a smaller sized nuclear sub that sacrifices speed for simplicity and ease of maintenance. The basic idea is that instead of hydraulic propulsion, the Pakistani subs will utilize an all-electric propulsion system that is charged by the nuclear power plant.
Such an arrangement fits in perfectly for the following reasons:
1. Pakistani SSNs/SSBNs do not need to keep up with a carrier group or large-scale task force; They are likely to operate solo, making the loss of possibly 3-5 knots in speed less relevant.
2. The Qing Class (and other SSKs) already have a highly advanced electric propulsion system. The Pakistani nuclear submarine would thus be a replacement of the diesel engine power generation with a nuclear power plant.
3. Electric propulsion has traditionally lagged behind hydraulic propulsion, but recent advances in the former has significantly reduced the gap in performance between the two.
4. Sets up future improvements in technology which are headed towards magnetohydrodynamic propulsion, saving on investment in hydraulic submarine propulsion which would have been a technological end investment.
Taking a closer look at the possible type of nuclear power plant to be utilized, it is likely to be a small pressurized light water reactor.Such a reactor would require some R&D given that Pakistan does not have much expertise in light water reactors, and because the need for miniaturization. However, given Chinese expertise and potential assistance, this should not prove to be a difficult challenge to overcome. Moreover, Pakistan has a highly qualified and competent nuclear establishment that should be able to meet the challenge.
Another potential help may have been the transfer of technology from France with the Agosta 90B submarine purchase. A number of key technologies were transferred including design and development skills and tools. Building of hulls and experience with Western subsystems, many of which are used in the French nuclear submarines would help the Pakistani SSN / SSBN, if it already has not found its way to the Chinese Qing Class.
In sum, while India is preparing her first indigenous nuclear submarine, Pakistan is well underway in making an equivalent capability upgrade. While the time-frame given in the media is 5-8 years, it is very possible that Pakistan is capable of building and fielding such a submarine in 3-5 years. The timeline for building and deploying such a sub is mainly dependent on how quickly and successfully the Indian nuclear submarine program is able to field and operate a submarine.