AIP and then pumpjet technology in the Yuan and the Qing would make them far quieter than the Kilo.
LOL. tropical terrain in the sea. where do you come up with this stuff?
Then your SSKs would be fighting SSNs that shadow PLAN ships in the open sea.
I have experience with ships and the shipbuilding industry what you said is vague and jumping to conclusions. There is not one system that guaranties that a submarine will be quieter than its competitors.
Some things to consider when constructing a submarine other than the engine itself:
The propellers-- the propellers are one of the noisiest systems on a submarine The design of the propellers, geometry, number of blades, the size and the RPM at which a propeller spins all has an effect on how much Cavitation or bubbles are produced by the propellers. Some submarines even have tarps cover its propellers when in port so no one can see just how the propellers look due to fear of the technology being copied.
acoustic damping--acoustic damping is a another major design feature and one that Russia has extensive experience in. What it is rubber, polymer or some other classified tile. What these tiles do is absorb sonar and reduce the noise levels emulated from submarines. Some Russian submarines such as the Akula has a noise reduction of up to
20 decibels from these tiles.
absorbers--without absorbers a submarine can never truly be 'stealthy'. Every good submarine will have absorbers, or shock devices to completely eliminate or reduce noise levels from certain systems. For instance, rubber or polymer mounts are sometimes used to cover pipes that pass through bulkheads in order to eliminate the rubbing or vibration due to metal on metal contact. Many other components of a submarine utilize absorbers.
On board plumbing from piping is an important factor in noise reduction. Liquid flowing inside pipes as well as pumps and the mounting systems (absorbers) are all taken into account. The goal here is have silent pumps that allow liquid to flow smoothly with minimal Cavitation. From there absorbers and valves play a critical role.
The hull--everything from the bridge to the to the rudder to the propeller and everything in between can create wakes, disturbances and cavitation. A good hydrodynamic hull will obviously make a submarine quiet. Something interesting to take into account, wakes can alter surface temperature which can be detected.
In short there are hundreds of things that generate noise onboard a submarine, some of these thing are not revealed to the public nor will I list off everything but my point should be clear.
1. The kilos you are getting in 6 years are already inferior to the Yuans China introduced 7 years ago.
Inferior based on what? Virtually everything about submarines are classified, noise levels and combat systems is not something that is revealed to the public.
2. Chinese warships have full compliments of nose, and Towed array sonar along with KA 31, and Z 8 ASW helicopters. All of them are capable of launching rocket propelled torpedos up to 50 kms away.They are also escorted by SSKs, and SSNs. A few Vietnamese kilos without any surface support would be massacred.3.
Wrong, there are submarines that are capable of staying virtually undetected. In fact during naval exercises one side tries to stalk certain vessels while other vessels try their best to locate or even detect the presence of the aggressor submarine, often a submarines design as well as passive systems can make it almost impossible to detect.
The Gepards you have do not have a helicopter bay. Its 1,500 ton displacement also means it carries a tiny sonar nose. It also does not have a towed array radar. A song class SSK of the PLA popped up next to a 100,000 ton aircraft carrier with dozens of AEW helicopters with Burke class destroyers and you expect a corvette to do what they couldn't with a sub thats 2 generations ahead? Your wet dreams are astounding.
No, that is not how it works. I have personally seen a sonar/sonar tube on a vessel that is approximately the size of the Gepard. Sonars are not the size of an automobile and even if they would be most ships have plenty of room in and around where the sonars are housed. For instance, the sonar on the ship I seen was right behind the bulbous bow, just in front of the crash bulkhead. Naturally the sonar tube is located on the lowest part of the ship (the Keel) so there is plenty of vertical room as well as room forward, aft, starboard and port.