Vietnam's Kilo 636 submarine has a Pump-jet propulsion system.

In the Russian Navy there is a very special Project 877 Kilo submarine, that is, instead of using a traditional propeller, it is equipped with a water jet engine.

The advantage of this type of engine is that the submarine runs very smoothly, can operate better in shallow water or improve the ability to maneuver in close range. This is also a common design on modern nuclear attack submarines.

However, only the Alrosa is equipped with a water jet propulsion system, the remaining Kilo submarines all return to the traditional propeller design, including the 636.1 for export or the 636.3 serving in the Russian Navy.

But surprisingly, the Russians recently released a special document about the two submarine classes. The notable information is that both versions 636.1 and 636.3 are equipped with two small water jet engines on the side.

According to the technical description, the Kilo 636 submarine is equipped with a total of 4 propulsion engines. The largest engine has a capacity of 5.5 MW at 500 rpm.

When the ship is running at low speeds below 3 knots, the main engine is shut down and the main propeller shaft uses smaller engines. The last two engines are to run the water jet system installed on both sides of the hull near the main propeller.

This auxiliary water jet propulsion system is used to maneuver the vessel at very low speeds, or to maintain position in the current at sea to help frogmen enter and exit the vessel from the torpedo tube.

It should be reiterated once again that this is a common design applied to all domestic and export versions of Kilo 636 submarines, which means that all 6 Kilo 636.1 submarines of Vietnam have this propulsion mechanism available.

The above superior features have earned the Kilo 636 submarine the nickname Black Hole of the Ocean. Perhaps it still has many hidden technical parameters that will only be gradually revealed by the Russians during its operation.