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Russian “Piranha” is scary only on paper

Non-nuclear submarines

Why Russian non-nuclear submarines lose to Japanese and German.

Russian designers are again approaching the problem of creating an air-independent power plant (AIP) for non-nuclear submarines.  At the Malakhit and Rubin design bureaus, the implementation of which will increase the stealth of submarines by significantly increasing the time spent in the underwater state without surfacing.


At the same time, a rather strange phrase was uttered that the design bureaus had been conducting the corresponding developments on the initiative for more than a year without federal support. And that the situation has changed – this summer the state allocated funds for the normal course of development work.


Yes, that sounds weird. Because before the start of initiative development, these design bureaus spent huge state funds on the same. And this money has been spent already since the 90s. However, no real results were obtained. And they gave and gave money, because AIP is extremely necessary for the Russian non-nuclear submarine fleet. Since diesel-electric submarines without AIP were tightly chained to the third generation of submarines. Without them, the excellent domestic diesel-electric submarines Varshavyanka, having record low noise, lost international tenders one after another.


So, what is it, and why is the Russian Navy in dire need of AIP?


A classic diesel-electric submarine is able to stay under water for about two days, during which the propulsion system (electric motor), as well as numerous electrical equipment and electronic systems, are powered by batteries. After discharging the batteries, you have to pop up to start the diesel engine, recharging the batteries. A diesel engine cannot work under water because it needs air.


It is also necessary to discharge exhaust fumes into the atmosphere. It is clear that in the surface position, and even with the internal combustion engines running, the boat can be easily detected by the enemy.


True, some time ago, quite a while ago, they started using a snorkel – a pipe through which air enters the boat. Also, combustion products are discharged through it. That is, the boat does not float completely, but only raises the snorkel above the water. Then the diesel starts. However, in connection with the recent development of anti-submarine defense means, with the advent of anti-submarine aircraft equipped with highly sensitive equipment, it has become not so difficult to find the boat by snorkel.


AIP works without the consumption of air (strictly speaking, oxygen). At the same time, substances capable of poisoning the team are not released. Therefore, a boat with such a power plant can be under water for 3-4 weeks.


Four principles of building are known. Stirling engine (SE). Its action is based on obtaining energy when creating a temperature difference in the working fluid (gas). Gas, moving in a closed volume, does the work by rotating the turbine. To create a temperature difference, liquefied gas is used.


Electrochemical generator (ECG), in which electricity is obtained as a result of chemical reactions. Two other principles — the closed-cycle diesel engine and the closed-cycle steam turbine installation — were not widely used in underwater technology.


The theory of AIP has been around for centuries. For example, Sterling engine was patented by a Scot in 1816. The first concrete results were obtained by the Swedes. In the late 80s of the last century, they operated three experimental boats, in which the SE played the role of an auxiliary power plant. And in the mid-90s, three production boats “Gotland” were built, in which, along with the diesel engine, two diesel engines were used with a total capacity of about 500 hp.


The Japanese began to use the same technology. But they got more impressive results. 4 AIP boats Soryu (“Blue Dragon”) generate a total of 8000 hp.


Based on the ECG, VNEU of German boats of project 212 was built. However, the low output power of the ECG allows the boat to move underwater at a speed of only 3-5 knots. In this connection, these boats have a hybrid power plant, which includes diesel. Much more successful are boats of Project 209, developing a speed of 11.5 knots with an underwater range of 400 miles.


The Rubin Design Bureau went the same way, creating the “fourth generation” boat of Project 677 Lada. However, the fourth generation did not work, because the designers could not create a AIP by the time the B-5 lead boat was launched.


However, the fourth generation did not succeed, because the designers could not create a AIP engines by the time the B-585 Saint Petersburg head boat was launched, by 2004. It did not appear in 2010, when the boat was accepted for trial operation.


Lada is indeed a beautiful submarine, the noise level of which is significantly lower than that of the famous Varshavyanka. Developers claim that twice. The boat has the latest navigation system with enhanced orientation capabilities. The highest degree of automation of all processes has been achieved, thanks to which the crew has been reduced to 35 people.


But AIP did not work. Although developers still praise it so far, claiming that a revolutionary breakthrough in the field of fuel cells has been used. In ECG, a chemical reaction is maintained in which hydrogen and oxygen are involved. The Germans use both gases liquefied stored in cylinders. Rubin receives hydrogen from diesel fuel through reforming.


Vigorous reports on the successful progress in the creation of the AIP continued after 2010, when the St. Petersburg boat was transferred to the Northern Fleet for trial operation.


The last peppy message came from the Rubin Design Bureau four years ago. It was stated that onshore testing of the installation was successful. Sea tests are being prepared. After that, it will come to the installation of AIP engine on two Lada under construction – the B-586 Kronshtadt and the B-587 Velikiye Luki.


But then there was silence. It turned out that the power taken from the installation was clearly not enough to ensure the normal operation of the submarine. And normal operation assumes that the underwater speed of the Lada will reach 21 knots. It is clear that the most advanced AIP engine will not pull such a load. Therefore, the power plant must be a hybrid type.


And now one more attempt will be made, it is already unknown what kind of account, an attempt to create the installation necessary for the fleet. And now the leadership of Rubin has announced that everything will be ready in 2021–2022.


The “Malachite” Design Bureau has a slightly different situation. This design bureau reanimates the  Piranha project 865 small non-nuclear submarine family with a displacement of 300 tons and a length of 28 meters that was ruined in the late 1990s. The crew consisted of three team members and six combat swimmers. The boat was supposed to be used off the coast for reconnaissance, sabotage, and the protection of naval bases. The working depth ranged from 10 m to 180 m.


High speed was not required from the boat, surface – 6 knots, subwater – 6.7. In the late 80s, two boats were built and assigned to the Baltic Fleet. In 1999, they were disposed of. One of the reasons for this decision was that the sailors in the boats were disappointed. That is, they were both difficult to operate, and their practical benefits were small.


The piranhas were equipped with a diesel engine. But at the same time, Malachite Design Bureau created an AIP engine for them. And certain results were achieved – the installation provided a speed of about 4 knots.


And now, Malachite announced the creation of small boats of the new P-750B project, which were announced at the Army-2019 forum. “Piranha” has grown pretty much – its surface displacement will reach 1,500 tons, and its length will be 66 meters. That is, tht should be the “colossus”, which AIP engine for “Piranha” obviously will not be able to pull. However, the developers claim that they have taken a huge step forward. The new installation should provide the boat with 1200 miles of underwater travel. The duration of the boat under water will approach two weeks.


AIP engine for the P-750B boat has a different principle of operation. It will be a gas turbine unit of a closed type. As an oxidizing agent, liquefied oxygen coming from a Dewar vessel is used. The gas mixture released during operation is frozen. The lead designer of Design Bureau “Malachite” Igor Karavaev claims that a promising boat with this installation will develop an underwater speed of 10 knots or more.


It remains to wait until the boat and AIP is ready for it, and find out how the designers managed to fulfill their promises. We have already heard pretty many promises.

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