Two Lada submarines are currently under construction at the Admiralty Shipyards in St. Petersburg. Launch of the second submarine named Kronstadt and commencement of its trials are scheduled for mid 2018. In 2017 the last hull butt on Kronstadt was welded, the casing was installed. As for the third boat, in 2017 the forward and aft pressure hull sections were completed and the hydraulic tests of both sections were carried out. At present various equipment is produced and installed in the hull.
The Russian Ministry of Defence has ordered two more class vessels.
In 2017 the leading ship Lada-class named "Saint-Petersburg" successfully completed missile firing as well as tactical training against another submarine while testing Lira sonar. The developer of the sonar concern Elektropribor points that functional capabilities of sonar Lira to excel considerably previous sonars of MGK-400 family (Rubikon) used on class conventional submarines. Therefore its comprehensive testing in various hydrological conditions is on the go. The purpose is to gain certain statistics, which will subsequently allow using this sonar with the specified efficiency under totally different conditions. Russian industry points Lira sonar in combination with small dimensions of the submarine and unusually silent propulsion motor with permanent magnets (used on a Russian submarine for the first time) to make Lada-class submarine an invisible underwater hunter.
As reported, "Saint-Peterburg" has demonstrated its qualities of a hunter at the test ranges of the Russian Northern Fleet. In duel situations it was the first to detect the "enemy" surface ships and submarines of other classes.
Torpedo tubes of 533-mm calibre fitted on class submarines are adapted for firing missiles. The submarine is capable of firing six-tube salvos, and quick loading gear allows firing the entire set of ammunition of 18 units within minutes.
AIP general info
The main reason behind adopting AIP systems is to increase a submarine's stealth by eliminating noisy snorkelling and remaining in contact with the atmosphere. The benefits of added stealth outweigh the increased cost of the submarine over its life cycle, stringent requirements for the infrastructure and crew training.
From both a theoretical and practical point of view, it is clear that none of today's AIP plant types are ideal in all respect; each has its merits and drawbacks. Besides, none of the navies have similar conditions. Each navy performs its tasks, operates in different geographical zones, and has varied level of crew training and conditions at naval bases.
Irrespective of all theoretical diversity of possible AIP types, the experience of recent years has shown that only two types of AIP systems are in demand in the market - Stirling AIP system and fuel cell AIP system. As for the closed cycle steam turbine MESMA, it has shown its practicality but has remained a niche product. Other exotic types of AIP plants have also remained on paper or in laboratories.
Stirling
The Stirling engine-based AIP system has become the first combat-ready system of new age. It is a relatively simple plant where diesel fuel (typical for the submarine) and liquid oxygen are used. Exhaust of the plant is discharged overboard rather easily at small and medium depths. Low power Stirling engines are much quieter than main diesel generators of submarine, which provides for considerable tactical gains. Accordingly, the introduction of such AIP system gave obvious advantages with acceptable investment in the engineering of the system itself, training of crews and modification of shore infrastructure. It took less than 15 years for the creation of this system from a concept to the implementation in a combat submarine.
Although this system cannot be considered ideal with respect to stealth it has proved relatively good in a small area, shallow , complex hydrology as well as heavy traffic that obviate the reduction of submarine acoustic signature to an absolute minimum. It is compact enough for small submarines. Hence it is good for countries like Sweden and Singapore as the conditions in the Strait of Malacca and adjacent water areas are quite similar to the Baltic ones.
The Japanese designers has gone the extensive way to enhance capabilities of AIP system - the Japanese submarines have the AIP system with four engines, not with two as the case with more compact Swedish submarines. Despite the level of industry development and the Japan Maritime Self-Defence Force preferred licensing the existing system, developed for noticeably different conditions instead of developing the indigenous one. This example once again shows that a choice of AIP system is due to many reasons, some of them not being seen at first glance.
Fuel Cells
The second type of AIP system - fuel cells - are firmly associated with German submarines of Class 212A and Class 214 though the works on various types of fuel cells are being conducted in other countries too, including Russia (alkaline fuel cells) and India (phosphoric-acid fuel cells).
Having passed a long way of theoretical and experimental investigations, German designers developed a submarine with a nearly "absolute" AIP system - low noise, low temperature, with ordinary water at the process output. These advantages were achieved at the expense of complexity and high cost of the system as well as considerable increase in submarine dimensions. The Class 212A submarines are three times larger than the previous submarines of the German Navy - Class 206. In addition, the fuel cell-based AIP system requires meticulous training of the crew and the setup of a dedicated infrastructure.
The implementation process of this AIP system turned out to be rather long. Twenty-five years have passed from the first activities on submarine AIP systems till the delivery of a combat submarine. Furthermore, the works of German designers were supported by the long-standing European efforts on bringing hydrogen energy into every field, most notably in automotive industry.
In addition to the development of the fuel cell as such - and complexity is inherent to this product - it was necessary to solve the problem of hydrogen storing. Hydrogen metal hydride storage used in submarines of Classes 212A and 214 makes it possible to achieve a high safety level, but requires considerable weights and volumes. The efficiency-safety conflict, so common for submarine design, in this particular case is expressed in large weight of metal hydride alloy and low hydrogen content in it. The increase of hydrogen quantity leads to an unacceptable weight of storage system and accordingly to an unacceptable size of the submarine. In addition, there are doubts in the applicability of metal hydride storage system for the submarine operating in the areas with high seawater temperature.
A specific feature of the metal hydride is to discharge hydrogen exactly when alloy temperature increases, which implies that there could be possible negative effect under tropical conditions as the discharge may take place spontaneously.
The German Navy who conceived their submarines for operations in the Baltic and Northern Seas have not been considering these limitations as essential ones. Submerged endurance of Class 212A submarine is sufficient for these theatres due to their constraints. When the Italian Navy joined the 212A programme, the picture did not change much - realities of the Mediterranean Sea do not require a high submerged endurance. Besides, one should bear in mind that German and Italian submarines both in the Mediterranean Sea and near western and northern coasts of Europe operate in the areas controlled by allied surface and air forces. These submarines may be deployed to the operational areas in any mode. Accordingly, they may use diesels for battery charging the most time switching over to the fuel cell mode only in case of extreme necessity.
Development of the hydrogen infrastructure necessary for hydrogen generation, storage and transfer to the ship is an important part of AIP system engineering. This is related to both stringent requirements for hydrogen purity and its potential hazard. Since the mid-1970s, the activities in the field of hydrogen power including the works on hydrogen storage and transportation have been carried out by many European companies, first of all, by automotive ones. From the late 1990s, these works were actively supported and financed by the European Community. The joint efforts brought positive results. Relying on the achievements of commercial sector, the German industry has successfully coped with the establishment of infrastructure for the Navy.
The Class 214 submarines intended for export also have the AIP system consisting of fuel cells and metal hydride cylinders for hydrogen storage. Their submerged endurance also turned out to be sufficient for the countries that bought these submarines - Portugal, Greece and Turkey. Their navies operate in the same conditions, and purchase of submarines, made with the use of proven technologies, reduces financial and technical risks. The European countries that buy the submarines with this AIP system relyon the one hand, on the already engineered hydrogen infrastructure, and on the other hand, they expand it because they have joined the users of Class 214 submarine.
In East Asia, the situation is quite different especially when it comes to the necessity to create a submarine with submerged endurance over two weeks and the non-availability of expensive hydrogen infrastructure. The deployment of such infrastructure would take dozens of years.
Types of reforming
These obvious problems made the designers look for new solutions of hydrogen storing. One of them is to store hydrogen in the form of certain chemical compounds with their further disintegration and recovery of hydrogen (reforming). Nowadays the activities are underway in several directions. The most known of them is reforming of methanol, ethanol and diesel fuel. Activities are being carried out for the reforming of other compounds too, for example, sodium borohydride that is stored as water solution. Transfer to the submarine and storage of these liquids is much easier compared to hydrogen and does not affect its safety directly. The volume of hydrogen containing liquids can be very large.
Application of each of the above-mentioned substances has its pros and cons. During development of submarine reformer, it is necessary to solve among others the issues related to fuel storage and compensation, cooling of the plant, exhaust, etc. All these aspects in their turn affect the submarine's all-round stealth.
Methanol is the easiest to decompose. The least amount of oxygen is required for its decomposition. The produced hydrogen has the highest purity. The decomposition process generates the least amount of carbon dioxide. The volume of carbon dioxide is essential for the submarine AIP plant because the exhaust not only requires an additional system and affect the submarine stealth but also requires the compensation for the weight of discharged carbon dioxide. Unfortunately, drawbacks of methanol are also considerable. It is extremely toxic; tanks, pipelines and fittings intended for this alcohol should be thoroughly sealed and monitored, during both operation and loading the fuel. The methyl alcohol dissolves in water, therefore it cannot be stored and compensated for in the same way as the diesel fuel by taking water in the same tank where the fuel is contained. It is evident that a relevant shore infrastructure will be required. Dedicated procedures and technical means will be necessary for purchase and storage of this toxic alcohol as well as its transfer to the submarine.
Ethanol is close to methanol by its properties, however it demands a more complicated reformer; the process takes place at higher temperatures and produces a larger amount of carbon dioxide. Formally, ethanol is not poisonous, however it is not of a less threat for the crew than methanol. Ethanol storage and compensation are prone to the same problems as for methanol. Its employment also requires a dedicated infrastructure. One can say that ethanol reforming could enhance the crew safety but with additional complexity and a rise in price of AIP plant and the entire submarine.
The obvious advantage of sodium borohydride reforming is that the process does not require oxygen and does not produce a gaseous exhaust.
Diesel fuel reforming is attractive from operational point of view. Use and
storage of diesel fuel has been mastered long ago, it is not expensive and quite safe; all naval bases of the world have an adequate infrastructure. In addition, only in case of the diesel fuel the submarine gets the possibility of storing only one type of fuel and use it for both diesel-generators, if any, and the AIP system. Hence, submarine operational cost reduces.
At the same time the diesel fuel reforming demands the highest consumption of oxygen, it takes place at highest temperatures, produces the largest exhaust volume and the hydrogen generated requires thorough purification. In this respect, it is similar to a nuclear reactor - the nuclear-powered plant is rather complicated too.
However, it is a "single engine" and provides for the greatest capabilities for the submarine.
Activities on Reforming
German designers commenced the activities on reformers as early as the 1990s and investigated different types of such plants including the building of demonstrators. Based on these results, methanol was selected as fuel in striving to get a compact and relatively cheap system that could be applicable for submarines of Class 212A (2nd batch) planned at that time for construction as well as for export submarines of Class 214. Howaldtswerke-Deutsche Werft (HDW) has developed and tested a methanol reformer demonstrator and then a prototype of methanol reformer. The activities on support systems were performed, primarily for an exhaust gas discharge system. However, the Class 212 A submarines have not received the reforming system due to two circumstances: size of the system did not allow its easy integration into the existing project, and the economic crisis forced the German Navy to abandon financing these activities.
Nevertheless, HDW (now part of ThyssenKrupp Marine Systems) continues to work on the methanol reformer and actively offers a methanol reformer based AIP for export, first of all', within a power plant of the Class 216 submarines.
Project S-80 (Isaac Peral) of Spain is based on fuel cells and ethanol reformer. Spanish designers successfully created a worldwide cooperation and obtained quite encouraging first results including a low power demonstrator. The transition to a plant of rated power turned out to be more difficult. Amid problems with financing,it is yet to be seen whether it will be fruitful.
In 2014 the French companies reported about work on the second-generation fuel cell system with a diesel fuel reformer. DCNS has developed the AIP system with the diesel fuel reformer offered for the Scorpene submarines. According to producer their submarines would achieve the submerged endurance of three weeks and more with such a system.
India develops an indigenous AIP system for the Kalvari-class submarines.
The activities on the AIP systems based on fuel cells and diesel fuel reforming are also underway in Russia. As early as the 1990s, the Rubin Design Bureau and the Russian Navy opted for fuel cells as the most suitable AIP technology. However, the development of the AIP system was slowed by both the country's economic problems and lack of pressing need to have an AIP based submarine as the Russian Navy could take advantage of nuclear-powered submarines.
At that time the issue of hydrogen storage did not have a clear answer. After longterm analysis and selection of hydrogen storage method, the Rubin Design Bureau and the Navy came to the conclusion that namely the diesel fuel reforming is an optimal way.
The Rubin Design Bureau continues the activities on the development of AIP system based on fuel cells and diesel fuel reforming. The results of this work can be instrumental for India as it has to a large extent similar requirements for the submarine - long submerged endurance, necessity to operate independently from naval bases for a long time, low noise, easy and safe operation, low requirements for basing system.
Diesel fuel reforming is attractive from operational point of view. Use and storage of diesel fuel has been mastered long ago, it is not expensive and quite safe; all naval bases of the world have an adequate infrastructure. In addition the submarine gets the advantage of storing only one type offuel and can use it for the diesel-generators and the AIP system. Hence, submarine operational cost reduces. It is a "single engine" and provides for the greatest capabilities for the submarine.
As early as the 1990s, the Rubin Design Bureau and the Russian Navy opted for fuel cells as the most suitable AIP technology. After long-term analysis and selection of hydrogen storage method, the Rubin Design Bureau and the Navy came to the conclusion that the diesel fuel reforming is an optimal way. That choice takes into account the geopolitical and geographical realities under which the Russian Navy operates since they differ considerably from the European ones. The Russian boats sail in open theatres at long distances from bases with most of the time being under threat of powerful and skilled adversaries and therefore are not able to use unstealthy modes, including during the deployment to operational areas. Accordingly, they require longer submerged endurance that can be provided only if the reforming system is available. Disconnection of theatres (Northern and Pacific), infrastructure of many disconnected naval bases at long distances from each other with many of them being in little-inhabited areas with severe climate - all this makes construction and maintenance cost reduction the top priority.
These considerations resulted in works on the demonstrator of low power diesel reformer in 2008. This unit was successfully tested; in 2010, it was additionally developed by adding a hydrogen purification system. In 2013, the trials were completed. In 2012, the activities began on the demonstrator with a carbon dioxide treatment system. Its trials were successfully completed in 2015. Concurrently from 2012 to 2014, a high power prototype implemented in the size of a submarine compartment was developed and tested. Its trials were also completed successfully. Operation of these plants was demonstrated to the Russian and other navies representatives on various occasions. The diesel fuel reforming has become the technology for the Russian Lada type non-nuclear submarine.
