Russia offers novel AIP for Indian submarine program
The reformed diesel-based AIP will be cheaper and more efficient, say designers

Russia is planning to offer its new Air Independent Propulsion (AIP) plant for the Indian Navy’s upcoming Project 75(I) program for the acquisition of six new submarines.

[stextbox id=’stratpost’ caption=’What is AIP?’ color=’000000′ ccolor=’ffffff’ bgcolor=’909090′ cbgcolor=’000000′ bgcolorto=’909090′ cbgcolorto=’000000′]An AIP is essentially a source of power for conventionally powered diesel-electric submarines that allows the boats to stay submerged and operational for extended durations of time, beyond the capacities of standard batteries and without a running internal combustion engine. This capability is much sought-after by the submarines arms of navies around the world, quite simply because it enhances the ability of submarines to maintain a presence without surfacing.[/stextbox]

On the sidelines of the 10th International Maritime Defence Show (IMDS 2021) held at St. Petersburg, last month, Chief Executive Officer (CEO) of Russia’s United Shipbuilding Corporation (USC), Alexey Rakhmanov told visiting Indian news media, “We have been preparing the Air Independent Propulsion for a long time, now and we’ve been continuously testing the system, with full tests next year. These tests basically, once again, highlight the novelty of the system compared to the systems offered by the other countries. In fact we are inviting specialists to co-invest in this technology to be part of this innovation, since we see a lot of benefits in terms of partnering with the Indian manufacturers.”

The government-owned United Shipbuilding Corporation is the largest shipbuilding company in Russia. It includes over 40 shipyards, design bureaus and associated production plants that are run by almost 95,000 employees, and are responsible for the production of 80 percent of Russia’s military and commercial vessels.

Rubin Design Bureau is part of USC and is responsible for the design of all classes of Russian submarines. Rubin is also responsible for the design and development of the Amur 1650 submarine, which Russia is planning to offer for the Indian Navy’s Project 75(I) program. A large part of the development work involves the development of an innovative new concept for Air Independent Propulsion (AIP) for the submarine, which StratPost reported in 2018.

And although the Request For Proposal (RFP) for the Project 75(I) program (expected this month) has been a long time coming, Deputy CEO of the Rubin Design Bureau, Andrei Baranov, explained that work on the new concept has been chugging along. “We’re also working on the AIP plant, for our own Russian Navy, as well,” he said.

Novel Concept

Chief Designer at the Rubin Design Bureau, Igor Molchanov, broke down the concept, which is significantly different from existing fuel cell-based AIP plants.

According to Molchanov, a submarine with this AIP plant would be capable of being submerged for as long as the stock of oxygen remained available for the plant.

More economical than the technology and process used by existing fuel cell-based AIP plants, he explained that the objective of both types of processes is the production of hydrogen, which is then mixed with oxygen to produce electrical power and water.

But while other technologies rely on storage of the hydrogen stock in special metal hydride or ‘intermettalic state’ cylinders, Molchanov explained that their AIP concept involves the storage of hydrogen simply in the form of carbon fuel from which it is extracted. This ‘reformer technology’ relies on carbon fuel that is already available in abundance on diesel-electric submarines: Diesel.

This has advantages over existing AIP technologies, which Molchanov pointed out rely on a ‘very specific chemical preparation technology that is quite expensive’. “It takes a lot of expertise, competence and technology to be able to create such a component, bond it with hydrogen and keep it in that state,” he said.

More importantly, existing technology has limitations in terms of how much hydrogen it can actually produce. “The saturation of hydrogen in the chemical component where the hydrogen is bonded is not very high as such, so the amount of hydrogen content released is also not very high. 1.5, maybe two percent — that’s the content,” explained Molchanov.

So What Is Rubin Working On?

“Globally, the most advanced way technology of getting producing this hydrogen is reforming of diesel. So, we are pursuing this way of producing hydrogen because this reformed diesel as a carbon agent has a high content of hydrogen. And diesel fuel is always available on any submarine, because it’s the standard, regular type of fuel that is used onboard,” he said, pointing out, “With this approach, with this technology, you don’t need to establish from a new enterprise process from point zero, which is very technology, labour and money intensive. So you don’t need to do that. That’s why its very advantageous from the point of view of economy.”

What Is The Process?

Hydrogen is released from diesel by way of reforming and purified. It’s then delivered to a chemical reactor where it is mixed with oxygen (stored in liquid state) to produce pure water (which is reused) and electrical energy, which powers all the systems onboard, via a special coupling device, including the propulsion motor, electronic warfare systems and weaponry. It will also charge the batteries.

“And by doing so the submarine is capable of being under water until the stock of oxygen is depleted,” explained Molchanov.

This AIP concept removes the requirement for managing the additional storage of hydrogen sources, both onboard submarines, as well as, at naval bases. It’s also noteworthy that this process involves the consumption (reformation) of a fossil fuel (diesel) for the production of electrical energy without combustion.

Does It Work?

According to Molchanov, the experimental model of this AIP plant has been undergoing tests, both land-based as well as on submerged platforms. “These trials will be carried out by next year,” he said, after which, “Based on the results of these particular trials that I’ve just mentioned, the model will be ready for full scale production and ready for integration onboard a submarine.”

Will It Meet Indian Specs?

Since the RFP hasn’t been issued yet, Rubin couldn’t comment on that, but Baranov explained that their reformed diesel AIP plant concept met the parameters that had been required in the earlier Request For Information (RFI) for the program. “It depends on requirements of the RFP,” he said, explaining, “That’s why when designing, we considered the particular requirements (of the RFI). ”

USC CEO, Alexey Rakhmanov thinks there might be potential for collaboration on this AIP with India. “We’ve started an analysis of whether some elements of the industrial version of this AIP might be easier or cheaper to produce in India than in Russia. And we’re analysing this possibility very, very thoroughly. And we still believe that there is place for other elements of submarines, such as batteries for example, in which I’m sure that India has certain experience and knowledge,” he said.

According to Rakhmanov, while their trials are expected to be completed next year, USC and Rubin are waiting for the exact specifications required by the RFP, which is expected to be issued by the Indian Navy this month.

But he’s optimistic that the novelty, simplicity and economy of the new AIP concept will have potential in India. “We don’t want to offer something that we developed twenty years ago, as the Germans are doing, and then convince you that this is the best you can get. We have the best and safest technology that could be available on the market and we offer it to the Indian Navy — design it, not only for the purpose of satisfying the needs of the Indian Navy, but also having the opportunity to go to third countries — why not?” he asked.