AIP Technology for Submarines

AIP Technology for Submarines

Subject: Defence and Security

Section: Submarines

Context: France’s Naval Group, one of five shortlisted Original Equipment Manufacturers (OEM) for the Navy’s P-75 India (P-75I) project to build six conventional submarines within the country, announced it would not bid for the project. The reason was that the Request for Proposal (RFP) “requires that the fuel cell AIP be sea proven, and the French Navy does not use such a propulsion system.”

Concept:

P75 & P75I Project:

• In June 1999, the Cabinet Committee on Security approved a 30-year plan for the Navy to indigenously build and induct 24 submarines by 2030. In the first phase, two lines of production were to be established— the first, P-75; the second, P-75I. Each line was to produce six submarines.
• The contract for P-75 was signed in 2005 with the Naval Group, then known as DCNS, in partnership with Mazagon Dock Shipbuilders Ltd (MDL). The first KalvariClass (Scorpene Class) submarine under the project was commissioned in December 2017. Another five submarines have been built since; the final one, Vagsheer, was launched last month, and will be commissioned by late 2023.
• While P-75 deliveries were delayed, P75I has seen long delays even before it has kicked off. The first Request for Information was issued in 2008, then again in 2010, but the RFP was issued only in July 2021.
• This will be India’s first project under the Strategic Partnership Model—the government will give the contract to an Indian Strategic Partner (SP), which will partner with a foreign OEM to build AIP-powered submarines in the country.

AIP Technology:

• AIP refers to Air-Independent Propulsion, a technology for conventional— that is, non-nuclear — submarines.
• There are different types of AIP mechanisms available; what India is looking for under the P-75I project is AIP based on fuel cells. These cells convert chemical energy into electrical energy, recharging the batteries of the submarine.
• AIP has a force multiplier effect on lethality of a diesel electric submarine as it enhances the submerged endurance of the boat several folds.
• Diesel electric submarines must come to the surface or close to it (2-3 days) to run their generators to recharge the batteries that propel them under water. AIP is a mechanism that allows the batteries to be charged even while the boat is submerged. However, even with AIP, the submarine needs to surface every three weeks or so (14 days).
• While the six P-75 submarines are diesel- electric, they can be fitted with AIP technology later in their lives. By the time P-75I is completed under the 30-year project, India is projected to have six diesel-electric, six AIP-powered, and six nuclear attack submarines (yet to be built).
• India has been working to develop AIP technology indigenously as well. A tableaux of the DRDO at this year’s Republic Day parade showcased AIP. In March2021, the Defence Ministry had said DRDO had achieved an “important milestone in the development of AIP System by proving the land-based prototype”. However, experts have certain doubts about it.
• Around 10 countries have developed or are close to building AIP technology, and almost 20 nations have AIP submarines.

Concerns:

• The Australian paper says “installing AIP increases the length and weight of the boats, requires pressurised liquid oxygen (LOX) storage on-board and supply for all three technologies”. Also, “MESMA and the Stirling engine have some acoustic noise from moving parts; and the…submarine’s unit cost [increases] by around10%.”
• Second is the requirement to demonstrate a sea-proven fuel cell AIP. While some manufacturers may have the technology, it may not have been proven at sea yet.
• Another problem for the OEMs, sources said, is the transfer of technology. Sources believe that the OEMs are unwilling to share all their expertise, especially the niche technologies that they have built.

What submarines does India have now?

• India has 16 conventional diesel-electric submarines, which are classified as SSKs. After the last two Kalvari Class subs are commissioned under P-75, this number will go up to 18.
• India also has two nuclear ballistic submarines, classified SSBN.
• Of the 16 SSKs, four are of ShishumarClass, which were bought and then built in India in collaboration with the Germans starting 1980s; eight are Kilo Class or Sindhughosh Class submarines bought from Russia (including erstwhile USSR) between 1984 and 2000; and four are Kalvari Class built in India at MDL.