Project 75I - Comparison Between Navantia S80+ and TKMS U212A Submarine

Indian Navy is looking to induct more conventional submarines. After the P75 project resulted in Scorpene submarines, 9 of which will be ultimately acquired; logic says Indian Navy must progress to SSNs under P76A under which 12 boats should be acquired. But for some reason it wants more conventional submarines after 9 under P75; these include 6 under P75I (to be acquired in collaboration from foreign nation) and 12 under P76 (to be completely built indigenously). So, under P75I bids were invited and ultimate TKMS U212A and Navantia S80+ remain in the fray. Both U212A and S80+ are notable examples of use of advanced maritime technology; but while TKMS U212A has been in service for about 20 years, Navantia S80+ has been in service for about 2 years. Below is a comparative analysis of the 2 submarines.

● India’s Experience

Indian Navy has previous experience with TKMS having operated the 4 U209/Shishumar submarines since 1980s. These submarines are known for their modular design and build. This makes them perfectly suited for consistent upgrades, which is why these 4 submarines having served nearly 40 years are still going strong and are set to serve another 10 years atleast. Indian Navy has never operated Navantia submarines, eventhough S80+ on offer are a derivative of Scorpene submarines that Indian Navy operates having acquired them from Naval Group. A key aspect of P75I is adherence to the Strategic Partnership (SP) model by Navantia and Naval Group and the Transfer of Technology (ToT).

● Similarities

Both submarines have similar sonar technology, although sourced from different vendors. Both are equipped with cylindrical, flank, towed, passive rangefinder and interceptor sonar among others.  Both are fitted with hydrogen-based fuel cell-based AIP technology, a key requirement for Indian Navy. The U212A has a proven AIP having been developed and deployed for several years across many submarines. Its compact size and advanced sensor suite that enables it to operate effectively in shallow waters and congested maritime environments. This makes it ideal for anti-submarine warfare (ASW) and reconnaissance missions in shallow waters.

The S80+ also submarine offers enhanced endurance allowing it to undertake long-range patrols and extended deployments in deep ocean waters. A drawback is S80+ has as yet unproven AIP, which yet to be deployed in the lead Spanish submarine Isaac Peral (to be deployed during 1st mid-life upgrade). A key risk with 212A is it carries a massive hydrogen fuel tank, while S80+ makes hydrogen onboard. Both have a modern platform control system and a state-of-the-art combat system that includes the latest technology to practice of TMA (Target Motion Analysis) based underwater tactics.

● Air Conditioning (A/C)

As with the diesel generator, U212A only has 1 A/C unit in command unit creating another serious redundancy problem. Remember when maximum silence is needed, for quite some time during patrols; submarines are many times forced to shutdown a/c raising the temperature inside the hermetically sealed steel tube/submarine. It is anybody’s guess the temperature the electronic equipment in command unit would be reaching during that time. The S-80, on other hand has 13 independent air conditioners distributed throughout the boat and a cooling system dedicated exclusively for the combat system, has more than enough redundancy.

● Diesel Generator Propulsion

Both U212A and S80+ submarines use diesel-electric propulsion for endurance and stealth. U212A is equipped with fuel-efficient diesel engines for surface propulsion and silent electric motors for submerged operations. The U212A has only one diesel generator has 2 very significant drawbacks; the first is snorkelling, it takes too much time at periscope depth performing noisy operations. The second drawback is that by having only one diesel generator (1 × MTU-396 16V (2,150 kW); 1 × Siemens Permasyn electric motor Type FR6439-3900KW (2,850 kW)) it doesn’t have a real back up system; the AIP can propel the ship, but this too is limited. Remember U212A’s AIP technology is based on a chemical reaction based on hydrogen and oxygen creating sufficient electrical current to propel the submarine, enough but not excess (a massive hydrogen tank carried on board). If for any reason the boat must increase speed, the AIP simply can’t do it by itself and the submarine must consume electricity from mixed sources (AIP and batteries). The submarine though has proposed to use Lithium-Ion batteries, allowing for higher speed and endurance under P75I.

This means U212A has no real redundancy when charging the batteries. It only has one diesel and if it fails, everything is at the expense of an AIP system that is not capable of generating the same amount of power as the diesel generator. On the other hand, S80+ submarines’ AIP system employs a diesel-electric propulsion system with new Bio-Ethanol Stealth Technology (BEST) that is also based on hydrogen using bio-ethanol reforming technology with no moving parts to generate hydrogen onboard without need to carry a hydrogen tank. Also, the S-80, with 3 diesel generators (1 shaft Etanol-AIP, 3 bio-ethanol engines (3 × 1,200 kW) MTU-16V-396SE-85L, 1 electric motor (3,500 kW), 1 AIP fuel cell unit (300 kW)), solves with guarantee the two deficiencies raised about U212A, ensuring significantly shorter snorkelling time. The three Diesel generators will be placed behind the AIP module. Do note though AIP increases endurance it cuts down on speed. The S80+ AIP allows it an extra endurance of up to 21 days atleast, allowing it to operate quietly and remain submerged for prolonged durations. This makes it ideal for covert missions and intelligence gathering.

● Combat Information Center (CIC) Layout

Both submarines come with a modern integrated combat system. Reportedly the console layout of S-80+ makes more sense than U212A. On U212A the Tactical Action Officer (TAO) is isolated from sonar display and needs to get up to see it.  On the S-80+, the TAO sits in between the sonar supervisor and the tactical supervisor.  In this way, the TAOs situational awareness is far better than the TAO on U212A.

● Crew Comfort

The U212A with total complement of 27 has a very limited space with any extra detachment meaning many are forced to hot bunk. There are only 26 bunks and each shift has 12 men. It implies U212A is designed to operate with 2 watches with 24 standing guard excluding commander, TAO, and cook resulting in fatigue on long patrols. S-80+ submarine on other hand with total complement of 32 + 8 SF is equipped with 46 bunks and requires 11 men to operate in each shift. It implies S80+ is designed to operate with 3 watches with 33 standing guard, with commander and cook exempt, a much less demanding situation than U212A with lesser chance of fatigue on long range patrol.

● Hull

The U212A submarine features a unique design optimized for stealth and agility. The submarine hull is built using non-magnetic materials, making it difficult for magnetic detection systems to detect. Its hull is coated with anechoic tiles to minimize its acoustic signature, further enhancing its stealth capabilities. On the other hand, the S80+ submarine incorporates advanced technologies and is touted as one of the most modern diesel-electric submarines. It features a new hull design specifically optimized for improved underwater performance and reduced noise levels.

● Armament

Both U212A and S80+ submarines can fire a wide range of torpedoes including DM2A4 Heavy Weight, MK48, Blackshark, Spearfish and missiles like Exocet and Tomahawk to engage surface ships and submarines. U212A typically carries both DM2A4 heavyweight and Black Shark Advanced heavyweight torpedoes and can also launch IDAS (Interactive Defense and Attack System for Submarines), a guided missile system that provides it with a self-defense capability against airborne threats originating from helicopters equipped with lightweight torpedoes for anti-submarine warfare.

Under P75I both U212A and S80+ submarines need to be tailored to fire missiles in VLS mode (most probably land attack cruise missile like 600 or 800 km range Brahmos SLCM or 1500 km range Nirbhay/ITCM). However, equipping VLS or Vertical Launch System on both U212A and S80+ submarines can increase cost and overall weight affecting the boats efficacy. The VLS module is to be installed (if agreed and provided for on both) behind the sail in 8-/10-/12- cell configuration. While, U212A is 1800 tons and can accommodate another 200-to-300 ton VLS module, but whether S80+ already a 2950+ ton behemoth can accommodate another 200-to-300 ton VLS module is a doubt. Although both have 6 533 mm torpedo tubes from which 300 km range anti-ship/anti-submarine Brahmos NG SLCM can be fired (if and when developed), which is both lighter and smaller than original Brahmos.

● Sonar

U212A uses a variety of German built sonar. These include STN Atlas CSU 90 (DBQS-40FTC) Sonar suite, that incorporates a TAS-3 passive low-frequency towed array sonar (deployed from sail); FAS-3 passive low and medium-frequency hull-mounted flank array sonar is mounted on the hull; and MOA 3070 mine detection sonar is dual mounted on different locations. TKMS shouldn’t have any issue with ToT as per P75I requirements and can ensure Indian made weapons be integrated in future.

S80+ uses Lockheed Martin's cylindrical array sonar system. Integrated combat system of S80+ includes flank array sonar, passive ranging sonar, mine and obstacle detection sonar all developed by Lockheed Martin. However, high degree of American systems in the S80+ can be roadblock in future, owing to India's stringent requirements for ToT that necessitate a comprehensive understanding of what is covered under the proposed agreement. Also, will Lockheed Martin agree to integrate Indian-made weapons into S80+’s submarines combat system for long-term operational autonomy and self-sufficiency is questionable (India’s Tejas suffered a lot from USA denial of technology).

● Conclusion

All this present Indian Navy with a peculiar problem. Whether to still persist with P75I or continue with P75 or move ahead with P76. There is issue of technology transfer, cost and efficacy as well. In U212A whether Indian will chose the Batch 1 or Batch 2 or Batch 3 or the 212 CD design is also a question. While U212A uses a tried and tested AIP but a risk of dangerous hydrogen tank onboard exists. The S80+ on the other hand has the most advanced AIP with no moving parts and doesn’t carry hydrogen in tank, making it onboard.

After the above finally the question is of integrating Indian weapons in future and last but not the least overall cost and operational efficiency. IMHO Indian Navy should either stick with P75 Scorpene, ordering total 12 to 15 increasing their capability in each batch; skip P75I and move to P76 ordering 12 to 15 of them; that way India will ultimately have 30 SSKs in total (with numbers cost per unit will come down). However, best case scenario is that Indian Navy should stick with P75 Scorpene, ordering total 12 to 15 increasing their capability in each batch; and then move straight to P75A 5000-ton SSNs building a total of 9 of them in total (1 each to protect the 3 S5 class SSBNs, keep 3 in docks for maintenance or reserve, and 3 to patrol the high seas).

Note that the 3 current S2 class SSBNs will eventually operate as SSGNs firing long range land attack Brahmos SLCM or Nirbhay/ITCM SLCM; once the S5 class SSBNs become operational. It remains to be seen what does Indian Navy opts for as best case scenario based on the expected changes in prevailing military and geo political situations.