On Friday, April 3, 2026, at the Indian naval base in Visakhapatnam, in Andhra Pradesh in the eastern part of the country, Defense Minister Rajnath Singh took part in a ceremony marking the commissioning into the Indian Navy (Bhāratīya Nau Senā) of two new warships: the third strategic submarine of the modified Arihant class, INS Aridhaman (S4), and the fourth Project 17A Nilgiri-class guided-missile frigate, INS Taragiri (F41).
Photo: Ministry of Defence of India
Although the ceremony focused on the commissioning of a new-generation frigate, the quiet star of the event was in fact the nuclear-powered submarine, the newest element of India’s sea-based nuclear deterrent.
This is especially significant because the new strategic submarine is larger than its predecessors built under the Advanced Technology Vessel program. The prototype INS Arihant (S2), commissioned in August 2016, is 111.6 m long, has a displacement of 6,000 t, and carries either 12 K-15 Sagarika ballistic missiles or 4 K-4 missiles; the same applies to the second boat, INS Arighaat (S3), which has been in service since August 2024.
The Aridhaman (S4) discussed here and Arisudan (S5), which is currently undergoing sea trials, form a sub-class with a lengthened hull of 130 m, increased displacement of 7,000 t, and twice the main armament load: 24 K-15 Sagarika missiles or 8 K-4 missiles.
The family of K-series submarine-launched ballistic missiles (with “K” standing for Kalam) includes the K-15 Sagarika model (alternatively designated B-05 and PJ-08), which carries a 1,000-kg conventional or nuclear warhead of undisclosed yield to a range of 750 km, as well as the larger K-4, which carries a 2,500-kg nuclear warhead of undisclosed yield to a range of up to 3,500 km.
These are therefore not strategic systems in the same sense as missiles of this class fielded by the major nuclear powers (the United States, Russia, China, France, and the United Kingdom). However, plans call for the K-5 missile (a 2,000-kg nuclear warhead delivered to a range of 5,000–8,000 km) and the K-6 (3,000-kg MIRVed nuclear warheads delivered to a range of 8,000–10,000 km). While the former are still expected to be deployed on Arihant-class boats as part of a rearmament effort, the latter are also intended for 4–6 planned next-generation S5 submarines, each of which is to carry 12 missiles.
Photo: MDL
As for the Project 17A guided-missile frigates, INS Taragiri (F41), commissioned yesterday, joins the first three ships: INS Nilgiri (F33), which has been in service since January 2025, and INS Himgiri (F34) and INS Udaygiri (F35), both in service since August 2025. Still this year, the following ships will enter service: Mahendragiri (F38), which is undergoing sea trials, Dunagiri (F36), which has been handed over for trials, and Vindhyagiri (F42), which has been launched. The commissioning of all seven ships will mark the completion of the program, which is being carried out by the shipbuilding companies Mazagon Dock Limited (MDL) in Mumbai and Garden Reach Shipbuilders & Engineers (GRSE) in Kolkata. The ships are being offered to Brazil as a complement to the four Tamandaré-class frigates, which are based on the German MEKO A-100 design.
Project 17A ships are 149 m long, have a beam of 17.8 m, a draft of 5.22 m, and a displacement of 6,670 t. Propulsion is provided by two MAN Diesel 12V28/33D STC diesel engines, each rated at 6,000 kW, and two General Electric LM2500 gas turbines. The main armament consists of Barak-8ER surface-to-air missiles in 32-cell vertical launch systems, 8-cell launchers for PJ-10 BrahMos cruise missiles for engaging surface and land targets, an OTO Melara 127 mm automatic gun, and torpedo launchers. Other equipment includes the BEL Humsa-NG hull-mounted sonar, the BEL Ajanta electronic warfare suite, and one HAL Dhruv or Sea King Mk. 42B multirole helicopter. The crew consists of 35 officers and 115 sailors.