Why in News
INS Taragiri, the fourth ship of the Nilgiri-class (Project 17A) stealth frigates, was commissioned into the Indian Navy on April 3, 2026 at Visakhapatnam by Defence Minister Rajnath Singh. On the same day, the Defence Minister laid the foundation stone for a Large Cavitation Tunnel (LCT) facility at the Naval Science and Technological Laboratory (NSTL), a DRDO lab in Visakhapatnam.
INS Taragiri — Key Details
| Parameter | Details |
|---|---|
| Class | Nilgiri-class (Project 17A) |
| Type | Stealth guided-missile frigate |
| Ship number | Fourth (of seven planned) |
| Displacement | ~6,670 tonnes |
| Builder | Mazagon Dock Shipbuilders Ltd (MDL), Mumbai |
| Steel supplier | SAIL — ~4,000 tonnes from Bokaro, Bhilai, and Rourkela plants |
| Commissioned | April 3, 2026, Visakhapatnam |
Nilgiri-Class (Project 17A) Fleet
| Ship | Status |
|---|---|
| INS Nilgiri (F49) | Commissioned 2024 |
| INS Udaygiri (F50) | Commissioned 2025 |
| INS Dunagiri (F51) | Commissioned 2025 |
| INS Taragiri (F52) | Commissioned April 2026 |
| INS Vindhyagiri (F53) | Under construction (GRSE) |
| INS Mahendragiri (F54) | Under construction (MDL) |
| Ship 7 | Under construction (GRSE) |
The Nilgiri class is an evolution of the Shivalik-class (Project 17) frigates with enhanced stealth features, advanced radar systems, and BrahMos missile capability. They are designed by the Warship Design Bureau of the Indian Navy.
Large Cavitation Tunnel (LCT)
What is Cavitation?
Cavitation is a hydrodynamic phenomenon where rapid pressure changes in water create vapour bubbles that collapse violently, causing noise, vibration, and structural damage to propellers and hulls. For submarines, cavitation is the primary source of acoustic signature — a noisy submarine is a detectable (and vulnerable) submarine.
Why LCT Matters
| Feature | Significance |
|---|---|
| Closed-loop simulation | Submarine hull and propeller testing under deep-water conditions |
| Free-surface simulation | Surface ship hull and propeller testing |
| Combined capability | Globally unique: both modes in one facility |
| Aatmanirbhar value | Eliminates need for critical testing abroad |
| Applications | Next-gen submarine design, ship propulsion, underwater weapons, torpedo shapes |
NSTL (Naval Science and Technological Laboratory)
- DRDO laboratory in Visakhapatnam
- Specialises in underwater weapons and systems — torpedoes, mines, underwater sensors
- Developed the Varunastra heavyweight torpedo (India’s first indigenous torpedo)
- Key contributor to the ATV (Advanced Technology Vessel) programme for nuclear submarines
India’s Naval Indigenisation
India’s naval shipbuilding programme reflects the broadest defence indigenisation effort:
| Ship/Programme | Builder | Status |
|---|---|---|
| INS Vikrant (Aircraft Carrier) | Cochin Shipyard Ltd | Commissioned 2022 |
| Arihant-class SSBNs (3 ships) | L&T, SBC Vizag | Operational |
| Nilgiri-class frigates (7 ships) | MDL + GRSE | 4 commissioned |
| Kalvari-class SSKs (6 Scorpene) | MDL | 6 delivered |
| Anti-Submarine Warfare Corvettes | GRSE | Under construction |
| Next-gen destroyers (Project 15B) | MDL | 4 commissioned |
SAIL’s role: SAIL supplies specialised naval-grade steel (DMR-249A) from Bokaro, Bhilai, and Rourkela plants — a strategic capability since importing warship-grade steel is subject to export controls and sanctions.
UPSC Relevance
GS Paper 3 — Security & Defence
- Aatmanirbhar Bharat in naval defence: indigenous shipbuilding
- Project 17A (Nilgiri-class): design and production timeline
- Cavitation in submarine design: noise signature and stealth
- DRDO labs: NSTL, NPOL, and their contributions
Prelims Fast Facts:
- INS Taragiri: 4th Nilgiri-class (Project 17A) stealth frigate
- Commissioned: April 3, 2026 at Visakhapatnam
- Project 17A total ships: 7 (4 MDL + 3 GRSE)
- LCT location: NSTL (DRDO), Visakhapatnam
- NSTL developed: Varunastra torpedo
- SAIL steel grade for warships: DMR-249A
Facts Corner
- INS Taragiri is named after a peak in the Western Ghats — following the mountain-naming tradition for Indian frigates (Nilgiri, Udaygiri, Dunagiri are all mountain peaks)
- Project 17A was sanctioned at an estimated cost of Rs 45,000+ crore for seven frigates — making it one of India’s largest warship programmes
- Cavitation noise is what enemy sonar uses to detect submarines — reducing cavitation through better propeller design is the single most impactful stealth improvement for any submarine
- India now operates the world’s largest warship construction programme by number of ships under simultaneous construction — over 60 ships and submarines are being built across Indian shipyards
- GRSE (Garden Reach Shipbuilders and Engineers), Kolkata, builds 3 of the 7 Nilgiri-class ships — the split between MDL (Mumbai) and GRSE (Kolkata) reflects the strategy of developing multiple shipbuilding centres rather than concentrating capability
