Indian Navy Seeks Low-RCS Stealth Upgrade for Heavy Frigates to Counter Sea-Skimming Threats

In a significant strategic shift aimed at future-proofing its fleet, the Indian Navy has reached out to the domestic private sector for advanced stealth technologies.

Under the 'Innovations for Defence Excellence' (iDEX) Winners-2025 challenge, naval leadership is seeking solutions to drastically reduce the Radar Cross-Section (RCS) of future warships, specifically targeting threats that approach near the water's surface.

The Challenge: Making Giants Invisible​

During a recent briefing at Navy Headquarters, industry leaders were presented with a complex engineering problem: how to effectively hide massive 6,000 to 9,000-ton frigates from radar detection at the horizon line.

While the specific technical parameters remain classified, the operational requirement is clear. The Navy needs designs and materials that can suppress radar signatures against "grazing-angle" threats—sensors looking at the ship from a very low elevation (0° to +5°).

This initiative targets the specific vulnerability of surface vessels to sea-skimming anti-ship missiles. These weapons, such as the advanced YJ-18, are designed to fly just 5 to 15 metres above the waves in their final approach (terminal phase), making them difficult to detect and intercept.

The Physics of "Grazing Angles"​

For decades, warship stealth has focused on deflecting radar waves upwards or downwards using angled surfaces (tumblehome hulls) and enclosed masts. This works well against radars searching from high altitudes. However, low-flying missiles and enemy ships present a different challenge.

At low angles, the ocean surface acts like a mirror. Conventional ship features—such as vertical walls, gun turrets, and deck equipment—can act as "corner reflectors," bouncing radar signals directly back to the enemy. This makes a warship appear as a large, bright blip on a radar screen, even if it is technically a "stealth" ship.

The Navy’s new mandate requires industry experts to eliminate these reflections so that a missile seeker fails to lock onto the ship during the critical final kilometres of its flight.

Moving Beyond Current Capabilities​

The Indian Navy currently operates several classes of ships with reduced radar signatures, including the Talwar, Delhi, and the newly inducted Nilgiri-class frigates.

While these vessels possess design features that complicate long-range targeting, they were not built to remain invisible to modern, high-tech seekers active in the terminal phase.

The proliferation of satellite surveillance and Unmanned Aerial Vehicles (UAVs) has changed the nature of naval warfare. Enemies can now track a fleet's general location from space.

Therefore, the primary defence is no longer just hiding the ship's location, but ensuring that when an incoming missile switches on its active radar seeker in the final minute of flight, it sees nothing but the ocean.

Industry Implications and Future Tech​

This iDEX challenge signals that the Indian Navy is moving toward "Next Generation" surface combatants, likely referencing the future Project 17B frigates or Next Generation Destroyers (NGD).

To meet these requirements, Indian defence firms and startups will need to look beyond structural shaping. Solutions may involve:

• Advanced Metamaterials: Surfaces that absorb radar waves rather than reflecting them.
• Active Cancellation: Electronic systems that nullify incoming radar signals.
• Deck Design Changes: Hiding deck hardware and smoothing out the "clutter" that usually sits on the sides of a ship.

By pushing for these "low-RCS" capabilities, the Indian Navy aims to ensure its capital ships can survive in contested waters where the window to react to a supersonic, sea-skimming missile is measured in mere seconds.

 

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[Pirthpall Sekhon]

There's a probability of magnifying a twin more concentrated image to absorb such missiles away from a frigate.

 

[Pirthpall Sekhon]

These stealth frigates are needed in the Andaman Sea. We are its guardians.