K-4 SLBM Test from INS Arighaat

Why in News ?

India recently conducted a successful test of the K-4 submarine-launched ballistic missile (SLBM) from the nuclear-powered submarine INS Arighaat in the Bay of Bengal. The test demonstrated India’s ability to strike targets at a distance of around 3,500 km from underwater platforms, significantly strengthening its sea-based nuclear deterrence.

Background & Context

India’s nuclear doctrine is anchored in credible minimum deterrence and a no-first-use policy, which requires a survivable second-strike capability.
To ensure this, India is developing a nuclear triad consisting of:

• Land-based ballistic missiles
• Air-delivered nuclear weapons
• Sea-based nuclear weapons (SLBMs)

The Arihant-class nuclear submarines, armed with long-range SLBMs like the K-4, form the most survivable leg of this triad, as submarines can remain concealed underwater for extended periods.

K-4 Missile: Overview

• Also known as Kalam-4 (K-4)
• A nuclear-capable, intermediate-range SLBM
• Designed primarily for deployment on Arihant-class nuclear submarines
• Each Arihant-class submarine can carry four K-4 missiles
• Indigenously developed by the Defence Research and Development Organisation (DRDO)

Key Features of the K-4 Missile

• Range: Approximately 3,500 km
• Propulsion:
  • Two-stage
  • Solid-fuel system
• Launch Capability:
  • Cold-launch from underwater
  • Missile is ejected from the submarine before engine ignition, enhancing platform safety
• Guidance System:
  • Advanced inertial navigation system
  • Supported by GPS and NavIC (India’s regional navigation satellite system)
• Accuracy:
  • High precision due to multi-layered navigation support
• Penetration Capability:
  • Equipped with manoeuvring features to evade missile defence systems

Strategic Significance of the Test

• Strengthens India’s sea-based nuclear deterrence
• Enhances the operational credibility of Arihant-class submarines
• Expands India’s strategic reach across key regions
• Demonstrates:
  • Technological maturity in SLBM development
  • Progress in defence indigenisation under Atmanirbhar Bharat
• Reinforces India’s position as a credible nuclear power with a functional triad

INS Arighaat and India’s SSBN Programme

• INS Arighaat is part of India’s Strategic Forces Command
• Represents the next phase of India’s indigenous SSBN programme
• Designed to:
  • Remain submerged for long durations
  • Conduct deterrent patrols
• K-4 missiles allow SSBNs to strike targets without approaching hostile coastlines, improving survivability

Comparison with Other Indian SLBMs

• K-15 (Sagarika):
  • Range: ~750 km
  • Suitable for regional deterrence
• K-4:
  • Longer range
  • Enables deterrence against distant adversaries
• Reflects a graduated evolution of India’s SLBM capabilities