The recently tested K-4 or Kalam-4 submarine-launched ballistic missile with a range of around 3,500 km from a nuclear-powered submarine in the Bay of Bengal is a major boost to India's nuclear deterrence and strategic capabilities.

With the test, India became part of a small group of nations having the capability to fire a nuclear missile from land, air and undersea.

The K4 missile was tested from submarine INS Arighaat off the coast of Visakhapatnam on Wednesday, Nov 27, 2024. It was the first test of the submarine-launched ballistic missile (SLBM) from a submarine.

The solid-fueled missile was tested at least five times in the last few years from submersible platforms.

The missile was tested for almost its complete range. The second Arihant-class submarine INS Arighaat was commissioned into the Indian Navy on Aug 29, 2024 with an aim to strengthen India's nuclear deterrence.

It has the distinction of having the indigenous systems and equipment that were conceptualised, designed, manufactured and integrated by the Indian scientists, industry and naval personnel.

The missile has a maximum range of about 3,500 km which offers greater operational flexibility compared to its predecessor K-15 having a limited shore-bounding range. On deployment, the missile will be the first to operationalise India's sea-based nuclear triad and can accommodate the demand of credible second-strike capability of its nuclear doctrine.

The INS Arihant and INS Arighaat have four vertical launching for the missile while S4 and S4* submarines have double the number of vertical launching system.

Generally, hypersonic missiles, capable of carrying conventional explosives or nuclear warheads, can fly in the range of five times the speed of sound (Mach 5 which is roughly 1,220 kilometres) per hour at sea level.

However, some advanced versions of hypersonic missiles can even fly at the speed of over 15 Mach.

The K-4 is a submarine-launched ballistic missile, which is composed of two stages. The missile is reported to be 12 metres (39 ft) long with a diameter of 1.3 metres (4 ft 3 in) and weighs nearly 17 tonnes (19 tons). It can carry a warhead weighing up to 2 tonnes (2.2 tons) and is powered solid rocket propellant. The DRDO stated that the aim of the missile was to achieve a high accuracy. As a countermeasure against ballistic missile defence systems, the K4 can perform three-dimensional maneuvers.

Specifications

• Range (exact is classified):
  Full load: ~3,000 kilometres (1,900 mi)
  Reduced load: ~4,000 kilometres (2,500 mi)

• Guidance system: Inertial navigationsystem with GPS/NavIC satellite guidance

• Circular error probable: <10 metres (33 ft). (Alleged)

The K-4 uses a powerful nose mounted motor which has two diametrically opposite mounted nozzles which fires underwater and enable the transition of missile through water, break the surface and continue the ascend into the atmosphere for the first few seconds. The gases ejected from this system is expected to create a gas bubble encapsulation around the missile which will reduce the drag during underwater transition. During the ascent into atmosphere, the four control surfaces at the base of the missile provide the necessary aerodynamic control to the missile.

After the burnout of the nose mounted motor, the base shrout at the bottom of the missile housing the control surfaces and control actuation system is ejected. The first stage will ignite to coincide with the burnout and ejection of nose mounted motor to prevent zero thrust condition. The flex nozzle control of the first stage will provide necessary steering during boost phase.  The airflow pattern over the nose cone of the missile is reminiscent of the one seen of blunt nose cones or nose cones with an aerospike which will reduce drag and heat load significantly.

In the last few years, India has been enhancing its overall military capabilities and test-fired a range of missiles with varying ranges.

Over 10 days ago, India successfully flight-tested a long-range hypersonic missile off the coast of Odisha. The weapon can strike with extreme speed and evade most air defence systems.

At present, Russia and China are way ahead in developing hypersonic missiles while the US is in the process of developing a range of such weapons under an ambitious programme.

Hypersonic missiles are considered highly manoeuvrable and agile as they can change course mid-way. The ballistic missiles, which can also fly at Mach 5, have limited manoeuvrability in view of predetermined trajectories.

India is focusing on bolstering its combat capabilities against the backdrop of China's aggressive military muscle-flexing.