K-4 (SLBM)

K-4 or Kalam-4 is a nuclear capable intermediate-range submarine-launched ballistic missile developed by the Defence Research and Development Organisation of India to arm its Arihant-class submarines. 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 system for the missile while S4 and S4* submarines have double the number of vertical launching system. The missile has completed developmental launch trials and has reportedly entered serial production after a final two consecutive launch trials in January 2020 within a gap of six days. In September 2024, ANI reported the deployment of the missile onboard the Arighaat, several days past her commissioning.

Development

The importance of submarine launched nuclear weapon capability has been recognised early due to its inherent flexibility, survivability and secrecy which aligned well with India's no first use and credible minimum deterrence policy. The first indigenous SSBN was launched in 2009 and was commissioned seven years later as INS Arihant. Concerns related to the limited range of K-15 ballistic missile operationalised by the submarine was addressed gradually with the development of a higher range version.

In January 2010, the K-4 was secretly tested off Vishakhapatnam. The 10 metre long and 1.3 metre wide 'black and white' missile emerged from a pontoon submerged 50 metre underwater and breached the surface. A second firing was also conducted in Visakhapatnam which has revalidated the critical ability of a 20-tonne projectile to withstand 50 kg of water pressure and eject from a submerged launcher before engaging its rocket booster.

Agencies responsible

The High Energy Material Research Laboratory (HEMRL) and the Advanced Centre for Energetic Materials (ACEM) of the DRDO have been involved in developing the three motors responsible for propelling the K-4, the systems responsible for separating the stages of K-4, the low-thrust boosters, the gas generator and other components. The launch system of K-4 has been developed by the Naval Systems Group of the Research and Development Establishment (Engineers).

Description

The K-4 is a submarine-launched ballistic missile which is composed of two stages. The missile is reported to be long with a diameter of and weighs nearly . It can carry a warhead weighing up to 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: ~
Reduced load: ~
* Guidance system: Inertial navigation system with GPS/NavIC satellite guidance
* Circular error probable: <. (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.

Testing

Operators

;

* The Indian Navy is the only operator of K-4. As of September 2024, the deployment capacity stands at 8 missiles on Arihant-class ballistic missile submarines:
** S2 ''Arihant''
** S3 ''Arighaat''
** S4 ''Aridhaman''
** S4* ''(Unknown designation)''

See also

*K Missile family
*Arihant-class submarine
*Submarine-launched ballistic missile

References

{{DEFAULTSORT:K-4 (SLBM)
Submarine-launched ballistic missiles
Defence Research and Development Organisation
Ballistic missiles of India