Why this matters now
K-Family is tested for: completing the sea-leg of India’s nuclear triad; SLBM survivability advantage (mobile undersea launchpad — cannot be pre-emptively neutralised); K-15 Sagarika (1st operational SLBM, 750 km); K-4 (long-range, 3500 km, reaches all of China); K-5 + K-6 (in development for MIRV+hypersonic); the Defence Strategic Programmes Office under PM’s direct oversight.
K-Family series
| Missile | Range | Stage | Status |
|---|---|---|---|
| K-15 (Sagarika) | 750 km | 2-stage solid | Operational on Arihant; 1st underwater test 27 Jan 2013 from pontoon; 1st test from Arihant 14 Oct 2022. 1-tonne nuclear warhead. |
| K-4 | 3,500 km | 2-stage solid; canisterised | Operational on Arihant + Arighat; 1st test 24 March 2014; from Arihant 19 Nov 2018; 2-tonne payload; length 12 m. |
| K-5 | 5,000 km | MIRV-capable | Under development; matches Agni-V land sea-leg; targeted 2028-29. |
| K-6 | 8,000 km | MIRV + hypersonic glide vehicle | Under development; matches Agni-VI sea-leg; targeted 2030-32. |
Technology & doctrine
K-15 (Sagarika): 1st underwater test from pontoon platform 26 February 2008 (failed); 27 January 2013 successful pontoon test; 14 October 2022 1st operational test from INS Arihant. 1-tonne nuclear warhead; two-stage solid propellant. Surface-launched cold-launch (gas-generator) before ignition. CEP ~10m thanks to ring-laser-gyro INS + GPS-INS fusion.
K-4: Length 12 m, diameter 1.3 m, 2-tonne payload — nuclear or conventional. Ranges all of China including Beijing, Lop Nur. K-5 (5,000 km) under development to match Agni-V’s sea-leg with MIRV.
Doctrinal role: SLBM is the most survivable leg of nuclear triad — SSBNs can hide undersea for months. India’s NFU (No First Use) doctrine requires assured second-strike capability; SSBNs guarantee this. The Defence Strategic Programmes Office (under PM) oversees K-Family.
Platforms & launches
SLBMs are launched from the 4 vertical launch tubes of Arihant-class SSBNs. INS Arihant carries 12 K-15 OR 4 K-4. INS Arighat (commissioned 29 August 2024) similar. INS Aridhaman + S-5 (under construction) will be longer with 8 launch tubes — can carry 8 K-4/K-5 each.
India’s SSBN fleet target: 4-6 boats. Continuous-At-Sea-Deterrence (CASD) doctrine requires at least 1 SSBN on permanent deterrence patrol — requires minimum 4 SSBNs for rotation (1 patrol + 1 transit + 1 maintenance + 1 reserve).
UPSC angle
Know K-FAMILY SLBM — India’s SUBMARINE-LAUNCHED BALLISTIC MISSILES, NAMED after DR APJ ABDUL KALAM; DRDO developed; carried Arihant-class SSBNs; OPERATIONAL: K-15 SAGARIKA 750 km 2-stage solid 1-tonne nuclear warhead, 1st underwater pontoon test 26 Feb 2008 (failed), 27 January 2013 successful pontoon, 1ST FROM ARIHANT 14 OCT 2022; K-4 3500 KM 2-stage solid canisterised 2-tonne payload, length 12 m diameter 1.3 m, 1st test 24 March 2014, from Arihant 19 NOV 2018, ranges all of China incl Beijing+Lop Nur; UNDER DEV: K-5 5000 KM MIRV match Agni-V sea-leg target 2028-29; K-6 8000 km MIRV + HYPERSONIC GLIDE match Agni-VI sea-leg target 2030-32; CEP ~10 m (ring-laser-gyro INS + GPS-INS fusion); cold-launch gas-generator before ignition; Arihant carries 12 K-15 OR 4 K-4 via 4 VLT; Arighat similar; Aridhaman + S-5 longer with 8 VLT carry 8 K-4/K-5 each; CASD Continuous-At-Sea-Deterrence requires 4 SSBNs (1 patrol + 1 transit + 1 maint + 1 reserve); Defence Strategic Programmes Office under PM oversight.
Frequently asked questions
What is the K-Family?
India’s family of submarine-launched ballistic missiles (SLBMs) named after Dr APJ Abdul Kalam — the sea-leg of India’s nuclear triad.
What are K-15 and K-4?
K-15 (Sagarika) is the 750-km operational SLBM. K-4 is the 3,500-km longer-range SLBM. Both are carried on Arihant-class SSBNs.
What is the K-5?
A 5,000-km SLBM under development — matches the land-based Agni-V with MIRV (multiple warhead) capability. Target deployment 2028-29.
Why are SLBMs important for India’s nuclear doctrine?
Under No First Use (NFU), India needs assured second-strike capability. SSBNs with K-Family SLBMs are the most survivable leg — submarines can hide undersea for months.