On October 2, North Korea conducted an underwater launch of its new Pukguksong-3 submarine-launched ballistic missile (SLBM) off the coast of Wonsan. The two-stage, solid-fuel missile flew on a steep, upward trajectory, reaching a peak altitude of 950 km, and landing about 450 km from the launch point. If the Pukguksong-3 had used a standard trajectory, it would have overflown Japan and covered 1,900 to 2,000 km, making it the longest-range solid-fuel missile North Korea has tested to date.

Photographs of the launch released by North Korea show a missile breaching the sea’s surface after being ejected from an underwater launch tube, and then igniting its first-stage motor. The missile was likely launched from a submersible barge rather than a submarine, as evidenced by the nearby surface ship that presumably towed the barge to a safe off-shore location. The use of submersible barges during initial flight trials of a new missile design is standard practice, as it eliminates the risk of damaging an expensive and crewed submarine if something goes awry during the launch process.

It is not possible to extract absolute dimensions of the missile from the available photographs, but given its flight details, the Pukguksong-3 is likely to be about 1.4 to 1.5 meters in diameter, and roughly 7.8 to 8.3 meters long, making it similar, if not the same as, the land-based Pukguksong-2, but with a substantially shortened and blunted nose cone. The shorter nose cone was likely adopted to fit the missile into a submarine-launch tube. The US Poseidon and Trident SLBMs and the Chinese JL-2 all employ similar front ends.

The Pukguksong-3’s size and configuration is consistent with other SLBM designs. The US Polaris SLBM had a diameter of 1.37 meters, early-French SLBMs were 1.5 meters in diameter and China’s JL-1 was 1.4 meters. The first stage motor of the Pukguksong-3 is roughly two times the size of the second stage motor. This ratio is similar to those found on the US, French and Chinese SLBMs. These similarities are driven by engineering optimization, and not by one country copying another’s design decisions.

The Pukguksong-3 represents another step forward in North Korea’s pursuit of a sea-based deterrent force. Additional flight tests are likely, including an eventual launch from a prototype submarine. North Korea will also need to build at least three, if not four or five submarines to ensure a constant at-sea presence for the second leg of its strategic arsenal, making operationalization of its SLBMs at least a half-dozen years, or possibly longer, away.