首尔4月23日电 据韩国联合参谋本部（联参）23日消息，朝鲜当天下午6时30分许在咸镜南道新浦市向半岛东北方向海域发射疑为潜射弹道导弹（SLBM ）的1枚飞行物。
While the missile is reported as only covering 30 km, far short of the expected capable distance covered by a typical SLBM, such a short distance should not necessarily be seen as a failure. It is possible that this was a deliberate reduction in range to minimise the political costs of testing, or to only test certain design goals as official KCNA reports suggest.
IHS Jane's has previously reported that the Polaris-1 appears to be similar to the original R-27 Zyb SS-N-6 'Serb': a Soviet liquid-fuelled missile with a 2,400 km range and a 650 kg payload. While it was deployed by the Soviet Union from 1968-88, in September 2003 it was reported that Pyongyang had acquired a number of R-27s. In turn, these are believed to be the basis for North Korea's Musudan (BM-25) land-based intermediate-range ballistic (IRBM) missile, and now the Polaris-1.
Unlike R-27 based missiles, which are liquid-fuelled, the North's references to a solid-fuel engine, however, appears to suggest that Pyongyang is developing a new model. Speculation over North Korean interest in longer-range solid-fuel missiles emerged in November 2011 when it was reported seven North Koreans were at the Bid Kaneh solid-fuel rocket motor plant in Iran when it was destroyed by an explosion. The first confirmation came on 23 March 2016 when Kim Jong-un hailed a "historic" advance in the country's nuclear strike capability, as the regime claimed it had successfully tested a solid-fuel rocket engine.
Progress in either SLBM programme is unclear. Despite the apparent May 2015 launching from a submarine, it is most likely that North Korea used a submerged launching platform for this testing. While it is unclear what platform was used in the latest test, the North has made apparent efforts to move towards a fuller SLBM capability. On 28 November 2015, it was reported that North Korea attempted a launch of a ballistic missile from a submerged Sinpo-class submarine. This is thought to have ended in failure so that the North reverted to testing from its platforms. As such, it is possible that these tests are more indicative of intent rather than capability. It is notable that earlier this month, on 15 April, South Korea reported that land-based missile tests - widely anticipated to have been of the 'Musudan' - failed. This suggests that further development of the base missile system is to be expected.
Given the need for fixed infrastructure, air- and land-based nuclear delivery systems are traditionally viewed as particularly vulnerable to an enemy's first nuclear strike attack. North Korea's decision to create a sea-based deterrent is based on the fact that given the size and impenetrability of the oceans, in the event of a nuclear attack, a ballistic missile submarine will be difficult to find and target. Pyongyang likely sees any future sea-based platform as part of a second strike capability that could still inflict unacceptable damage after a nuclear strike on the mainland. Second strike capabilities are generally seen as a stabilising factor as they help remove the 'use it or lose it' dilemma faced by nuclear-armed countries with more vulnerable platforms. As such, they could, arguably, help reduce Pyongyang's future anxieties, but a future second-strike capability will further entrench the importance of the North's nuclear programme and will be far from comforting for its neighbours.