The experimental test flight of a submarine-launched ballistic missile (SLBM) by North Korea, conducted on April 22, caught most of the world by surprise. Many analysts who kept a watchful eye on North Korea’s missile programs thought that the country’s sole missile technology is based on liquid propulsion, and that this type of rocket engine is of Soviet origin (some even wrote that the DPRK lacks the technical knowhow to build the engines – and that the missiles are either just mock-ups/fakes/old Soviet stock).

Furthermore, the previous experiments by North Korea (basically underwater ejection tests