“North Korean ballistic missile scientists carried out a static test of a new type of solid-fuel engine early last week, a U.S. government source with knowledge of North Korea’s ballistic missile programs told The Diplomat. According to the source, the test took place at North Korea’s solid-fuel engine testing site in Hamhung, on the country’s east coast.”
Source: North Korea Has Tested a New Solid-Fuel Missile Engine | The Diplomat