Wednesday morning, the Democratic People's Republic of Korea successfully launched what the US Pacific Command has identified as a KN-15 medium-range ballistic missile—a solid-fuel rocket based on enhancements to the submarine-launched “Pukguksong” missile (“North Star,” designated by the US as the KN-11) the DPRK tested in 2015 and last summer. This is the second launch of a KN-15 (called the Pukguksong-2 by North Korea), and it raises concerns that the North Korean regime may be working on a solid-fuel intercontinental ballistic missile (ICBM).

The test comes the day before China's president, Xi Jinping, begins his visit with President Donald Trump at Trump's Mar-A-Lago resort in Florida. Secretary of State Rex Tillerson acknowledged the launch in a remarkably brief statement. "North Korea launched yet another intermediate range ballistic missile," Tillerson said. "The United States has spoken enough about North Korea. We have no further comment."

There are signs that North Korea will be doing more to get the world's attention during the Xi visit. Activity at a nuclear weapons test site observed by satellite imagery indicates that another nuclear weapon test is imminent.

Doing a solid

So far, the long-range rockets developed by the DPRK have been liquid-fueled—requiring that they be fueled before they can be made ready—a process that can be spotted by satellite or aerial surveillance to provide early warning of an impending launch. Early Soviet submarine-launched ballistic missiles used liquid fuel, and the fueling process could be picked up on US Navy sonar. Solid-fueled ballistic missiles require less preparation time to launch and can more easily be made mobile. A solid-fueled ICBM system could also potentially be made land-mobile or launched from hardened sites with little warning.

During a military parade in April 2012, North Korea's military displayed a mockup of a mobile ICBM system referred to as the Hwasong-13 (designated by the US as the KN-08). At the time, it was believed to be a design based on liquid-fueled rockets, but it was unusual in that the mock-up had three stages—a configuration more common in solid-fueled systems. In a 2012 Rand Corporation analysis, former Rand fellow Markus Schiller (now CEO of ST Analytics GmbH) characterized North Korea's ICBM program as a “bluff” and contended that the DPRK lacked the technology to develop effective solid-fuel boosters. That situation appears to have changed dramatically over the past five years.

Making a splash

It's not clear whether the KN-15 launch today was successful. The missile flew only 60km (less than 40 miles), when a previous launch of the same system flew about 310 miles in February. But the test launch, which took place near a North Korean submarine base, may have been to demonstrate new launch capabilities.

The development of medium-range solid-fueled ballistic missiles by the DPRK capable of potentially carrying a nuclear warhead has already prompted enough concern in the Republic of Korea that the government there has approved the deployment of the Terminal High Altitude Area Defense (THAAD) missile defense system—a system China does not want deployed in South Korea because of its powerful radar system.