The CIA assessment notes that based on the two observed flight tests of the Hwasong-14 to date, North Korea’s reentry vehicle technology is likely sufficiently advanced to pose no performance problem should the missile be fired at a minimum energy trajectory. The assessment of the reentry vehicle is supported by analysis of data “gathered from ground, sea, and air-based sensors” by the U.S. National Air and Space Intelligence Center (NASIC), one source told The Diplomat.

A ballistic missile’s reentry vehicle contains its explosive payload and must withstand immense structural and temperature pressures during its descent through the earth’s atmosphere to its intended target. These physical stresses are exceptionally severe in the case of ICBMs, which fly higher than shorter-range systems and reach speeds several multiples of the speed of sound during descent.