A 50% failure rate is not considered productive...JL
Tom Balmforth and David Gaultier-Villars report in Reuters:
Ukrainian state prosecutors have examined debris from 21 of 50 North Korean ballistic missiles launched by Russia between late December and late February. "Half of the North Korean missiles lost their programmed trajectories and exploded in the air; in such cases the debris was not recovered." Hwasong-11 missiles, which are called KN-23 in the West, were identified by looking at their flight trajectories, speed and launch sites. The last recorded use of a KN-23 was on Feb. 27. The total number of launches tallied with intelligence showing North Korea delivered 50 ballistic missiles to Russia.