The Hwasong-14 (), also known under alternative US designation codename KN-20, is a mobile intercontinental ballistic missile developed by North Korea. It had its maiden flight on 4 July 2017, which coincided with the United States' Independence Day. North Korea is the only known operator of this missile. Design The Hwasong-14 is likely a two-staged version of the Hwasong-12 first tested in May 2017. The second stage appears to have increased its range. The first stage engine appears very similar to the Hwasong-12. With a single liquid fuel engine, it has four Vernier thrusters for stability and guidance. A detailed analysis by the Bulletin of the Atomic Scientists claims that the current variant of the Hwasong-14 may not even be capable of delivering a first-generation nuclear warhead to Anchorage, Alaska. But even if North Korea is now capable of fabricating a relatively light-weight, "miniaturized" atomic bomb that can survive the extreme reentry environments of long-range rocket delivery, it will, with certainty, not be able to deliver such an atomic bomb to the lower 48 states of the United States with the rocket tested on July 3 and July 28. A first-generation North Korean nuclear missile warhead is estimated to weigh . Calculations of the range of the Hwasong-14 carrying such a payload vary from , enough to reach Anchorage, to as much as , enough to reach Honolulu, Hawaii and Seattle, Washington; the Bulletin of the Atomic Scientists claimed the payload would need to be lighter at to be able to reach Seattle. The July 2017 tests were conducted with a reentry vehicle, giving the missile its maximum range of , enough to reach New York City but not Washington D.C., although such a payload is much lighter than North Korea is believed to be capable of weaponizing. The missile is launched from a detachable platform on a concrete pad. This could have several operational ramifications. It may increase the time required to launch the Hwasong-12, and limit the number of launch locations to pre-sited and pre-constructed launch pads. Engine Michael Elleman of IISS and the Bulletin of the Atomic Scientists both claim that available evidence clearly indicates that the engine is based on the Soviet RD-250 family of engines for the R-36 missile, and has been modified to operate as the boosting force for the Hwasong-12 and -14. According to his theory an unknown number of these engines were