Since North Korea’s missiles are in the news and seem to be generating confusion, I’m giving here my understanding of where these various systems stand, based in part of my modeling of their capabilities.
Scud missile (called Hwasong in North Korea): tested, operational
Several variants of this missile exist with ranges of 300 to 500 kilometers (km) when carrying a 700 to 1000-kilogram (kg) warhead. That range would allow them to reach most of South Korea (see Figure 1). The size and mass of a North Korean nuclear weapon is not known, but it may be small enough to be carried by such a missile. Scuds are believed to have an accuracy of 0.5 to 1 km, which is too inaccurate to effectively attack military targets but could be used against a large target like a city. Scuds use liquid propellants and can be transported and launched from large trucks.
Nodong missile: tested, operational
This missile is believed to be able to carry a 700 to1000 kg warhead to a range of 1,000 to 1,300 km, which would allow it to reach most of Japan (see Figure 1). It uses Scud-level rocket technology, and has an accuracy of several kilometers, again limiting its use to large targets like a city. It can be transported and launched from large trucks. Nodongs use liquid propellants and must be filled with fuel in the field once they have reached their launch position, a process that may take an hour or two. Nodongs have had several successful tests, but not enough to give North Korea a clear idea of how reliable they are.
Musudan missile: not tested, not operational
North Korea has displayed this missile in parades but there are no known flight tests. While there have been reports that North Korea has put some of these missiles in the field on trucks, since North Korea has not test-launched a Musudan it is difficult to imagine that North Korea considers it operational. Moreover, speculation is that the Musudan uses a generation of missile engines and fuel more advanced than that used in the Nodong, but North Korea has not flight tested a missile using that technology. North Korea seems unlikely to fire one of its few nuclear warheads on an untested missile.
Estimates show that if the Musudan used this advanced technology it could carry a 700 to 1,000 kg warhead to a distance of about 3,000 km, which is too short to target Guam (see Figure 2). If instead it uses Scud-level technology, the range would be significantly less. Like the Nodong, it is carried on a mobile launcher and would be filled with liquid fuel in the field prior to launching. Its accuracy is likely several kilometers.
Taepo-Dong 2: not tested, not operational
Taepo-Dong -2 is the name given to a missile based on the technology used in the Unha-3 space launcher that put a North Korean satellite in orbit in December 2012. An analysis based on the December launch and rocket parts recovered by South Korea shows that the first two large stages of that rocket use Scud-level technology. If the Unha were modified to carry a 700-1,000 kg warhead rather than a light satellite, the missile could have enough range to reach Alaska and possibly Hawaii, but might not be able to reach the continental U.S. (Figure 2).
A ballistic missile version of the Unha has not been tested. Because of its large size it is unlikely to be mobile, and instead would be assembled and launched from a large pad, as in the December Unha launch. Its accuracy would likely be many kilometers.