North Korea’s May 21 Missile Launch

, former co-director | May 21, 2017, 12:10 pm EDT
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A week after the test launch of an intermediate-range Hwasong-12 missile, North Korea today tested a medium-range missile. Based on press reports, this appears to be a Pukguksong-2 missile, which is the land-based version of the submarine-launched missile it is developing. This appears to be the second successful test of this version of the missile.

South Korean sources reported this test had a range of 500 kilometers (km) (300 miles) and reached an altitude of 560 km (350 miles). If accurate, this trajectory is essentially the same as the previous test of the Pukguksong-2 in February (Fig. 1). Flown on a standard trajectory, this missile carrying the same payload would have a range of about 1,250 km (780 miles). If this test were conducted with a very light payload, as North Korea is believed to have done in past tests, the actual range with a warhead could be significantly shorter.

Fig. 1: The red curveis reportedly the trajectory followed on this test. The black curve (MET=minimum-energy trajectory) is the same missile on a maximum range trajectory.

The Pukgukgsong-2 uses solid fuel rather than liquid fuel like most of North Korea’s missiles. For military purposes, solid-fueled missiles have the advantage that they have the fuel loaded in them and can be launched quickly after they are moved to a launch site. By contrast, large liquid-fuel  missiles must be without fuel and then fueled after they are in place at the launch site. This process can take an hour or so, and the truck carrying the missile must be accompanied by a number of trucks containing fuel. So it is easier to detect a liquid missile before launch and there is more time  to attack it.

However, it is easier to build liquid missiles, so that is typically where countries begin. North Korea obtained liquid fuel technology from the Soviet Union in the 1980s and built its program from there. North Korea is still in early stages of developing solid missiles.

Building large solid missiles is difficult. If you look at examples of other countries building long-range solid missiles, such as France and China, it took them several decades to get from the point of building a medium-range solid missile, which North Korea has done, to building a solid ICBM. So this is not something that will happen soon, but with time North Korea will be able to do it.

Posted in: Missiles and Missile Defense Tags: , ,

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  • Andrew Klepatsky

    Dear David. According to my calculations, you have overrated the maximum range of the missile. Using equations for conservation of energy and angular momentum, with the given trajectory length (500 km), trajectory height (560 km), the assumed time of active flight (150s) and the assumed altitude of engine cutoff (100 km) I found the initial absolute velocity (3.150km/s) and the angle of throwing (beta=66.9 degrees). I took into account that the missile flew strictly to the East and the Earth velocity at the latitude was 0.357(km/s). Maximum distance of flight in the Eastern direction of the same missile (Lmax=1045km) would be achieved at the angle beta=35 degrees (the absolute velocity would amount to 3.246 km/s). You give the range 1250 km. The discrepancy is too high. Someone of us must be wrong.

    • dwrightucsusa

      For a relatively short-range missile like this, the rotation of the earth makes very little difference. When the range is significantly less than the radius of curvature of the earth, you can imagine the launch took place on a flat plane moving to the east. So the missile gets an extra component of velocity in that direction that makes up for the landing location moving eastward during the flight. For a range of 1250 km and burnout range and altitude of about 60 km, the MET angle is 40.8 degrees with a speed of 3.16 km/s.