North Korea is Launching a Rocket Soon: What Do We Know About It?

, co-director and senior scientist | February 5, 2016, 9:49 am EDT
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North Korea has announced that it will launch a rocket sometime in the next two weeks to put a satellite in orbit for the second time. What do we know about it, and how worried should we be?


Fig.1. The Unha-3 ready to launch in April 2012. (Source: Sungwon Baik / VOA)

What We Know

North Korea has been developing rockets—both satellite launchers and ballistic missiles—for more than 25 years. Developing rockets requires flight testing them in the atmosphere, and the United States has satellite-based sensors and ground-based radars that allow it to detect flight testing essentially worldwide. So despite North Korea being highly secretive, it can’t hide such tests, and we know what rockets it has flight tested.

North Korea’s military has short-range missiles that can reach most of South Korea, and a longer range missile—called Nodong in the West—that can reach parts of Japan. But it has yet to flight test any military missiles that can reach targets at a distance of greater than about 1,500 kilometers.

(It has two other ballistic missile designs—called the Musudan and KN-08 in the West—that it has exhibited in military parades on several occasions over the past few years, but has never flight tested. So we don’t know what their state of development is, but they can’t be considered operational without flight testing.)

North Korea’s Satellite launcher

North Korea has attempted 5 satellite launches, starting in 1998, with only one success—in December 2012. While that launch put a small satellite into space, the satellite was apparently tumbling and North Korea was never able to communicate with it.

The rocket that launched the satellite in 2012 is called the Unha-3 (Galaxy-3) (Fig. 1). North Korea has announced locations of the splashdown zones for its upcoming launch, where the rocket stages will fall into the sea; since these are very similar to the locations of the zones for its 2012 launch, that suggests the launcher will also be very similar (Fig. 2).

Fig. Fig. 2. The planned trajectory of the upcoming launch. (Source: D Wright in Google Earth)

Fig. Fig. 2. The planned trajectory of the upcoming launch. (Source: D Wright in Google Earth)

We know a lot about the Unha-3 from analyzing previous launches, especially after South Korea fished parts of the rocket out of the sea after the 2012 launch. It is about 30 m tall, has a launch mass of about 90 tons, and consists of 3 stages that use liquid fuel. A key point is that the two large lower stages rely on 1960s-era Scud-type engines and fuel, rather than the more advanced engines and fuel that countries such as  Russia and China use. This is an important limitation on the capability of the rocket and suggests North Korea does not have access to, or has not mastered, more advanced technology.

(Some believe North Korea may have purchased a number of these more advanced engines from the Soviet Union. But it has never flight tested that technology, even in shorter range missiles.)

Because large rockets are highly complex technical systems, they are prone to failure. Just because North Korea was able to get everything to work in 2012, allowing it to orbit a satellite, that says very little about the reliability of the launcher, so it is unclear what the probability of a second successful launch is.

The Satellite

The satellite North Korea launched in 2012— the  Kawngmyongsong-3, or “Bright Star 3”—is likely similar in size and capability (with a mass of about 100 kg) to the current satellite (also called Kawngmyongsong ). The satellite is not designed to do much, since the goal of early satellite launches is learning to communicate with the satellite. It may send back photos from a small camera on board, but these would be too low resolution (probably hundreds of meters) to be useful for spying.

In 2012, North Korea launched its satellite into a “sun-synchronous orbit” (with an inclination of 97.4 degrees), which is an orbit commonly used for satellites that monitor the earth, such as for environmental monitoring. Its orbital altitude was about 550 km, which is twice as high as the Space Station, but lower than most satellites, which sit in higher orbits since atmospheric drag at low altitudes will slow a satellite and cause it to fall from orbit sooner. For North Korea, the altitude was limited by the capability of its launcher. We expect a similar orbit this time, although if the launcher has been modified to carry somewhat more fuel it might be able to carry the satellite to a higher altitude.

The Launch Site and Flight Path

The launch will take place from the Sohae site near the western coast of North Korea (Fig. 2). It would be most efficient to launch due east so that the rocket gains speed from the rotation of the earth. North Korea launched its early flights in that direction but now launches south to avoid overflying Japan—threading the needle between South Korea, China, and the Philippines.

North Korea has modified the Sohae launch site since the 2012 launch. It has increased the height of the gantry that holds the rocket before launch, so that it can accommodate taller rockets, but I expect that extra height will not be needed for this rocket. It has also constructed a building on the launch pad that houses the rocket while it is being prepared for launch (which is a standard feature of modern launch sites around the world). This means we will not be able to watch the detailed launch preparations, which gave indications of the timing of the launch in 2012.

Satellite launch or ballistic missile?

So, is this really an attempt to launch a satellite, or could it be a ballistic missile launch in disguise? Can you tell the difference?

Fig. 3. Trajectories for a long-range ballistic missile (red) and Unha-3 satellite launch (blue).

Fig. 3. Trajectories for a long-range ballistic missile (red) and Unha-3 satellite launch (blue).

The U.S. will likely have lots of sensors—on satellites, in the air, and on the ground and sea—watching the launch, and it will be able to quickly tell whether or not it is really a satellite launch because the trajectory of a satellite launch and ballistic missile are very different.

Figure 3 shows the early part of the trajectory of a typical liquid-fueled ballistic missile (ICBM) with a range of 12,000 km (red) and the Unha-3 launch trajectory from 2012 (blue). They differ in shape and in the length of time the rocket engines burn. In this example, the ICBM engines burn for 300 seconds and the Unha-3 engines burn for nearly twice that long. The ICBM gets up to high speed much faster and then goes much higher.

Interestingly, the Unha-3’s longer burn time means that its upper stages have been designed for use in a satellite launcher, rather than a ballistic missile. So this rocket looks more like a satellite launcher than a ballistic missile.

Long-Range Missile Capability?

Of course, North Korea can still learn a lot from satellite launches about the technology it can use to build a ballistic missile, since the two types of rockets use the same basic technology. That is the source of the concern about these launches.

The range of a missile is based on the technology used and other factors. Whether the Unha-3 could carry a nuclear warhead depends in part on how heavy a North Korea nuclear weapon is, which is a topic of ongoing debate. If the Unha were modified to carry a 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. (Fig. 4). If instead North Korea could reduce the warhead mass to around 500 kg, the missile would likely be able to reach large parts of the continental U.S.

North Korea has not flight tested a ballistic missile version of the Unha or a reentry heat shield that would be needed to protect the warhead as it reentered the atmosphere. Because of its large size, such a missile is unlikely to be mobile, and assembling and fueling it at the launch site would be difficult to hide. Its accuracy would likely be many kilometers.

Fig. 4: Distances from North Korea. (Source: D Wright in Google Earth)

Fig. 4: Distances from North Korea. (Source: D Wright in Google Earth)

The bottom line is that North Korea is developing the technology it could use to build a ballistic missile with intercontinental range. Today it is not clear that it has a system capable of doing so or a nuclear weapon that is small enough to be delivered on it. It has shown, however, the capability to continue to make progress on both fronts.

The U.S. approach to dealing with North Korea in recent years through continued sanctions has not been effective in stopping this progress. It’s time for the U.S. to try a different approach, including direct U.S.-Korean talks.


Posted in: Missiles and Missile Defense, Space and Satellites Tags: , ,

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  • J_kies

    David; you are aware that the orbit insertion is the simplest means to discern the difference between an ICBM doing a very inefficient satellite launch and a system actually designed to launch satellites? Specifically the Unha applies the exact same means of continuous burn until the desired orbit is achieved as the R-7 (SS6 Sapwood) ICBM performed when used for Sputnik-1.

    Bottom line; its a two stage ICBM being tested ‘covertly’ as a three stage satellite launcher in a very inefficient manner.

    • dwrightucsusa

      Thanks for your comment. I haven’t looked at how much less efficient this means of orbital insertion is, and whether it is prohibitively costly. Given North Korea’s lack of experience operating launchers, etc, it’s maybe not surprising it used the same simple insertion process as early Soviet launches. My point is that the upper stages of the Unha-3 have low thrust and burntimes of 200 s or longer, which is inefficient for a ballistic missile. If I were building the first two stages as a ballistic missile, I would design the second stage to use a Nodong engine, or possibly a couple Scud engines, to give higher thrust and a shorter burntime. You can show that makes a significant difference in range.

    • Jonathan McDowell

      This seems completely wrong – it’s a 3 stage vehicle. The first two stages are suborbital (as shown by the NOTAMs) and then the third stage coasts to apogee, before performing the yawed insertion burn. Totally standard satellite launch vehicle, and quite distinct from the Sputnik-1 profile. So I am confused by your assertion.

      • J_kies

        Jonathan; you have a well deserved reputation as a careful analyst. Can you source your assertion “then the third stage coasts to apogee, before performing the yawed insertion burn” as that’s clearly not what was done on 12/12/2012 and this looks no different.

        • Jonathan McDowell

          I guess I’m confused. Why do you say ‘that’s clearly not what was done on 12/12/2012’ – I drew the opposite conclusion based on the stage 2 impact zone and matching back the TLEs to the apogee of the stage 2 trajectory. But my calculations were certainly approximate.

          • J_kies

            Jonathan; I am using the DPRK asserted flight profile that was not contradicted by other public sources in track or for satellite ephemeris 2-lines. 12/12/2012 was unlofted without coast periods and after 2-3 separation the third stage clearly did a plane change burn to approach a sun-synchronous condition. Compare the flight azimuth that drops the 2nd stage in the NOTAM zone with the final orbit – you will see what I mean. Holmann this isn’t.

          • Jonathan McDowell

            Ah, gotcha, I thought you were challenging the 3rd stage yaw, not the coast period. We both agree that stage 3 made a plane change burn at the apogee of the stage 2 trajectory. I’m prepared to believe the stage 2 burn time was long enough that there was no coast phase, but I’m surprised.

          • J_kies

            My read on stage 1 & 2 shows a total ~ 280 second burn; not terrible as an ICBM optimization given the Titan was ~ 300 seconds. I am unsure of the sourcing that people are applying for the ‘long stage 2’.

          • Jonathan McDowell

            Seems reasonable, I’m just not convinced that 280s gets you to 500 km altitude right away, but that’s not my area of expertise – your analysis is interesting.

          • J_kies

            It doesn’t I don’t recall the exact values but its between 250 and 300km; the third stage handles the additional velocity, plane change and elevation to the final orbit. According to the President of Iran; it was nearly 300 seconds in operation as the SAFIR stage 2 (looks to be the same propulsion set).

          • dwrightucsusa

            By my estimates, the 2nd stage burns for 200 s and the 3rd stage for 260 s. NK may use a continuous burn to orbit both to avoid having to restart the engine and also to keep the stage stable, ie, to avoid tumbling during a coast phase. My point here is simply that if you, for example, replaced the low-thrust 2nd stage engine with something like a Nodong engine, that would cut the 2nd stage burntime in half and would give a significantly longer range as a 2-stage ballistic missile. So the low-thrust, long burntime stage seems to be designed for a satellite launcher rather than a ballistic missile.

          • J_kies

            David thanks for sharing; I agree that what has been shown is less than the optimal ICBM approach but the DPRK engineers are clearly aware of the pertaining physics. I suggest that what they have chosen to show you is unlikely to be the real capability in hand. What is your 200s source for stage 2 burn time? I used the DPRK asserted profile.

    • John_Schilling

      The continuous burn also makes sense if North Korea were trying to launch a satellite but were not confident of their ability to restart a rocket engine after a long coast period in zero gravity, which would certainly be prudent of them at this point. The Unha-3 design is just about right for either a pure satellite launch vehicle or a dual-use vehicle designed around a no-inflight-restart constraint, but that inherently makes it look very much like a pure ICBM designed around the constraint that its flight tests have to look like satellite launches. I lean towards David’s assessment that a dedicated ICBM would have more thrust in the second stage, but it’s really too close to call.

      And I suspect North Korea likes it that way.

  • KM

    David, thanks for the post. Just a consideration – is it possible that North Korea could be launching a nuclear warhead into orbit disguised as a satellite? In other words, the weapon would resemble a satellite, the launch and its rocket trajectory would effectively be that of a satellite launch, everyone would think it’s a satellite and no one would shoot it down, but in reality it would be a warhead. Then, the warhead would circle the earth in orbit, and at a later time of its choosing, North Korea could decide to detonate it as it flies over another country (say, the USA, Japan, or South Korea), which could cause an electromagnetic pulse and potentially knock out that country’s electric grid. Or they could bring the satellite down to earth and explode it on a city.

    Is any of this feasible for North Korea to get away with, or would it be unrealistic for them to be able to disguise and operate a nuclear warhead in this manner? I’m not technically knowledgeable in this area at all, but wanted to ask because I’ve seen speculation on the internet as to the possibility. Thanks.

    • Jonathan McDowell

      As my UCS colleagues have repeatedly pointed out in the past, doing this would be much more expensive and difficult than just launching an ICBM to do the same thing. Utterly pointless and stupid as a strategy. And the mass of the satellite is less than a typical US reentry vehicle, much less an NK one

    • dwrightucsusa

      As Jonathan notes, North Korea can’t do this for a couple reasons. First, a nuclear warhead would be 5 to 10 times more massive than the satellite it plans to launch, and its launcher doesn’t have the capability to put that much mass into orbit. Even if it did, once the weapon was in orbit you can’t just “drop” it back down to earth–being “in orbit” means that it is moving fast enough that it feels a balance of forces and wants to remain in orbit. Instead you would need to launch enough propellant it to kick it out of orbit and back down to earth. Because it is moving so fast in orbit, it takes a surprisingly large amount of propellant to do that. If it was a 1000 kg warhead in a 500 km altitude orbit, you would need to launch about 400 kg of propellant with it to be able to kick it out of orbit back and down to earth relatively quickly (ie, 10 minutes). So in this case the launcher would have to put the warhead and that de-orbiting propellant–a total mass of 1,400 kg–into orbit. That’s difficult and costly, and is why orbiting weapons that are intended to attack targets on the ground don’t make sense.

      If you want to see more about this, look at our report The Physics of Space Security at
      and see pages 59 and 70.

      • KM

        Thanks to both of you for the replies. I appreciate it. They both make sense, but just to clarify further, what if North Korea has miniaturized a warhead to be the same size as the satellite? Couldn’t they launch it into orbit then? How do we know they haven’t achieved such a level of miniaturization?

        And let’s say they did this and then sent it into orbit. As you explained, they subsequently wouldn’t be able to de-orbit it due to lack of propellant, which would rule out a direct strike on a ground target. But couldn’t they still detonate it high up in the atmosphere, while it’s on its orbital path? And if this is done, wouldn’t the detonation then cause an electromagnetic pulse that could take down the electrical grid of everything on the earth below it?

        Thanks again for your insights.

      • John_Schilling

        I’ve looked at high-altitude electromagnetic pulse, but it’s a very unreliable sort of attack. The limited data we have from the 1960s suggests it would produce widespread (~800 km radius) but scattered and transient disruption of power and electronics systems, rather than massive total blackouts. Power grids have changed since the 1960s, in some ways more robust, in some ways less so, but this is probably not an attack that will devastate a nation. More importantly for North Korea, the command and control system for America’s nuclear arsenal is very definitely hardened against such an attack, so they would likely face immediate and massive retaliation.

        And unless they have done far better than we suspect on the warhead-miniaturization front, they’ll still need a bigger rocket than this one to carry such a device.