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North Korea’s Largest Engine Test Yet

By
21 September 2016


Summary

On September 20, KCNA reported that Kim Jong Un had overseen the testing of a large new rocket engine at the Sohae Satellite Launching Station. They claimed this new engine had a thrust of 80 tons and would be use for a new space launch vehicle. Rocket engine thrust isn’t normally measured in “tons,” and there is some ambiguity in how to interpret that figure. It is also possible that the North Koreans are exaggerating; we can’t directly verify thrust from the images they released. Regardless, we can tell that the engine is substantially larger and more powerful than anything North Korea has tested before, even than the new ICBM engine tested in April, and the thrust may well be in the range of 160,000 pounds or 80,000 kilograms force.

And, while this particular engine may not be slated for an ICBM, we have now seen that North Korea can build large rockets using both solid and high-energy liquid propellants, to their own requirements. Whatever missiles North Korea may roll out in coming years, we can no longer expect to be limited to what can be cobbled together from old Russian cold-war leftovers.

The Engine

The plume coloration indicates that this engine probably uses the high-energy UDMH (unsymmetrical dimethylhydrazine) and NTO (nitrogen tetroxide) propellants used by the Musudan intermediate-range ballistic missile and the April 9 engine test—both derived from the old Russian R-27 submarine-launched ballistic missile whose technology North Korea illicitly acquired in the 1990s. However, a side view clearly shows the exhaust of a gas generator turbo-pump, rather than the more advanced staged-combustion cycle of the R-27. North Korea has previously used the gas-generator design on its (mostly) home-grown Nodong engine. The new engine does not have either vernier nozzles or jet vanes, suggesting the entire engine may be gimballed for steering purposes. This does not appear to be a copy of any Russian engine, but represents a mix of technologies well suited to a North Korean large engine development program.

 

(Photo: Rodong Sinmun)

(Photo: Rodong Sinmun)

(Photo: KCTV screengrab)

(Photo: KCTV screengrab)

 

It is reasonable to wonder whether North Korea might have had help in taking this unprecedented step, and two potential collaborators come to mind. China’s space launch vehicles, and some of their older ICBMs, use an engine called the YF-20 that is of the same size, performance and general technology as the new North Korean engine. However, there are visible differences between the new engine and the YF-20. We shouldn’t assume that China is helping Pyongyang. However, as we know, North Korea can sometimes connive with Chinese merchants to buy goods that are pretty obviously on the military side of the dual-use spectrum. For instance, while they probably couldn’t procure complete rocket engines, they could maybe get blueprints or critical components like turbo-pumps. Iran is another potential collaborator. There have long been ambiguous and difficult to pin down reports that Iranian engineers have been working with their North Korean counterparts on an “80-ton rocket booster.” The two nations have long collaborated in rocketry, with similar goals and technologies, and while their missile programs have diverged in recent years, their space programs are still in some respects a joint effort. Still besides the similarity in size, there is no additional evidence to prove this assertion.

The bottom line is that the North Koreans have the engine, it seems to work, and they can probably build more of them for whatever purpose they see fit.  The question is, what are they going to do with it? Given the size of the engine, they probably aren’t going to build an intercontinental ballistic missile (ICBM) with it. The engine is too big and powerful for the KN-08 and KN-14 road-mobile ICBMs under development in North Korea.

Space launch vehicles are another matter. North Korea has upgraded its Sohae launch site over the past few years to accommodate new, larger space launch vehicles that we have not yet seen. We may have just seen its engine. Or, more likely, one of its engines—liquid-fuel space launch vehicles typically use more than one engine on the first stage, and North Korean practice so far has been to use four engines. Iran, too, seems to favor a four-engine design. And a launch vehicle using four of these new engines would be about the right size for the upgraded launch pad and gantry tower at Sohae.

North Korea recently announced it plans to launch rockets to the Moon within the next ten years, along with launching increasingly capable satellites into Earth orbit. This engine would be suitable for launching modest unmanned lunar probes, along with geostationary communications satellites and various sorts of reconnaissance satellites in lower orbits. They still have a way to go on the necessary satellite technology, of course, but they are now one step closer to demonstrating a basic operational capability in outer space. We should start thinking about how we might live with a North Korea that has such a capability.

And, while this particular engine may not be slated for an ICBM, we have now seen that North Korea can build large rockets using both solid and high-energy liquid propellants, to their own requirements. Whatever missiles North Korea may roll out in coming years, we can no longer expect to be limited to what can be cobbled together from old Russian cold-war leftovers.

Credit for photo of young North Korean girl: T.M. All rights reserved, used with permission.