Surpass the Cutting Edge: Reflections on North Korea’s Failed May 27 Satellite Launch

On May 27, 2024, a “new-type” rocket carrying the Malligyong-1-1 spy satellite blasted off from the Democratic People’s Republic of Korea’s (DPRK or North Korea) Sohae Satellite Launching Station. The rocket exploded during the first stage of flight (Figure 1). On May 28, Kim Jong Un reportedly stated that the “mission failed with a destruct system being activated due to malfunctioning of the first-stage engine” when visiting the Academy of Defence Sciences.

The May 27 launch was the ninth satellite launch attempt and the sixth failed one in North Korea (Appendix).

Figure 1. Explosion of North Korea’s new-type carrier rocket over the West Sea/Yellow Sea, reportedly recorded by a South Korean patrol ship. (Image: South Korean JCS/AP)

Judging by the drop zones announced by North Korea, the intended orbit for the Malligyong-1-1 spy satellite is a sun-synchronous orbit, a type of low Earth orbit frequently used for Earth observation satellites.[1] Currently, the size and configuration of this new type of rocket are unclear. But, if the North Korean state media announcement is true, the “new-type” rocket would be the first North Korean carrier rocket powered by liquid oxygen (LOX)-kerosene propellants. This would reflect a notable departure in the country’s liquid-propellant engine development, in pursuit of more efficient SLVs, but is unlikely to have much practical impact on the country’s ballistic missile capabilities.

Choice of LOX-kerosene

Historically, LOX-kerosene was used as the oxidizer and fuel for early liquid-propellant intermediate-range ballistic missiles (IRBMs) and intercontinental ballistic missiles (ICBMs). In fact, LOX was the oxidizer for Nazi Germany’s V2, the world’s first ballistic missile. However, as LOX boils off easily, it is not friendly for outdoor handling and cannot be stored in a silo-based missile for an extended period of time. As such, Earth-storable oxidizers[2] with low handling requirements soon replaced LOX in liquid-propellant ballistic missiles. That said, due to relatively high combustion efficiency, LOX-kerosene has remained the most popular combination for dedicated space launch vehicles (SLVs), such as the Russian Soyuz and US Falcon-9.[3] Due to the characteristics of LOX, this combination is often categorized as a “semi-cryogenic” propellant.

North Korea has already developed the “March 18” series IRBM/ICBM engines (Figure 2) with a maximum thrust of approximately 80-ton force that use storable (not LOX) propellants. With this engine, North Korea can build a whole family of carrier rockets that could satisfy a wide range of missions ranging from high orbit launches to crewed space missions. For reference, China has been using storable liquid-propellant, ICBM-based carrier rockets (powered by about 70-ton force engines) for almost 50 years. The family of CZ-2/3/4 rockets has proven to be versatile, cheap and reliable—its human-rated variant has sent crewed spacecraft into space 19 times without fail.[4] To date, these rockets are still workhorses despite the introduction of the new generation of LOX-kerosene rockets. In Europe, the Ariane 1 to 4 series carrier rockets, powered by approximately 70-ton force storable propellant engines, established the European Space Agency as one of the leading launch service providers in the world.

As such, storable liquid-propellant, ICBM-based carrier rockets offer North Korea the following advantages:

• Minimizing developmental costs and resources, especially given the weak economy of North Korea;
• reducing the risk of failures and delays while offering decent capacities; and
• increasing the reliability and credibility of North Korean ICBMs using the same engines, especially when the number of North Korean ICBM flight tests has been limited.

While LOX-kerosene engines could provide better performance, they no longer have practical applications in ballistic missiles, only SLVs.

It remains unclear when exactly North Korea embarked on a LOX-kerosene engine program. However, when the “March 18” engine was first revealed to the outside world in September 2016, state media stated the engine test “provided the DPRK with a scientific and technical guarantee for confidently developing and completing the carrier rocket for the geo-stationary satellite.” A geostationary orbit is much higher and more difficult to reach than the low Earth orbit that has been used by North Korea to date. This may imply that the North’s plan was to stick to storable propellants for more demanding missions and that the decision to go for the LOX-kerosene engine may have occurred sometime after 2016.

Possible Rationales Behind the Choice

Given the context above, a combination of the following factors may have led to the choice of LOX-kerosene engines.

First, North Korea appears to be moving from developing liquid-propellant IRBMs and ICBMs to solid-propellant ones, largely reducing the need to improve the reliability of liquid-propellant ICBM engines through space launches. However, Kim Jong Un reportedly visited a vehicle factory to inspect at least eight transporter-erector-launchers (TELs) for Hwasong-17 liquid-propellant ICBMs and eight TELs for Hwasong-18 solid-propellant ICBMs on May 17. This indicates that the Hwasong-17 still plays a considerable role in North Korea’s ICBM force thanks to its high throw weight[5] and that it may still be produced. Nonetheless, solid-propellant ICBMs have, in general, reduced the importance of liquid-propellant ICBMs in the DPRK.[6]

Second, possible Russian technology transfer may have facilitated North Korea’s choice of LOX-kerosene engines. During his summit with Russian President Vladimir Putin in September 2023, Kim Jong Un was briefed on the assembling of an Angara rocket and characteristics of the Soyuz-2 carrier rocket at Russia’s Vostochny Cosmodrome, while Putin vaguely signaled his willingness to assist North Korea in space and satellite programs.[7] Before the May 27 launch, a South Korean official stated that many Russian technicians had entered North Korea after the Putin-Kim summit, and that North Korea has staged more engine tests than expected to “likely meet high standards of Russian technicians.” South Korean media have speculated that the RD-191 engine powering Russia’s Angara rocket had been transferred to North Korea. To date, however, none of those reports have been confirmed in the open-source domain.

Third, in some areas of weapon development, North Korean leadership appears to have shown a tendency to take higher risks in the spirit of “surpassing the cutting edge.” This tendency could lead to rapid technological updates in a short period of time, but at the expense of higher investment of resources and at the risk of encountering more hurdles and delays.[8] In addition, North Korea beat South Korea in 2012 as the first to put a satellite into orbit using a domestic rocket.[9] However, South Korea’s Nuri, powered by domestic LOX-kerosene engines, has become the most capable carrier rocket on the peninsula.[10] The development and/or the subsequent success of Nuri might have prompted Kim Jong Un to go for LOX-kerosene engines so that the North could compete with the South on an equal footing.[11]

Initial Observations

If North Korea has indeed developed LOX-kerosene engines for its SLVs, this may imply that the North may be turning to high-energy, “civilian” propellant (meaning no practical applications in ballistic missiles) in pursuit of world-class propulsion efficiency for its SLVs. However, this is unlikely to have any practical impact on the North’s IRBM or ICBM forces, especially as the country moves toward more solid-propellent systems.[12]

1. [1]

   North Korea’s Unha and Chollima-1 rockets also aimed at sun-synchronous orbit.

2. [2]

   These typically include nitrogen tetroxide and its variants, as well as red-fuming nitric acid. The fuel in such combinations normally includes unsymmetrical dimethylhydrazine and its variants, and kerosene.

3. [3]

   The LOX-liquid hydrogen (LH2) propellant combination has the highest combustion efficiency. However, LH2 is even more difficult to handle than LOX and has a low density, which in turn requires a larger rocket body to store fuel. For this reason, this combination is often used for high performance in the second and third stages. There are also quite a few carrier rockets that use this combination for the first stages, such as Japan’s H-II and H-III series and the US Delta IV.

4. [4]

   With another four successful crewless spaceship missions to date.

5. [5]

   Estimated to be 1.7 tons by a member state of the United Nations (UN) Security Council, according to a report by the UN Panel of Experts.

6. [6]

   Silo-based liquid-propellant heavy ICBMs are still used in Russia and China. However, North Korea has not developed heavy-weight, silo-based liquid ICBMs, and has been focusing on land-mobile, liquid-propellant ICBMs, presumably because the North could not provide enough protection to fixed ICBM silo sites given its limited territory.

7. [7]

   Both rockets are powered by LOX-kerosene. The Angara rocket is powered by the RD-191, a single-chamber variant of the world’s most powerful liquid engine, the RD-170 (four chambers in total). The Soyuz-2 is powered by RD-107/108 engines, whose simple design and high reliability made the Soyuz family rocket the most frequently used carrier rocket in the world with over 1,700 launches.

8. [8]

   For example, in the late Kim Jong Il era, North Korea initiated a project to develop a modern long-range surface-to-air missile system similar to the Russian S-300. However, after 2020, the project appeared to have been halted in favor of another, more advanced project. To date, North Korea still relies on obsolete Soviet-era liquid-propellant surface-to-air missiles as the backbone of its air defense network.

9. [9]

   South Korea achieved this goal about one month later, in January 2013, with a Naro-1 rocket powered by an RD-191 engine provided by Russia.

10. [10]

    The three-stage Nuri could deliver a 1.5-ton payload to a 600-800-kilometer sun-synchronous orbit. China’s three-stage CZ-4C, an ICBM-based rocket with similar lift-off thrust, could place 2.8 tons of payload in an 800-km sun-synchronous orbit. To date, CZ-4C has conducted 54 missions with a success rate of 96.3 percent. This comparison does not intend to dismiss the inherently higher combustion efficiency of LOX-kerosene propellants but is meant to show that with optimized design, ICBM-based carrier rockets could also have satisfactory performance and a long service life.

11. [11]

    As written above, the decision was likely made after 2016.

12. [12]

    Though, in the foreseeable future, the large, land-mobile liquid ICBM, namely the Hwasong-17, may still play a considerable role in North Korea’s ICBM force thanks to its high throw weight.