The Hwasong-15: The Anatomy of North Korea's New ICBM

On November 29, at 2:47 a.m. local time, North Korea carried out the first launch of what is to date its largest and most powerful ballistic missile, the Hwasong-15. The launch ended a more than two-month pause in North Korean ballistic missile testing and refocused attention on the country’s rapid advances in ballistic missile technology in 2017.

Designated the KN22 by the U.S. intelligence community, the Hwasong-15 is North Korea’s second-ever liquid-fueled intercontinental-range ballistic missile (ICBM) design to see flight testing. Prior to its November 29 launch, the missile had never been seen publicly.

The missile, which appears both wider in diameter and longer than the KN20, was delivered to a paved launch pad at a previously unused launch site on a new nine-axle transporter-erector. It appeared to be an indigenously modified version of the eight-axle WS51200 lumber truck that has previously been seen carrying three different North Korean ICBM designs, including the Hwasong-14.

Following the launch, which North Korea claimed was “successfully carried out,” Kim Jong-un, the country’s supreme leader, was paraphrased by North Korean state media as claiming that the country had “finally realized the great historic cause of completing the state nuclear force.”

The First Flight of the Hwasong-15

During the November 29 flight test, the missile was tested on what is known as a “lofted” trajectory, like the two previous North Korean ICBM launches. The missile flew to a height of nearly 4,500 kilometers on this shortened trajectory while flying to a range of 950 kilometers from a new launch site at Pyongsong.

According to a U.S. government source with knowledge of North Korea’s weapons programs who spoke to The Diplomat, the exact flight time of the missile was 53 minutes and 49 seconds. The source added that the missile’s first stage engine burned for 128 seconds of flight and the second stage burned for 161 seconds. According to the source, the missile’s powered flight ended after its second stage burned out. The KN22 did not feature a post-boost vehicle despite the larger payload fairing, which concealed a single reentry vehicle of an unknown weight.

Following the launch, the KN22 was described by North Korea’s Korean Central News Agency (KCNA) as “an intercontinental ballistic rocket tipped with super-large heavy warhead.” Critically, the KCNA announcement of the launch claimed that the missile could strike “the whole mainland of the U.S.”

The U.S. government does not appear inclined to challenge that technical claim. According to a joint assessment released by the Central Intelligence Agency (CIA) and the National Air and Space Intelligence Center (NASIC) described to The Diplomat, the KN22 is already assessed to be capable of ranging the entire U.S. homeland, depending on its payload weight.

The Hwasong-15’s Reentry Vehicle Performance

It is unclear what payload weight North Korea used during the November 29 flight test, but on-board camera footage from within the payload fairing visible on a monitor near Kim Jong-un in video footage released by North Korean state media appeared to show a single conical reentry vehicle with extra space within the fairing. The extra space could one day accommodate a larger reentry vehicle, penetration aids, which would help the missile evade U.S. missile defenses, or multiple warheads.

Currently, there is no consensus assessment in the U.S. intelligence community on the performance of the KN22’s reentry vehicle. The CIA-NASIC assessment suggested that it was more likely than not that the reentry vehicle exhibited satisfactory performance during the November 29 flight test. However, as reported by CNN, other assessments in the U.S. intelligence community may vary. Regardless, technical analysis of the missile remains ongoing. (Eyewitness reports from a Cathay Pacific airlines crew of a suspected disintegrating reentry vehicle over the Sea of Japan shortly after launch may have instead involved the missile’s second stage fairing.)

The 4,500 kilometer apogee was considerably higher than the observed apogees of the first two KN20 launches, which came in at 2,802 kilometers and 3,725 kilometers respectively. (Based on the November 29 missile flight trajectory and time data alone, some analysts expected North Korea to debut a new ICBM design, even before Pyongyang confirmed this with images a day later.)

“Lofted” trajectories for long-range ballistic missiles shorten the actual flight range while allowing for an extended burn time for the missile’s engines, allowing North Korean engineers to gather valuable data on the performance of the missile in boost phase within range of the country’s missile telemetry receiver stations.

As The Diplomat has explored before, data on the performance of North Korea’s reentry vehicles gleaned from lofted tests may be misleading. For instance, while the U.S. intelligence community assessed that North Korea’s highly lofted July 28 ICBM test did not see the reentry vehicle survive, the CIA went on to assess in August that North Korea’s reentry vehicle design is already sufficient to credibly threaten the U.S. homeland.

Meanwhile, according to a U.S. government source who spoke to The Diplomat, the two long-range Hwasong-12 intermediate-range ballistic missile tests in August and September that overflew Japan saw the reentry vehicle tumble during reentry. As The Diplomat explored in August, North Korea’s reason for conducting these sorts of long-range tests is to allow the reentry vehicles to experience in-flight stresses and temperatures at magnitudes and durations most similar to what they might see during operational use. Lofted trajectory tests can’t match that.

North Korea has already claimed to have a sufficiently robust reentry vehicle design and, while it may seek to demonstrate this with future flight-testing along a minimum energy trajectory, it remains unclear if it has developed the long-range telemetry means necessary to succeed in gathering useful data. (Without space-based receivers, North Korea would have to likely use a ship-based receiver near its intended reentry vehicle splashdown point.)

The Hwasong-15’s Engines

One of the most notable features of the KN22, in addition to its sheer size, was the configuration of its first-stage liquid-propellant engine. Unlike the KN20, which used a single thrust chamber along with four smaller vernier engines for steering, the KN22 appeared to use twin-chamber thrusters with no auxiliary engines for steering.

The lack of external steering thrusters may suggest a more efficient gimbaled steering mechanism, whereby the thrust chambers are able to swivel to steer the missile. The relatively simpler gimbaled steering mechanism may allow the missile to exhibit to a lower mass ratio than if it used auxiliary thrusters for steering.

This engine may be the 80-ton-force twin-chambered engine first tested by North Korea in September 2016 or a twin-chambered version of the “March 18 revolution” engine (an indigenously modified variant of the Soviet-origin RD250 family of liquid propellant engines), which was tested earlier this year and is used in a single-engine configuration on board the first stage of both the KN17 IRBM and the KN20 ICBM. U.S. intelligence has not yet assessed which engine North Korea may have included in the first-stage of the KN22.

The missile’s second stage, which is considerably larger than the second stage seen on the KN20 and equivalent in diameter to its first stage, remains somewhat of a mystery for now. One source told The Diplomat that the second stage also uses a liquid-propellant engine. It’s unclear, however, if North Korea is using a previous engine for this stage of the KN22 or if it has inaugurated a new engine altogether.

Prior to the KN20’s first test-flight on July 4, North Korea tested the missile’s second-stage engine. In October, leading up to the November flight test of the KN22, North Korea tested both a new and unknown type of solid-fuel engine at Hamhung, which The Diplomat first reported, and an unknown liquid-propellant engine at the Sohae engine test stand. This liquid-propellant engine, if new, may have been the KN22’s second stage engine.

The new solid-fuel engine, while not in use on the KN22, may be intended for a new submarine-launched ballistic missile (SLBM) or a new generation of IRBMs and ICBMs based on a fuel type that would confer substantial tactical advantages on North Korea’s nuclear forces.

What the U.S. Knew Before the Launch

While the appearance of a brand-new North Korean ICBM design this shortly after the introduction of the KN20 was not widely expected, the U.S. intelligence community had anticipated this launch. (Officials may have hinted at the KN22’s existence to CNN in early November.) At least 72 hours before the early morning launch in North Korea, U.S. military intelligence had detected preparations for the event.

Usually, one of the most reliable indicators of an upcoming developmental North Korean missile launch is the construction of an observation stand for Kim Jong-un near a known launch site or near a known ballistic missile operating area. In 2017, North Korea has diversified its range of launch sites, adding previously unused sites like Pyongyang’s Sunan Airfield, Pukchang Airfield, and Mupyong-ni. The site near Pyongsong used for the Hwasong-15’s first test flight was also previously unused.

Instead of a static observation stand, this test featured a new mobile trailer for Kim. The usual telemetry and on-board-camera monitors were included inside this trailer, along with a large, glass observation area. In one photograph released by North Korean state media, Kim is seen standing in this observation area looking up at the presumably just-launched Hwasong-15.

The introduction of this new trailer suggests that North Korea may intend to make it more challenging for foreign intelligence agencies to detect upcoming developmental launches by obviating the need for a static observation stand for Kim Jong-un.

A U.S. government source told The Diplomat that, in addition to the 72 hours of anticipation of some launch activity, the United States was able to observe preparatory work for the paved launch pad where the Hwasong-15’s firing table was set up before midnight local time on November 28, nearly three hours before launch. Moreover, the United States observed the Hwasong-15 missile erected on the firing table nearly two hours before launch. These observation windows approximately match the warning time U.S. intelligence had during the two previous ICBM launches as well.

As others have observed, North Korea’s timing of this launch at nearly 3 a.m. local time was intended to display the Korean Strategic Rocket Force’s ability to operate missiles at nighttime, simulating potential operational use. After the July 28 ICBM launch, KCNA noted that the nighttime launch demonstrated “the capability of making surprise launch of ICBM in any region and place any time.” This was also the case with the Hwasong-15.

A Moment of Completion or a New Beginning?

Earlier this year, The Diplomat had prognosticated that 2017 would become the “year of the North Korean intercontinental ballistic missile.” After three lofted ICBM tests introduced two previously unseen ICBM designs, that appears to have held up.

Kim Jong-un’s declaration that North Korea’s nuclear force had been completed with the Hwasong-15, too, was unsurprising. North Korean defector and former high-ranking diplomat Thae Yong-ho told the South Korean press earlier this year that North Korea wanted to be able to declare the completion of its nuclear forces this year, based around the successful flight-testing of an ICBM credibly able to threaten the U.S. homeland with a compact nuclear device. The KN22 certainly does that, but so does the KN20.

However, it would be a grave mistake to take Kim’s statement of completion at face value. North Korea is unlikely to end its development of ballistic missile technology now and deploy an operational ICBM force based on these two successfully flight-tested liquid-propellant designs.

First, ICBM basing modes remain a challenge for North Korea. The country is thought to possess a handful of the eight-axle trucks (converted to a nine-axle truck for the KN20) for its ICBM force. Road mobility is a valuable commodity and so North Korea may attempt to indigenously produce heavy launch vehicles.

Its introduction of tracked transporter-erector-launchers (TELs) and canisters with other ballistic missile systems this year suggests increased competence in this area, but it remains unclear just how reliably it might be able to produce its own homegrown road-mobile ICBM TELs. Instead, it may look to inaugurate rail-mobile launchers or perhaps explore even more exotic basing modes for its ICBMs.

Second, in addition to the KN22 and KN20, North Korea has two untested ICBM designs: the three-stage Hwasong-13 mod 1 (KN08), first seen publicly at a parade in 2012, and the two-stage Hwasong-13 mod 2 (KN14), first seen publicly at a 2015 military parade. The fate of those designs remains unclear. Neither missile appeared at the April 15 parade this year, but that does not mean that they have been shelved. North Korean engineers may revisit these designs with the experience of the KN20 and KN22 with them.

Third, even if North Korea chooses not to introduce new ICBM designs, the KN22’s payload fairing leaves plenty of room for growth. Penetration aids to defeat U.S. homeland missile defense and multiple warheads are all viable development paths for North Korea from here; given its inherently offensive nuclear strategy that depends on a credible ICBM strike capability, Pyongyang is almost certain to invest resources into the development of penetration aids.

Fourth, North Korea’s solid-fuel program remains relatively new, with only the Pukguksong-2/KN15 medium-range ballistic missile and Pukguksong-1/KN11 SLBM using this fuel type. At its April 15 parade this year, North Korea displayed two mysterious ICBM-sized canisters that suggested an ambition, at least, for solid-fueled, road-mobile, canisterized ICBMs.

While it may seem far-fetched now to imagine a flexible and responsive North Korean ICBM force comprising missiles akin to Russia’s Topol-M or China’s DF-41, consider the country’s great pace of indigenous innovation in ballistic missile technology thus far.

After joining the exclusive club of countries that possess staged thermonuclear weapons after this September’s test of a claimed hydrogen bomb with a yield in excess of 100 kilotons, North Korea has, with the KN22, successfully manufactured and flight tested a ballistic missile that few countries would able to produce. If the KN22 (and the KN20) sends a message, it’s that the rest of the world underestimates North Korea’s indigenous knowledge base and capabilities at its own peril.