N. Korea holds “crucial test” that lasts for seven minutes at night

A post by 38 North, a website devoted to analyzing events concerning North Korea, concerning “another crucial test” at the Sohae Satellite Launching Ground in Tongchang Village,n Cholsan County, on Dec. 13.

Statement refers to “bolstering strategic nuclear deterrent”

A post by 38 North, a website devoted to analyzing events concerning North Korea, concerning “another crucial test” at the Sohae Satellite Launching Ground in Tongchang Village,n Cholsan County, on Dec. 13.

North Korea’s Academy of National Defense Science reported on the afternoon of Dec. 14 that it had carried out “another crucial test [. . .] at the Sohae Satellite Launching Ground,” a site in Tongchang Village that also tests missile engines, on the evening of Dec. 13. North Korea had announced a “very important test” at the same place on Dec. 7, just six days ago. Unlike the previous announcement, the academy took the unusual step of specifying the exact time of the test (from 10:41 to 10:48 pm on Dec. 13). What was North Korea hoping to communicate to the outside world by disclosing a “crucial test” that lasted for seven minutes?

As of the afternoon of Dec. 15, the South Korean military and intelligence agencies hadn’t given the press the results of their analysis of intelligence related to the Dec. 13 test. But their apparent conclusion is that the two tests, on Dec. 7 and 13, were designed to develop a new multistage rocket. Seoul is apparently reserving its judgment about whether the rocket that North Korea is apparently developing will be used to launch an upgraded intercontinental ballistic missile (ICBM) or to launch a satellite. Either of these would technically require two engines.

In a statement, Chief of the General Staff Pak Jong-chon, of the North Korean People’s Army (KPA), said that the “new technologies” used in the tests on Dec. 7 and 13 “will be fully applied to the development of another strategic weapon.”

While North Korea hasn’t released a detailed description or any photos of the process or outcome of these tests, a seven-minute test appears to refer to a missile engine combustion test. In light of these circumstances, experts are leaning toward the possibility that the “new technologies” North Korea tested are a new two-stage liquid-fuel engine, small or medium in size. With a small liquid engine, combustion typically takes 7-8 minutes, though sometimes as long as 10.

Experts analyze second stage engine test for rockets

The propulsion from the first-stage engine is what lifts a missile off the ground and into the sky. After reaching a high altitude, the missile continues its flight, propelled by the second-stage engine. Generally speaking, first-stage engines don’t burn for seven minutes, given their necessarily massive output. The first-stage engine (called the “Mt. Paektu engine) used in the ICBM fired in 2017 had a combustion time of 200 seconds (that is, 3 minutes and 20 seconds). In light of this, the second engine that North Korea tested is probably a second-stage engine, experts said.

Experts explained that a second-stage engine could burn for as long as seven minutes. For one thing, a second-stage engine’s combustion period is longer than a first-stage engine’s, given lower output; for another, a second-stage engine burns intermittently, being activated and deactivated to adjust its trajectory. These observations apply whether the engine in question is used to launch an ICBM or a satellite.

Considering that North Korea’s Academy of National Defense Science said in its Dec. 14 statement that this test would “be applied to further bolstering [. . . North Korea’s] strategic nuclear deterrent,” this test is more likely to concern an ICBM than a satellite. But technically speaking, this kind of test could be used for both purposes. Given a combustion period of seven minutes, a missile carrying the engine in question would be capable of steadily and continuously transporting several warheads, or a warhead heavier than those on North Korea’s current missiles.

North Korea carried out this test at an unusually late time, around 11 pm, which many experts believe was designed to minimize the risk of the test being exposed to American surveillance and reconnaissance assets. A hard-to-detect late-night test basically shows how North Korea is pressuring the US to change its attitude.

By Noh, Ji-won, staff reporter

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