The Cause of the 'Hyeonmu Naktan Accident' Is a Gyroscope Error

Military "Will Develop Additional Devices to Enhance Flight Safety"
Complete Inspection of Same Model Missiles by March Next Year
Launch Sites Also Adjusted to Ensure 'Public Safety'

Hyunmoo-2C Missile Misfire Accident Site
[Image Source=Yonhap News]

[Asia Economy Reporter Jang Hee-jun] The final analysis suggests that the cause of the Hyunmoo-2C ballistic missile misfire accident was an error in the 'gyroscope,' a device that measures the missile's attitude. Based on this result, the military authorities plan to conduct a full inspection of the missile and develop additional devices to enhance flight safety.

According to the investigation and disclosure by the Ministry of National Defense, the Joint Chiefs of Staff, and the Agency for Defense Development (ADD) on the 16th, the Hyunmoo misfire accident that occurred last October 10 is presumed to have been caused by an error occurring during the process of transmitting information measured by the gyroscope inside the missile to the actuator.

Typically, a missile is divided into the front section equipped with the warhead, the guidance and control section that determines the missile's trajectory, the propulsion section that generates thrust, and the actuator section containing the missile's wings and nozzles.

Among these, the guidance and control section consists of an Inertial Navigation System (INS) that measures flight status and a guidance control device that calculates control commands based on the flight status information identified by the INS. When the information processed by the guidance control device is transmitted to the actuator, the wings and nozzles move according to the commands. This guidance and control section and the actuator section are classified as the 'control system.'

The missile involved in the accident did not have a device to collect measurement data. Accordingly, the military began analysis based on the trajectory estimated through eyewitness testimony and visual observation immediately after the accident, suspecting a problem in the control system.

The military created a fault tree, which is a 'predicted result system diagram' of various possible errors in the device, classified the types of failures, and conducted over 30,000 simulations to examine how the missile's trajectory would behave in each failure scenario.

Assuming possible failures in the INS and guidance control device of the guidance and control section, the experiments showed that when there is an error in the information transmitted from the INS, the missile trajectory resembles that of the misfired missile.

The INS contains several sensors such as gyroscopes and accelerometers, and the military judged that the gyroscope, which measures the missile's attitude and provides measurement values, had an error.

However, a military official involved in the investigation stated, "There are many components inside the gyroscope, so we do not know exactly which part is faulty. Although we have developed missiles for a long time, there has never been a case where the missile turned backward like this," describing the gyroscope defect as 'unprecedented.'

In particular, simulation results indicated that a failure in the actuator section could not produce the trajectory observed in this misfire accident. At the time, the missile flew in the intended direction immediately after launch but then flew backward, drawing a trajectory. In the case of an actuator failure, the missile would tumble unstably without such a trajectory, according to the analysis.

When the fallen missile was recovered and analyzed, the military official explained that the wings and nozzles were presumed to have operated normally.

Missile Configuration and Control System
[Image Source: Ministry of National Defense Data]

The military plans to develop a flight safety device to be installed on the Hyunmoo-2C missile to prepare for similar accidents. This device will separate the warhead from the propulsion unit if the missile deviates from its intended trajectory, causing it to fall as close as possible without flying far.

Additionally, from the end of this month until March next year, a full inspection of the Hyunmoo-2C missile model will be conducted to reconfirm its safety. The control system, presumed to be the cause of the misfire, will be the focus, and missiles produced at the same time as the accident missile will be disassembled and inspected in detail.

The manual for responding to similar accidents will also be revised. During the accident, the military failed to promptly inform residents near the launch site in Gangneung, causing confusion.

A military official explained, "The previous launch site was Gangneung, but we plan to avoid densely populated areas and adjust to locations that can ensure public safety as much as possible," adding, "We are also working on improving the notification process to residents, which was insufficient."

However, the military authorities denied claims that 'insufficient training' was the cause of the misfire accident. A military official said, "It is difficult to specify the exact number, but this was not the first time firing the Hyunmoo-2C this year, and all previous launches were successful," adding, "We conduct numerous training sessions right up until pressing the launch button."

Earlier, on October 4, in response to North Korea's intermediate-range ballistic missile (IRBM) provocation, the Army Missile Strategy Command conducted a counter-fire exercise using the Hyunmoo-2C ballistic missile. However, the missile flew in the opposite direction immediately after launch and crashed inside the military base.

This content was produced with the assistance of AI translation services.