한국항공우주연구원

Nuri Launch Investigation Committee’s Final Investigation Results
- Loose helium tank anchor within third-stage oxidizer tank causes damage to internal structure

□ The Ministry of Science and ICT (hereinafter “MSIT”, Minister Lim Hyesook) and Korea Aerospace Research Institute (hereinafter “KARI”, President Lee Sang-ryool) appointed the Nuri Launch Investigation Committee (hereinafter “the Committee”) to conduct an investigation and announced the reasons behind the failed attempt to place the dummy satellite into orbit during Nuri’s first launch on October 21, 2021.
ㅇ The Nuri Launch Investigation Committee, comprising KARI researchers and independent experts was established in late October 2021 and has held five rounds* of meetings thus far on top of seven internal meetings among KARI researchers to examine the technical aspects that went wrong during Nuri’s first launch.
*First meeting: November 3, 2021, second meeting: November 11, 2021, third meeting: November 30, 2021, fourth meeting: December 20, 2021, fifth meeting: December 27, 2021

□ The investigation focused on more than 2,600 types of telemetry data acquired in-flight to identify abnormalities that occurred during the flight and reasons thereof.
ㅇ Upon confirming during the early stages of the investigation that the premature shutdown of the third-stage engine was caused by abnormal depressurization in the oxidizer tank, the Committee zeroed in on pinpointing the exact causes.

<Breakdown of Events Post-Launch>
‣ (T+ 36 seconds) Abnormal vibrations detected during flight (third-stage tank truss supporting structure, payload adapter), helium starts to leak from the helium tank, oxidizer tank pressure increases
‣ (T+ 67.6 seconds) Oxidizer tank pressure starts to drop and surface temperature of upper half of oxidizer tank plummets
‣ (T+ 115.8 seconds) Helium tank pressure falls and third-stage oxidizer tank pressure rises

□ Ultimately, the causes behind the premature shutdown of the third-stage engine were determined as follows.
ㅇ Failed to sufficiently account for increased buoyancy in flight when designing the anchor for the helium tank equipped inside the third-stage oxidizer tank.
ㅇ As a result, the helium tank fell off its anchoring device due to increased buoyancy of liquid oxygen that was exerted on the helium tank during the flight.
ㅇ The detached helium tank began to move around, damaging the tank pipes and causing cracks in the oxidizer tank, which led to helium leakage and oxidizer leakage, respectively. The lack of oxidizer flowing into the third-stage engine eventually caused the engine to burn out earlier than expected.
ㅇ Building on this investigation, MSIT and KARI will prepare detailed measures and make concrete plans for future launches by incorporating technical improvements, focusing on but not limited to strengthening the anchoring device of the helium tank and structure of the oxidizer tank.

□ KARI’s Vice President Choi Hwan‑Seok who serves as the Chairperson of the Committee expressed his regret in “failing to deliver on the expectations of the public due to the lack of compensation in design for the rise in buoyancy during the flight” and added that “meticulous improvements will be made in preparation for the second launch.”
ㅇ In addition, Director General Kwon Hyun-joon of the Space, Nuclear and Big Science Policy Bureau of MSIT stated that “future timelines regarding technical improvements will be determined by the Project Steering Committee and the National Space Council Expert Committee.”