[Nuriho Launch] "Issue in 7t-class Engine of 3rd Stage... To Be Fixed for Next Launch in February"

[Asia Economy Reporter Kim Bong-su, Goheung Naro Space Center=Joint Coverage Team] The Korean space launch vehicle Nuri, launched at 5 p.m. on the 21st, is being evaluated as a near success, falling short by only 2%. The entire flight process, from first-stage ignition to reaching the target orbit (700km) and satellite mock-up separation, was carried out normally. However, the 7-ton class engine of the third stage prematurely shut down for unknown reasons, causing the satellite mock-up to fail to reach its intended orbit, leaving some regret. The Ministry of Science and ICT announced that it will form a launch investigation committee to identify the cause and make improvements before the second launch scheduled for May next year.

Below is a Q&A with Minister Im Hye-sook of the Ministry of Science and ICT and other officials.

- Was it a success or failure?

▲ (Im Hye-sook) I want to say it was one step away. The clustering technology engine combustion of the first stage, which was considered a technical challenge, was all successfully completed. Difficult technologies such as first and second stage separation, ignition, and fairing separation proceeded well. It is regrettable that the satellite mock-up could not be placed into orbit due to insufficient final speed. I think it was just one step away.

- What is the significance of this launch?

▲ It has raised expectations for the era of private space. Until now, it was government-led. In the future, once launch vehicle technology is completed and transferred to the private sector, a space industry ecosystem will be established. Until the private sector reaches a certain level, public demand stimulation will enhance the private sector's space competitiveness.

- There were failures this time; what about the improvement project?

▲ The repetitive launch project to improve Nuri's reliability will be conducted four times starting from 2022. The preliminary feasibility study for the improved version is currently being planned. I understand that the procedures are already underway and it will proceed.

- There is a call for a dedicated space agency?

▲ It is time for Korea to open a new era in the space industry. Many people seem to agree on the need for a dedicated organization. An organization with expertise and continuity is necessary. However, I cannot say now when and how this will be done.

- What are the achievements of this launch?

▲ (Lee Sang-ryul, Director of Korea Aerospace Research Institute) Our biggest concern was whether the 75-ton engine clustering would operate during actual flight. That part seems to have been perfectly achieved. The normal combustion and separation of each stage, as well as fairing separation, were also successfully carried out, which is a great achievement. The combustion time of the third stage engine was insufficient, so the desired speed was not achieved. The technical team will analyze the detailed cause. But I think there was success in the flight test of the 75-ton engine clustering, which was our biggest concern. The shortcomings will be supplemented through the investigation committee and internal review for the May launch next year.

- From an expert's perspective, is there anything to point out?

▲ (Ko Jeong-hwan, Head of Launch Vehicle Development Division, KARI) It appears that the third stage ended about 40 to 50 seconds earlier during flight. We have not yet reviewed all the measurement data. We need to download and analyze it. Early shutdown can have various causes, such as insufficient internal pressure or incorrect shutdown commands. We need to analyze the data to know.

- Final evaluation?

▲ (Lee Sang-ryul) Since the important parts were achieved, I want to lean towards success. The short combustion time of the third stage engine needs analysis, but I believe we can find the cause and establish countermeasures.

- How is the investigation committee formed?

▲ (Kwon Hyun-jun, Director of Large Public Research Policy, Ministry of Science and ICT) This was a flight test. There will be a second test. The committee will be centered on KARI members, and external experts will also participate. We have a candidate pool, but since we need to see the data to understand the problem and invite those experts, it is not yet finalized.

- Will the second launch be tested under the same conditions?

▲ (Ko Jeong-hwan) First, we must identify the cause of the first launch and clearly implement improvements to prevent the same problem. The second launch will carry a performance verification satellite into the same orbit. This part will likely be decided based on the investigation committee's results and consultation with the Ministry of Science and ICT.

- Any estimated causes?

▲ (Oh Seung-hyeop) It is presumed that the propulsion system of the 7-ton liquid engine in the third stage did not perform as well as it did on the ground. It could be a fuel oxidizer supply issue to the engine or a problem with the pressurization system inside the tank. There are many valves supplying propellant to the third stage. Any one of them could have malfunctioned. The fuel propellant was likely sufficient based on experimental data, but there could be issues with the pressurization system or valve malfunction.

- Any final words?

▲ (Ko Jeong-hwan) Watching the flight in real-time today and after it ended, I felt regret. From first stage ignition, everything proceeded accurately, but the one thing that was disappointing was the short combustion time of the third stage engine, which prevented orbit insertion. Personally, although some issues may not be visible, proper control during flight is necessary to enter the correct orbit. It was confirmed that attitude control and guidance algorithms operated during today's flight, but the result is very disappointing. We want to improve the early combustion shutdown in the third stage and show perfect results in the second launch next year.

▲ (Kwon Hyun-jun) As I said earlier, this launch was a flight test. The second flight test is prepared for May. This is part of the development process, and it is difficult to define the development process as success or failure. Many people at KARI think it is just one step away. (Choking up) Please encourage us so that we can succeed.