Independently made Nuri rocket takes S. Korea into stratosphere

한겨레 입력 2021. 10. 22. 17:46 수정 2021. 10. 22. 18:06
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Ko said, "All the launch processes, such as projectile position control and induction algorithms, were exactly correct, but it's a shame that the final combustion time for the third stage was short and thus the dummy satellite could not enter orbit. It shouldn't be too difficult to ascertain the cause of the premature termination of combustion in the third stage."

President Moon said, "Simply sending a projectile up to an altitude of 700 km in space is a great achievement and we have come closer to space," adding, "If we check and improve on what we lacked today, we can surely achieve perfect success in our second launch in May next year."

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The rocket's flight proceeded without issue until it failed to put its payload into orbit, but is still being hailed as a de facto success
After blasting off from Naro Space Center in Goheung County, South Jeolla Province, South Korea’s domestically designed and produced rocket Nuri (KSLV-II) heads upward to the stratosphere. (Yonhap News)

Nuri, Korea’s first space launch vehicle developed exclusively with domestic technology, was only half successful in space. This "rehearsal" showed the shortcomings the domestic space industry must resolve, though the historic launch had many cheering and looking up at the heavens.

Minister of Science and ICT Lim Hye-sook held a briefing Thursday evening on the results of the rocket’s launch at Naro Space Center in Goheung County, South Jeolla Province.

“Nuri was launched at 5 pm and its entire flight process proceeded normally,” she said. “But though the three-stage engine finished combustion early and the dummy satellite attained its intended altitude of 700 km, it failed to enter a low orbit around Earth because its speed didn’t reach 7.5 km per second.”

President Moon Jae-in provided a more detailed update on Nuri’s performance, which is being called a de facto success following news that the projectile reached an altitude of 700 km. In a message to the public an hour and 10 minutes after the launch, he said, “From launch control to liftoff, the ignition of the two engines and rocket separation in the air, fairing and separation of the dummy satellite proceeded smoothly. This is entirely our own technology. But putting a dummy satellite on track remains an unfinished job.”

A Korea Aerospace Research Institute (KARI) analysis found that Nuri's seven-ton liquid engine used in the third stage burned for 475 seconds, short of the intended 521. This 46-second gap sealed the rocket’s fate.

But the Nuri rocket was nearly successful in projectile operations as the first stage and fairing and second-stage separation went smoothly, as did the separation of the dummy satellite. This means the country has acquired a great deal of homegrown space transportation know-how through its independently developed projectile since the successful launch in 2013 of Korea's inaugural rocket, Naro. Korea purchased the Naro's first-stage engine from Russia.

Minister Lim said, “KARI will immediately form a launch investigation committee of researchers and external experts to accurately identify why combustion ended early in the third-stage engine and resolve problems and push for a second launch.” Her ministry and KARI plan a second launch next year on May 19 regardless of the outcome of Nuri’s first launch.

Ko Jeong-hwan, head of KARI’s KSLV-II R&D Directorate, said, “Several more days are needed to see all the measured data. A number of reasons could explain the cause of the premature termination of combustion, such as insufficient pressure in the third-stage fuel and oxidizer tank and incorrect command of combustion termination. But we can draw conclusions by analyzing telemetry [from remote data transmission equipment] data and the input and output data of mounted valves.”

The third stage alone had 49 valves in the gas supply system and 35 in the engine supply system.

One day prior to launch, on Wednesday at 7:20 am, Nuri was moved from its assembly facility to its launch pad. The next day, all of its electric and electronic equipment was inspected and its fuel and oxidizer were filled. Nuri entered automatic launch operation (PLO) at 4:50 pm and liftoff came 10 minutes later.

The launch was originally scheduled for 4 pm Thursday but saw an hour delay after an abnormality was detected in the valve connecting the projectile to the external system. After the automatic launch system began at 4:50 pm, the first flight of the 12-year project commenced ten minutes later.

Due to the failure of the dummy satellite to stay in its intended orbit, Korea failed to become the seventh nation to launch its own satellites by one step. The country also missed out on being the fourth to succeed in its first launch.

When asked if the launch was a success, KARI President Lee Sang-ryul said, “While we failed to achieve 100% of our original goal, we nearly attained the important part, so I want to emphasize our success. We can quickly look for why the engine’s combustion was cut short and take measures [to ensure success].”

Ko said, “All the launch processes, such as projectile position control and induction algorithms, were exactly correct, but it’s a shame that the final combustion time for the third stage was short and thus the dummy satellite could not enter orbit. It shouldn’t be too difficult to ascertain the cause of the premature termination of combustion in the third stage.”

President Moon said, “Simply sending a projectile up to an altitude of 700 km in space is a great achievement and we have come closer to space,” adding, “If we check and improve on what we lacked today, we can surely achieve perfect success in our second launch in May next year.”

For the qualitative growth of the domestic space industry, the title of chair of the National Space Committee next month will be promoted from science and ICT minister to prime minister.

By Lee Keun-young, senior staff writer

Please direct questions or comments to [english@hani.co.kr]

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