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S. Korea seeking clues after nearly successful space mission

Health 17:27 October 22, 2021

By Yi Wonju

SEOUL, Oct. 22 (Yonhap) -- South Korea said Friday it will set up a committee to closely look into what went wrong in a mission to put a dummy satellite into orbit with its first homegrown space rocket.

The committee -- to be composed of researchers of the Korea Aerospace Research Institute (KARI) and other aerospace experts -- will comb through data to fix technological glitches ahead of a second launch in the coming months, officials of the state-run institute said.

Nuri, also known as the KSLV-II, flew to a target altitude of 700 kilometers but failed to put the dummy satellite into orbit, as its third-stage engine burned out 46 seconds sooner than expected.

South Korea's first homegrown space launch vehicle, known as Nuri, lifts off from the Naro Space Center in Goheung, South Jeolla Province, 473 kilometers south of Seoul, on Oct. 21, 2021. (Pool photo) (Yonhap)

Aerospace experts said a possible malfunction in the valves or the pressure system may have led the third-stage engine to burn up sooner than planned but stressed that determining the exact cause requires further data analysis.

"It's possible the valve that controls the fuel shut down sooner than expected for various reasons, like a sensor malfunction," Kong Changduk, professor of Aerospace Engineering at Chosun University, said. "But if we can analyze the problems in the launch and fix them, I believe we'll have no problem launching the Nuri next year."

South Korea plans to launch the Nuri rocket in May next year as part of its four other scheduled launches until 2027.

President Moon Jae-in has called the launch "a very creditable achievement," though it did not perfectly reach the goal.

South Korean President Moon Jae-in delivers a public message after the country's first homegrown space launch vehicle, known as Nuri, lifted off from the Naro Space Center in Goheung, South Jeolla Province, 473 kilometers south of Seoul, on Oct. 21, 2021. (Yonhap)

Aerospace experts described this week's mission as a major advancement in South Korea's space program, which began in 1990.

They said the Nuri rocket marked significant progress from South Korea's rocket launches in recent years, noting Nuri successfully completed all flight sequences using domestic technology.

In 2010, South Korea's two-stage Naro-1 rocket exploded about 137 seconds after liftoff following a failure in 2009. In 2013, South Korea successfully launched the Naro rocket, but the key first-stage rocket was built in Russia.

"I believe the launch was a remarkable success as we succeeded in the clustering, separating the fairing and all other sequences up until the last steps. ... I'd say we succeeded up to 80 to 90 percent," Kong said.

Nuri uses a clustering of four 75-ton liquid engines in its first stage, propelling the rocket forward with a 300-ton thrust. The clustering of the engines requires advanced technology, as each of them must ignite simultaneously at exactly equal thrusts to ensure the rocket flies along the intended trajectory.

So far, only six countries -- Russia, the United States, France, China, Japan and India -- have developed a space launch vehicle that can carry a more than 1-ton satellite and have the technology to develop 75-ton liquid engines.

KARI said the success rate for newly developed rockets on the first attempt is 30 percent to date.

Chang Young-keun, a missile expert at Korea Aerospace University, also hailed the development and successful testing of the 75-ton engine as a "remarkable achievement."

"The problem was at the end when the satellite had to reach a speed of 7.5 kilometers per second at an orbital altitude of 700 kilometers, but the rocket only gave a thrust of around 6.7 kilometers per second," he said.

Chang said researchers will now analyze all data that the ground controllers received from the rocket, including pressure and temperature, to find the exact cause, a process that could take as little as a week or up to several months.

"Since the rocket did not explode and successfully reached the target altitude, I think it's unlikely to be a serious problem, and the analysis won't take long," he added.

South Korea, a relative latecomer to the global space development race, has recently ramped up efforts in its space program, with plans to launch its first lunar orbiter next year.

South Korea has invested nearly 2 trillion won (US$1.8 billion) in building the three-stage Nuri since 2010. The whole process of the launch of Nuri was carried out with domestically made technology on its own soil, including design, production, testing and launch operation.

People watch South Korea's first homegrown space launch vehicle, known as Nuri, lifting off from the Naro Space Center in Goheung, South Jeolla Province, 473 kilometers south of Seoul, on Oct. 21, 2021. (Pool photo) (Yonhap)

julesyi@yna.co.kr
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