[DEBRIEFING] What you need to know about Nuri and the North's response

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Published: 08 Jun. 2023, 16:33 Updated: 08 Jun. 2023, 19:24

[DEBRIEFING] What you need to know about Nuri and the North's response

The Korea Space Launch Vehicle (KSLV-II), or Nuri, lifts off from the launch pad at the Naro Space Center in Goheung County, South Jeolla, at 6:24 p.m. on Thursday. [KOREA AEROSPACE RESEARCH INSTITUTE]

In Debriefings, the Korea JoongAng Daily discusses a topical issue in depth in a Q. and A. format. In this Debriefing, we look at the third launch of the Nuri rocket and its significance in Korea's space program, as well as the subsequent rocket launch from North Korea.

When Korea’s domestically-built Nuri rocket took off with a roar for its third launch two weeks ago, the country celebrated the 1,138-second flight as a landmark success.

And when North Korea launched its own space launch vehicle a week later, which was presumed to be spurred on by the successful launch of the South's Nuri rocket, the failed attempt at sending a satellite into space once again fueled speculations over possible military utilization of carrier rockets.

The string of events over the past weeks following the Nuri rocket's liftoff triggered a number of questions: How is the Nuri rocket launch related to, and different from North Korea's attempted satellite launch? Can we call the latest Nuri space mission a success when two of the eight satellites are missing? If so, how much of a success was it?

Below are some frequently asked questions about the third launch of the Nuri rocket and answers based on recent reporting by the Korea JoongAng Daily.

Is the Nuri rocket’s launch mission considered a success?

Yes. The space mission to launch a carrier rocket into the targeted altitude with payloads on board was carried out successfully, according to the Ministry of Science and ICT and the Korea Aerospace Research Institute (KARI).

However, while the rocket’s mission was a success, the satellites’ missions are “still ongoing,” with the developers of the two missing small-sized cube satellites (CubeSats) continuing to attempt to make contact with them.

The third launch of the Nuri rocket, formally known as the Korea Space Launch Vehicle-II, has two main goals, according to Cho Sun-hak, the ministry’s head of space policy and nuclear energy bureau.

“The first is to test whether we can successfully use our rocket to carry satellites into space, and the second stage is to make the said satellites actually carry out missions in orbit,” Cho said during a press briefing held a day after the launch.

The official explained that “the first part of the mission that involves the launch vehicle was successful, while the second part, the utilization of the satellites, is still ongoing.”

What happened to the two satellites that are missing? And how are the rest of the satellites faring?

Six out of Nuri’s eight satellites successfully entered their target orbits and are sending signals, while engineers are still attempting to communicate with the remaining two satellites.

On May 25, the Nuri rocket lifted off from the launch pad at the Naro Space Center carrying eight payloads, which included one main payload and seven small CubeSats.

The payloads were: the Next Generation Small Satellite 2, or NEXTSat-2, which was the main payload developed by the Satellite Technology Research Center at KAIST; JLC-101-v1-2, also known as JAC, developed by Justek, a local company; Lumir’s Lumir-T1; Cairo Space’s KSAT3U; and four nanosatellites, codenamed SNIPE, from the Korea Astronomy & Space Science Institute.

The payloads were ejected one by one at intervals of 20 seconds starting with the main payload NEXTSat-2 after the rocket reached the targeted altitude of 550 kilometers (341 miles) above ground.

However, as one of the four SNIPE satellites was in the blind spot for the monitoring camera, KARI engineers could not confirm whether the CubeSat was ejected successfully. While the attempted communication with the missing CubeSat is still ongoing, the satellite is presumed to have not been released from the rocket.

Justek’s JAC satellite was confirmed to have been ejected from the rocket, but it is also not responding to signals. The company is still attempting to communicate with the missing JAC satellite.

KAIST’s NEXTSat-2, the main payload, is currently undergoing three months of functional checks, which will be followed by an eight-month performance verification before its mission begins at full scale in April next year.

The 179.9-kilogram (396-pound) satellite is equipped with a small-sized synthetic aperture radar that can capture high-resolution images regardless of weather conditions. Circling the Earth 15 times each day, the satellite will carry out its two-year mission, which includes monitoring cosmic radiation.

How is the Nuri rocket different from North Korea's space launch vehicle, the Chollima-1?

On May 31, six days after the Nuri rocket's lift-off, North Korea launched a projectile, the Chollima-1 satellite launch vehicle, setting off air raid alarms across Seoul.

The satellite launch rocket failed due to faulty engines during second-stage separation, with some of its components crashing in the Yellow Sea, off the North Jeolla coast.

After the National Intelligence Service briefed the parliamentary intelligence committee that day, People Power Party Rep. Yoo Sang-bum relayed the spy agency’s belief that the failure of the launch vehicle's second-stage separation was the result of “an excessive trajectory adjustment” and launch preparations being rushed after the South successfully fired its Nuri space vehicle the week prior.

The North Korean satellite launch attempt was condemned by the South's National Security Council as "a grave violation of U.N. Security Council resolutions," and also by United Nations Secretary-General António Guterres, who called it “contrary” to Security Council resolutions, according to his spokesman Stéphane Dujarric.

The North is barred from conducting any launches that employ ballistic missile technology, including that of satellites, under multiple United Nations Security Council resolutions.

A white metal cylinder that the Joint Chiefs of Staff believe was part of the North Korean space launch vehicle that crashed into the Yellow Sea on May 31 [JOINT CHIEFS OF STAFF]

Long-range missiles and space rockets feature several stages or sections stacked on top of each other, each with its own engine and propellant. Stages are jettisoned from bottom to top until the final desired velocity is reached.

The major difference is that missiles are designed to fall back to the Earth for an attack, while carrier rockets aim to put payloads into targeted orbits, and therefore employ a different set of technologies during operation.

Fuels burnt for propulsion also vary depending on the purpose. While both the Nuri and Chollima rockets were three-stage liquid-fuel projectiles, the former burnt kerosene, which has higher efficiency and requires low temperature for storage, while the latter used unsymmetrical dimethylhydrazine, or UDMH, and dinitrogen tetroxide, which are often used for ballistic missiles.

When using kerosene, the rocket needs to be fired immediately after the fuel injection, whereas UDMH and dinitrogen tetroxide can be stored at room temperature and for a longer period of time.

How was the Nuri rocket's third launch different from the previous two launches?

The third launch of the Nuri rocket was its first attempt to bring “practical satellites” into mission orbit, as the Science Ministry described them, representing the program’s shift from the testing phase to operational deployment and performance refinement.

Before the third launch in May, there were two test launches in October 2021 and June 2022.

With the success of the second launch on June 21 last year, KARI became the seventh space agency to succeed in putting a satellite weighing more than 1 ton into space, following Russia, the United States, the European Union, China, Japan and India.

During the latest launch, the specifications of the Nuri rocket remained largely the same from previous test launches, yet the weight and number of payloads the space vehicle carried into suborbital space differed.

In the second test launch last year, the Nuri rocket carried a 1,500-kilogram payload, including a performance verification satellite, four CubeSats and a dummy payload.

As the small-sized CubeSats were placed inside the performance verification satellite during the second launch, the latest launch on Thursday was the Nuri rocket’s first attempt at deploying multiple satellites with the vehicle.

Where does the Nuri program go now?

Three more launches are scheduled until 2027 under the launch vehicle advancement program, aimed at improving the reliability of the Nuri rocket with a budget of 687.4 billion won ($526.6 million).

The plan is to put the NEXTSat-3 satellite aboard the carrier rocket in the fourth launch slated for 2025, and five microsatellites each during the fifth launch in 2026 and the sixth in 2027.

Moreover, the government aims to develop a two-stage launch vehicle, the Korea Space Launch Vehicle-III, with a budget of 2.132 trillion won. The next-generation launch vehicle development program will run through 2032, with the aim of bringing a lunar lander into space.

BY SHIN HA-NEE [shin.hanee@joongang.co.kr]