South Korea scheduled to launch research satellites on third Nuri flight


On the southern coast of South Korea, the first entirely home-grown launch vehicle in the country’s history is scheduled to make its third flight from the Naro Space Center. Liftoff is scheduled for 09:24 UTC on Wednesday, May 24 from Naro’s Launch Complex 2 (LC-2).

The Nuri rocket, also known as KSLV-2, pioneered the use of the South Korean-developed first-stage KRE-075 SL engines. The original KSLV, also known as Naro, used a Russian Angara first stage and RD-191 engine – though it was launched from South Korea.

This is the first operational flight of the Nuri vehicle, which is carrying the 180 kg NEXTSat-2 X-band synthetic aperture radar (SAR) technology demonstrator and four SNIPE 6U CubeSats with a total mass of 40 kg. Three other CubeSat missions, JLC-101-v1-2, Lumir-T1, and KSAT3U, are also on board.

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대한민국 독자 우주발사체 누리호가 다시 우주를 향한 도전을 시작합니다.

누리호의 3차 발사 예정일은 2023년 5월 24일 수요일이며, 발사 예정시간은 오후 6시 24분(±30분)입니다.#누리호 #누리호_3차발사

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At T0, the first stage’s four KRE-075 sea-level engines, using Jet A-1 fuel (a form of kerosene) and liquid oxygen, ignite with a thrust of 2,942 kN.

After liftoff, the engines operate for around two minutes and five seconds. During this time, Nuri will fly along a launch azimuth of 170 degrees, taking the rocket on a southerly trajectory.

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After stage separation, the second stage’s single KRE-075 vacuum engine, with a maximum thrust of 788 kN, ignites for two minutes and 28 seconds. While under second stage flight, the fairing separates from the rocket near the four-minute mark in the launch.

The second stage engine will shut down around 34 seconds after fairing separation, and the third stage uses its single KRE-007 vacuum-optimized engine to finish the climb to orbit. During the third stage burn, this stage will make a “dogleg” maneuver to an azimuth of 191 degrees, which will place the stage and payloads in the intended Sun-synchronous polar orbit.

The KRE-007, with a thrust of 68.7 kN and using the same propellants as the rest of the vehicle, finishes its burn approximately 13 minutes after liftoff, right as the stage reaches orbit. This will be a circular orbit with an altitude of 550 km and an inclination of around 98.2 degrees, which all satellites on this flight will be deployed into.

Payload separation will then occur just after 13 minutes into the flight (around 783 seconds) for NextSat-2 and around 803-923 seconds for the CubeSats. All deployments will be complete just past 15 minutes after launch.

Nuri’s first flight occurred on Oct. 21, 2021, carrying a 1,500 kg dummy satellite payload. The vehicle reached the Kármán line and even to the targeted apogee of 700 km, but the third stage shut down 46 seconds early and did not reach orbital velocity.

The vehicle’s second flight, on June 21, 2022, went much more smoothly. Nuri carried a 1,300 kg dummy satellite payload, four CubeSats, and the 180 kg PVSAT technology demonstrator spacecraft into a circular 700 km high Sun-synchronous polar orbit.

Infographic released for the third Nuri launch. (Credit: KARI)

The NEXTSat-2 spacecraft is the main payload for this flight. NEXTSat-2, developed by the Korea Advanced Institute of Science and Technology’s Satellite Technology Research Center (KAIST SaTRec), has an X-band SAR antenna as its primary instrument.

NEXTSat-2’s Sun-synchronous orbit will allow it to pass over a given place at the same local time on a consistent basis and will allow the solar panels to generate power continuously. This is needed because the X-band SAR antenna draws a great deal of power.

NEXTSat-2 also will observe radiation from cosmic rays in its orbit. Cosmic rays originate from the Sun as well as from outside the Solar System, including energetic events like supernovae elsewhere in the universe. However, Earth’s atmosphere largely absorbs these rays – protecting life on the surface.

The spacecraft is designed for a two-year lifetime in orbit and is a demonstrator of core technologies that will be used on future South Korean spacecraft.

The NEXTSat-2 payload being prepared for launch. (Credit: KARI)

Besides the NEXTSat-2 microsatellite, seven CubeSats are on board. Four of these are known as SNIPE A through D, which are all 6U CubeSats designed to observe the microstructure of the plasma environment in orbit. The CubeSats were developed by the Korea Astronomy and Space Science Institute (KASI).

These satellites are equipped with Langmuir probes, fluxgate magnetometers, and high-energy particle detectors. In addition to their HF and S-band communications equipment, they have Iridium modules to communicate with the ground as a secondary data link.

The group of SNIPE satellites was originally set to launch on a Russian rocket, but that was changed after international sanctions took effect due to the Russian invasion of Ukraine.

Artist’s impression of the SNIPE cubesats flying in formation. (Credit: KASI)

The 4 kg JAC CubeSat, developed by Justek, is a testbed for an attitude control system and will use an optical payload to verify the attitude control system’s performance.

Lumir-T1, a 10 kg CubeSat developed by Lumir, is designed to measure cosmic radiation as well as test error correction features using a microprocessor board. Cosmic radiation can affect computer data, and CPUs used in spacecraft are typically hardened against this radiation.

Finally, KSAT3U, a 6 kg CubeSat developed by Kairospace, has a dual mission of observing weather phenomena using a polarized camera and demonstrating space debris removal.

JAC and Lumir-T1 are designed to last six months in orbit, while KSAT3U and SNIPE satellites have an intended mission life of one year. All satellites on this flight are developed and manufactured in South Korea, as part of the country’s effort to grow its space industry.

The next flight of Nuri is expected in 2025, carrying the CAS 500-3 satellite. The launch cadence of the Nuri vehicle is expected to be one flight per year after this, at least through 2027. However, the follow-on KSLV-III project is expected to become the mainstay of South Korean spaceflight ambitions.

KSLV-III, scheduled to come online in 2030, is being designed to launch up to 10 metric tons to low Earth orbit or 3.5 metric tons to geosynchronous orbit and could become at least partially reusable as well.

Image of Earth with the lunar surface in the foreground, taken from the Danuri spacecraft in lunar orbit. (Credit: KARI)

South Korean plans include a robotic lunar lander to succeed the Danuri probe currently orbiting the Moon, and this lander is currently planned to fly in 2032. The new launch vehicle under development would enable a domestic launch of the lunar lander as well as other ambitious South Korean plans like a national satellite navigation system.

The Nuri vehicle and its flights this decade are initial steps to a much more capable South Korean space program in the future.

(Lead image: Nuri on the pad at the Naro Space Center’s LC-2. Credit: KARI)

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