KSLV-II the Korean challenge that comes in from the cold

On May 25, 2023, at 09:24 UTC, from the Naro Space Center in South Korea, KSLV-II successfully launched the NEXTSat-2 microsatellites, a technological demonstrator for a radar satellite operating in the X band, SNIPE microsatellites equipped with a Langmuir detector for the study of the plasma in the ionosphere and the CubeSats JLC-101-v1-2, Lumir-T1 and KSAT3U.

This is the first operational flight of the South Korean KSLV-II NURI launcher, a launch vehicle that comes from far away…

나로우주센터 #누리호 (KSLV-II, ヌリ) 발사
1·2단 성공 분리후 정상비행중pic.twitter.com/wjVmZOV9rJ

— 김타쿠닷컴 일본뉴스 강운마권 (@kimtaku999) May 25, 2023

The search for a partner

South Korea, since 1992, has developed systems for suborbital launches, using structures from other countries, such as the solid fuel KSR-1 and KSR-2, and the liquid fuel KRS-3. On the basis of the latter, in 2002, the intention to develop its own light launcher and its own launch structure was announced.

The conditions following the peace that sanctioned the end of the Korean War prevented South Korea from developing its own launch technology therefore, at the time, an international tender was called and it was Russia who won it, offering its technical collaboration both in the construction of the Naro Space Centre, on the island of Goehung in the south of the country, and in the supply of the entire first stage universal module (URM-1) for the launchers of the Angara family.

Basically the first stage of the Angara 1.2 light launcher with an engine, the less powerful RD-151 (1.7 Mn less) than the single-chamber RD-191 that equips the Russian carrier.

The difficult beginnings of the KSLV-I

In October 2008 the KSLV-I was presented to the public. In the first stage, the Angara URM-1 with the RD-151 engine instead of the RD-191, and in the second stage a solid fuel engine of South Korean production.

Its first launch, which took place on Aug. 25, 2009, was a failure: the launcher performed its task but the aerodynamic fairing failed to open, causing the failure to insert the STSAT-2A telecommunications satellite in low orbit.

A similar fate occurred in the second test, which took place on Jun. 10, 2010; the vehicle signal was lost 137 seconds after launch. Finally, on Jan. 30, 2013, the first KSLV-1 succeeded in placing the STSAT-2A in its orbit.

Out of Russia, into Ukraine

Although the success of the KSLV-I could advance the South Korea-Russia cooperation program with the development of an all-South Korean engine for the first stage as well, in fact, the third launch of the vehicle was the last with technology borrowed from the Angara.

The need to upgrade the KSLV launcher to carry payloads into geostationary orbit required that the second and eventual third stages used a liquid fuel engine. In this sense, the first option for the future South Korean KRE-75 engine was offered by NPO Energomash with the Rd-107 and RD-111 engines, reliable but outdated technology.

In 2008 KARI turned to the Yuzhnoe design office, in Ukraine, to construct the KRE-075 with a thrust of 30 tons using dated technology, that of the RD-808, with a gas-generator, but reliable. The next development would be to make a 70-ton engine based on the Ukrainian RD-8 closed cycle.

Russia’s last attempt to resume the supply with South Korea occurred with the request to purchase an RD-191 engine to be able to copy its structure and create its own engine with a 250-ton thrust. The Russian counter-proposal was to supply the engines directly, which led the Seoul authorities to partner with Yuzhnoe for an engine with 200 tons of thrust derived from the future RD-815.