Nuri (rocket)

Nuri (Korean: 누리, meaning "world" ), also known as KSLV-II, is South Korea's second carrier rocket and the successor to KSLV-1. Nuri is under development by KARI / Korea Aerospace Research Institute, and is planned to have its first flight in February 2021.[4][5] All three stages are planned to use indigenously developed rocket engines. The South Korean government has set SpaceX (founded by Elon Musk, and formed by former McDonnell Douglas and TRW alumni) as a 'role model', striving to develop relatively cheap and reliable rockets competitive enough for the commercial launch market. Currently the goal is to launch a 1,500 kg payload into a 600–800 km low Earth orbit (LEO)[5] and 2,600 kg into a 300 km LEO.[6]

Nuri (KSLV-II)

CGI render of a Nuri rocket at the launch pad
Function	Orbital launch vehicle
Manufacturer	KARI
Country of origin	South Korea
Size
Height	47.2 m (155 ft)[1]
Diameter	3.5 m (11 ft)[1]
Mass	200,000 kg (440,000 lb)[1]
Stages	3[1]
Capacity
Payload to LEO (300km)[2]	2,600 kg (5,700 lb)
Payload to LEO (600~800km)	1,500 kg (3,300 lb)
Launch history
Status	Under development
Launch sites	Naro Space Center LC-2
First stage
Engines	4 KRE-075 SL
Thrust	266.4 tf (2,612 kN; 262.2 LTf; 293.7 STf)[2]
Specific impulse	261.7s (SL), 289.1s (Vac.)[3]
Burn time	127s[2]
Fuel	LOX / Jet A-1
Second stage
Engines	1 KRE-075 Vac.
Thrust	80.4 tf (788 kN; 79.1 LTf; 88.6 STf)[2]
Specific impulse	315.4s (Vac.)[2]
Burn time	148s[2]
Fuel	LOX / Jet A-1
Third stage
Engines	1 KRE-007 Vac.
Thrust	7.0 tf (69 kN; 6.9 LTf; 7.7 STf)[2]
Specific impulse	325.1s (Vac.)[2]
Burn time	498s[2]
Fuel	LOX / Jet A-1

Specification

Nuri is a three-stage rocket. The first stage booster uses four KRE-075 SL engines generating 266.4t of thrust with a specific impulse of 289.1s. The second stage booster uses a single KRE-075 Vac. engine, which has a wider nozzle for increased efficiency in vacuum with a specific impulse of 315.4s. The third stage booster uses one KRE-007 engine with a specific impulse of 325.1s. Both engine models use Jet A-1 as fuel and liquid oxygen (LOX) as oxidizer.

Future Versions

Further improvements will be added after the success of KSLV-II program, mainly increasing the thrust of the KRE-075 from 75.9 tf to 86.6 tf and specific impulse from 261.7s to 315.4s. There are also plans on making the engine lighter by methods such as removing the pyrotechnic ignitor or limiting its gimbal range. This will allow the payload capacity of the modified KSLV-II to increase from 1.5 tons to 2.8 tons.[7]

Development

Engines development

• In March 2014, the first combustion test of the 7-ton class combustor was successfully completed, and the total assembly and initial ignition test of the KRE-007 engine started in July 2015. In addition, the first phase of the project was completed with the addition of a three-stage engine combustion test facility and a combustor combustion test facility. However, the problem of combustion instability in the KRE-075 burner required rework.
• Hanwha Techwin Co. has signed on January 25, 2016, a 14.1 billion won (US$11.77 million) contract with the Korea Aerospace Research Institute (KARI) to produce both types of liquid propellant rocket engines for Nuri.[8]
• On January 8, 2016, the second phase of the project was carried out to overcome the difficulties of combustor combustion instability and welding technology of the liquid engine fuel tank, and a combustion test of the KRE-075 engine for a few seconds was successful.
• On May 3, 2016, the KRE-075 engine underwent a 1.5 second long spark ignition test. It was later burned for 75 seconds on June 8, 2016. Following these successes, on July 20, 2016, at 1:39 pm, the final target combustion time of 145 seconds (147 seconds) was successfully achieved. During the combustion test, the engine performed nominally, with all values such as combustion safety and combustion thrust within the expected error range. During an actual launch, the first stage engine will burn for 127 seconds and the second stage engine for 143 seconds.
• Starting from October 2016, there has been over 200 combustion tests of the second KRE-075 engine.

KRE-075 SL Engine

An artist's render of Nuri's 75-ton-class engine

KRE-075 Engine

Fuel	Jet A-1/LOX
Thrust	66.6tf (SL), 75.9tf (Vac.)[3]
Specific Impulse	289.1s[3]
Height	2.9m
Diameter	2m
Cycle	Gas Generator

The KRE-075 engine was developed after the 30tf engine development program.[9]

KRE-075 Vac. Engine

Fuel	Jet A-1/LOX
Thrust	80.3tf (Vac.)[3]
Specific Impulse	315.4s[3]
Cycle	Gas Generator

KRE-007 Engine

Fuel	Jet A-1/LOX
Thrust	7.0tf[3]
Specific Impulse	325.1s[3]
Cycle	Gas Generator

KSLV-II TLV

The Test Launch Vehicle (TLV) is a two stage-rocket, qualifying the performance of the KRE-075 engine which will power the KSLV-II. The TLV is 25.8 meters in length, 2.6 meters in diameter, and with a mass of 52.1 tons. The main-stage Kerolox engine is fully gimballed.[10][11] With the 2nd stage engine installed, the TLV will perform as a Small Sat Launch Vehicle.[12]

2018 flight

Wet Mass	52.1t[13]
Dry Mass	38 tons
Height	25.8m
Diameter	2.6m
Stages	1
Engine	1 KRE-075
Payload	mass simulator

The TLV was launched from the Naro Space Center in Goheung, South Jeolla Province, on November 28, 2018. The main objective of the first suborbital flight was for the single-stage rocket's main engine to burn 140 seconds, reaching a 100 km altitude before splashing down in the sea between Jeju Island and Okinawa Island.[14]

The maiden flight was first delayed from October 25, 2018 for two months, due to abnormal readings detected in the rocket propellant pressurization system.[15] The test flight was then rescheduled for November 28, 2018, at 16:00 KST(UTC+9). No payload was to be placed into orbit.[16]

The launch of the TLV while deemed successful with its main engine burning for 151 seconds in a 10-minute flight,[17] was not broadcast live.[18] After reaching a maximum altitude of 209 kilometers, the rocket stage splashed down in the Pacific Ocean, 429 kilometers southeast of Jeju Island.[19]

As the TLV was meant to serve as a test craft, and as the flight ended in a success, there will not be a second TLV launch.

GEO KSLV

An upgraded variety of KSLV-II for geostationary equatorial orbit is under development. It will cluster four KRE-090 engines in the core stage, with four side boosters equipped with one KRE-090 engine each. The second stage will be powered with a vacuum-optimized variety of the same KRE-090 engine (KRE-090V), and the third stage will implement a newly developed KRE-010V oxidizer-rich staged combustion engine.[20]

Usage

Nuri will be used in launching several Earth observing satellites, such as KOMPSAT, medium-class satellites and LEO reconnaissance satellites. It is planned to support South Korea's Moon exploration mission to send orbiters and landers. Nuri will be South Korea's first rocket to enter the commercial launch service market. The launch cost is estimated to be around $30 million, which is cheaper than its Asian counterparts. This will allow for South Korea to provide cheap launch services for South East Asian countries.

An improved version of Nuri is expected to launch a Korean lunar lander by 2030.

See also

• KSLV-I
• Naro Space Center
• KARI
• Polar Satellite Launch Vehicle
• Unha-9 (North Korean competitor)

References

1. "Korea Space Launch Vehicle KSLV-Ⅱ". Korea Aerospace Research Institute.
2. "대한민국, 이제는 누구? - 한국형발사체 "누리호"!".
3. "7톤/75톤급 엔진의 스펙/성능 + 누리호 발사대 설계".
4. Ko, Jun-tae (7 June 2019). "Space: The final frontier, but not for much longer". Korea JoongAng Daily. Retrieved 2 October 2019.
5. "Korea Space Launch Vehicle KSLV-II". Korea Aerospace Research Institute. Retrieved 7 December 2016.
6. "네이버 뉴스".
7. "누리호 75톤급 엔진의 개량, 정지궤도 투입, 페이로드 옵션 그리고 재사용에 대하여".
8. "Hanwha Techwin to Produce Liquid Rocket Engine for Korea Space Launch Vehicle". 비즈니스코리아 - BusinessKorea. 26 January 2016. Retrieved 7 February 2019.
9. 한국항공우주연구원(KARI). "[KARI]연비가 향상된 로켓엔진 연소시험(100초) 공개". Retrieved 7 February 2019 – via YouTube.
10. 한국항공우주연구원 (10 September 2018). "올 10월로 다가올 #시험발사체 조립 장면 타임랩스 영상으로 만나 보시죠!pic.twitter.com/25hDmf2lAg". twitter.com. Retrieved 7 February 2019.
11. "사진 > KARI IMAGE >". www.kari.re.kr. Retrieved 7 February 2019.
12. "누리호 75톤급 엔진 시험발사체를 활용한 "소형발사체" 후속 개발에 대하여 (메탄 엔진을 사용하는 2단) > KARI IMAGE >".
13. https://i.servimg.com/u/f48/19/39/35/83/scree261.jpg
14. 김한주 (28 November 2018). "S. Korea to test launch space rocket engine". Yonhap News Agency. Retrieved 7 February 2019.
15. "S. Korea delays test launch of space rocket engine". English.yonhapnews.co.kr. 2018-10-17. Retrieved 2019-02-07.
16. 한국항공우주연구원 (13 November 2018). "11월 28일, 한국형발사체 '누리호'의 엔진시험을 위한 시험발사체 발사가 추진될 예정입니다.pic.twitter.com/9eOHhufcym". twitter.com. Retrieved 7 February 2019.
17. 김한주 (28 November 2018). "(2nd LD) Space rocket engine burn time test meets target goal". Yonhap News Agency. Retrieved 7 February 2019.
18. 한국항공우주연구원 (27 November 2018). "#시험발사체 발사 성공! 발사 모습을 영상으로 공개합니다.pic.twitter.com/lTkonvL7ax". twitter.com. Retrieved 7 February 2019.
19. 김한주 (28 November 2018). "(2nd LD) S. Korea successfully tests space rocket engine". Yonhap News Agency. Retrieved 7 February 2019.
20. Yu, Byungil; Lee, Kwang-Jin; Woo, Seongphil; Im, Ji-Hyuk; So, Younseok; Jeon, Junsu; Lee, Jungho; Seo, Daeban; Han, Yeoungmin; Kim, Jinhan (April 2018). "Development Status and Plan of the High Performance Upper Stage Engine for a GEO KSLV". Journal of the Korean Society of Propulsion Engineers. 22 (2): 125-130.