Nuri (rocket)
Nuri, 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. All three stages are planned to use indigenously developed rocket engines. The South Korean government has set SpaceX 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 and 2,600 kg into a 300 km LEO.
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 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.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 contract with the Korea Aerospace Research Institute to produce both types of liquid propellant rocket engines for Nuri.
- 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 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
| Fuel | Jet A-1/LOX |
| Thrust | 66.6tf, 75.9tf |
| Specific Impulse | 289.1s |
| Height | 2.9m |
| Diameter | 2m |
| Cycle | Gas Generator |
The KRE-075 engine was developed after the 30tf engine development program.
KRE-075 Vac. Engine
KRE-007 Engine
| Fuel | Jet A-1/LOX |
| Thrust | 7.0tf |
| Specific Impulse | 325.1s |
| Cycle | Gas Generator |
KSLV-II TLV
The Test Launch Vehicle 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.
With the 2nd stage engine installed, the TLV will perform as a Small Sat Launch Vehicle.
2018 flight
| Wet Mass | 52.1t |
| 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.
The maiden flight was first delayed from October 25, 2018 for two months, due to abnormal readings detected in the rocket propellant pressurization system.
The test flight was then rescheduled for November 28, 2018, at 16:00 KST. No payload was to be placed into orbit.
The launch of the TLV while deemed successful with its main engine burning for 151 seconds in a 10-minute flight, was not broadcast live.
After reaching a maximum altitude of 209 kilometers, the rocket stage splashed down in the Pacific Ocean, 429 kilometers southeast of Jeju Island.
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, and the third stage will implement a newly developed KRE-010V oxidizer-rich staged combustion engine.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.