Nuri (rocket)

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.[8]

• 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.[9]
• 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.

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

KRE-075 Engine

The KRE-075 engine was developed after the 30tf engine development program.[10]

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.[11][12] With the 2nd stage engine installed, the TLV will perform as a Small Sat Launch Vehicle.[13]

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.[15]

The maiden flight was first delayed from October 25, 2018 for two months, due to abnormal readings detected in the rocket propellant pressurization system.[16] The test flight was then rescheduled for November 28, 2018, at 16:00 KST(UTC+9). No payload was to be placed into orbit.[17]

The launch of the TLV while deemed successful with its main engine burning for 151 seconds in a 10-minute flight,[18] was not broadcast live.[19] After reaching a maximum altitude of 209 kilometers, the rocket stage splashed down in the Pacific Ocean, 429 kilometers southeast of Jeju Island.[20]

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.

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.[21]