On October 21 at 0800 UTC, the first South Korean Nuri rocket launched from the Naro Space Center on an island off the coast of South Korea. Also known as the KSLV-II, Nuri is South Korea’s first homemade orbital launch vehicle.

All of the flight events — including nominal engine cut-off and payload separation — were accomplished successfully. Unfortunately, the three-stage rocket failed to place a 1.5-ton mass simulator into a 700-kilometer sun-synchronous orbit. The third stage cut off 45 seconds earlier than planned, leaving the payload without the necessary velocity to achieve orbit. 

Because of acceleration, rockets gain a large component of their total velocity near the end of the burn, so the early cut-off meant that it almost — but not quite — made it to orbit. It seems the third stage simply burned propellant faster than planned for some reason, running out early. The dummy payload fell back to Earth, splashing down in the ocean south of Australia.

While the launch was a failure, it still got a lot further than many other rockets do on their first launch attempt. The Nuri is a lot more complicated than a typical rocket: it uses three liquid-fueled stages with four clustered engines on the first stage producing 750 kilonewtons of force each. The second stage has a single 750-kilonewton engine that is optimized for firing in space. The third stage engine only produces 70 kilonewtons of force. Because the third stage is only fired once in space, it doesn’t need all of that extra force to fight against the gravitational pull of Earth. All three stages burn a mix of Jet-A and Liquid Oxygen. 

In case you were wondering, yes, Jet-A is jet fuel. We’re used to seeing rockets fly using a combination of Rocket Propellant-1 (RP-1) and Liquid Oxygen. Both Jet-A and RP-1 are basically refined petroleum kerosene.

South Korea’s first orbital rocket, the KSLV-1, used a slightly modified Universal Rocket Module from the Russian Angara rocket as its first stage with a South Korean-made solid motor as its second stage. The KSLV-1 failed in its first two launches in 2009 and 2010, while the third and final launch in 2013 successfully put a 100-kg satellite into orbit.

The next planned launch of the Nuri rocket is in May 2022, though that may be delayed because of this failure.

More Information

KARI press release (Korean) (via Internet Archive)

Nuri info page (via Internet Archive)

S. Korea fails to put dummy satellite into orbit (Yonhap News Agency)

Nuri info page (Gunter’s Space Page)

Naro info page (Gunter’s Space Page)

Launch video