Navy retrieves Naro rocket debris

By Kim Tong-hyung
Staff reporter

The Korean navy Friday recovered what is believed to be debris from the Korea Space Launch Vehicle 1 (KSLV-1) that exploded shortly after liftoff, Thursday.

According to officials at the Ministry of Education, Science and Technology, two pieces of wreckage were retrieved in international waters, south of Jeju Island, and were brought to Korean and Russian experts for further inspection.

However, engineers at the Korea Aerospace Research Institute (KARI), the country's space agency, will have limited access to the recovered material, as the technology standard agreement (TSA) signed between Russia and Korea bans any technology transfer regarding their joint project.

The ministry also said that Korean and Russian engineers have agreed to open a failure review board (FRB) meeting on Monday to officially begin their investigation into the cause of the failed launch.

In the country's second major space setback in less than a year, the two-stage KSLV-1, carrying a satellite aimed at observing the atmosphere and ocean, exploded 137 seconds into its flight Thursday from the Naro Space Center in Goheung, South Jeolla Province.

In a first flight in August last year, a KSLV-1 achieved the desired speed and altitude, but failed to deliver its payload satellite into orbit.

Korean government officials didn't comment on exactly where the debris were picked up or their size, but said they were separately found at 7:21 p.m. and 8:20 p.m. Thursday, hours after the rocket exploded.

A day after the doomed take-off, beleaguered government officials were scrambling to discuss the possibility of roping in Russian technology partners for a third launch.

Sources close to the project say that the chances of this are murky at best and that any future Russian rocket delivered to Korea will surely come with an attached lavish price tag.

The part-Russian, part Korean KSLV-I was a result of a 502.5 billion won ($418 million) investment by Korea. Russia's Khrunichev State Research and Production Space Center designed and manufactured the first stage of the two-stage rocket, which contained the rocket engine and a liquid-fuel propulsion system.

KARI built the second-stage, the smaller upper-part of the rocket that holds and releases the payload satellite.

The Russians are under contract to provide at least two launches, and a possible third, should their technology related to the first-stage be found responsible for the failure of any of the first two attempts.

KARI was faulted for the bungled first attempt.

Korea appears to have enough to deflect criticism onto the Russians this time around, and KARI was quick to declare that an explosion of the KSLV-1's first stage was what doomed the sequel.

Most rocket experts reached by The Korea Times found it evident that Thursday's explosion was caused by a failure of the rocket's main RD-151 rocket engine, developed by Russia's NPO Energomash, as its performance seemed to be reduced considerably as the vehicle began to veer off course.

However, pinning all the blame on the KSLV-1 first-stage may prove to be difficult. Some Russian engineers are reportedly suggesting the possibility that the explosion may have been caused by a premature separation of the rocket's first and second stages.

According to KARI's data, the KSLV-1 exploded at 137.19 seconds after liftoff, about a minute and a half before the rocket's first-stage was supposed to separate from the second stage.

The footage from an onboard camera on the second stage shows a bright flash just before communications were lost and the rocket was believed to have exploded.

Although KARI engineers suggest this as a proof of an explosion in the first stage, Russian engineers say this may also indicate a flawed separation of the two stages.

If the explosion is indeed confirmed to have been caused by an improper separation, KARI will likely get most of the blame. Although the Russians were solely responsible for making the first stage, it was KARI that handled the assembly of the two.

Lee Chang-jin, a Konkuk University aerospace scientist, admitted that a premature separation could be a remote possibility, saying it was more likely that the explosion was caused by an engine failure.

Lee suggested two plausible theories.

First, the massive vibration and chemical reactions created around the rocket's nozzle during lift-off may have triggered the ``resonance'' phenomenon, which may have led the rocket to explode. This refers to energy transfers becoming markedly more efficient by the applying of a certain frequency, such as when a singer shatters a wine glass by hitting the exact right tone.

Lee's other theory is based on a problem in the rocket's turbo pump, which pumps fuel and oxidizers into the rocket's engine. It's crucial that the pump maintains a consistent flow, as the engine could explode when it's fed with an excessive quantity of fuel and oxidizers too quickly.

``We can't make up too many theories about the cause of the explosion when we really haven't looked into the data yet,'' Lee said.

``At least from the video, the bright spark didn't seem related to an abnormal separation from the first and second stages.''