SEOUL -- South Korean technicians scrutinizing the debris of the North Korean rocket launched earlier this month have found evidence suggesting the rocket's military purposes and the North's technological ties with Iran in its efforts to develop an intercontinental ballistic missile, South Korean officials said Sunday.
North Korea insists that its Unha-3 rocket, launched Dec. 12 to put an earth-observation satellite in orbit, was part of its peaceful space program. But intelligence officials and rocket scientists affiliated with the South Korean Defense Ministry said Sunday that through the rocket launching, which they said marked an advance for Pyongyang, North Korea was testing a ballistic missile that can fly more than 10,000 kilometers, or more than 6,000 miles, with a warhead of 500 to 600 kilograms, or about 1,100 to 1,300 pounds, putting the United States West Coast in range.
They spoke to the media after analyzing the rocket's flight data and the debris of its oxidizer tank, which they recovered in waters off South Korea two days after the rocket launching. Over the weekend, the South Korean Navy also salvaged the remnants of the rocket's fuel tank and part of its engine, which officials hoped would provide more clues to the North's rocket technology.
So far, the officials said they have concluded that the rocket's first-stage engine was made of four North Korean "Rodong" missile engines latched together, and that the North Koreans used their Scud-type missile engine for the rocket's second-stage booster.
"They efficiently developed a three-stage long-range missile by using their existing Rodong and Scud missile technology," a senior military intelligence official said on Sunday, briefing reporters on condition of anonymity.
For an oxidizer, North Korea used red fuming nitric acid, commonly used as rocket propellant in old Soviet-built Scud missiles, as well as Iranian and North Korean missiles, the official said. Most space-program rockets use liquid oxygen as oxidizer, he said. Unlike liquid oxygen, which must be kept in extremely cold temperature, red fuming nitric acid can be stored in normal temperatures, which makes it a convenient propellant for missiles, the official said.
The design of the oxidizer tank also suggested an "Iran connection" in North Korea's rocket program, he said.
Officials found the welding on the oxidizer tank to be "crude," "uneven" and "done by hand." They also found some foreign-made components, despite North Korea's claim that its rocket was "indigenously produced 100 percent." But they said it marked a great technological advance for North Korea to launch a three-stage rocket successfully and put an object into orbit. All North Korea's previous rocket tests had failed to reach orbit, according to Western officials.
Analysts doubted that North Korea has mastered the technology needed to miniaturize a nuclear bomb to mount on a missile. South Korean officials also said Sunday that there was no confirmation of whether the North had the "re-entry" technology needed for the warhead of an intercontinental ballistic missile to survive the heat and vibration when it crashes through the Earth's atmosphere.
United Nations Security Council resolutions, imposed following the North's nuclear teats in 2006 and 2009, ban the country, a U.N. member, from any rocket launching that uses ballistic missile technology. They mandated economic sanctions aimed at blocking North Korea from acquiring or proliferating nuclear and missile technology, but analysts have long suspected that Iran and North Korea were closely cooperating in their missile and nuclear programs, sharing components and test data.
The rocket's successful launching was a great boost for the North's young leader, Kim Jong-un. On Saturday, North Korea awarded a "hero's title," one of the highest accolades in the country, to 101 scientists and technicians involved in the rocket development, its state-run news media reported Sunday.
On Friday, Mr. Kim threw a massive banquet for the scientists and called for the development and launching of "a variety of more working satellites" and "carrier rockets of bigger capacity."
This article originally appeared in The New York Times.