North Korea’s latest satellite launch exploded in a fireball before dropping into the Yellow Sea just minutes after lifting off, but analysts say the attempt showcased new strides in the nuclear-armed country’s race for space.

North Korea said its latest attempt to launch a military reconnaissance satellite failed in flight on Monday during the rocket’s first stage, which featured a new “liquid oxygen and petroleum engine”.

An initial analysis suggested that the cause of the failure involved the newly developed liquid-fuel rocket motor, but other possible causes were being investigated, a report carried by state media KCNA said.

Although state media did not name the rocket or release photos, analysts said it was most likely different from the Chollima-1 rocket used in the successful satellite launch in November 2023. The Chollima-1, which also suffered several explosive test failures, uses hypergolic fuels, substances that can be stored at room temperature but ignite on contact each other, requiring careful handling.

TIMELINE-North Korea’s long-range missile projects

Pyongyang successfully placed its first spy satellite in orbit in November, after two failed attempts last year. The U.S. and its allies say the launches violate U.N. Security Council resolutions banning the nuclear-armed North’s use of ballistic missile technology.

The following is a timeline of North Korea’s space program, satellite launches and development of rocket technology.

Aug. 31, 1998: North Korea begins its space program by launching a Kwangmyongsong-1 satellite on a Paektusan rocket from the Tonghae Satellite Launching Ground. Pyongyang declares it a success, but U.S. officials say it broke up over the Pacific Ocean.

April 5, 2009: Then-leader Kim Jong Il oversees the launch of the Kwangmyongsong-2 satellite from the Tonghae complex, but it again fails and crashes in the ocean. State media suggest 14 North Korean soldiers were killed during the launch.

April 13, 2012: The Kwangmyongsong-3 satellite is launched from the newly completed Sohae Satellite Launching Station in the western region. Foreign media are invited to observe the launch, which once again is unsuccessful.

Dec. 12, 2012: North Korea successfully launches a second version of the Kwangmyongsong-3, putting an object in orbit. While the North claims it to be an observation satellite, it is not believed to carry a functioning transmission system.

April 2013: North Korea establishes the National Aerospace Development Administration (NADA) which purports to pursue space exploration for peaceful purposes.

Feb. 7, 2016: North Korea launches a satellite. The United States calls it a disguised test of an engine powerful enough to launch an intercontinental ballistic missile (ICBM). International observers say the satellite appears to be under control, but there is debate over whether it sent any transmissions.

Aug. 24, 2016: Hyon Kwang Il, director of scientific research at NADA, says “our aerospace scientists will conquer space and definitely plant the flag of North Korea on the moon”.

June 23, 2016: North Korea says it successfully tested an intermediate range ballistic missile (IRBM), with a range of 2,000 to 3,400 miles (3,200-5,400 km).

July 4, 2017: North Korea tests an ICBM for the first time, which it says has the potential to reach the continental United States. The missile, Hwasong-14, is tested again three weeks later.

Jan. 13, 2021: During a party congress, Kim Jong Un reveals a wish list that includes developing military reconnaissance satellites.

Dec. 19, 2022: North Korea says it has conducted a “final phase” test for the development of a spy satellite.

March 16, 2023: North Korea test-launches the Hwasong-17 ICBM, its biggest missile, which some analysts believe incorporates technology for space launch vehicles.

May 31, 2023: North Korea attempts to launch a reconnaissance satellite, but the rocket plunges into the sea.

July 5, 2023: South Korea’s military says it retrieved the wreckage of the spy satellite, and found it had no meaningful military use as a reconnaissance platform.

Aug. 24, 2023: North Korea makes a second attempt to put a spy satellite in orbit, but it fails when the rocket booster experiences a problem. North Korea’s spy agency says it was not a major issue and vows to try again in October.

Sept. 13, 2023: President Vladimir Putin says Moscow will help North Korea build satellites during a tour he gives to Kim Jong Un of Russia’s space station in eastern Russia. Neither leader elaborates.

Nov. 21, 2023: North Korea notifies Japan of its plan to launch a satellite between Nov. 22 and Dec. 1.

Nov. 21, 2023: North Korea launches a rocket and says it successfully put a reconnaissance satellite in orbit.

Nov. 28, 2023: North Korean state media says Kim Jong Un reviews spy satellite photos of the White House, Pentagon and U.S. aircraft carriers. Analysts say while it is feasible for a medium-resolution camera to get such images, many more satellites would be needed to be useful in a conflict.

Dec. 31, 2023: North Korea vows to launch three new spy satellites in 2024.

Jan. 15, 2024: North Korea says it tested a new solid-fuel hypersonic missile amid an intensifying race for the next generation of long-range rockets that are difficult to detect and intercept.

May 26, 2024: North Korea notifies Japan of a plan to launch a satellite between May 27 and June 4.

May 27, 2024: North Korea says its launch of a new satellite carrier rocket fails when it exploded during the flight of the first stage. An initial analysis suggested that the cause was a newly developed liquid fuel rocket motor, state media reports.

U.S. officials and independent analysts said the Chollima-1 appeared to be based on systems developed for North Korea’s nuclear-tipped intercontinental ballistic missiles, which typically do not use liquid oxygen because of frigid temperatures required for storage.

A petroleum fuel and liquid oxygen engine may suggest that Russia, which vowed last year to help North Korea’s satellite programme, may have provided assistance, said Lee Choon-geun, an honorary research fellow at South Korea’s Science and Technology Policy Institute.

“Even if it failed, it is a huge leap,” he said, noting that some of South Korea’s space rockets were initially developed with Russia decades ago and use similar technology. “Russia is the strongest country for liquid oxygen-kerosene fuel, and our Naro and Nuri rockets have adopted it through technical cooperation with Russia.”

Liquid oxygen boils at -183°C (–297°F), and requires specialised fuel storage and other equipment, Lee said. That may account for why North Korea conducted multiple static rocket tests late last year, he added.

“It is quite difficult to solve combustion instability problems of this fuel system and apply materials and parts that can withstand extremely low temperatures,” Lee said.

Some analysts questioned why North Korea would switch engine types, but Lee said it could allow Pyongyang to separate its civilian space program from the ballistic missiles banned by the United Nations Security Council.

Russian experts have visited North Korea to help with the satellite and space rocket program, Yonhap news agency reported, citing an unnamed South Korean senior defence official.

Neither Moscow nor Pyongyang have detailed what aid is being provided.

Shin Jong-woo, a senior researcher at the Korea Defense and Security Forum, said that if Russia helped design the new rocket or satellite, North Korea would also most likely need Russian components well into the future, deepening the cooperation.

“North Koreans can re-launch soon if they obtain and analyse data correctly for that two-minute flight,” Shin said.

South Korea’s military, however, said it could take North Korea some time before it can try to launch again.

South Korea released video footage on Tuesday that its military said showed the moment the launch ended in failure.

The one-minute black-and-white video provided by the South’s Joint Chiefs of Staff (JCS) showed what appeared to be an explosion in the sky followed by flashes.

The footage was filmed by an observation device on a South Korean patrol vessel, the JCS said.

Footage released on Monday by Japanese broadcaster NHK, filmed from the Chinese border city of Dandong, showed a similar ball of flame that officials said was probably exploding fuel.

Nuclear envoys of South Korea, the United States and Japan had a phone call on Tuesday and strongly condemned the launch as a direct violation of the U.N. Security Council resolutions banning the North’s use of ballistic missile technology, Seoul’s foreign ministry said.

The launch came hours after China, South Korea, and Japan wrapped up a rare three-way summit in Seoul.