Long March 5B rocket stage makes fiery uncontrolled reentry over Indian Ocean

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HELSINKI — Wreckage from a Chinese Long March 5B rocket first stage made a fiery reentry into Earth’s atmosphere over Southeast Asia Saturday, six days after launching a space station module into orbit.

Debris from the roughly 30-meter-long, five-meter-wide empty and roughly 22 metric ton core stage of the Long March 5B at 12:45 p.m. Eastern (1645 UTC) July 30, U.S. Space Command announced at 1:45 p.m.

“We refer you to the PRC [People’s Republic of China] for further details on the reentry’s technical aspects such as potential debris dispersal+ impact location,” a U.S. Space Command tweet read.

China’s human spaceflight agency announced minutes later that debris from the Long March 5B  reentered the atmosphere at around 12:55 p.m. Eastern, with a debris landing area of 119.0 degrees East and 9.1 degrees North, in the Sulu Sea, close to Palawan Island in the western Philippines.

Possible footage of the reentry was posted on Twitter by an apparent onlooker in Kuching, Malaysia, matching the ground track during a 20-minute window from an U.S. Space Force’s 18th Space Defense Squadron (18 SDS) Tracking and Impact Prediction message.

While much of the empty rocket stage is expected to have burned up on reentry, roughly 20 to 40 percent of a stage typically survives reentry according to experts, such as engine components designed to withstand high temperatures.

NASA Administrator Bill Nelson commented on the situation via Twitter shortly after confirmation of reentry.

The Long March 5B rocket launched July 24, sending the Wentian space station module into orbit. Wentian is the second module for China’s space station and successfully docked with the already-orbiting Tianhe core module 13 hours after launch.

The Long March 5B is a variant of China’s largest rocket. It consists of a core stage and four side boosters. Exceptionally, the first and largest stage of this rocket also acts as the upper stage, inserting the payload into orbit.

As the rocket’s YF-77 liquid hydrogen-liquid oxygen engines apparently cannot restart once in orbit, the large first stage deorbits due to atmospheric drag, or an uncontrolled reentry. The vast majority of rocket first stages do not reach orbital velocity and fall within a calculated, safe area downrange from launch.

The Aerospace Corporation, EU Space Surveillance and Tracking (EU SST) and 18 SDS provided regular reentry prediction updates on the Long March 5B as the orbit of the rocket stage decayed. 

China’s human spaceflight agency tracked the stage, issuing daily updates on the basic orbital parameters of the Long March 5B, but did not provide estimates for time of reentry.

Where and when the stage would reenter is impossible to predict with certainty, due to atmospheric fluctuations, the challenges of modeling and unknown aspects of the rocket’s design. Predictions however narrowed down the possible ground tracks as the orbit decayed and the window of uncertainty closed. The initial predictions and window of uncertainty issued two days after launch was plus or minus 24 hours. 

“It’s customary international practice for rockets’ upper stages to burn up in the Earth’s atmosphere,” Chinese foreign ministry spokesperson Zhao Lijian said during a July 27 press conference. 

The Aerospace Corporation noted in a July 27 press briefing that around 50 objects weighing more than one ton reenter randomly per year. However the exceptionally large tonnage of the Long March 5B means that the debris from the rocket posed a relatively high threat. 

Ted Muelhaupt stated that odds of debris from this reentry event harming someone range from one in 230 to one in 1,000. This did not include the likelihood of damage to property. Muelhaupt added that this was more than an order of magnitude greater than internationally accepted casualty risk threshold for the uncontrolled reentry of rockets of one in 10,000, stated in a 2019 report issued by the U.S. Government Orbital Debris Mitigation Standard Practices.

Meanwhile in orbit, the Shenzhou-14 astronauts aboard China’s space station entered Wentian for the first time at 10:03 p.m. Sunday Eastern. 

The new module carries a range of cabinets for conducting science experiments. Wentian also provides backup life support and propulsion for Tianhe, which launched in April 2021, as well as  new working and living quarters and an EVA hatch for astronauts.

“This is the second working and living module that we have in space. The construction of China’s space station has taken another big step. We couldn’t be prouder and happier,”  Shenzhou-14 mission commander Chen Dong said, according to Chinese state media.

China plans to launch a third module in October to complete the three-module, T-shaped Tiangong space station. The mission will once again rely on a Long March 5B rocket.

Both Wentian and Mengtian will be transpositioned from Tianhe’s forward docking port to respective lateral docking ports using a 10-meter-long robotic arm which launched with Tianhe.

China intends to operate the station for at least a decade, with crews of three astronauts six-month-missions. It will also launch a co-orbiting optical telescope module, named Xuntian, in late 2023 or 2024. It will be capable of docking with Tianhe for repairs, maintenance, refueling and upgrades, and aims to survey 40 percent of the sky across a decade.

Officials with the China Aerospace Science and Technology Corporation (CASC), the country’s main space contractor, have previously suggested that Tiangong could be expanded to six modules.

China has stated it welcomes international participation in Tiangong, including payloads through an initiative with the United Nations Office for Outer Space Affairs (UNOOSA), as well as international astronauts and potentially additional modules.