Big Chinese Rocket To Make Uncontrolled Reentry This Weekend

Big Chinese Rocket To Make Uncontrolled Reentry This Weekend

A very large Chinese rocket is about to make an uncontrolled reentry, posing a threat to large portions of the globe. The Long March-5B launched China’s Wentian space station module into orbit on July 24. Like two predecessors, this rocket does not have onboard systems to direct its reentry into an unpopulated area. The U.S. Aerospace Corporation is closely monitoring it and periodically publishing updated estimates using available data. At the moment the prediction is sometime between Saturday and Sunday morning EDT.

Instead of having multiples stages that detach during ascent with the first stage never reaching orbit, the Long March-5B, or Chang Zheng-5B, has just one stage. It goes into orbit along with its payload, in this case a module with its own propulsion system to finish its journey to China’s space station. Wentian docked with the Tianhe space station core module hours after launch.

China’s Long March-5B rocket launches the Wentian space station module to orbit, July 24, 2022. Photo credit: Xinhua

But the approximately 22 Metric Ton rocket body remained in orbit and with no means to control its flight will come crashing down this weekend.

This is the third Long March-5B rocket ever launched. The first, in May 2020, was a test flight and spread debris over the African country of Ivory Coast prompting a rebuke from then-NASA Administrator Jim Bridenstine. The second launched the first module, Tianhe, for China’s space station in April 2021. Fortunately that came down over the Indian Ocean, but NASA Administrator Bill Nelson issued his own criticism of China for failing to follow “responsible standards regarding their space debris.” As Nelson repeatedly says it could just as easily have landed on Europe or Saudi Arabia.

China appears to have ignored those complaints. Most countries that launch rockets do so over water or unpopulated areas so falling stages pose little danger. China has a long history of showing a lack of regard for its population, however, as photographs of rocket parts in Chinese villages like these tweeted by journalist Andrew Jones illustrate.

When and where the rocket body will reenter depends on factors like its size, shape and mass as well as the intensity of solar activity that affects atmospheric density and creates drag. Last year, it took about 10 days for Tianhe’s Long March-5B rocket stage to reenter, but solar activity is higher this year so this one is coming down more quickly.

At this moment, the Aerospace Corporation predicts reentry on Saturday, July 30, 2022, at 23:21 UTC ± 16 hours.  Universal Coordinated Time, UTC, also known as GMT or Zulu, is 4 hours ahead of EDT, so that would be July 30, 7:21 pm EDT ± 16 hours.

The window will narrow as time progresses. Aerospace is posting updates on its website.

China’s space station is in an orbit inclined 41.5 degrees to the equator, so it and the Long March-5B rocket body trace a sinusoidal path around the globe between 41.5 degrees north and 41.5 degrees south latitude.

Source: The Aerospace Corporation, July 27, 2022

Aerospace, a federally funded research and development corporation (FFRDC) that focuses on national security space, estimates 88 percent of the world’s population lives under that path.

Nonetheless, the risk of any specific individual being hit by debris is extremely low in part because 70 percent of that area is water. Aerospace’s Center for Orbital and Reentry Debris Studies calculates the risk to an individual at 6 in 10 trillion. As low as that is, Aerospace’s Ted Muelhaupt reminded reporters today that the risk is not zero and debris did land in populated areas of Ivory Coast on the first flight.

He also pointed out that at least 10 launches of this version of the Long March 5 are planned so this will be a problem in the future, too.  The next space station module, Mengtian, is scheduled for launch in October.

How much debris might survive the fiery descent through the atmosphere is difficult to predict especially since little is known about the exact construction and composition of the rocket. Muelhaupt said typically 20-40 percent of dry mass survives, which would be between 4 and 9 Metric Tons in this case.

The European Union’s Space Surveillance and Tracking (EUSST) Operations Centre is also monitoring the reentry.  Its current prediction is July 31 at 01:41:49 UTC ± 1021 minutes (17 hours, 1 minute).

Green lines: ground track during the re-entry window. Red lines: part of ground track over EU Member States. Marker: centre of the predicted re-entry window. Note: possible re-entry locations lie anywhere along the green lines. The re-entry point is considered to be at an altitude of 80 km.  Graphic and caption credit: EUSST.

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