Another Guessing Game on Where and When Chinese Rocket Stage Will Reenter

by Douglas Messier
Managing Editor

China has once again put another massive rocket stage in orbit, triggering a week-long guessing game as to where and when it will reenter the atmosphere and whether debris will rain down over a populated area.

The object in question is the core stage of a Long March 5B rocket, which entered orbit after launching the new Wentian module to the Chinese space station. The stage is 53.6-meter-tall and weighs approximately 23 metric tons.

“Due to the uncontrolled nature of its descent, there is a non-zero probability of the surviving debris landing in a populated area—over 88 percent of the world’s population lives under the reentry’s potential debris footprint. If this sounds familiar, it’s because similar uncontrolled reentries of Long March rockets occurred in 2020 and 2021. A reentry of this size will not burn up in the Earth’s atmosphere, and the general rule of thumb is that 20–40 percent of the mass of a large object will reach the ground, though it depends on the design of the object,” according to an updated posted by The Aerospace Corporation, which is tracking the object.

China’s engineers designed Long March 5B so that the massive core stage must enter orbit for a launch to be a success. (Most rockets have a first stage that reenters the atmosphere over an ocean after stage separation.) However, the engineers apparently didn’t include the capability of performing a controlled reentry over a remote part of an ocean.

As a result, the stage will spend about a week with its orbit steadily decaying until it reenters somewhere along its orbital path. The Aerospace Corporation is tracking the stage and predicts it will likely reenter on Sunday, July 31.

It is, to say the least, irresponsible to put such a large stage into orbit without any way to deorbit it in a controlled manner. China’s defenders on Twitter have pointed to Skylab and the Columbia space shuttle disaster as examples of the U.S. hypocrisy on the issue. But, these arguments are rather hollow and miss the main issue, which is intent.

Columbia was a tragic accident. The shuttle was attempted a controlled reentry when it suffered catastrophic failure. The fact that it scattered debris over multiple states is an example of what can happen in an uncontrolled reentry of a large object. It was tragic for the crew, and lucky no one on the ground was injured or killed.

NASA had a plan to safely deal with Skylab. The last crew to occupy the station in 1974 raised the station’s orbit. NASA had a mission planned to fly a space shuttle to Skylab, attach a booster rocket to it, and either raise the station’s orbit for later visits or safely deorbit it over a remote section of ocean.

Unfortunately, greater than anticipated solar activity caused Skylab’s orbit to decay faster than anticipated. And the shuttle program suffered years of technical and schedule delays. NASA simply ran out of time.

Luckily, Skylab debris scattered across the ocean and a remote part of Australia in 1979. The only known casualty was a rabbit. But, things could have been much worse.

China has not always acted responsibly with rocket launches. Decades ago, a rocket failed and crashed into a nearby city with an unknown number of casualties. Since the advent of cell phones, videos have surfaced of rocket stages with toxic propellant crashing down near towns after they were launched from one of China’s inland spaceports.

Hopefully, the world will dodge another bullet after this latest launch. At some point, however, luck will run out. China should really deal with this problem before the next Long March 5B launches the Mengtian module to the station in October.