Space boffins are watching the skies for a 23-tonne Chinese rocket booster set to crash back to Earth.
The debris is 53.6 meters long and is the remains of a mission earlier this week to deliver the Wentian Laboratory Module to China’s Tiangong space station. Wentian itself is an exciting addition to China’s orbital complex and is the first module to expand on the existing Tianhe core module, which was launched in 2021.
However, being a strong beast, Wentian needed a heavy missile. In this case, the Long March 5B heavy-lift previously used to launch Tianhe. Other variants of the Long March 5 were used to launch the Chang’e 5 lunar mission and the Tianwen-1 mission to Mars.
The problem is that the Long March 5B’s massive first stage also functions as the upper stages of other rockets, so it wasn’t jettisoned downward. Instead, it entered orbit and will inevitably return back to Earth. The problem is figuring out when and where.
While other rockets (including some of China’s own) are capable of restarting their engines in orbit and ejecting in a controlled manner, that is not the case this time. Instead, the descent will be uncontrolled as the orbit breaks up and, according to federally funded researchers at The Aerospace Corporation, “there is a non-zero probability that the surviving debris will land in a populated area.”
Our latest forecast for #CZ5B re-entry into the rocket body is: 🚀 Jul 31, 2022 07:52 UTC ± 22 hours Re-entry will be along one of the ground lines shown here. It is still too early to determine a meaningful debris footprint. Follow this page for updates: pic.twitter.com/xsDqC8rOEt
— The Aerospace Corporation (@AerospaceCorp) July 26, 2022
How much debris? Aerospace engineering and space experts believe that something this large would not simply burn up in the atmosphere. Instead, a rule of thumb of 20 to 40 percent of the mass reaching the ground is cited.
To make matters worse, approximately 88 percent of the world’s population lives below the current estimated debris footprint, although that figure and footprint will decrease in the coming days as new data becomes available and projections are refined. With luck, there’s every chance that whatever comes back to Earth will just fall into the ocean.
“Due to its inclination (41.48 degrees), the object may re-enter the ±41.48° latitude range,” notes the EU’s space surveillance and tracking service.
This is not China’s first rodeo when it comes to the uncontrolled return of rocket stages; debris from two previous Long March 5B launches also returned to Earth. Other countries, including Russia and the US, have also had problems with uncontrolled incursions at large sites; the first with the return of Salyut 7 in 1991 and the second with Skylab’s infamous dispersal over Western Australia in 1979.
Earlier this morning, China’s Tianzhou-3 cargo spacecraft made a controlled re-entry into the atmosphere with a small amount of debris deposited in the South Pacific Ocean. It is a pity that the same possibility was not applied to the remnants of the Long March 5B. ®
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