A 23-Ton Chunk of Rocket Is Set to Slam Into Earth and No One Knows Where

A massive piece of space junk from a Chinese rocket is forecast to come crashing back to Earth on Friday.

The 23-ton rocket part is the core stage booster from China's Long March 5B rocket, which delivered the third and final piece of China's Tiangong space station on October 31.

Usually, when jettisoned rocket pieces reenter the atmosphere, they are designed to do so at a particular location, crashing into predetermined parts of the ocean. However, this chunk of Long March 5B is undergoing an uncontrolled reentry, meaning that it could land anywhere.

"Uncontrolled entry means there are no measures in place to ensure the remnants of this large debris object lands in an unpopulated zone. This is because the first stage core of these CZ-5B rockets actually reach orbit, so its reentry point is not able to be controlled," Ralph Cooney, an advanced materials professor at the University of Auckland in New Zealand, told Newsweek.

Luciano Anselmo and Carmen Pardini, researchers at the Space Flight Dynamics Laboratory in Pisa, Italy, told Newsweek, "In the specific case of the Long March 5B core stage, even though some spare propellant was probably left in the tanks—to be used as a margin for contingencies during the launch phase—it cannot be used anymore because the stage rocket motors cannot be restarted in space. They can be started only once at the launch pad.

"Therefore, the core stage is currently dead, un-maneuverable and tumbling," they continued. "Its motion is only subject to natural forces, such as gravitation and atmospheric drag, the latter causing the progressive loss of mechanical energy leading at the end to a totally uncontrolled reentry. That is, without any possible human intervention."

When pieces of space debris enter the Earth's atmosphere at high speeds, they undergo extreme acceleration and experience severe temperatures. The debris may break up into smaller pieces, some of which will burn up from the heat, with others falling to the ground.

However, because of the large size of this piece of debris, only a small amount of it will be burned up.

"This object is very large and massive, more than 20 tons, so cannot be completely vaporized during the harsh reentry into the atmosphere," Anselmo and Pardini said. "High-temperature-resistant components of the 3-ton rocket motors block, small tanks and larger structural components may survive the reentry conditions and hit the ground.

"This already happened for this kind of stage in Ivory Coast [in 2020] and in Borneo, in July this year. We do not know the fabrication details of the stage, but a surviving debris mass between 2 and 5 tons may be expected," they said.

According to Cooney, between 20 and 40 percent of the booster is likely to survive the fall and collide with the Earth's surface, depending on the composition of the components and especially the proportion of the two key light metals (aluminum and titanium) present.

Current estimates from the Aerospace Corp. show that the booster pieces are likely to fall into the Indian Ocean, just off the Horn of Africa.

"Because 70 percent of the Earth's surface is ocean, the probability of the rocket stage landing in the ocean is high," Cooney said.

The chances of the debris hitting an inhabited area are very low. NASA estimates that the odds of a person being hit by a piece of space debris are around 1 in 3,200.

But Anselmo and Pardini said that the risks might be higher than we think, especially when we take into consideration the large number of defunct satellites and other pieces of space junk in orbit around the planet.

"Eighty-eight percent of the world population is overflown by the stage trajectory, and the probability of someone in the world being hit by a falling debris, between 42 degrees north and south, is about 1 in 500, more than the 1 in 10,000 threshold for which, at international level, a controlled reentry is recommended," Anselmo and Pardini said.

"According to our estimates, currently the global casualty probability from uncontrolled reentries is around 2 to 3 percent per year," they continued. "Approximately one-third of the risk comes from satellites, two-thirds of the risk comes from rocket bodies. However, the situation is evolving, due to the changes in space activity."