Chinese rocket falls back to Earth this weekend, but where will it land?

One optimistic outlook is that the rocket could mostly disintegrate in the atmosphere with a debris field raining down in another hemisphere, but that depends on solar winds from the sun, which could speed up or slow down the rocket booster and change its entire trajectory.

The Aerospace Corp., a nonprofit agency financed by the federal government that performs research and analysis, on Thursday said the reentry could occur about 11:43 p.m. Saturday. If so, debris could shower down over northeastern Africa, over Sudan.

However, there is much uncertainty surrounding the timing and location. Just a day before, the same body put reentry more than one hour earlier, and over the eastern Indian Ocean.

The U.S. Space Command and Russia’s space agency are both said to be tracking the rocket, and Space Command said it plans to offer regular updates ahead of the reentry.

The rocket was used in the April 29 launch of the main module of China’s first permanent space station that will host astronauts long term. It was the first of 11 missions to complete, supply and crew the station by the end of next year.

While the first mission was successful and another major advance for the country’s space exploration program in recent years, the “uncontrolled” reentries of rockets into the Earth’s atmosphere have been less precise and potentially perilous to people all over the world.

China’s space program has repeatedly failed to control the paths of the rockets that fall back to Earth, reports say.

“I think it’s negligent of them,” said Jonathan McDowell, an astrophysicist at the Center for Astrophysics in Cambridge, Massachusetts, who tracks the comings and goings of objects in space. “I think it’s irresponsible.”

The piece that will drop out of the sky this weekend is the core booster stage of the Long March 5B, which was designed to lift the big, heavy pieces of the space station, according to The New York Times. For most rockets, the lower stages usually fall back to Earth immediately after launch. Upper stages that reach orbit usually fire the engine again after releasing their payloads, guiding them toward reentry in an unoccupied area such as the middle of an ocean.

During the past three decades, only China has lifted rocket stages this big to orbit and left them to fall somewhere at random, McDowell said.

For the Long March 5B booster, that could be anywhere between 41.5 degrees north latitude and 41.5 degrees south latitude. That means Chicago, located a fraction of a degree farther north, is safe, but major cities including New York could be hit by debris.

Because the booster is traveling at 18,000 mph, a change of minutes shifts the debris by hundreds or thousands of miles. It is only a few hours before reentry that the predictions become more precise.

“It’s an engineering decision based on probabilities,” McDowell said. He said the Chinese engineers could have designed the trajectory to remain suborbital, falling back to Earth right after launch, or they could have planned an additional engine firing to drop it out of orbit in a way that posed no possible danger.

“It’s not a trivial thing to design something for a deliberate reentry, but it’s nevertheless something that the world as a whole has moved to because we needed to,” said Ted Muelhaupt, principal director of Aerospace’s Center for Orbital and Reentry Debris Studies.

Information provided by The New York Times was used to compile this report.