China has successfully launched a key module of its new space station – but the 20-tonne vehicle that delivered it into orbit looks set to plummet back to Earth in an “uncontrolled” descent that could lead to it landing anywhere between North America and New Zealand.
The Long March 5B rocket carried the 22.5-metric-ton Tianhe module into a stable earth orbit on Thursday, April 29.
But the massive rocket is now itself in a deteriorating orbit around the earth and, according to some ground observers, is tumbling out of control.
The Long March is designed, unlike most expendable rocket first stages, to attain orbital velocity along with its payload. That means its re-entry is less predictable.
After a previous use of the Long March core stage, NASA Administrator Jim Bridenstine criticised China’s space agency, saying: “It was seemingly a successful launch, until we started getting information about a reentry of a rocket body, a reentry that was really dangerous.
“It flew over population centres and it reentered Earth’s atmosphere,” he added. “It could have been extremely dangerous. We’re really fortunate in the sense that it doesn’t appear to have hurt anybody.”
Among the pieces of debris from that launch that survived re-entry was a metal pipe over 30 feet in length. A re-entry just 30 minutes earlier, says NASA, could have resulted in debris landing on U.S. soil.
Holger Krag, head of the Space Safety Programme Office for the European Space Agency, says that it’s hard to estimate how much of the 20-tonne booster will make it to the ground but “a reasonable ‘rule-of-thumb’ is about 20-40% of the original dry mass.”
The final destination of this latest rocket is almost impossible to predict.
At its current speed of 16,000 mph it takes just 90 minutes to circle the globe, so even a small variation in its re-entry time can translate to a distance of thousands of miles.
Jonathan McDowell, an astronomer at the Harvard-Smithsonian Centre for Astrophysics. told SpaceNews that the previous Long March 5B launch had resulted the biggest and most dangerous uncontrolled re-entry since the 1980s.
“The Long March 5B core stage is seven times more massive than the Falcon 9 second stage that caused a lot of press attention a few weeks ago when it reentered above Seattle and dumped a couple of pressure tanks on Washington state,” he said.
He added that he thought China had been irresponsible in letting the rocket crash back to earth in this way: “I think by current standards it’s unacceptable to let it reenter uncontrolled,” he said.