A large, uncontrolled piece of rocket debris hurtled towards Earth over the weekend – more than 20 tonnes travelling at about 27,000 km/h. Understandably, some were a little nervous about the damage bits of China’s biggest rocket – the Long March 5B – might cause.
Ultimately most of the debris burned up in the atmosphere, and the rest splashed into the Indian Ocean.
(Australian cricketers “stranded” in the Maldives say they were woken by the sonic boom on Sunday morning. David Warner said it was not the impact of the craft but “the crack in the atmosphere, which sets off a wave of sound”.)
But wait – there’s more.
China is using the Long March 5B rocket to send modules for their planned Tiangong (“Heavenly Palace”) Space Station into orbit, and it has more launches planned. The usual etiquette is for the rocket boosters to detach before the rocket enters orbit, so they can fall back to a pre-planned, uninhabited spot on Earth – like the Spacecraft Cemetery, for example.
But the booster for the Long March 5B rocket, carrying the Tianhe (“Heavenly Harmony”) module, careened into orbit. That orbit decayed, and it re-entered the Earth’s atmosphere.
Space archaeologist Alice Gorman, from Flinders University, says there are “three more planned launches of 5B between 2022 and 2024 to launch space station modules”.
“So it’s possible that these are all planned to be uncontrolled re-entries too, unless China bows to international pressure,” Gorman says.
NASA is among those applying international pressure. Administrator Bill Nelson says spacefaring nations had to minimise the risks of space object re-entries and “maximise transparency regarding those operations”.
“It is clear that China is failing to meet responsible standards regarding their space debris,” he says.
“It is critical that China and all spacefaring nations and commercial entities act responsibly and transparently in space to ensure the safety, stability, security, and long-term sustainability of outer space activities.”
Gorman says while there’s a trend towards smaller rockets – to carry smaller satellites – that won’t be the end of big rocket launches.
“Large rockets will be more likely used for interplanetary missions and geostationary launch…there’s also going to be more of those with so many nations intent on going to the Moon and Mars,” she says.
The European Space Agency (ESA) sensibly says that avoiding the creation of debris in the first place is the best form of defense. ESA works with other agencies to monitor and predict uncontrolled re-entries and to analyse potential risk.
For now, parts of spacecraft hit Earth’s atmosphere every day, mostly burning up before they pose any danger. Only larger parts, or those made of stainless steel or titanium (which is less likely to be destroyed by the heat), will reach the ground.
Even then, the chances are they’ll hit water or uninhabited land.
The chances of a person getting hit by parts of a spacecraft may be tiny, but it’s not impossible, as one American woman found out the hard way.