Sometime this weekend the upper stage of a Chinese Long March 5B rocket will plunge back to Earth and most of it will burn up on re-entry – but perhaps not all.
Military experts in the US expect the booster stage to come down on Saturday or Sunday, but have warned it is difficult to predict where it will land and when and how much material might hit the ground – or if it could knock a plane out of the sky.
The Chinese government, perhaps predictably, is playing it calmly. “The probability of causing harm to aviation activities or [on people and activities] on the ground is extremely low,” the foreign ministry spokesman, Wang Wenbin, said on Friday.
But the fiery fate of the booster, wherever it comes down, speaks to the larger issue of space debris and space sustainability, especially as space becomes a target not just for national space programs but also increasingly the private sector. Under international treaty, private space actors, who are expected to put 45,000 satellites in low Earth orbit over the next several years, are under the legal responsibility of their host nations.
Add to that, an estimated 9,300 tons of space junk that’s already orbiting the planet and the issue of space collisions and debris pollution is an issue of concern.
Last month, mission controllers at SpaceX headquarters in California warned orbiting astronauts to put on their spacesuits and get back in their seats because a piece of space debris could strike the capsule. Previously, a piece of paint the size of a fingernail struck the windscreen of a space shuttle, piercing two of three layers of glass.
“Space debris has been known for a while, but now you have more competition in space. You don’t just have two space-faring nations – the Chinese are very significant, as is the European Space Agency, among others. When you have more actors and more stuff, it gets more complicated,” said Joanne Gabrynowicz a professor at the National Center for Remote Sensing, Air, and Space Law at the Mississippi Law Center.
Experts have repeatedly voiced their worry about the risk of collisions since 2009, when two satellites – Iridium 33 and the derelict Russian military Kosmos-2251 –accidentally collided at 26,000mph over Siberia, shattering both in thousands of pieces. The European Space Agency hosted a major conference on the subject last month.
“There’s a lot of stuff being put into low Earth orbit, and some of it could possibly hit one another,” said Gabrynowicz.
According to Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, China had every reason to know Long March 5B was unpredictable and would become uncontrollable. “It’s my judgment that the Chinese are negligent. China says it will probably fall in the ocean. But probably is doing a lot of work here. The last one would probably fall in the ocean, except it didn’t. It fell on the Ivory Coast,” he said.
The fate of Long March 5B could refocus governments and international bodies on the issue of space sustainability, and that could provide more opportunity to firms like UK-based Astroscale that are preparing to tackle the debris problem with commercial junk-collecting services.
According to the European Space Agency, about 6,900 of 11,370 satellites placed into Earth orbit are still circulating, with about 4,000 functioning. But the number of debris objects regularly tracked by Space Surveillance Networks stands at 28,160. The discrepancy is accounted for by more than 560 “break-ups, explosions, collisions, or anomalous events resulting in fragmentation”.
Astroscale is currently demonstrating a vehicle called “ELSA-d” in lower Earth orbit to show that space debris clean-up is indeed possible. It’s a fiendishly difficult task, especially if the target satellite is spinning and tumbling. The test is using a satellite to capture a test drone using a magnet; in time, larger objects will require a robotic arm.
The company’s managing director, John Auburn, said the real problem might not be the big pieces of debris that create the headlines and cause people back on ground to cast a nervous eye in the skies.
“The big problem in space is not big debris, but when big debris breaks up and becomes small debris,” Auburn said. “A one-centimetre fragment can destroy your spacecraft and it’s traveling so fast you don’t know it’s there from the ground. We don’t want a disaster, so it’s very important that governments build into licences requirements that old and broken stuff is brought back down.”