The Sky Really Is Falling

 

Chicken Little – originally known as Henny Penny – took a lot of flak for constantly touting the end of the world.

If you watched the news over the preceding weekend and looked to the skies, you might be forgiven for giving Chicken Little a bit of a reprieve. Space scientists around the world issued warnings for large swaths of the planet, as a Chinese rocket reentered the atmosphere unexpectedly. The location of the debris could not be accurately predicted. Though the likelihood always pointed toward a watery splashdown, since three-quarters of the planet is covered by oceans, many populated areas lay under the zone of possibility.

Possible landing locations of the reentering Chinese Rocket in May 2021

The Chinese launched Long March 5b in late April in their continuing efforts to create a space station, so the massive rocket lived in space for just a few weeks. Because it only reached low Earth orbit it was destined to succumb to drag and reenter the planetary atmosphere. Most parts of the rocket would burn up as they came back to Earth, but some portions were certain to survive, posing a risk to humanity.

Most rocket missions feature controlled reentry if they come back at all. Astronomer Jonathan McDowell, of the Harvard-Smithsonian Center for Astrophysics, told the BBC, “Small US and European upper stages also re-enter uncontrolled (and burn up entirely) but the big US or European rockets are specially designed not to leave big stages in orbit. China decided they would rather use a simpler design and hope that they get lucky with the stage re-entering uncontrolled but not hurting anyone.”

Thanks, China!

In the end, we got lucky, as the rocket landed in the Indian Ocean, south of India, near the Maldives. Reentry occurred over the Middle East during the day, so the footage was not spectacular.

As easy as it is to blame China for reckless behavior, they don’t have a monopoly on causing the sky to fall.

On 4 March, SpaceX launched a Falcon 9 to continue work on its Starlink program. The second stage of the spacecraft should have made a deorbit burn, which would have taken it safely out of gravity’s swirling pull and into a fiery atmospheric death. But things didn’t go quite as planned and the rocket remained in orbit for over three weeks, each moment teetering closer and closer to coming back into the atmosphere.

This engineering mistake was not quite as dangerous as the Long March reentry, but, nonetheless, a lot of uncertainty surrounded the Falcon 9’s return. Also unlike the Long March’s reentry, the Falcon 9 put on quite a show for the Pacific Northwest! The nighttime reentry had some in Oregon wondering if, indeed, the sky was falling:

Obviously, falling junk from space can be an issue for those of us on the ground. But space debris is also a serious and growing problem outside our atmosphere, too. 

With the launch of Sputnik in 1957, humans started sending material into space. We haven’t been great stewards when it comes to trash and pollution at sea level, so it should come as no surprise that we didn’t really put much emphasis on what happened to all the stuff we sent to space. From the beginning, we started to fill up orbital space with space waste. 

After nearly seven decades of exploration, hundreds and thousands of missions from numerous countries have created quite a minefield in the three-dimensional space that surrounds the planet. It’s a big problem. Some of it might eventually follow in the footsteps of the Falcon 9 or the Long March and pose a threat to living beings down here. But it might remain in orbit for the foreseeable future, which constantly threatens spacecraft and satellites.

Computer-generated image of space debris as seen from high Earth orbit; note the ring in the geosynchronous region and the cloud of low Earth orbit - NASA

In the zeitgeist, spaceships are obliterated by hulking masses, not tiny specks. But space pollution runs the gamut when it comes to size. Non-functioning spacecraft, rocket stages, and decommissioned satellites do prowl Earth’s orbit, but space debris can be much tinier. When you’re moving thousands of miles per hour, flecks of paint and droplets of expelled liquid can pack quite a punch. After all, force equals mass times acceleration.

According to the European Space Agency, in 2019, the amount of space junk is insanely large. 34,000 pieces larger than 10 centimeters float around the orb; 900,000 chunks of trash measure between 1 and 10 centimeters; the number of sub-1-cm particles is mind-boggling: 128 million shards. Approximately 20,000 artificial objects orbit Earth, of which only 2,218 are operational satellites. Space seems like a big empty void, but we’ve made the region around our home planet more like a sci-fi asteroid field.

In 2011, the U.S. National Research Council warned NASA that space debris was at a critical level. Computer models predicted junk “has reached a tipping point, with enough currently in orbit to continually collide and create even more debris, raising the risk of spacecraft failures.” Important spacecraft, such as the International Space Station, are clad with protective layers to fend off micro-threats, but they have to actively maneuver away from larger objects. As we add more and more refuse to orbit, the situation becomes increasingly complex for exploration.

An impact to the radiator of Spaceshuttle Endeavour's 2007 mission

The SpaceX reentry in Oregon was a beautiful sight, but we’d be much better served if our space fireworks were natural.

Thankfully, space agencies seem to have awakened to the dangers of leaving junk in orbit. The European Space Agency is set to launch the first clean-up mission in 2025. Still, the Chinese luck strategy shows not everyone is on the same mission. A variety of creative ideas floats around for de-littering space. Hopefully, one of them becomes common practice and we don’t have to worry about the sky falling on us unexpectedly.

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