A space junk disaster is a real possibility -- here's how the US government helps prevent a chain of collisions that would threaten human access to space

ShutterstockA thick ring of space junk orbits Earth in this fanciful artist’s concept of a ‘Kessler syndrome’ event.

China’s school-bus-size Tiangong-1 modular space station is expected to fall to Earth in a fiery blaze on or around Easter Sunday.

The US government is tracking the orbit of Tiangong-1 and about 23,000 other human-made objects larger than a softball. These satellites and chunks of debris zip around the planet at more than 17,500 mph – roughly 10 times the speed of a bullet.

However, there are millions of smaller pieces of space junk orbiting Earth, too.

“There’s lots of smaller stuff we can see but can’t put an orbit, a track on it,” Jesse Gossner, an orbital-mechanics engineer who teaches at the US Air Force’s Advanced Space Operations School, told Business Insider.

As companies and government agencies launch more spacecraft, concerns are growing about the likelihood of a “Kessler syndrome” event: a cascading series of orbital collisions that may curtail human access to space for hundreds of years.

Here’s who is keeping tracking of space junk, how satellite collisions are avoided, and what is being done to prevent disaster on the final frontier.

Thousands of launches since the dawn of the Space Race have led to a growing field of space debris. Most space junk is found in two zones: low-Earth orbit, which is about 250 miles up, and geostationary orbit, about 22,300 miles up.

ESAA simulation of all the space debris orbiting Earth.

In addition to 23,000 objects the size of a softball or larger — like rocket stages, satellites, and even old spacesuits — there are more than 650,000 objects that are softball-to-fingernail-size.

NASANASA astronaut Mike Hopkins in a spacesuit outside the International Space Station on Dec. 24, 2013.

Another 170 million bits of debris as small as a pencil tip may also exist – including things like explosive bolts and paint flecks.

Source: ESA

Countless pieces of tiny debris were added to orbit in 2007, when China intentionally smashed one of its old satellites with a “kill vehicle.” Then in 2009, an old Russian satellite and US satellite collided, adding even more dangerous junk.

Celestrak/Analytical Graphics, Inc.Red dots are known pieces of China’s destroyed FY-1C satellite. Green dots are low-Earth orbit satellites.

Leftover rocket bodies often have fuel remaining. As the harsh environment of space weakens the rocket parts over time, fuels can mix, explode, and spray more debris every which way.

ESAAn illustration of a rocket-body explosion in space.

No piece of space debris is insignificant, since each one travels at speeds high enough to inflict catastrophic damage to vital equipment. A single small hit could be deadly to astronauts aboard a spacecraft.

NASAA space-debris hit to space shuttle Endeavour’s radiator found after one of its missions. The entry hole is about 0.25 inches wide, and the exit hole is twice as large.

Jack Bacon, a senior scientist at NASA in 2010, told Wired that a hit by a 10-centimeter sphere of aluminium would be akin to detonating 7 kilograms of TNT.

If the space junk problem were to spiral out of control, one collision could beget other collisions, and in turn spread even more debris: a chain of crashes known as a Kessler event.

ShutterstockAn illustration of a runaway space junk event called the Kessler syndrome.

Astrophysicist Donald J. Kessler, who used to work for NASA’s Johnson Space Center, penned the idea in a 1978 study. Kessler and his NASA colleague Burton G. Cour-Palais calculated that more and more launches in the coming decades would increase the risks of collisions in space.

In the study, titled “Collision Frequency of Artificial Satellites: The Creation of a Debris Belt,” they also described important sources of space debris and possible sinks that would remove dangerous junk from orbit.

As Kessler’s study explains, the more massive an object, the more space debris it can create if hit. Thus, large objects pose a much higher risk of fuelling a cascade of collisions if there are many other satellites in similar orbits.

NASAThe football-field-size, 450-ton International Space Station.

A Kessler syndrome event could create an Asteroid Belt-like field of debris in large regions of space around Earth. These zones may be too risky to fly new satellites or spaceships into for hundreds of years, severely limit human access to the final frontier.

NASA/FlickrA view of Africa taken by Apollo 11 astronauts on July 20, 1969.

Source: Inter-Agency Space Debris Coordination Committee

The Kessler syndrome plays center-stage in the movie “Gravity,” in which an accidental space collision endangers a crew aboard a large space station. But Gossner said that type of a runaway space-junk catastrophe is unlikely.

Warner Bros./YouTubeA scene from the movie ‘Gravity’.

“Right now I don’t think we’re close to that,” he said. “I’m not saying we couldn’t get there, and I’m not saying we don’t need to be smart and manage the problem. But I don’t see it ever becoming, anytime soon, an unmanageable problem.”

There is no current system to remove old satellites or sweep up bits of debris in order to prevent a Kessler event. Instead, space debris is monitored from Earth, and new rules require satellites in low-Earth orbit be deorbited after 25 years so they don’t wind up adding more space junk.

David Ducros/ESAAn illustration of the e.Deorbit system to net and remove old satellites from orbit.

“Our current plan is to manage the problem and not let it get that far,” Gossner said. “I don’t think that we’re even close to needing to actively remove stuff. There’s lots of research being done on that, and maybe some day that will happen, but I think that – at this point, and in my humble opinion – an unnecessary expense.”

A major part of the effort to prevent a Kessler event is the Space Surveillance Network (SSN). The project, led by the US military, uses 30 different systems around the world to identify, track, and share information about objects in space.

Alan Baker/ESA (CC BY-SA 3.0 IGO)An illustration of a future space-debris surveillance system that uses ground-based optical, radar, and laser technology, as well as in-orbit survey satellites.

Many objects are tracked day and night via a network of radar observatories around the globe.

NASAThe Haystack and HAX radars located in Tyngsboro, Massachusetts collect 600 hrs of orbital debris data per year. They are NASA’s primary source of data on centimeter-sized orbital debris.

Optical telescopes on the ground also keep an eye out, but they aren’t always run by the government. “The commercial sector is actually putting up lots and lots of telescopes,” Gossner said. The government pays for their debris-tracking services.

ShutterstockAn amateur astronomer peers through a small telescope.

Gossner said one major debris-tracking company is called Exoanalytic. It uses about 150 small telescopes set up around the globe to detect, track, and report space debris to the SSN.

Telescopes in space track debris, too. Far less is known about them because they’re likely top-secret military satellites.

Objects detected by the government and companies get added to a catalogue of space debris and checked against the orbits of other known bits of space junk. New orbits are calculated with supercomputers to see if there’s a chance of any collisions.

Michael Seeley/Flickr (CC BY 2.0)A satellite track left by the International Space Station in a long exposure of the night sky.

Diana McKissock, a flight lead with the US Air Force’s 18th Space Control Squadron, helps track space debris for the SSN. She said the surveillance network issues warnings to NASA, satellite companies, and other groups with spacecraft, based on two levels of emergency: basic and advanced.

NASAOrbital debris photographed from a NASA space shuttle in 1998.

The SSN issues a basic emergency report to the public three days ahead of a 1-in-10,000 chance of a collision. It then provides multiple updates per day until the risk of a collision passes.

ESAAn illustration of space junk. Satellites and debris are not to scale.

To qualify for such reporting, a rogue object must come within a certain distance of another object. In low-Earth orbit, that distance must be less than 1 kilometer (0.62 mile); farther out in deep space, where the precision of orbits is less reliable, the distance is less than 5 kilometers (3.1 miles).

Advanced emergency reports help satellite providers see possible collisions much more than three days ahead. “In 2017, we provided data for 308,984 events, of which only 655 were emergency-reportable,” McKissock told Business Insider in an email. Of those, 579 events were in low-Earth orbit (where it’s relatively crowded with satellites).

When a space company receives a SSN alert, they typically move their satellite into a different orbit — and out of harm’s way — by burning a little propellant.

NASA’s Goddard Space Flight Center/CI LabAn illustration of the Fermi Gamma-ray Space Telescope firing its thrusters to avoid a potential collision.

Although companies like SpaceX are launching more and more objects into space, McKissock said “our everyday concern isn’t something as catastrophic as the Kessler syndrome.”

Elon Musk/SpaceX via InstagramThe last photo of ‘Starman’ in Elon Musk’s red Tesla Roadster as it flies toward Mars orbit. Earth is the bright crescent seen in the background.

The biggest priority is avoiding damage to multi-million-dollar satellites and keeping astronauts safe. “It’s just a matter of watching and, with our active satellites that we do control, avoiding collisions,” Gossner said. “It becomes a very important problem not just for that satellite, but then for the debris that it would create.”

ShutterstockAn illustration of a satellite damaged by space debris.

So any time something massive returns to Earth, such as China’s 9.4-ton Tiangong-1 space station, it’s a cause for celebration — not despair.

Aerospace Corporation/YouTubeAn illustration of China’s large modular space station, Tiangong-1, burning up in Earth’s atmosphere.

The next very large object to fall to Earth after Tiangong-1 may be NASA’s 12.25-ton Hubble Space Telescope, which could be deorbited as soon as 2021.


Like other objects that can be guided toward their doom, Hubble (as well as the International Space Station, eventually) will be deorbited in the “spacecraft graveyard”: the most remote point of the Pacific Ocean.

Google Earth; Business InsiderPoint Nemo, also known as the Oceanic Pole of Inaccessibility.

Source: Business Insider

NOW WATCH: Briefing videos

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.