The Problem of Space Junk — How We Block Our Way Into Space

~6 min

Since the beginning of the space exploration era in the 1950s, we’ve been filling space with rockets, satellites, and garbage. And one day, we’ll have to face the consequences. What are they, and can we stop polluting space? Let’s find out.


What is space junk?

Space junk or space debris (also space trash) are unwanted objects or materials left in space by humans — such as pieces of dead satellites. Here are some examples of objects found in space:

  • Discarded rocket stages;
  • Screws and bolts;
  • Pieces of paint fallen off a spaceship;
  • A glove;
  • A blanket;
  • A toothbrush;
  • A pair of pliers;
  • A briefcase-sized tool bag.

Space trash mainly refers to objects in the Earth’s orbit, but humanity manages to leave trash everywhere — including the Moon.

How much space junk is there?

As of August 2022, ESA reported about 31,870 debris objects regularly tracked by Space Surveillance Networks. But not all space debris is tracked and cataloged. Our surveillance systems can observe only space objects with diameters larger than 10 cm in the low-Earth orbit and larger than 1 m in the geostationary orbit. Based on statistical models, there are about 131 million not-tracked pieces (most of them are from 1 mm to 1 cm in size).

Space junk growth in numbers

The number of in-orbit cataloged objects has been increasing relatively linearly for the past several decades. Here is the approximate amount of tracked debris in the Earth’s orbit according to IAA Situation Report on Space Debris.

  • 1993: 7,700 objects
  • 2001: 8,700 objects
  • 2005: 10,300 objects
  • 2013: 16,600 objects
  • 2016: 17,700 objects
  • 2022: 31,870 objects

Where does the space junk come from?

Space junk is a result of humans launching rockets and satellites into space. Rocket launches leave boosters, fairings, interstages, and other debris in the Earth’s orbit. Satellites have a limited lifetime and eventually stop operating, turning into pieces of metal floating in space. Astronauts lose some stuff in space — such as their tools, while repairing spacecraft.

Some space debris results from satellite collisions. When satellites collide, they can break up into thousands of pieces, creating numerous new debris. Besides, some countries like the U.S., China, and India have used ASATs (anti-satellite weapons) to blow up satellites, creating thousands of new pieces of debris.

Why is space debris a problem?

The current biggest threat of space debris is potential damage to operational satellites, spacecraft, and the International Space Station. Meanwhile, the predictions about its possible threat to space exploration in the future are different.

The number of space junk mainly grows in low-Earth orbit. Humanity constantly increases the number of satellites there, which leads to a higher possibility of collisions. To avoid a collision, satellites have to get out of the way of the space debris’ pieces. Every year, all the satellites (including the ISS) perform hundreds of collision avoidance maneuvers.

Some sources claim that the growing debris will make orbit operations more costly and troublesome. Satellites will have to perform more avoidance maneuvers making them more operationally difficult. They will also require extra fuel for these maneuvers and possibly shields to protect crucial areas.

Other researchers consider space debris to become a serious problem after 2055, making further space exploration nearly impossible. They say that the level of debris in low-Earth orbits is so high that measures aimed at reducing it are useless.

What is Kessler syndrome?

Kessler syndrome (or collisional cascading) is a scenario where there is too much space junk in the Earth’s orbit which results in more objects colliding, creating more debris. Therefore, the likelihood of further collisions would increase. Eventually, it would lead to the point where Earth's orbit becomes unusable. You can see some representation of this theory in the movie Gravity. The Kessler syndrome is named after Donald Kessler, a NASA scientist, who came up with this idea in 1978.

Incidents of damage associated with space junk

Now that we know the theories let’s see the real accidents that involve space junk.

Space debris hitting the ISS

Since 1999, the International Space Station has changed course more than 25 times to avoid known debris. However, it didn’t save the ISS entirely. By 2019, there were over 1,400 meteoroid and orbital debris recorded impacts with the ISS. They damaged several sections, including solar arrays, US and Russian windows, radiators, and others.

Space junk hitting the Moon

In 2022, a piece of space garbage hit the lunar surface for the first time. The upper stage of a Chinese rocket launched in 2014 hit the far side of the Moon on March 4, 2022. No one watched the impact, but according to computer simulations, the piece of the rocket landed somewhere near the Hertzsprung crater and should have left a crater about 20 m (65 feet) in diameter.

Space junk hitting the Earth

Although most of the space junk burns up in the atmosphere, pieces of debris have hit the Earth’s surface multiple times. But they didn’t cause any significant damage. Here are some of the occasions:

  • One of the earliest recorded events occurred on September 5, 1962, when a piece of Sputnik IV fell in Manitowoc, Wisconsin. The piece was 0.15 m (5.9 inches) in size and 9.5 kg (20.9 lbs) in mass.
  • The first person injured by the (almost) direct impact from the space junk was Wu Jie, a 6-year-old boy from China in 2002. 10 kg (22 lbs) piece of aluminum from the launch of the Ziyuan-2B spacecraft struck a persimmon tree under which the boy was playing. Wu Jie suffered a fractured toe and swelling on his forehead.
  • On July 31, 2022, the empty core stage of Long March-5B made an uncontrolled reentry over Indonesia and Malaysia. Many people witnessed this, but no one got hurt.

Can we get rid of space junk?

Normally, space junk circles the Earth until it reenters the atmosphere and burns up there. Depending on an object’s altitude, this takes from several to thousands of years. Objects below 600 km can reenter the atmosphere after a few years. Debris at altitudes of 800 km can continue to circle the Earth for centuries. Above 1,000 km, they will continue orbiting our planet for thousands of years.

But we can’t just stop launching stuff into space to clean it up. The Earth’s orbit is already filled up with numerous objects, and even without new launches, they will multiply by colliding with each other. As calculated, only pieces between 10 and 20 cm across will increase by 3.2 times.

So, obviously, we can’t wait until all space debris disappears. Currently, companies worldwide are working on removing dead satellites from orbit and dragging them back into the atmosphere, where they will burn up. These projects include a harpoon, net, magnets, and even firing lasers!

The first such mission is scheduled for 2025, when ESA will launch a four-armed robotic junk collector to remove a single piece of debris called Vespa. According to the plan, the probe will grab Vespa and drag it into the atmosphere, where they both will burn up. The mission will cost €120 million.

Another more realistic and less expensive method is to not leave objects in orbit once they are no longer useful. There are international guidelines for doing this from the Inter-Agency Space Debris Coordination Committee (IADC).

Space junk map

You can track some space junk on your own. Use a space junk map that shows a 3D model of the satellites in the Earth’s orbit (including debris and inactive satellites). Or get the Satellite Tracker app that allows you to track some space debris. You can find them by tapping the satellite icon in the upper right corner of your screen in the “Space Debris” section. Also, most pieces of debris have “DEB” at the end of their names.

Bottom line: Space junk or space debris are man-made materials left in space. They include a wide variety of objects, from dead satellites to a single toothbrush. If humans keep trashing the Earth’s orbit, in the worst-case scenario, space exploration will become impossible. Space-related companies are working on a solution to this problem.