So What's the Problem with Space Junk?
Despite the common perception of outer space as a vast, empty expanse, the area surrounding Earth is filled with millions of pieces of man-made debris that present alarming risks to operational satellites and spacecraft. Numerous roadblocks for space operations are created from this space junk, derived from defunct satellites, spent rocket stages, and fragments from collisions and explosions, having implications for life on Earth.
The origin of space debris dates back to the beginning of the space age. Every satellite launched, every discarded rocket stage, and every failed mission has added to the growing cloud of orbital debris. Over time, collisions between objects and explosions of defunct spacecraft have fragmented this debris into even more hazardous pieces. Notable incidents contributing to this debris field include the 2009 collision between the inactive Russian satellite Kosmos-2251 and the operational U.S. satellite Iridium 33, as well as the 2007 Chinese anti-satellite missile test.
Falling Objects
Earth's orbit is divided into three main regions: Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Earth Orbit (GEO). LEO (125-1,250 miles above Earth) is affected by atmospheric drag, causing debris to fall back to Earth, and is popular for piloted spacecraft. MEO (6,000-12,000 miles above Earth) is used by navigation and communication satellites. GEO (over 22,000 miles high) hosts satellite telecommunications and weather satellites, with objects remaining in orbit for millions of years. The lower the orbit, the shorter the debris' lifespan.
Debris constantly falls from space, with most burning up in the atmosphere. Larger pieces, over 4 inches, often survive and break into smaller fragments. On average, one piece of debris falls to Earth daily, usually landing in the ocean, which covers about 70% of the Earth's surface. According to NASA, there have been no confirmed serious injuries or significant property damage from falling debris.
Space Junk’s Risk to Space Exploration
Fortunately, space junk currently poses a minimal risk to space exploration efforts, with the primary danger being to other satellites in orbit. These satellites must constantly perform collision avoidance maneuvers to avoid potential damage or destruction from incoming debris. Across all satellites, hundreds of such maneuvers are executed annually, including by the International Space Station (ISS) where astronauts reside. Despite this, actual collisions are rare: the most recent incident was in March 2021, when a Chinese satellite broke up following a collision, with the previous noteworthy collision occurring in 2009. The limited amount of space junk beyond Earth's orbit also does not threaten deep space exploration.
How Can We Clean Up Space Junk and Will the Issue Improve?
The United Nations urges companies to remove their satellites from orbit within 25 years after their mission ends. Even so, enforcement is challenging due to satellite failures being common. To address this issue, a number of companies globally have developed innovative approaches. These solutions involve methods such as retrieving defunct satellites and guiding them back into the Earth's atmosphere, where they will safely disintegrate upon reentry.
The RemoveDEBRIS mission, initiated in late 2014 and funded by an EC grant, marked a huge milestone as the first mission to demonstrate in-orbit technologies for actively removing space debris. Led by the Surrey Space Centre, the consortium developed and tested various technologies from concept to execution, concluding in March 2019. Successful demonstrations included the use of a net and harpoon for capturing large debris, alongside advanced hardware and software to analyze the motion of non-cooperative target debris through onboard cameras. The mission culminated in deploying a drag-sail to enhance atmospheric drag, hastening the satellite's reentry and disposal.
