Space Debris: The Threat of Orbital Junk to Astronauts and Satellites

What is a space debris?

Space debris, also known as space junk, refers to any human-made object in orbit around the Earth that no longer serves a useful function. This includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris and fragmentation debris. Space debris can be as large as an inactive satellite or as small as a flake of paint. The real danger of space debris is the speed at which these objects move - more than 28,000 kilometers per hour - which makes even small pieces of debris potentially lethal to spacecraft and satellites.

Space debris is a significant problem for space exploration and poses a threat to both crewed and uncrewed spaceflight. The risk of catastrophic collision between space shuttles and pieces of space debris was estimated to be 1 in 300. In the first collision between an operational satellite and a piece of space debris in July 1996, a fragment from the upper stage of a European Ariane rocket collided with Cerise, a French microsatellite. Cerise was damaged but continued to function[4].

Since the beginning of the space era in 1957, tons of rockets, spaceships, and satellites have been launched into space. At least initially, no one foresaw what to do with them at the end of their useful life. The European Space Agency (ESA) estimates that there are some 900,000 objects over one centimeter in size orbiting Earth today.

Size and types of space junk

Space debris, also known as space junk, is any piece of machinery or debris left by humans in space. It can refer to big objects such as dead satellites that have failed or abandoned launch vehicle stages. It can also be as small as a microscopic chip of paint. The amount of space debris in orbit increases with the growth of the space industry on Earth.

Space debris poses a significant threat to the astronauts and spacecraft that work in Earth's orbit, according to NASA. Even tiny pieces of space junk can cause incredible damage because objects in orbit move at high speeds. For example, during an STS-120 EVA to reinforce a torn solar panel, a pair of pliers was lost, and in an STS-126 EVA, Heidemarie Stefanyshyn-Piper lost a briefcase-sized tool bag.

Rocket upper stages which end up in orbit are a significant source of space debris. In characterizing the problem of space debris, it was learned that much debris was due to rocket upper stages (e.g. the Inertial Upper Stage) which end up in orbit and break up due to decomposition of unvented propellants or residual pressure within fuel tanks. By one estimate, there are a hundred million bits of debris that are a millimeter in size and a hundred million as small as a micron.

Threat to astronauts and spacecraft

Space debris poses a significant threat to astronauts and spacecraft. Space debris can damage spacecraft or space stations due to the high speed at which it travels. The rising population of space debris increases the potential danger to all space vehicles, including the International Space Station. Fortunately, at the moment, space junk doesn't pose a huge risk to our exploration efforts. The biggest danger it poses is to other satellites in orbit.

NASA recognizes the dangers of space debris and has an Orbital Debris Program Office that tracks more than 8,000 orbiting objects larger than 4 inches (10 cm), of which only 7% are operational. The rest are debris - dead satellites, parts of exploded rockets, nuts, bolts, other lost hardware, etc. NASA is also working on ways to mitigate the risks posed by space debris. For example, NASA's Restore-L project aims to refuel and service a satellite in low Earth orbit that was not designed for servicing.

Solutions and Future Challenges

Space debris is a growing problem that poses a significant threat to current and future space missions. It is essential to address this issue to ensure the sustainability of space exploration. There are several solutions for managing space debris, including prevention, removal, and mitigation. Prevention involves designing spacecraft with end-of-life disposal in mind and avoiding in-orbit explosions. Removal involves capturing debris or deorbiting old satellites. Mitigation involves reducing the creation of debris from collisions by employing collision avoidance techniques or removing large objects from orbit.

Several organizations are working on addressing the issue of space debris. The World Economic Forum has launched the world's first Space Sustainability Rating, which aims to reduce space debris and ensure that rapidly increasing space exploration missions are "managed safely". Aerospace's Center for Orbital and Reentry Debris Studies (CORDS) is developing tools and techniques that will analyze potential collision scenarios, study reentry breakups of upper stages and spacecraft, and model debris objects in orbit. ESA is working on mitigating space debris generation by preventing in-orbit explosions and applying both prevention and removal measures broadly and in a timely manner.

In conclusion, addressing the issue of space debris is crucial for ensuring the sustainability of current and future space missions. Several solutions exist for managing space debris, including prevention, removal, and mitigation. Organizations such as the World Economic Forum, Aerospace's CORDS, and ESA are working on developing tools and techniques to address this issue.