How to capture defunct satellites and other space junk and bring it back to Earth

More than half of the thousands of satellites in orbit are now out of service, and this accumulation of floating space debris has been described as a “deadly problem” for current and future space missions and human spaceflight.

According to the European Space Agency (ESA), an estimated 130 million objects smaller than 1 cm and 34,000 objects larger than 10 cm orbit at speeds of thousands of kilometers per hour. A report presented at this year’s European Space Debris Conference suggests that the amount of space debris could increase fifty-fold by 2100.

Although many fragments of space debris are small, they travel so fast that their impact has enough energy to disable a satellite or cause significant damage to space stations.

Both the Hubble telescope and the Solar Maximum Mission (SMM) satellites had coin-sized holes punched in them by flying debris, and a mirror on NASA’s James Webb Space Telescope was damaged by micrometeoroids.

Most satellites were not designed with the end of their useful life in mind. About 60% of the 6,000 satellites in orbit are now out of service. Along with the smaller objects, these defunct satellites pose a major problem for both existing and future satellites and space stations.

Megaconstellations of satellites currently being sent into space by companies like SpaceX and Amazon are set to transform internet access for all countries. But these private telecom companies will also contribute 50,000 more satellites to already dangerously populated orbits.

Scientists have warned that the rapid development of mega-constellations harbors several “tragedies of the commons,” including ground-based astronomy, Earth’s orbit and Earth’s upper atmosphere.

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Methods for removing space debris

There is a growing fear, dubbed Kessler Syndrome, that we may be creating a shell of space debris that could prevent human spaceflight, space exploration, and satellite deployment in some parts of Earth’s orbit. This scenario, continued by collisions between space objects and causing more and more debris, could also damage our global communication and navigation systems.

For this reason, the development of practical soil removal technologies is important and urgent. So far, various strategies have been devised to solve the space debris problem, and some have recently been prioritized.

To date, not a single orbiting object has been successfully recovered from space.

Harpunen, Roboter und Laser: Wie man nicht mehr funktionierende Satelliten und anderen Weltraumschrott einfängt und zur Erde zurückbringt

A ClearSpace chaser is designed to use robotic arms to capture space debris. Photo credit: ESA, CC BY-ND

One of the key issues in developing space debris removal strategies is the energy transfer between the debris (target) and the pursuer during first contact. There are two prioritized approaches and a third in development:

  • Impact energy dissipation methods aim to reduce the impact energy of the debris. In one approach, the Chaser satellite uses a harpoon to penetrate space debris. After the successful shot, the chaser satellite, harpoon, and target would be connected by an elastic band and the chaser would drag the debris to reenter the atmosphere and burn together.
  • Neutral energy balance involves a magnetic acquisition method that uses magnetic coils to achieve perfect energy balance between tracker and target. This is a soft docking process that is a preliminary step for a subsequent waste disposal process.
  • Destructive Energy Absorption aims to destroy small debris targets with a high power laser. The challenge, however, is to develop a laser and battery combination that is powerful but light enough. A lab in China has developed a space-based laser system to be installed on a Chaser satellite that can target debris up to 20cm in size. The Nasa Orion project uses ground-based lasers to destroy small debris.

The first space-distance project is planned for 2025 and will be led by ESA. It is a consortium approach based on a Swiss spin-off company, ClearSpace.

The ClearSpace Tracker meets the target and locks onto it with four robotic arms. The pursuer and captured launcher are then deorbited and burn up in the atmosphere.

High costs and more pollution

A key challenge is the significant cost associated with these proposed solutions, given the immense scale of the space debris problem. Another important consideration is the potential impact of space clearance on our planet’s atmosphere.

The idea that a growing number of satellites and other objects in the atmosphere would be incinerated if they were removed from space worries climate scientists. Space debris is naturally pulled down and burns up in the lower atmosphere, but increasing levels of carbon dioxide are reducing the density of the upper atmosphere, which could reduce its ability to pull debris back to Earth.

The burning of more and more satellites and other space debris (currently 80 tons per year) falling either naturally or through the new removal methods will also release decomposition products into the atmosphere.

These will certainly contribute more carbon dioxide and other greenhouse gases. Decomposition of certain materials in satellites is also likely to release chlorofluorocarbons (CFCs), which could damage the ozone shield.

One cannot overlook the parallels between the space debris problem and waste recycling. It is clear that we need to develop a circular economy strategy for our space waste.

Currently, the legal responsibility for space debris lies with the country of origin. This seems to argue against future international collaborative programs to clean up space debris.

Video: How to clear Earth’s orbit of space debris

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