Laser helps bring back space junk

More than half of the thousands of satellites in orbit have now failed, and the accumulation of this floating space debris has been described as a "deadly problem" for current and future space missions and human space travel. Researchers are studying ways to capture failed satellites and other space junk and bring it back to Earth.

The European Space Agency (ESA) estimates that 130 million objects smaller than 1 centimeter and 34,000 objects larger than 10 centimeters are orbiting 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 junk could increase 50-fold by 2100.

Although many pieces of space junk are small, they are traveling so fast that their impact energy is enough to disable satellites or cause significant damage to space stations.

Both the Hubble telescope and the Solar Maximum Mission (SMM) satellite have been hit with coin-sized holes from flying debris, and a mirror on NASA's James Webb Space Telescope was damaged by a micrometeoroid.

Most satellites are not designed with their purpose in mind. Of the 6,000 satellites in orbit, about 60 percent are now malfunctioning. Together with smaller objects, these end-of-life satellites constitute a major problem for existing and future satellites and space stations.

The study highlights a fundamental shift like crust formation 3.75 billion years ago, which contributed to the formation of Earth's unique, stable continental crust. Source: CC0 Public Domain

Ways to remove space debris

Currently, there is a whole concern that too much space debris could affect human space travel, space exploration, and the use of satellites in certain parts of Earth's orbit. There is also concern that the increasing amount of debris created due to collisions between space objects could damage global communication and navigation systems.

This is why the development of practical debris removal technologies is important and urgent. To date, various strategies have been developed to address the space debris problem, some of which have recently been prioritized. To date, not a single orbital object has been successfully recovered from space.

The Clearspace tracker is designed to capture space debris using a robotic arm. Source: ESA, CC BY-ND

One of the main problems in designing a space debris removal strategy is how to transfer energy during the first contact between the debris (the target) and the tracker. There are two preferred approaches, and a third is under development.

1 The impact energy dissipation approach aims to reduce the impact energy of debris. One approach is for the chase satellite to deploy a harpoon to penetrate the space debris. After a successful launch, the tracking satellite, harpoon, and target would be connected by an elastic cable, and the tracker would pull the debris back into the atmosphere and burn it up together.

2 Neutral energy balance includes a magnetic capture method that uses magnetic coils to achieve a perfect energy balance between the pursuer and the target. This is a soft docking method and is a preliminary step to subsequent debris processing methods.

3 Destructive energy absorption aims to destroy small debris targets using high-powered lasers. The challenge, however, is to develop a laser and battery combination that is powerful but light enough. A Chinese laboratory has been developing a space-based laser system that will be mounted on a tracking satellite capable of targeting debris up to 20 centimeters in size. NASA's Orion project uses ground-based lasers to destroy small debris.

The first space removal project is scheduled for 2025 and is led by ESA. It involves a consortium approach based on the Swiss subsidiary Clearspace. the Clearspace chaser will rendezvous with the target and capture it using four robotic arms. The chaser and the captured launcher will then deorbit and burn up in the atmosphere.

Visualization of orbital space debris. Source: European Space Agency

High cost and more pollution

Given the enormous scale of the space debris problem, a key challenge is a huge cost associated with these proposed solutions. Another important aspect is the potential impact of space cleanup efforts on the Earth's atmosphere.

The idea that a growing number of satellites and other objects will be incinerated in the atmosphere as they leave space has raised the concerns of climate scientists. Space debris is naturally pulled downward and burned 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 growing amount of satellite and other space debris (currently 80 tons per year) falling naturally or burning through new removal methods will also release decomposition products into the atmosphere.

These will certainly produce more carbon dioxide and other greenhouse gases. The decomposition of certain substances in satellites could also release chlorofluorocarbon (CFC) gas, which could damage the ozone layer.

One cannot ignore the parallels between the space junk problem and waste recycling. We need to develop a circular economy strategy for our space waste.

Currently, the legal responsibility for space debris rests with the country of origin. This seems to be detrimental to future international cooperative programs for space waste removal.