Orbital overload: looming threat of space debris

Massive space activity over the past few decades has led to unintended orbital debris. Each launch of a satellite or rocket adds to the problem, increasing the risk that threatens not only space missions but also the safety of future endeavours.

This ever-increasing threat can be best understood through the concept of Kessler syndrome in space. This phenomenon occurs when objects in Low Earth Orbit (LEO) become so cluttered that they begin to collide with each other, creating more debris and more collisions, thus resulting in chain reactions of mergers and fissions. Many experts warn that the LEO is moving towards Kessler’s Syndrome.

Though every space activity adds to the debris problem, anti-satellite (ASAT) missile tests are highly irrational act considering the indiscriminate threat it poses to human space exploration by exponentially increasing the orbital overload. The US was the first to test its ASAT in 1984, with China (2007) and Russia (2014 and 2021) following suit. India is the latest in the list and attracted widespread condemnation after it undertook a kinetic kill ASAT under the codename Mission Shakti in 2019. Apart from that, accidental collisions in space also increase the orbital overload, such as the 2009 collision between two satellites, Kosmos 2251 and Iridium 33. Such events have made the problem of orbital debris worse and raised the prospect of disastrous space conditions.

Around 128 million pieces of debris smaller than a centimeter and about 900,000 fragments between 1 and 10 cm are estimated to be present in LOE. Some 12,170 satellites have been launched into the Earth’s orbit since the space age began. These include about 3,000 decommissioned spacecraft, which contribute significantly to the debris along with other large objects, such as high-phase rocket lumps. There are some immediate risk factors for operational satellites and space missions. The International Space Agency has issued 29 maneuvers for debris avoidance since 1999, highlighting the present dangers.

The need for sustainable space activities and the reduction of space debris is being emphasised globally to address the rising space pollution. Therefore, governments have proposed many regulatory and mitigation measures, including Active Debris Removal (ADR) technologies or pollution prevention, which are either planned, being tested, or already implemented to protect both existing spacecraft and ones set to be launched.

The US space waste management regulations state that no country may retain a satellite after it has completed its 25-year useful life. However, these laws have been modified to only allow a satellite to remain in space for a maximum of another five years. In addition to the European Space Agency (ESA), under its ‘Zero Debris Approach’, which is part of Agenda 2025, aims to significantly limit the amount of debris produced on Earth and in lunar orbit by 2030.

Apart from regulatory measures, several mitigating methods are also used to reduce the orbital overload. One such method involves causing a satellite to naturally decay by bringing it closer to the Earth’s surface to produce natural atmospheric incineration known as natural aerodynamic decay. Because the defunct satellite can be pushed toward the Earth’s surface at a lower altitude using a physical tool like a net or an air-bursting tool, this method is thought to be cost-effective. Another similar technology uses a harpoon that is fired in the direction of the targeted spacecraft to capture it and direct it toward Earth in an active manner, causing the debris to deorbit and plan atmospheric incineration.

In order to reduce the long-term risk of collisions, the focus needs to be on reducing the amount of debris in the orbit. Initiatives in this regard include the reduction of mission-related components in spacecraft i.e. deployment and operations, which currently account for 13% of total space inventory. Implementing such measures to prevent explosions can significantly contain future debris growth. To avoid accidentally severing the spacecraft and rocket bodies, the remaining potentially explosive systems need to be disabled.

To sum up, reducing space debris is crucial for maintaining a sustainable space environment for future missions.