How Can We Tackle the Growing Space Junk Problem?
Space exploration has always fascinated humans. The ability to explore space became a reality in the latter half of the 20th century, when rockets were developed that were powerful enough to overcome the force of gravity to reach orbital velocities. The first satellite was launched by the Soviet Union in 1957, and over the past few decades many countries have contributed to space exploration and earth observation through innumerable space missions and satellites. Space exploration has provided solutions to some eminently practical challenges, such as monitoring climate change and connecting people via satellites.
The advancements in satellite technology have paved the way for enhanced earth observation and remote sensing. With an increasing number of agencies worldwide that can afford to send satellites to spaces, satellite operators have now begun to launch mega constellations (groups of hundreds or even thousands of small satellites that work together) into orbit around Earth, for various applications. Aimed at covering the entire globe at once, these constellations are being used by civil, military, and corporate operators to provide worldwide and continuous coverage of the Earth. Climate monitoring, disaster management, and digital communication, such as satellite broadband, are among services that constellations can provide. The usability of these constellations is maximised by making them orbit close to earth. Given the growing number of such satellites, space junk has become a major problem that could lead to obstructing our view of the night and give rise to more space crashes among other dangers.
What is Space Junk?
Space Junk, also called space debris, consists of manmade objects that orbit Earth but are no longer useful. This material can range in size from a discarded rocket stage to a minuscule paint chip. All space junk is the product of humans releasing objects into orbit, where it will remain until it re-enters the atmosphere.
In lower orbits of a few hundred kilometres, some objects can return to earth swiftly. After a few years, they re-enter the atmosphere and, for the most part, burn up, preventing them from reaching the ground. However, debris or satellites left at higher altitudes of 36,000 kilometres, where communications and weather satellites are typically positioned in geostationary orbits, can circle the Earth for hundreds or even thousands of years.
Space junk in numbers
Last updated on 9th July, 2021, the following space debris figures have been provided by ESA’s Space Debris Office at ESOC, Darmstadt, Germany.
The number of debris objects estimated by statistical models to be in orbit are:
- 34000 objects greater than 10 cm
- 900000 objects from greater than 1 cm to 10 cm
- 128 million objects from greater than 1 mm to 1 cm
How is space junk harmful?
Since objects circle Earth at great speeds (up to 8 km per second), even a small piece of space debris can cause harm to a spacecraft. Astronauts constantly monitor spacecraft to avoid catastrophic collisions. If a known piece of debris has a greater than a 1 in 100,000 chance of colliding with the International Space Station (ISS), a collision avoidance maneuver is executed to raise the ISS’s orbit. The first time a functioning satellite collided with space debris was on 24th July, 1996. A component from the upper stage of a European Ariane rocket had collided with Cerise, a French microsatellite. Cerise suffered damage as a result of this collision but continued to function.
On 10th February, 2009, an active American communications satellite, Iridium 33, collided with an inactive Russian military communications spacecraft, Cosmos 2251, about 760 kilometres above northern Siberia, thus shattering both satellites. The worst space debris accident to date occurred on 11th January, 2007, when Chinese military destroyed a weather satellite, Fengyun-1C, while testing an anti satellite system. This resulted in almost 3,000 pieces of space debris having coalesced into a cloud of debris that surrounded the planet within two years. Fragments from Fengyun-1C, Iridium 33, and Cosmos 2251 account for about one-half of the debris below 1,000 km above earth.
Although space junk has no direct impact on the Earth’s atmosphere, its density may increase to the point where it interferes with our capacity to use weather satellites and hence monitor weather changes caused by our own ground-based pollution. Fortunately, space debris doesn’t affect space exploration, but with its growing number, there is concern that collisions like the one between Iridium 33 and Cosmos 2251 could trigger a chain reaction in which the resulting space debris destroys other satellites and so on, rendering low Earth orbit useless. This is called the Kessler Syndrome and was first introduced by NASA space debris expert Don Kessler.
Efforts to clean up space junk
Having acknowledged its dangers, several companies and organizations have offered solutions for removing defunct satellites and other space debris. 7 of the proposed solutions as reported by space.com in 2014 are:
- Snagging and moving space junk — The ESA has considered using nets, harpoons, robotic arms, and tentacles as the “capturing methods” gather up the debris.
- Pushing debris out of space — This involves using spacecraft to push debris out of Earth’s orbit.
- Using the power of electricity — This proposal from the Japanese Aerospace Exploration Agency proposed to use an electrodynamic tether whose current would slow down the speed of satellites or space debris, and make it gradually fall closer to Earth’s atmosphere, where it will burn up.
- A space debris slingshot — This was proposed by Texas A&M University to save on fuel. involves capturing an object, swinging it towards Earth’s atmosphere, and then using the momentum to sail on to the next piece of space debris for removal.
- Solar sail — This was a British proposal that intended to use the drag of a solar sail to push orbiting space debris down to lower orbits.
- Huffing and puffing — This method (called Space Debris Elimination, or SpaDE) was proposed by Daniel Gregory of Raytheon BBN Technologies in Virginia. It was intended to push satellites into a lower orbit by using air bursts within the atmosphere.
- Knock junk down with a net — A solar powered Electrodynamic debris eliminator was proposed by Star Technology and Research, Inc. It involves a network of nanosatellites, connected with a piece of electrically conducting tape (as long as 3 kilometers), that could knock satellites down as it passes through Earth’s magnetic field and produces voltage.
In late September 2018, scientists from the University of Surrey deployed the RemoveDEBRIS satellite that successfully fired out a net and trapped a piece of space debris that was in orbit around Earth. In December 2019, ESA commissioned the world’s first space mission to remove an item of debris from orbit. Named ClearSpace-1, the mission was procured as a service contract with a startup-led commercial consortium, to help establish a new market for in-orbit servicing, as well as debris removal.
Magnetic Spacecraft — new solution to clean space junk
In March 2021, Japanese orbital clean-up company Astroscale proposed a potential solution to space junk. ELSA-d was launched by GK Launch Services into a 550 km orbit on a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan on March 22. This 6-month long mission is aimed at demonstrating the pioneering method to capture and safely remove space debris from orbit using magnetic retrieval.
Now that ELSA-d is in orbit, it is undergoing tests wherein the service satellite will release and then magnetically dock with the smaller satellite; capture it while it is tumbling out of control; and then intentionally lose and recapture it.
Satellite system to monitor threat of space debris
Over 50,000 satellites are scheduled to be launched into orbit over the next decade. This is a significant increase since the inception of satellite launch. Fewer than 10,000 satellites have been launched till now, with around half still in orbit. As new satellites, particularly mega-constellations like SpaceX’s Starlink and Amazon’s Project Kuiper, are launched, tackling space junk will become very crucial.
NorthStar Earth and Space, a Canadian business, has hired Thales Alenia Space to manufacture the first three satellites of its Skylark space traffic monitoring system, with Seattle-based LeoStella managing the final assembly. NorthStar will be the first commercial firm to monitor space traffic from orbit. The programme will notify users of probable collisions between active and defunct satellites, as well as other significant bits of debris.
NorthStar’s Skylark constellation will be a tiny constellation with only 12 satellites. It will be able to follow its targets more frequently than ground stations because its satellites are in orbit. In 2022, the first three satellites are expected to launch. Over the next two years, the next nine will ascend in phases.
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References:
https://www.weforum.org/agenda/2021/06/60-years-space-exploration-images-nasa/
https://www.britannica.com/technology/space-debris
https://www.nhm.ac.uk/discover/what-is-space-junk-and-why-is-it-a-problem.html
https://www.sciencefocus.com/space/does-the-debris-around-earth-affect-the-atmosphere/
https://www.space.com/24895-space-junk-wild-clean-up-concepts.html
https://www.space.com/astroscale-launches-space-junk-cleanup-mission
https://www.weforum.org/agenda/2021/05/space-junk-clean-satellite/
https://www.businessinsider.co.za/astroscale-mission-to-clean-up-space-junk-magnets-2021-3
