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This illustration from an artist reveals how an electrostatic tractor beam may be used in extracting obsolete satellites from geostationary orbit circling Earth. The beam wouldn’t be visible in reality.(Image credit: Tobias Roetsch – gtgraphics.de)ShareShare by:
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In movies of science fiction, few things amplify suspense like seeing the heroes’ spacecraft seized by a seemingly invisible tractor beam, allowing the villains to pull them in slowly. However, this once fictional concept could soon materialize.
Researchers are currently creating an authentic tractor beam, referred to as an electrostatic tractor. But rather than ensnaring hapless starship pilots, this tractor beam will utilize electrostatic attraction for gently shifting perilous space refuse beyond Earth’s orbit to safety.
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The underlying science is quite advanced, but the funds aren’t there.
The electrostatic tractor beam has the prospect of easing the problem by carefully relocating dead satellites to distant orbits, where they can drift safely indefinitely.
Although it may not entirely resolve the space debris issue, experts speaking to Live Science have pointed out that the idea provides several advantages over alternative space waste removal concepts, potentially making it a useful instrument for confronting the issue.
A prototype may demand million-dollar investments, and a fully functional version even more. However, the builders suggest it could be ready in about ten years, should the financial challenges be addressed.
“The science is essentially ready, it is just lacking funding,” said Kaylee Champion, a doctoral candidate in the Department of Aerospace Engineering Sciences at the University of Colorado Boulder (CU Boulder) and a researcher in the project, to Live Science.
Avoiding Disaster
Tractor beams often appear in sci-fi movies and television programs, such as Star Trek.
The tractor beams portrayed in “Star Wars” and “Star Trek” engulf spacecraft using fabricated gravity or an unclear “energy field.” Such technology is most likely beyond the scope of what humans can achieve. Nonetheless, the concept sparked Hanspeter Schaub, a professor of aerospace engineering at CU Boulder, to envision a more practical version.
Schaub first considered the idea following the first significant satellite collision in 2009, wherein an active communications satellite, Iridium 33, crashed into a non-operational Russian military satellite, Kosmos 2251, which resulted in the distribution of over 1,800 fragments of debris into Earth’s orbit.
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In the aftermath of this crisis, Schaub sought ways to prevent recurrences. His solution involved using the attractive force that brings positively and negatively charged items together to “glue” spacecraft together, enabling them to be displaced from dangerous zones.
Over the following decade, Schaub and his team enhanced the concept. Their hope is to use it for shifting inactive satellites beyond geostationary orbit (GEO) one day — an orbit around Earth’s equator where a satellite’s velocity matches the planet’s spin, creating the illusion that the satellite is stationary above a specific location. According to Schaub, this action would clear room for more items in GEO, which is viewed as “prime real estate” for satellites.
How does it work?
The scientists have been evaluating the electron gun on metal fragments in the laboratory.
Champion told Live Science that the electrostatic tractor would employ a servicer spacecraft fitted with an electron gun to shoot negatively charged electrons at a dead target satellite. The target will gain a negative charge, while the servicer will be left with a positive charge due to the electrons. She added that the two would remain connected via electrostatic attraction, despite being separated by 65 to 100 feet (20 to 30 meters) of open space.
Once the servicer and target are “stuck together,” it would then be able to pull the target out of orbit without any contact. Ideally, the inactive satellite will be dragged into a “graveyard orbit” further from Earth, where it can safely drift for good, Champion explained.
Project researcher Julian Hammerl, a doctoral student at CU Boulder, told Live Science that because of the limitations of the electron gun technology and the distance needed between the two to avert impacts, the electrostatic attraction between the two spacecraft would be exceptionally weak. Thus, the servicer must proceed very slowly, and it could take over a month to completely shift a single satellite from GEO, he further mentioned.
That stands in stark contrast to movie tractor beams, which rapidly draw in their targets with no escape. Hammerl said that is the “major distinction between sci-fi and reality.”
Advantages and limitations
The quantity of space waste that surrounds Earth has significantly increased recently. Here’s a comparison between the volume of space waste in 1965 (left) and 2010 (right).
Compared to other proposed methods for clearing space junk like harpoons, vast nets, and physical docking systems, the electrostatic tractor has a notable benefit: complete touchlessness.
Hammerl pointed out that the large, inert spacecraft rotate quite fast, and are about the same size as a school bus. He noted that any physical contact while trying to catch, harpoon, or dock could damage the spacecraft and only worsen the [space junk] problem.
Scientists have suggested alternative contactless methods, such as using strong magnets; however, according to Champion, creating enormous magnets is costly and would likely hinder the servicer’s controls.
Its sluggishness is a major drawback of the electrostatic tractor. There are currently over 550 satellites orbiting Earth in GEO, with a projected substantial rise in the following years.
If only one satellite can be moved at a time, a single electrostatic tractor cannot keep up with the rate at which satellites go out of service. A further constraint is that it is too slow to be practical for removing smaller parts of space junk, meaning it cannot maintain a completely debris-free GEO.
Another major hurdle is the cost. According to Schaub, a full cost assessment for the electrostatic tractor has not been carried out by the team as of yet, but it will likely cost tens of millions of dollars. Still, he added that running the servicer will be relatively cost-effective once in space.
Next steps
Researcher Julian Hammerl shown next to the ECLIPS machine at CU Boulder.
The researchers are running tests in their Electrostatic Charging Laboratory for Interactions between Plasma and Spacecraft (ECLIPS)