There may be a new way to control satellites in space
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It may be possible to keep space exploration missions running longer and avoid spacecraft colliding with each other using a technique that harnesses magnetic fields to move satellites.
Currently, most space missions and satellites have a finite lifespan because the objects are moved around in space using propellant fuel, which often runs out. One alternative method called Electromagnetic Formation Flying (EMFF) relies on renewable power sources, such as solar panels, to power electromagnetic coils on board the satellites. These generate a magnetic field which, through interaction with similar magnetic fields generated on any nearby satellite, can theoretically be used to manoeuvre the spacecraft.
But researchers have encountered difficulties in using EMFF to move objects in space because of an issue called magnetic coupling. The magnetic field generated by a satellite doesn’t interfere with just one nearby satellite but with all the satellites around it, making it tricky to move more than two nearby satellites in a controlled way.
A team of researchers at the University of Kentucky has found a potential solution through the use of a different approach, called Alternating Magnetic Field Forces (AMFF).
This approach allows two satellites to communicate and control their movement relative to each other without interfering with a third nearby satellite. To do this, the researchers used unique interaction frequencies, which means that two satellites can communicate and coordinate their movement on one frequency while simultaneously communicating with other nearby satellites on different frequencies.
The AMFF concept was tested on Earth rather than in space. Three satellites were placed on special linear rails that use high-pressure air to create a low-friction environment. The satellites successfully managed to interact with each other, moving to precise distances the researchers had defined with the help of in-built laser ranging modules.
The team behind the project did not respond to interview requests. But Alvar Saenz Otero at the University of Washington says that the paper is a step forward in a long-running area of research. “The complexity of formation flying systems takes a big jump from two units to three units,” he explains.
But Otero is less certain whether we’re likely to see this driving satellites in low Earth orbit, including in the mega constellations of satellites like those powering Starlink. “Everything we ever did for EMFF was always about deep space operations,” he says.
Earth’s atmosphere, as well as the moon and sun, can create interference at the frequencies used for either EMFF or AMFF, he says.
And while three units can now fly in unison and be moved using magnetic fields, scaling that up to control the movement of thousands of satellites is a different task entirely. “It’s not something that applies at a constellation level,” says Ray Sedwick at the University of Maryland.
“The range that EMFF can work over increases significantly if you employ superconducting magnetic coils, but there are technical challenges here,” explains Sedwick – suggesting that magnetic movement at a grand scale is a while off yet.
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