They keep saying these two words, but I don't think those words mean what they think they mean. A messy sentence if ever there was one, but the phrase the authors keep tossing around is a "Tractor Beam" and the article is about real work being done in universities to develop one.
Everyone who has watched sci-fi movies or TV shows is probably familiar with the term tractor beam. They are energy beams that one ship uses to hold onto another ship and keep it from doing what the second ship's crew wants it to do. Like here, where a Borg cube ship holds the Enterprise (from Star Trek:TNG) and keeps it from fleeing - or keeps it from doing what Captain Picard wants.
There have been scenes in these shows where one ship tows another, as if connected by physical ropes and chains. Same idea.
Instead what the researchers are working on developing is an electrostatic field generator. Their goal is to use this electrostatic field to pull (or push) satellites out of the Geostationary Orbit when they reach End of Life. Space junk and getting rid of it is becoming a big name field, with the Senate recently working on bills telling NASA to manage it better.
What's the difference? Well, the tractor beam imagined in the picture above, holds the Enterprise motionless. If the Enterprise tries to leave, the force gets stronger to keep it from leaving. I've seen shows use a tractor beam as some sort of landing assistance to get a ship into a large space station or other dock.
The system I see described is going to impart a charge on the satellite and on itself; if those charges are opposite (which they will be unless they have some fancy tricks) they will be attracted to each other. If the charges are the same, they'll repel each other. Slowly, barely perceptibly at first, but accelerating with time, unless those charges are bled off to reduce the attraction. Further, they aren't going to do this with one satellite in low Earth orbit and the other in the GEO, the satellites will be close to each other.
The electrostatic tractor would use a servicer spacecraft equipped with an electron gun that would fire negatively charged electrons at a dead target satellite, Champion told Live Science. The electrons would give the target a negative charge while leaving the servicer with a positive charge. The electrostatic attraction between the two would keep them locked together despite being separated by 65 to 100 feet (20 to 30 meters) of empty space, she said.
Once the servicer and target are "stuck together," the servicer would be able to pull the target out of orbit without touching it. Ideally, the defunct satellite would be pulled into a "graveyard orbit" more distant from Earth, where it could safely drift forever, Champion said.
The person referred to by the name Champion is project researcher Kaylee Champion, a doctoral student in the Department of Aerospace Engineering Sciences at the University of Colorado Boulder (CU Boulder).
I can't get past some gigantic holes I see in what they're saying. Maybe they think they're keeping their ideas confidential, but I don't see how they keep the target satellite from closing the distance to the servicer. They go on to say that the field would have to be weak and work over long periods of time, but eventually, there's nothing to stop the target from hitting the servicer. This is zero gravity and zero friction, after all, and there's nothing to slow or stop that target once it's moving. If they suddenly reduced the charge differential between the two, the target may stop accelerating, but it doesn't slow or stop moving unless they change it to being repelled. Perhaps they need to modulate the charge periodically back and forth between attraction and repulsion?
The electrostatic attraction between the two spacecraft would be extremely weak, due to limitations in electron gun technology and the distance by which the two would need to be separated to prevent collisions, project researcher Julian Hammerl, a doctoral student at CU Boulder, told Live Science. So the servicer would have to move very slowly, and it could take more than a month to fully move a single satellite out of GEO, he added.