Most of the talk around servicing satellites has this shiny, affirmative air. But the same type of technology that allows you to get intimate with one satellite and improve it also lets you harm it. Servicing satellites could double as weapons.

Restore-L and RSGS’s maker doesn’t put much weight to that argument. They're not designed for that, he says. "Just about anything could be seen as a weapon," says Tadros. "My kids throw their toys at me, and I’m sure that wasn’t the designer’s intent, but it hurts."

Besides, he says, people on Earth—governments, as well as amateur satellite-spotters—are watching what happens up there. It’s hard to hide in space. In part because of that transparency, operators tend to play nice. "There’s already kind of an implied trust there that people are behaving," says Tadros.

"There are a lot of cheaper ways to make a weapon than billion-dollar satellite servicing," he adds. "But maybe I’m not a criminal mind."

Still, Darpa realizes the situation in space is touchy. Soon after the agency started RSGS, it also funded a kind of consciousness-raising group to talk through complications and come up with best practices. It’s called Confers, which is (of course) an acronym, standing for Consortium for Execution of Rendezvous and Servicing Operations.

Brian Weeden, who works at the Secure World Foundation, a think tank, heads the group, which currently has 11 companies on the roster. "We’re focused on a level of transparency that’s going to assuage concerns," says Weeden, "and will create confidence that these companies are doing what they’re supposed to be doing."

There’s a loud voice of dissent out there. That voice bellows from Brian Chow, a policy analyst who’s written extensively about the threat that servicing satellites can pose, in academic papers and op-eds. He uses terms like "space stalkers," "the silent Apocalypse Next," and "Pearl Harbor in Space." He is not kidding around.

"When you talk about a major technology revolution, it comes with good and bad," says Chow. But this time, it's different: The good and the bad are identical twins. "It’s not two different applications in two different systems," he says, like nuclear bombs and nuclear power. A space servicer is, by its very design, a space stalker.

Because servicing satellites have a peaceful purpose, it's not practical to ban them. That, says Chow, makes them the perfect cover. Launch 'em. Say, "They’re for servicing!" Service something sometimes. Then go bend the antenna on a foe's GPS satellite.

And while, of course, the US is not always a stand-up actor, Chow is concerned about China and Russia, where engineers are also developing and launching such satellites, and their militaries are more enmeshed with even the peaceful parts of the space programs. "At a moment’s notice, at any time, they can just redirect those things," he says.

Amateurs on the internet and the Air Force could see that redirection. Satellites, streaking across the sky faster than stars, are often visible from the ground, even with the naked eye. Their radio communications can sometimes be intercepted with homemade antennas. If you're more sophisticated, like the Air Force, you can use big telescopes and radar systems to watch passively and ping satellites like you would ships. But while the Outer Space Treaty prohibits harmful interference (like breaking antennas), no definitive laws spell out when to perceive proximity as a threat, and react accordingly. Respond too soon and you could set off an international incident.

A few solutions exist, as Chow sees it: Establish "self-defense zones" around satellites, a circumference beyond which the US could take action if sufficiently threatened. The specific size of that zone would be for others to decide, but right now, if two satellites could probably come within a kilometer or so of each other, the Joint Space Operations Center sends its highest-level emergency message. And if the US establishes these zones, says Chow, the country should pledge to give the same space to others.