Naturally, NASA spends a lot of time working on not dropping things. Every tool is attached to a tether that should be linked to a suit or the station at all times: Wray says astronauts learn a protocol known as “make before you break,” to remember to hook each tool down before they lose contact with it. But over the course of a six-hour spacewalk, concentration can lapse—especially when all those tethers are floating in micro-gravity and bumping into each other in your tool box.

“I also come up with the most efficient tool configuration,” Wray says. “The best way to reduce the risk of losing a tool is to reduce the number of tools on a spacewalk, but you never know if you’re going to need an extra pry bar or torque wrench in case you encounter something off-nominal.”

The good news when it comes to lost objects in low-earth orbit, about 250 miles (402 kilometers) above the earth, is that most soon drift into the atmosphere below and burn up. The most important thing is avoiding near-term damage to the space station.

“Ideally if a crew member were to drop something, we’d want it to be heading nadir—towards the earth—and in the aft direction, so its falling orbit would be lower than the space station,” Wray says. “If it went zenith, in a way, you’re sort of pushing it into a higher orbit and possibly a higher velocity, its next orbit could collide.”

Luckily, the ISS is usually equipped to boost its altitude thanks to rocket engines on the Russian module, which it does to maintain altitude and dodge orbital debris, whether created by astronauts or anyone else.

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