When astronauts work outside the International Space Station, they remain tethered to it with a very strong cable. Nonetheless, NASA has made preparations for the unlikely event that the tether breaks. Astronauts have an emergency jetpack that they can use to move back to the station. But what if the astronaut is unconscious or the jetpack fails?
Jim Oberg, a space journalist who worked at the space shuttle’s mission-control center for 22 years and specialized in rendezvous procedures, weighs in on the options for rescue. The station’s robotic arm, he explains, is usually not within range of where the astronauts work and moves too slowly to grab someone. The Soyuz vehicles need a full day to power up and undock. By then, the carbon dioxide filters in the astronaut’s spacesuit would run out, asphyxiating him. And the ISS cannot redirect its positioning rocket quickly enough to catch up to a runaway astronaut.
In a worst-case situation, the only rescue option, according to Oberg, would be for a second astronaut to link together several tethers end-to-end, attach them to the station, and then use his Safer pack to jet over to his crewmate and haul him in. Certain conditions could make a rescue easier, he says. If an astronaut floated away more or less at a right angle from the station’s orbit, orbital dynamics (which require too much math to explain here) dictate that he would float back toward the station in about an hour.
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