What Would Happen if Astronauts Were Detached From ISS During a Spacewalk?


Answer by Clayton C. Anderson, Retired US Astronaut, Author of The Ordinary Spaceman: From Boyhood Dreams to Astronaut

Becoming detached from the International Space Station (ISS) during an EVA (spacewalk) is a low probability occurrence. While not likely to happen, since it is possible, astronauts prepare for it.

For each and every spacewalk, one of the first — and most critical — steps occurs before ever departing the station’s airlock. With hatches still closed and locked, astronauts verify their individual safety tethers (85 foot braided steel cable w/retractable reel) are appropriately “closed and locked” on their spacesuits. In addition, while inside the station’s “porch,” the two spacewalkers hook their safety tethers together, in a move we call the “daisy chain.” Now, both astronauts are connected to each other, and one of them is also anchored firmly inside the station.

When the hatch finally opens, another critical procedure is executed. The lead spacewalker — EV1 — will exit the airlock headfirst and attach the other (free) end of their safety tether to an anchor point outside. Now, the two still-daisy-chained astronauts are anchored inside and out. At this point, EV1 will break the daisy-chain and hook partner EV2’s safety tether to the external anchor point. Now both crewmembers are safely, and separately, anchored externally.

Exiting the ISS airlock, for my first EVA July 23, 2007.

It is now time for the still-inside EV2 astronaut, to disconnect his/her internal anchor point and exit the hatch. Voila! Two spacewalkers, each safely anchored outside the ISS, ready to go to work.

All of that effort may still not be enough if proper “tether protocol” is not exhibited by our brave spacefarers throughout the spacewalk. As they both —> Read More