EVA Systems
Section 4.3.8.
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EVA Safety Tether Design

The off-the-shelf design for the EVA safety tether: it's 50 feet long and rolls up on a retractable reel. Normally the reel keeps 1-2 lbs force on the tether, to keep it from making a mess.

(Anecdote: On one Shuttle flight, that light pull on the safety tether lead to an interesting moment when an astronaut let go of his handrail. He was working at the bottom of the payload bay when he came loose, and wound up sailing out over the Shuttle wing before his tether reel hauled him in.)

At each end of the tether is a latching hook reminiscent of mountain climbing equipment -- a small hook attached to a D-ring on the space suit waist ring, and a large hook for attaching to tether points (the yellow EVA handrails). The latches on the large tether hooks are designed to be operated by an astronaut wearing EVA gloves; they've worked without failure for several years now, and only one astronaut (that I know of) has had difficulty with their operation.

The smaller hook, normally attached to the suit waist ring, is difficult to operate with gloves on. That's good, because it forces the crewmember to work hard in order to kill himself.

The tethers are attached to the yellow handholds on the outside of the SpaceHab module, and will play a major safety role in the docking of the ascent vehicle and LTV after the crew departs fromt the lunar habitat.

EVA Systems

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