STS-121 – First spacewalk complete

by Chris Bergin

Astronaunts Piers Sellers and Mike Fossum have completed the opening EVA (spacewalk) of STS-121.

The spacewalk saw the astronauts perform Orbiter tile repair worksite stabilization tests – which appeared to go well, while they also restored one of two failed ISS mobile transporter umbilical guides, and transfered logistics items.

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Seven hours and 39 minutes was the total duration of EVA-1. Official start Quest repressurization was called at 4:49 pm CDT.

Fossum and Sellers departed from the Quest Airlock to begin maintenance of the ISS Mobile Transporter by either safing or replacing an automatic cable-cutter unit, housed in the Interface Umbilical Assembly.

The Trailing Umbilical System cable which provides power, command, data and video connections to the Mobile Transporter will then be re-routed back through the Interface Umbilical Assembly. The cable was moved out of range of the cable cutter during Expedition 12 to prevent accidental severing.

Crewmembers tested a manned orbital boom to determine the stability of the Shuttle’s robot arm when equipped with a 50-foot extension. On the end of the arm they performed simulated EVA inspections and repair movements as the arm is moved to various positions while the loads are being measured.

That include ‘pushing’ against a truss section to test how much loading the boom can handle – in case of a requirement for the boom to be a work platform for any future TPS (Thermal Protection System) repair work in the future.

Results will be used to develop load-minimizing techniques, worksite stability requirements, and associated hardware in order to accomplish EVA inspection and repair of the Shuttle tiles.

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