NASA Replaces a Critical Computer on the ISS During Emergency Spacewalk

NASA astronauts Peggy Whitson and Jack

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Fischer are carrying out a spacewalk today, Tuesday May 23, to replace a computer system on the outside of the International Space Station that unexpectedly failed on Saturday. Whitson, commander of Expedition 51, is replacing the primary multiplexer-demultiplexer (MDM) data relay box used to control a number of systems on the ISS, including the solar arrays, radiators, cooling loops, and other equipment.

The backup MDM is functioning properly and the astronauts are in no immediate danger, but until the new system is installed there will be no redundancy for a number of computer control systems on board the station. Whitson assembled and tested a new MDM box on Sunday, and today she successfully slotted the new data relay box into the S0 truss of the ISS and secured it with bolts, precisely drilled in using NASA's space drill, called the pistol-grip tool. Flight controllers on the ground powered up the new system and declared the mission to replace the MDM a success after 2 hours and 18 minutes of work.