This NASA article covers a 3-day management and crew research procedure from ground control to crew activity to complete replacement of a faulty data relay (MDM) and installation of new wireless antennas while on a short, planned spacewalk. Please follow the time-stamped threads below.
Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer of NASA concluded their spacewalk at 10:06 p.m. EDT. During the spacewalk, which lasted two hours and 46 minutes, the two astronauts successfully replaced a computer relay box, and installed a pair of antennas on station to enhance wireless communication for future spacewalks.
Spacewalkers have now spent a total of 1,250 hours and 41 minutes working outside the station during 201 spacewalks in support of assembly and maintenance of the orbiting laboratory. This was the 10th spacewalk for Whitson, who moves into third place all-time for cumulative spacewalking time, and the second for Fischer.
About three hours earlier the two astronauts began their spacewalk excursion outside the Destiny module:
The relay box, known as a multiplexer-demultiplexer (MDM), is equipped with upgraded software installed in the truss March 30 during a spacewalk by Whitson and Expedition 50 commander Shane Kimbrough. Whitson prepared a spare data relay box on Sunday and tested components installed in the replacement. She reported the spare MDM was ready to be brought outside to replace the failed unit.
While Whitson is replacing the MDM, Fischer will install a pair of antennas on the U.S. Destiny Laboratory module to enhance wireless communication capability for future spacewalks. That task was deferred from Whitson and Fischer’s May 12 spacewalk.
Whitson is wearing the suit with red stripes as extravehicular crew member 1 (EV 1). Fischer, extravehicular crew member 2 (EV 2), is wearing the suit with no stripes.
The day before the spacewalk, preparations were underway:
Astronauts Peggy Whitson and Jack Fischer are getting ready for a contingency spacewalk Tuesday morning. Whitson and Fischer are set to begin the spacewalk at 8 a.m. Tuesday for about two hours of maintenance work. NASA Television coverage will begin at 6:30 a.m.
The spacewalkers are gathering their tools and checking their spacesuits today with assistance from Flight Engineer Thomas Pesquet. The trio are also reviewing the contingency spacewalk procedures.
The spacewalk’s primary task is the removal and replacement of a data relay box, known as a Multiplexer-Demultiplexer (MDM), which failed Saturday morning. The MDM controls the functionality of station components such as the solar arrays, radiators, cooling loops and other systems.
Whitson will replace the failed MDM with a spare unit on the Starboard Zero truss. The truss is attached to the space-facing side of the U.S. Destiny lab module and is the centerpiece of the station’s truss structure which houses the solar arrays, radiators and cooling loops. Fischer will install a pair of wireless communications antennas on the Destiny Lab, a task that was postponed during the May 12 spacewalk.
Tuesday’s spacewalk will be the 201st in support of station assembly and maintenance. This will be Commander Whitson’s 10th spacewalk likely moving her to third place all-time in cumulative spacewalking time. Flight Engineer Fischer will be embarking on his 2nd spacewalk.
Earlier, the planning continues:
Whitson and Fischer will replace a critical computer relay box that failed on Saturday, May 20. The relay box, known as a multiplexer-demultiplexer (MDM), is one of two units that regulate the operation of radiators, solar arrays and cooling loops. They also will route commands to other vital station systems and install a pair of antennas to enhance wireless communication.
Because each MDM is capable of performing the critical station functions, the crew on the station was never in danger and station operations have not been affected.
The spacewalk will be the 201st in support of space station assembly and maintenance, the sixth spacewalk conducted from the Quest airlock this year, the 10th for Whitson and the second for Fischer.
After much planning for the upcoming spacewalk to address present issues:
International Space Station Program managers met Sunday and gave approval for a contingency spacewalk no earlier than Tuesday by two Expedition 51 crewmembers to change out a multiplexer-demultiplexer (MDM) data relay box on the S0 truss that failed on Saturday morning. The cause of the MDM failure is not known. A final decision on a firm date for the spacewalk and who will conduct the spacewalk will be made later in the day Sunday.
The data relay box is one of two fully redundant systems housed in the truss that control the functionality of radiators, solar arrays, cooling loops and other station hardware. The other MDM in the truss is functioning perfectly, providing uninterrupted telemetry routing to the station’s systems. The crew has never been in any danger and the MDM failure, believed to be internal to the box itself, has had no impact on station activities.
On Sunday, shortly before managers met to discuss the forward plan for dealing with the failed MDM, station commander Peggy Whitson of NASA prepared a spare data relay box and tested components installed in the replacement. She reported that the spare MDM was ready to be brought outside to replace the failed unit. Back on March 30, Whitson and Expedition 50 commander Shane Kimbrough of NASA conducted a spacewalk to install the MDM with upgraded software that failed Saturday.
A similar MDM replacement spacewalk was conducted in April 2014 by Expedition 39 crewmembers Steve Swanson and Rick Mastracchio.
The spacewalk will last about two hours in duration to replace the failed box. No other tasks are planned for the excursion. It will be the sixth spacewalk conducted from the Quest airlock this year.
The decision was made by station control managers for a go ahead spacewalk:
International Space Station Program managers have given the green light for a contingency spacewalk on Tuesday by two Expedition 51 crewmembers to change out a multiplexer-demultiplexer (MDM) data relay box on the S0 truss that failed on Saturday morning. The cause of the MDM failure is not known. After a review of spacewalk preparations and crew readiness throughout the day Sunday, the decision was made to press ahead with the spacewalk on Tuesday. It will be conducted by Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer of NASA.
The data relay box is one of two fully redundant systems housed in the truss that control the functionality of radiators, solar arrays, cooling loops and other station hardware. The other MDM in the truss is functioning perfectly, providing uninterrupted telemetry routing to the station’s systems. The crew has never been in any danger, and the MDM failure, believed to be internal to the box itself, has had no impact on station activities.
On Sunday morning, Whitson prepared a spare data relay box and tested components installed in the replacement. She reported that the spare MDM was ready to be brought outside to replace the failed unit. Back on March 30, Whitson and Expedition 50 commander Shane Kimbrough of NASA conducted a spacewalk to install the same MDM with upgraded software tat failed Saturday.
A similar MDM replacement spacewalk was conducted in April 2014 by Expedition 39 crewmembers Steve Swanson and Rick Mastracchio of NASA.
Tuesday’s spacewalk will last about two hours in duration to replace the failed box. An additional task was added for Fischer to install a pair of wireless communications antennas on the Destiny Lab while Whitson replaces the failed data relay box. The antenna installation task was originally planned for the last spacewalk on May 12.
The contingency spacewalk will be the 201st in support of space station assembly and maintenance and the sixth conducted from the Quest airlock this year.
This will be the 10th spacewalk in Whitson’s career and the second for Fischer. Whitson will be designated as extravehicular crewmember 1 (EV 1) and will wear the suit with the red stripes. Fischer will be extravehicular crewmember 2 (EV 2) and will wear the suit with no stripes.
Tuesday’s spacewalk is expected to begin around 8 a.m. EDT, or earlier, if the crew is running ahead of schedule with its spacewalking preparations. NASA Television coverage will begin at 6:30 a.m.
Written By: Mark Garcia NASA
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