14 DAY TRIAL // On Friday, April 11, Expedition 39 crew members aboard the International Space Station (ISS) reported that an external backup computer relay system in the S0 truss, called a multiplexer demultiplexer (MDM), had failed. Though it affects numerous systems both inside and outside the space lab, the issue was not deemed severe enough to delay the launch of a new private resupply mission to the space station.
However, the planned launch attempt scheduled for yesterday was scrubbed, and the SpaceX Dragon capsule and Falcon 9 rocket will launch into space on Friday, April 18. Throughout the weekend, NASA experts met to determine whether or not the failed MDM affected the SpaceX mission in any way. The risk was deemed acceptable, and the mission allowed to proceed, Space Fellowship reports.
The affected computer provides data on how the external cooling loops on the ISS are faring and helps control the motions of the Mobile Transporter shuttle, of the Solar Alpha Rotary Joints, and of the truss system in general. NASA said that a spacewalk is currently being planned to replace the affected MDM with an existing spare part, but added that the event would take place beyond April 22.
This should give SpaceX ample time to launch its Dragon cargo capsule on Friday and have the spacecraft dock to the ISS by Sunday, April 18. Since the vehicle does not feature autonomous rendezvous capabilities, Expedition 39 astronauts will have to capture and reel it in using the Canadian-built Canadarm 2 robotic arm on the station.