Astronauts aboard the International Space Station may need to perform an unplanned spacewalk to repair a computer. This incident could also delay the launch of a cargo ship bringing supplies to the international crew.
The Multiplexer-Demultiplexer (MDM), a backup computer aboard the ISS, failed on April 11. The device controls several of the robotics systems on the space station. A primary robotics computer is still operating normally, so there is no immediate cause for alarm, according to NASA.
ISS mission planners still have hopes of bringing the secondary computer back online. If the problem cannot be resolved between ground controllers and the crew inside the craft, replacing the defective unit may become necessary. This would require a spacewalk to remove the old MDM and replace it with a new unit.
A SpaceX Dragon spacecraft is due for launch to the space station on April 14. The robotics systems the MDM computers control are needed to perform the rendezvous with the resupply vessel. The Dragon is due to launch aboard a Falcon 9 rocket from Cape Canaveral. If a spacewalk is necessary to restore backup systems, the launch of the resupply vessel will be delayed.
The Dragon resupply mission will deliver about 5,000 pounds of needed supplies to the crew aboard the station.
The Optical Payload for Lasercomm Science (OPALS) will test new communications technology for a laser-based communication system that promises to be 10 to 100 times faster than equipment in use today. The experiment will send a video from the ISS to the ground, using a two-way system of lasers.
"It's like trying to use a laser to point to an area that's the diameter of a human hair from 20 to 30 feet away while moving at [one-third of a mile per hour]. It's all about the pointing," Bogdan Oaida, OPALS systems engineer at JPL, said.
The capsule will depart with around 3,500 pounds of materials, headed back for Earth. Among these are samples from science experiments and assorted hardware.
"The station is set for an orbital reboost Saturday morning when the ISS Progress 53 resupply craft, docked to the Zvezda service module, will fire its thrusters for 13 minutes, 32 seconds. This will put the orbital lab at the correct altitude for a crew swap in May," NASA wrote in a press release announcing the MDM failure.
The crew of the ISS had April 11 off as a holiday - Cosmonautics Day, celebrating the anniversary of Yuri Gagarin becoming the first human in space in 1961.
Rick Mastracchio, Mikhail Tyurin, and Koichi Wakata will return to Earth on May 14 aboard a Soyuz spacecraft. On May 29, Maxim Suraev, Alexander Gerst, and Reid Wiseman will arrive at the ISS, as part of Expedition 40/41.
