NASA has scheduled an unplanned spacewalk to replace a failed computer outside the International Space Station (ISS). The announcement was made last Tuesday, May 23.

The astronauts will replace a major system, said NASA. The unit to be replaced is a relay box that's considered as a primary device. Currently, the ISS is using the backup system due to the technical glitch. Although the space station system connected with the computer still works, the failed unit had to be replaced immediately.

Reports say the malfunctioning computer is linked to routing commands for the solar power system, radiators, cooling loops and other equipment of the ISS. Thus, the emergency spacewalk to replace the faulty computer is the only solution to the predicament.

The ISS currently has five crew members composed of astronauts and cosmonauts from NASA, ESA and Roscosmos. Assigned astronauts for the emergency spacewalk are station commander Peggy Whitson and flight engineer Jack Fischer. Both are NASA astronauts.

According to NASA, the emergency spacewalk will last for about two hours. As early as 7:20 am Tuesday, NASA astronauts already initiated battery power systems of their spacesuits in preparation for the emergency spacewalk.

"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," a NASA official said in a press release. "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 replaces the failed relay box, Fischer is responsible for installing two antennas to enhance wireless communications for future spacewalks. The said emergency spacewalk will be aired on NASA TV and NASA's official website.

Spacewalks are performed in a routine in order to maintain equipment, troubleshoot devices and enhance systems aboard the ISS. Usually, two astronauts walk in tandem while ISS crew inside the space station and the ground control systems assist the astronauts during a spacewalk.