Nasa astronauts are being scrambled for an emergency spacewalk on the International Space Station (ISS) after critical control systems failed over the weekend.

Engineers will step outside the orbital station on Tuesday (23 May) to replace a failed computer that regulates major power, heating and cooling systems alongside other ISS equipment, reports Reuters.

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The malfunctioning computer is one of the two primary devices that control major systems aboard the $150bn space station, which orbits some 400km above the Earth's surface.

Nasa said the space station's five-person crew from the US, France and Russia are not in any danger. However, they will have to rely on a backup system until the repairs, expected to take up to two hours, can take place.

A spare electronics box to replace the failed device has already been prepared and tested, according to the space agency. Nasa veteran and ISS commander Peggy Whitson and flight engineer Jack Fische will be charged with installing the device during the spacewalk.

Telerobotic handshake received from International Space Station
The ISS orbits the earth at nearly 28,000 km/h and has been continually staffed since 2000. NASA

The last emergency spacewalk on the ISS took place in December 2015, when two crew members were sent out to fix a problem with the satellite's Mobile Servicing System – the robotic arm used for maintenance and receiving cargo payloads sent up from earth.

The ISS has been continually manned for the past seven years and serves as an observational outpost as well as a research lab for scientific experiments.

NASA