This article is more than 1 year old

This article is more than 1 year old

The International Space Station has been hit by a major power shortage that has forced a delivery from SpaceX to be delayed.

SpaceX was supposed to launch a shipment on Wednesday. But an old power-switching unit malfunctioned at the space station on Monday and knocked two power channels offline. The six remaining power channels still worked normally, according to Nasa.

Nasa said on Tuesday that the station and its six astronauts were safe. But because of the hobbled solar-power grid, the SpaceX launch of a Dragon cargo capsule was put off until at least Friday. Nasa wants to replace the failed unit to restore full power before sending up the SpaceX Dragon cargo capsule.

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The breakdown has left the station’s robot arm outside with one functioning power channel instead of two. Two power sources are required – one as a backup – when the robot arm is used to capture visiting spacecraft like the Dragon cargo capsule.

Flight controllers will use the robot arm to replace the faulty unit with a spare later this week, saving the astronauts from going out on a spacewalk.

There is no rush for this delivery. Northrop Grumman launched supplies two weeks ago.

Solar wings collect and generate electricity for the entire space station. Any breakdown in this critical system can cut into power and affect operations.

SpaceX, meanwhile, is still investigating this month’s loss of its new Dragon capsule designed for astronauts.

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Six weeks after a successful test flight without a crew to the space station, the crew Dragon was engulfed in flames during a ground test. SpaceX was in the process of firing the capsule’s thrusters on a test stand.

SpaceX and Nasa have offered few details. But the accident is sure to delay launching a crew Dragon with two Nasa astronauts on board.

• This article was amended on 8 May 2019. An earlier version carried a photograph of the SpaceX crew Dragon. This has been replaced with an image of the space craft whose launch was delayed – the Dragon cargo capsule.