Nasa explores how to keep international space station in orbit without Russian help

Space agency says Northrop Grumman and SpaceX could assist after Russia raises prospect of pulling out over sanctions punishing its invasion of Ukraine

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Nasa is exploring ways to keep the international space station in orbit without Russian help, but doesn't see any immediate signs Moscow is withdrawing from the collaboration after the invasion of Ukraine.

The US side of the international space station (ISS) supplies power and life support, Russia is responsible for propulsion and keeping the station afloat: it does this by using docked Progress spacecraft to periodically give the station a boost to maintain its altitude of approximately 400km (250 miles).