SpaceX delays flight to replace stranded astronauts after launch pad problem

A SpaceX Falcon 9 rocket with the Crew Dragon spacecraft (John Raoux/AP)

A launch pad problem has prompted SpaceX to delay a flight to the International Space Station to replace Nasa’s two stranded astronauts.

The new crew needs to get to the ISS before Butch Wilmore and Suni Williams can head home after nine months in orbit.