Boeing Starliner launch to space station on extended hold after valve problem

The launch of Boeing's Starliner crew capsule on an unpiloted test flight to the International Space Station, a critical stepping stone before astronaut ferry flights can begin, was scrubbed Tuesday because of suspect valves in the capsule's propulsion system.

After troubleshooting, mission managers decided to haul the spacecraft, perched atop a United Launch Alliance Atlas 5 rocket, off the launch pad and back to a processing facility for more extensive inspections to understand why instrumentation readings did not match the actual positions of multiple valves. "We're not proceeding with #Starliner launch tomorrow," Boeing tweeted, ruling out a Wednesday launch attempt. "Our team cycled the Service Module propulsion system valves and is taking time to gather data for next steps. We've ruled out software as a cause for the unexpected position indications."