Private mission to space station scrubbed half a second before liftoff

The historic launch of SpaceX's Falcon 9 rocket, with its Dragon capsule filled with food, supplies and science experiments, was halted when a flight computer detected "high pressure in the engine 5 combustion chamber," the company said in a statement.

"We have discovered the root cause and repairs are underway," it said.

SpaceX now plans a pre-dawn launch as early as Tuesday at NASA's Kennedy Space Center. Liftoff is scheduled for 3:44 a.m. ET, according to the statement released late Saturday.

"During rigorous inspections of the engine, SpaceX engineers discovered a faulty check valve on the Merlin engine. We are now in the process of replacing the failed valve," the company said Saturday. "Those repairs should be complete tonight."

SpaceX president Gwynne Shotwell told reporters earlier in the day that aborting the liftoff at the last second was not a failure.

"We aborted with purpose. It would have been a failure if we lifted off with an engine trending in this direction."

The mission is designed to establish whether SpaceX can deliver cargo to the station.

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