SpaceX has called off its second attempt in as many days to launch a Falcon 9 rocket on a satellite-delivery mission because of a technical difficulty, a launch commentator says.
The rocket was less than two minutes from lift-off from Cape Canaveral Air Force Station in Florida on Thursday when the launch was scrubbed, SpaceX commentator John Insprucker said during a live launch webcast.
The launch team was overseeing the final loading of super-chilled liquid oxygen propellant into the rocket's first and second stages when the countdown was halted, Insprucker said.
"Preliminary (information) is that we were ... looking at how much time we had left in the count to finish loading the liquid oxygen, and at that time the launch team decided that we would need to hold the countdown," he said.
There was no immediate word on when the launch would be rescheduled.
A launch attempt for the same mission was cancelled on Wednesday to allow more time to chill the liquid oxygen. Lower temperatures increase the fuel's density, adding to its power.
Perched atop the rocket is a 5721kg Boeing-built satellite owned by Luxembourg-based network operator SES SA.
SpaceX is aiming to deliver the satellite as high as 39,000km above earth and still have enough fuel to fly the first stage of the Falcon rocket to a platform floating about 645km off Florida's coast for a return landing at sea.
Three previous attempts at an ocean landing have failed. But in December, a returning Falcon 9 rocket successfully touched down on a ground-based landing pad in Florida, an unprecedented milestone in Elon Musk's quest to develop a cheap, reusable booster.
