SpaceX delays rocket launch and ocean-landing over propellant issue

SpaceX on Wednesday postponed for at least 24 hours the scheduled Florida launch of a Falcon 9 rocket on a satellite-delivery mission and attempted return-landing at sea to allow extra time to chill the rocket's propellant, the company said.

Blast-off of the 23-story-tall booster and its payload, a SES SA communications satellite, was rescheduled for 6:46 p.m. EST (2346 GMT) on Thursday from Cape Canaveral Air Force Station, SpaceX said.

"Rocket and spacecraft remain healthy," the company said in a message posted on Twitter as the delay was announced. Hours earlier SpaceX had described weather conditions at the launch site as a "60 percent go" and said it was tracking thick clouds and high winds.

Following the delay, the company issued a further statement explaining: “The team opted to hold launch to ensure liquid oxygen temperatures are as cold as possible in an effort to maximize performance of the vehicle.”

The statement left unclear how much, if any, weather was a factor in the postponement.

Meteorologists forecast an 80 percent chance that weather would be suitable for liftoff on Thursday.

In addition to boosting the 12,613-lb (5,721-g) satellite built by Boeing Co toward orbit, the rocket’s first-stage will attempt to turn around and fly itself back to a platform floating in the Atlantic about 400 miles (645 km) east of Cape Canaveral.

The mission would mark the second of more than 12 planned launches this year by Space Exploration Technologies, the private rocket service owned and operated by high-tech entrepreneur Elon Musk. It also would be the fourth attempt at a sea-based return landing of the Falcon 9's main stage, a milestone in Musk's goal to develop a cheap and reusable booster.

A returning SpaceX rocket successfully touched down at a ground-based landing site near the launch pad in December, but three previous attempts to land a returning rocket on an ocean platform failed.

SES, which currently operates a constellation of 53 satellites, has three more under contract to fly on SpaceX Falcon rockets through 2017, SES Chief Technology Officer Martin Halliwell told reporters at a prelaunch news conference.

SES has started talking with SpaceX about buying a used rocket to fly a future SES satellite but they have not yet agreed on a price.

A new Falcon 9 costs about $61 million, the company’s website shows.

(Reporting by Irene Klotz; Editing by Steve Gorman and Lisa Shumaker)