By Irene Klotz
A SpaceX Falcon 9 rocket was being readied for launch from Florida on a mission to thrust a European satellite toward orbit and then attempt a return touchdown on an ocean platform, company officials say.
The 23-storey-tall rocket, carrying a commercial communications satellite for Luxembourg-based SES SA, was scheduled to blast off from Cape Canaveral Air Force Station at 6:46pm EST on Wednesday.
Meteorologists forecast a 60 per cent chance that weather at the cape would be suitable for liftoff.
The flight would be the second of more than 12 planned this year by Space Exploration Technologies, the private rocket launch service owned and operated by high-tech entrepreneur Elon Musk.
It would also mark the fourth attempt at a return sea-based landing of the Falcon 9's main stage, a milestone in Musk's goal to develop a cheap and reusable booster.
The rocket's main section is supposed to separate from the second stage about 2.5 minutes after launch, turn around and attempt to land itself on a platform floating in the Atlantic about 400 miles (645 km) east of Cape Canaveral.
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.
The rocket flying on Wednesday, which will be carrying the 12,613-pound (5721kg) Boeing-built SES-9 satellite, will be travelling too fast to try to get back to a landing pad at Cape Canaveral, prompting SpaceX to try the ocean landing instead.
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 would have no problem in flying a re-used (rocket's) first stage. If it's flight-worthy, we're happy," Halliwell said.
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 US$61 million, the company's website shows.