SpaceX has set back the date for its next Falcon 9 launch until sometime in January. The company says the much anticipated return after a Falcon 9's launchpad explosion on September 1 was delayed to make time for close-out vehicle preparations and complete extended testing to ensure the safety of the flight.

The Falcon 9 carrying 10 Iridium communications satellites was originally scheduled to lift off from Vandenberg Air Force Base in California on December 16 after previous delays due to the accident where a Falcon 9 booster suffered a second stage explosion while refueling. The accident resulted in the destruction of the rocket and payload.

The exact cause of the malfunction has yet to be officially determined, but it's believed to be the failure of one of the helium bottles in the liquid oxygen tank of the second stage. In a media interview, SpaceX founder and CEO said the bottle failure was due to the liquid oxygen solidifying around the helium bottle, where it interacted with the graphite fibers used to reinforce the bottle, but this hasn't been confirmed by the company.

One factor in the delay is that the accident is currently under investigation by a team from SpaceX, the US FAA, US Air Force, industry experts, and NASA. Until the FAA signs off on the final accident report and gives SpaceX a license to fly, the Falcon 9 will remain grounded. In addition, NASA has voiced concerns about SpaceX's use of supercooled liquid oxygen, which requires unconventional fueling schedules.

Source: SpaceX