Steve Helber / AP
Orbital Sciences Corp.'s Antares rocket vents fuel as it sits on its Virginia launch pad.
Orbital Sciences Corp. is postponing the maiden launch of its two-stage Antares rocket until Saturday at the earliest, due to an unfavorable weather forecast for Friday.
The Antares rocket was originally due to blast off Thursday from the Mid-Atlantic Regional Spaceport on Wallops Island, Va., and go on an orbital test flight in preparation for cargo trips to the International Space Station. That first launch attempt was aborted with 12 minutes to go in the countdown, because an umbilical data cable was unplugged prematurely from the rocket's upper stage.
Orbital determined that the cable was pulled out because of a "slight hydraulic movement" of a launch pad structure. The company also said there wasn't enough slack in the cable. "Neither issue alone would have caused the umbilical disconnect, however, the combination resulted in the anomaly," Orbital said in a mission update on Thursday. Small adjustments were made to the launch pad equipment to fix the problem, and the launch team started making preparations for liftoff on Friday.
Later Thursday, Orbital said weather conditions at the Virginia pad were expected to deteriorate on Friday and then improve significantly. The launch team decided to wait out Friday's weather and aim for launch at 5 p.m. ET Saturday. Sunday would serve as a backup launch opportunity.
The Antares is due to launch a dummy payload into orbit as a rehearsal for future flights that would send robotic Cygnus cargo carriers to the space station. If Orbital's test flights are successful, the Virginia-based company could begin cargo runs under the terms of an eight-mission, $1.9 billion resupply contract with NASA. California-based SpaceX is already flying its Dragon cargo capsules to and from the space station under a separate 12-mission, $1.6 billion contract.
NASA struck deals with Orbital and SpaceX to provide U.S.-based cargo transfer capability in the wake of the space shuttle fleet's retirement in 2011. The space agency is also working with SpaceX and two other companies, Boeing and Sierra Nevada Corp., to develop crew-capable spaceships for space station trips. Yet another NASA program is aimed at creating a new heavy-lift rocket and Orion crew vehicle for journeys beyond low Earth orbit.
More about the Antares rocket:
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.