WASHINGTON — Orbital Sciences Corp. has delayed by one day, to July 12, the launch of its second cargo resupply mission to the international space station after severe thunderstorms the night of July 8 prevented the company from rolling its Antares rocket out to its launch pad on Wallops Island, Virginia, the following morning, Orbital said in a July 9 press release.

Despite the one-day slip, which Orbital attributed to a compressed schedule of events leading up to the launch, the company’s Cygnus cargo capsule is still expected to berth with the space station the morning of July 15, the press release said.

Backup launch dates are available through July 17, Orbital spokesman Barron Beneski wrote in an email. However, “a launch after the 14th would require additional consultation with NASA,” he said.

The mission, dubbed Orb-2, was once scheduled to lift off in May but was put on hold after an AJ-26 rocket engine slated for use in a 2015 Antares/Cygnus cargo mission failed on the test stand at NASA’s Stennis Space Center in Mississippi. Orbital, along with its main propulsion contractor, Aerojet Rocketdyne of Sacramento, California, are still investigating what went wrong. 

However, tests in Virginia have determined the pair of AJ-26s integrated with the Antares at the Mid Atlantic Regional Spaceport on Wallops are ready for the upcoming flight, the second of eight Orbital owes NASA under a $1.9 billion Commercial Resupply Services contract signed in 2008. The contract runs through 2015 and calls for delivery of at least 20,000 kilograms of cargo.

The Orb-2 Cygnus capsule will remain at the space station for about 30 days, after which it will separate from the orbital outpost and dispose of some 1,300 kilograms of trash during destructive re-entry into Earth’s atmosphere.

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Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...