Orbital Sciences Corp. of Dulles, Va., will postpone by at least 24 hours the launch of its Antares rocket and Cygnus spacecraft on a demonstration mission to the International Space Station. The new launch window is targeted for Wednesday, Sept. 18 between 10:50 to 11:05 a.m. EDT from the Mid-Atlantic Regional Spaceport Pad-0A at NASA’s Wallops Flight Facility in eastern Virginia.