Update at 6:21 p.m. ET. Launch Delayed:
Space.com reports that the Antares rocket launch has been delayed for two days, "after an unexpected glitch."
"With just minutes remaining before a planned 5 p.m. EDT (2100 GMT) launch Wednesday (April 17) from a newly refurbished pad here at NASA's Wallops Flight Facility, a connecting cable popped free from the Antares rocket's second stage, forcing controllers to abort the attempt."
Our Original Post Continues:
Orbital Sciences Corp., a commercial space contractor, hopes Wednesday to conduct the first test launch of its Antares rocket, designed to ferry cargo to the International Space Station.
The two-stage rocket, a milestone for commercial space flight, is scheduled to lift off from NASA's Wallops Flight Facility in Virginia at 5 p.m. ET. In theory, millions of people along the Eastern Seaboard should be able to see the launch.
Frank Culbertson, vice president at Orbital Sciences Corp., said "it's going to be the biggest and loudest and brightest thing that ever launched from Wallops, I believe, so it'll be visible up and down the coast."
"If all goes as planned, the unmanned rocket's practice payload will be vaulted into orbit from Wallops Island before burning up in the atmosphere on its return to Earth several months later."
The newspaper says the goal of the launch is "to make sure the rocket works and that a simulated version of a cargo ship that will dock with the space station on future launches separates into orbit. Orbital officials say that should occur about 10 minutes after liftoff."
NPR's Geoff Brumfiel says Wednesday's launch is only a test and that "if successful, the next trip will deliver supplies to the station. That would make Orbital the second private company after California's SpaceX to dock with the space station."
As of early afternoon, Wallops reported "a 45 percent chance for launch based on weather. The primary weather constraint of concern is a cloud layer at the opening of the launch window."