WALLOPS ISLAND, Va. — Orbital Sciences Corp. has been cleared to launch the Antares rocket April 17 on its inaugural flight.

Weather permitting — and forecasts show a chance of showers here around launch time — liftoff is scheduled for 5 p.m. EDT.

Orbital aborted a countdown rehearsal April 13 because of a faulty valve in one of the two Aerojet-supplied AJ-26 liquid kerosene engines that power the Antares’ first stage. The valve was replaced April 14.

NASA Wallops Flight Facility Site Director Bill Wrobel on April 16 gave the test launch the formal go-ahead. The so-called Authority to Proceed followed a launch readiness review “at which Orbital managers gave a ‘go’ to proceed to toward launch,” NASA said in a statement.

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...