WASHINGTON — Following a successful test firing of its main engine Feb. 25, the Antares rocket developed by Orbital Sciences Corp. is in final integration at its Virginia launch site and scheduled to roll out to the pad in mid-March in preparation for an early April debut, a company official said Feb. 28.

Antares, developed with financial assistance from NASA, will be used to launch Orbital’s Cygnus cargo to the international space station (ISS) under an eight-flight, $1.9 billion services contract awarded by the space agency in 2008.

Before Dulles, Va.-based Orbital can begin routine deliveries, however, it must carry out two successful Antares demonstrations, the second of which will carry a station-bound Cygnus capsule. The first will attempt to place a simulated Cygnus capsule into the initial orbit used for space station deliveries.

The Antares team at NASA’s Wallops Flight Facility in Wallops Island, Va., and the Virginia Commercial Space Flight Authority that operates the launch pad will spend the next five to six weeks refurbishing the platform and parsing a mountain of data from the 29-second hot fire of the rocket’s core stage.

According to the data examined so far, Antares passed “with flying colors,” Mike Pinkston, Orbital’s program manager for Antares, said Feb. 28.

Pinkston said the just-fired core stage will remain on the pad through the first week of March, and then be brought back to Orbital’s nearby Horizontal Integration Facility, where it will be refurbished for a future station resupply mission. A week later, a fully integrated Antares, carrying a Cygnus mass simulator, will be brought to the pad.

“The test-mission rocket itself is really all but done,” Pinkston said. “It’s actually tracking to a schedule that’s ahead of the activities we’ve got going on at the pad, so the rocket itself won’t be our critical path.”

Once raised at the pad, Antares will undergo a roughly two-week series of checks to verify the fully integrated rocket along with its interfaces with the pad and launch range, Pinkston said. “Then we will go through a wet-dress rehearsal, which will fuel and then defuel the rocket.”

Pinkston would not say what day Orbital has targeted for launch.

Antares will launch from Pad-0A at the Mid-Atlantic Regional Spaceport, which is operated by the state of Virginia. The Virginia Commercial Space Flight Authority leases Pad-0A to Orbital, which last year signed a deal with the state for 10 Antares launches. The state is charging Orbital $1.5 million per launch.

Dale Nash, executive director of the Virginia Commercial Space Flight Authority, said Pad-0A fared well after the Antares hot fire.

“We thought we would have to do a fair amount of repair to the flame trench, but it really came through well,” Nash said March 1 in a phone interview.

The authority, which outfitted Pad-0A to handle the liquid-fueled Antares, has one more construction item on its to-do list ahead of the rocket’s debut: connecting an additional helium subcooler to the pad’s network of plumbing.

“There is an existing cooler right now that cools liquid oxygen and chills helium,” Nash said. “We wanted to get better chilling on the helium, so there’s an additional subcooler that’s been there that hasn’t been hooked in yet.”

 During the April demonstration launch, NASA technicians at Wallops will conduct “tracking and telemetry, range safety and surveillance, control center operations, optical support, security, and a host of other facility activities,” NASA spokesman Jeremy Eggers said in a Feb. 28 email.

Eggers said representatives from Orbital, NASA and the state of Virginia will meet nine days before the launch for a range readiness review, and again for a launch readiness review two days out.

Assuming Antares is successful, a demonstration mission to the space station would take place sometime this summer, followed by the first contracted cargo delivery mission late this year or early next.

Pinkston said one of the two AJ-26 core-stage engines that would be used for the first contracted delivery has completed acceptance testing at NASA’s Stennis Space Center in Mississippi. The second will complete similar testing in about a month, he said.

Each Antares rocket uses two AJ-26 engines — built in Russia and refurbished by Sacramento, Calif.-based Aerojet — in its Ukrainian-built core stage.

“Roughly speaking, we’re about one engine acceptance test away from having four rockets worth of hardware at Wallops,” Pinkston said.

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...