WASHINGTON — Orbital Sciences Corp. on Oct. 1 rolled the first stage of its Antares rocket out to the launch pad at NASA’s Wallops Island Flight Facility to prepare for a series of tests that, if successful, will clear the way for the company to begin routine cargo deliveries to the international space station sometime next year.

Dulles, Va.-based Orbital wanted to move the Antares stage to the pad Sept. 27, but a power problem with a transporter vehicle used to haul the rocket from its hangar to the pad, coupled with expectations of foul weather on the Virginia coast during the weekend, prompted the company to delay rollout until Oct. 1, spokesman Barron Beneski said.

With Antares now vertical at the pad, Orbital is preparing for a series of wet dress rehearsals ahead of a planned hold-down test now scheduled to take place over the next several weeks.

“We will conduct a series of three wet dress rehearsals that will take place toward the end of October,” Beneski wrote in an Oct. 3 email. “The first test will flow only liquid oxygen to the launch vehicle. The second test will flow both liquid oxygen and RP-1 fuel to the launch vehicle. The third will replicate an actual mission sequence with a pre-planned countdown hold of three minutes.”

Orbital holds a $1.9 billion NASA contract signed in 2008 that calls for eight cargo flights to the space station. Orbital will deliver that cargo with its unmanned Cygnus space freighter, which Antares will loft to low Earth orbit from Wallops. Before it can collect on the delivery contract, however, Orbital has to complete a hold-down test of the Antares first stage and then conduct two Antares demonstration flights out of Wallops.

The first-stage hold-down test will take place at the pad sometime in the next four to five weeks, Orbital said in its Oct. 1 press release. In the hold-down test, the rocket core’s two liquid engines — Soviet-vintage NK-33s refurbished by Sacramento, Calif.-based Aerojet and rebranded as AJ-26s — will be lit for about 30 seconds. Antares would have its maiden flight a month after a successful hold-down test, Orbital said Oct. 1. Assuming a successful test flight, a full-up Antares-Cygnus stack would be cleared to fly a demonstration cargo run to the space station before the end of the year, Orbital said. In that mission, Cygnus would deliver 550 kilograms of freight and relieve the outpost of about 1,000 kilograms of trash, Orbital said.

Antares will launch all of its space station resupply missions from Pad 0-A at the Mid-Atlantic Regional Spaceport (MARS), a facility at the southern tip of Wallops Island that is operated by the state-funded Virginia Commercial Spaceflight Authority.

Because MARS and Pad 0-A are on a NASA range, the agency had to give its approval for Orbital to begin operations at the launch pad.

“When it comes to the pad, NASA’s role has been in ensuring the pressure systems have been designed, fabricated, and tested in accordance with national and NASA standards,” NASA spokesman Jeremy Eggers wrote in a Sept. 28 email to Space News. “NASA, and the MARS contractor responsible for engineering those systems, reviewed the systems and the data and provided permission for the operations of those systems at Pad 0-A.”

Difficulties with some of this fluid transfer and handling infrastructure at Pad 0-A had delayed critical Antares tests. Orbital blamed the difficulties, and the subsequent delays, on the spaceport. David Thompson, Orbital’s chief executive, has said the Antares schedule would be at the mercy of the Virginia Commercial Spaceflight Authority until work on the pad was complete.

“Once the pad turnover happens, we’ll have only ourselves to blame if we miss the schedule,” Thompson said during a February earnings call with investors and analysts.

Since 2008, Orbital and the state of Virginia had been de facto partners at MARS, with each contributing funding and expertise to build a liquid fueled-rocket launch pad at the state-operated spaceport.

That relationship changed significantly this year, with Orbital transitioning from co-operator to spaceport tenant. In April, Virginia Gov. Bob McDonnell signed legislation that increased the Virginia Commercial Spaceflight Authority’s annual budget, allowing the state to fund more capital improvements at MARS, effectively relieving Orbital from the need to fund construction or equipment purchases at the spaceport. In a subsequent memorandum of understanding, which was made public Sept. 17, the state agreed to refund Orbital some $26 million the company had spent for Pad 0-A’s cryogenic plumbing.

Orbital, according to the memorandum, has made “a capital investment of at least $45 million” in Virginia in connection with the Antares project.

With the space shuttle fleet retired, NASA is now relying on private operators to send supplies to the space station, which is also served by European, Japanese and Russian cargo vehicles. Orbital is one of two U.S. companies NASA tapped for cargo runs. The other, Space Exploration Technologies Corp. of Hawthorne, Calif., completed a demonstration cargo run in May and is preparing to launch its first regular resupply mission Oct. 7.

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...