WASHINGTON — With the inaugural launch of its Antares medium-lift rocket in the books, Orbital Sciences Corp. of Dulles, Va., is now preparing for another maiden flight: that of the Cygnus space freighter the company developed with help from NASA.

The first Cygnus mission is tentatively scheduled for June or July, and its successful completion would clear the way for Orbital to start flying 20,000 kilograms of cargo to the international space station for NASA under an eight-flight, $1.9 billion contract signed in 2008.

Right off the launch pad, those missions will be much trickier than the one-off launch of a Cygnus stand-in payload Antares lofted to orbit in its April 21 debut from Pad 0-A at the Mid-Atlantic Regional Spaceport in Wallops Island, Va. For one thing, the long launch window available for the first Antares flight will shrink dramatically for the operational missions.

“When we do this with the Cygnus spacecraft and we have cargo to deliver, we’re not going to have the luxury of a two-hour [launch] window,” Frank Culbertson, executive vice president and general manager for Orbital’s Advanced Programs Group, said in a press briefing following a scrubbed Antares launch attempt April 20. “We’re going to have anywhere from five to zero minutes of window. We’re going to have to get it right the first time.”

After two scrubbed attempts the week of April 15, Antares heaved itself slowly off Pad 0-A at 5 p.m. EDT April 21. About 10 minutes later, the vehicle dropped off its main payload — a sensor-equipped dummy satellite with roughly the same mass as the Cygnus spacecraft Orbital will use for cargo deliveries — in a 51.6-degree inclined orbit about 250 kilometers above Earth’s surface. This is the same orbit where the real Cygnus would be dropped off at the start of a cargo run.

Also carried aloft by Antares were four experimental cubesats, all of which made it to their intended orbits, according to Orbital officials. The hitchhiker payloads were Dove-1, a triple cubesat built by Cosmogia Inc. to demonstrate low-cost imaging technology, and three single-unit cubesats with consumer smartphone cores, which were built at NASA’s Ames Research Center in Mountain View, Calif.

It took Orbital three tries to get its new rocket off the ground. The first launch attempt April 17 was scrubbed about 10 minutes before the scheduled liftoff because a data cable linking ground computers with Antares’ second-stage flight computer disconnected prematurely. Orbital said the cable was hung too tautly to tolerate a sudden movement of a hydraulic arm on the Transporter Erector Launcher vehicle that holds Antares at the pad.

An April 20 attempt was scrubbed due to wind conditions.

The Antares configuration that flew April 21 can send 5,000 kilograms to low Earth orbit. Future configurations will be able to haul 6,350 kilograms to orbit. By Orbital’s fourth contracted cargo run, now very loosely scheduled for 2014, Cygnus will get an upgrade, too: The volume of the vehicle’s Italian-built Pressurized Cargo Module will increase to 27 cubic meters from 18.9 cubic meters, and its Orbital-built service module will use some lighter-weight structures, a different solar array, and some different sensors and communication electronics than the Cygnus variant the company will use for its first three cargo missions, Frank DeMauro, Orbital’s vice president and program manager for Cygnus, said April 17 during a press briefing.

Meanwhile, the Cygnus headed to the international space station for the summer delivery demo has been loaded with cargo, sealed and fueled, and is now waiting to be mated with a launcher at Orbital’s Horizontal Integration Facility about a mile down the beach from Pad 0-A, Culbertson said.

If the second Antares flight goes according to plan, Orbital intends to make at least one paid cargo run to the space station this year.

“After the demo, we’re in a position where we can deliver two full-up missions to the space station before the end of this year,” Mark Pieczynski, Orbital’s vice president for space launch strategic development, said April 16 during a press tour of the company’s Virginia launch complex.

Mike Laidley, Orbital’s program director for Antares, said the minimum turnaround time between Antares missions will be about one month. Under a memorandum of understanding signed last summer, Orbital pays the state of Virginia, which built and operates Pad 0-A, $1.5 million for every launch. The pad is located at NASA’s Wallops Island Flight Facility.

Orbital currently has parts for about four Antares rockets stored near its coastal Virginia launch site. Half of the Cygnus spacecraft that will fly on the company’s first contracted cargo run, the Orbital-built service module, has completed post manufacturing tests in Dulles. The other half, a Pressurized Cargo Module built by Thales Alenia Space, Turin, Italy, is standing by to ship, along with completed pressurized modules for two more Cygnus freighters. Orbital expects the first of these three modules to ship to the United States for integration in about a month, DeMauro said.

But there are factors besides vehicle integration and pad turnaround that affect Antares’ launch pace. The biggest of these is the availability of docking space at the international space station, which is set to be visited this year by spacecraft from Europe, Japan, Russia and the United States.

Orbital will be the second of NASA’s Commercial Resupply Services contractors to attempt a flight to the space station. Space Exploration Technologies Corp. (SpaceX) of Hawthorne, Calif., completed its demonstration cargo run to the space station in May 2012 and has flown two contracted cargo runs since. The second wrapped up March 25.

Antares was supposed to have launched Cygnus on a demonstration flight to the space station by December 2010, under the schedule Orbital and NASA agreed upon in 2008. In 2011, NASA added several milestones to Orbital’s demonstration effort, including the April 21 Antares test launch, which was supposed to have happened by October 2011.

Antares is a big part of Orbital’s plan to win new business from NASA, the U.S. military and commercial customers. In each of those segments, the company will face competition from SpaceX, and incumbent military launch services provider United Launch Alliance (ULA) of Denver.

Orbital does not plan to compete with ULA for the largest payloads in the government market, but SpaceX plans to make a grab for them with the Falcon Heavy launcher slated to debut later this year at Vandenberg Air Force Base, Calif.

For now, veteran rocket operator ULA — a 50/50 joint venture of Boeing Co. and Lockheed Martin with a long history of successful launches — remains the dominant player in the government launch business. ULA operates the Atlas 5 and Delta 4 rockets.



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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...