An Antares rocket stands on its launch pad at Wallops Island, Virginia, Oct. 15, one day before the vehicle's return to flight. Credit: NASA/Bill Ingalls

Updated at 1:15 p.m. Eastern Oct. 16.

WALLOPS ISLAND, Va. — The return to flight of Orbital ATK’s Antares rocket carrying a Cygnus cargo spacecraft has been postponed at least a day because of a problem with ground support equipment.

Orbital ATK said about seven hours before the scheduled 8:03 p.m. Eastern launch Oct. 16 from the Mid-Atlantic Regional Spaceport here that a problem with a ground support equipment cable had forced them to delay the launch by a day. There are no problems with the Antares rocket itself or the Cygnus spacecraft, the company said.

“We have spares on hand and rework procedures are in process,” Orbital ATK said in a statement. If those repairs are completed, the launch will be rescheduled to Oct. 17 at 7:40 p.m. Eastern, with a 90 percent chance of acceptable weather.

The launch represents the return to flight of the Antares after an October 2014 mission that suffered an engine failure seconds after liftoff, causing the vehicle to fall back to the ground and explode. That explosion caused $15 million in damage to the launch site.

An investigation blamed the accident on an explosion in the liquid oxygen turbopump of an AJ26 engine in the rocket’s first stage. Orbital ATK decided after the failure to replace the AJ26, a Soviet-era rocket refurbished by Aerojet Rocketdyne, with new RD-181 engines from NPO Energomash.

That engine swap did require some other work to the rocket to accommodate the more powerful engines. That included changes to the vehicle’s structure, different control systems and additional instrumentation, said Mike Pinkston, Antares program vice president and general manager at Orbital ATK, in an Oct. 15 briefing at NASA’s Wallops Flight Facility here.

“It was a very detailed, meticulous process, but as evidenced by the stage test, we got it right, and we’re ready to go,” he said, referring to a static-fire test of an Antares first stage on the pad in May.

Frank Culbertson, president of Orbital ATK’s Space Systems Group, said the teams were working no issues with either the Antares rocket or the Cygnus spacecraft. “I’m very optimistic,” he said, expressing no specific concerns about placing a payload on the first flight of an upgraded rocket. “We understand those changes, and we feel like all the tests have covered the risks people have been able to think of.”

A tracking station in Bermuda, forced to shut down because of a passing hurricane and thus delaying the launch by two days, is ready to support the mission. “It fared remarkably well in that weather,” said Sarah Daugherty, test director at NASA Wallops, of that tracking station. “They are green and functioning normally at this time.”

The Cygnus, named the SS Alan Poindexter after the former astronaut who died in 2012, is carrying 2,425 kilograms of cargo for the ISS. That cargo includes science experiments, crew supplies and station hardware.

An Oct. 16 launch would have allowed the Cygnus to arrive at the station early Oct. 19, with berthing scheduled shortly after 7 a.m. Eastern. With the delay, though, the Cygnus will wait until after the Oct. 21 docking of a Soyuz spacecraft carrying three new ISS crew members. Joel Montalbano, NASA space station deputy manager, said that, even in a worst-case scenario, the Cygnus could loiter in orbit for more than 20 days after launch.

Montalbano also said that NASA added some cargo to the Cygnus after the Sept. 1 pad explosion of a SpaceX Falcon 9, which is expected to delay the next Dragon mission to the station that was previously scheduled for November. “We originally had some ballast that we were flying on this vehicle,” he said. “We’ve removed all that ballast and replaced it with crew supplies,” including food and clothing, as well as computer hardware and “a very small amount” of extravehicular activity hardware.

The Cygnus mission will continue for several days after it departs from the space station in late November. The spacecraft will carry out the second in a series of experiments known as Saffire that test how materials burn in weightlessness. The Cygnus will also maneuver to an altitude about 45 kilometers above the ISS to deploy four Lemur cubesats for Spire, a San Francisco company developing a constellation for ship tracking and weather data collection.

The higher altitude will allow the satellites to remain in orbit far longer than if they were deployed directly from an airlock on the ISS, as many other cubesats are. “We are estimating that these cubesats will be up there for three years, versus, out of the airlock, anywhere from six months to a year,” said Henry Martin, external payloads coordinator for NanoRacks, the company that arranged the satellite deployment.

Culbertson hinted that, in addition to the scientific and other cargo on the Cygnus, there will be something extra for the station’s crew. “Every cargo mission is like Christmas, right?” he said. “They never know what they’re going to find when they open the hatch.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...