Weather delays Orbital spacecraft's return to International Space Station

Rain and cloudy skies delayed Orbital ATK's planned resumption on Thursday of cargo runs to the International Space Station, a year after the company's Antares rocket exploded during launch.

An Orbital Cygnus spacecraft, perched atop an Atlas 5 rocket from United Launch Alliance - a Lockheed Martin Corp and Boeing Co joint venture - had been slated for liftoff at 5:55 p.m. EST (2255 GMT).

But poor weather at the seaside Florida launch site forced ULA to postpone the launch. The next opportunity is at 5:33 p.m. (2233 GMT) on Friday.

The Cygnus, an upgraded cargo ship, is due to carry more than 7,700 pounds (3,500 kg) of food, clothing, supplies and science experiments to the space station, including a prototype satellite astronauts will put together like a Lego kit. Also aboard are two Microsoft HoloLens headsets, which will provide station crew – and onlookers in ground control centers – with digitally enhanced images of whatever the astronauts are looking at.

Dulles, Virginia-based Orbital had completed two flights under its original $1.9 billion NASA contract, delivering about 8,400 pounds (3,800 kg) pounds of a promised 22 tons of supplies, when Antares faltered on Oct. 28, 2014. Investigators blamed the botched launch on a defective turbopump in one of Antares’ two main engines, a Soviet-era motor refurbished and sold by Aerojet Rocketdyne Holdings . Exactly what went wrong remains a matter of debate, but Aerojet paid Orbital $50 million to settle the dispute and the companies ended their collaboration.

Orbital accelerated plans to outfit Antares with new engines and purchased two Atlas rocket rides to fly Cygnus capsules to the station. Orbital expects to start using its own Antares rocket again in May 2016.

Orbital is competing against privately owned Space Exploration Technologies, or SpaceX, and Sierra Nevada Corp for follow-on station cargo delivery contracts, now due to be awarded in January.

Resupplying the station has been a challenge for NASA, following not only Orbital’s accident, but the loss of a Russian Progress ship in April and a SpaceX Dragon capsule in June.

(Reporting by Irene Klotz; Editing by Tom Brown)