Orbital Sciences (News - Alert) Corporation is in full swing preparing its Antares rocket and Cygnus cargo spacecraft for a mid-September trip to the International Space Station. The demonstration flight with a planed rendezvous and berthing with the International Space Station (ISS) is the final milestone in Orbital's Commercial Orbital Transportation Services (COTS) development contract with NASA, with a successful mission opening the door to eight resupply flights under a separate contract.

If all goes as planned, Orbital will attempt a launch of the mission on September 14, 2013, with the Antares rocket lifting off from Wallops Island, Virginia and putting the new Cygnus spacecraft into orbit for checkout. Berthing with ISS is penciled in for September 22, with Cygnus to deliver around 1550 pounds of cargo during the demonstration.

Orbital is a victim of its own successes and hiccups in many respects. The COTS demo flight was originally scheduled over the summer and Orbital officials are prepping the Antares and Cygnus for a late August launch. But Orbital and NASA have the Lunar Atmosphere and Dust Experiment Explorer (LADEE) mission schedule for a September 6-10 launch window, causing a bit of a traffic jam at the facility. 

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If LADEE is delayed, Orbital could move up the COTS launch to a late August launch window. Already, the two stages of the Antares rocket have been put together, with the launch vehicle in final integration and testing. The Cygnus is already fueled and loaded with about 1,300 pounds of cargo; about 250 pounds of "late load" cargo is expected to go onboard a couple of days before launch. For full launch readiness, the Cygnus spacecraft needs to be connected to the Antares rocket.

Orbital needs to successfully complete the COTS demonstration flight in order to launch its first fully operational -- and paying -- resupply flight under the Commercial Resupply Services (CRS) program. Under the CRS contract, Orbital will provide an initial eight cargo flights to ISS; the company wants to conduct the first CRS flight by the end of this year.

Longer-term, Orbital would be one of two commercial companies with a demonstrated ability to deliver cargo to the International Space Station. The CRS agreement covers cargo services through 2015, while the space station is certified to operate through at least 2020 and potentially to 2028. It's a lot of future business for Orbital.