An unmanned Antares rocket, developed by Orbital Sciences Corp. was poised for launch from Virginia on Wednesday to send a new cargo capsule to the International Space Station.
Liftoff from the Mid-Atlantic Regional Spaceport on Wallops Island was scheduled for 10:50 a.m. (1450 GMT). Meteorologists expected a 75% chance the weather would be suitable for launch.
The Antares rocket and Cygnus capsule were developed in partnership with NASA, which committed $288 mln to the program.
The U.S. space agency, which retired its space shuttles in 2011, also contributed $396 mln to a similar effort by privately owned Space Exploration Technologies, or SpaceX, to develop its Falcon 9 rocket and Dragon cargo ship.
"The Orbital investment far exceeds the NASA investment," Orbital Sciences executive vice president Frank Culbertson told reporters at a prelaunch press conference on Tuesday.
Culbertson declined to be more specific about how much the company has spent to develop Antares and Cygnus.
"We're hoping for a long series of cargo resupply missions to recoup some of that (investment)," Culbertson added.
So far, NASA has committed to eight Cygnus cargo runs under a contract worth $1.9 bln. SpaceX has a 12-flight, $1.6 bln contract, with ten flights still remaining.
Orbital Sciences expects to quickly transition from this week's trial run to the space station into its first operational mission for NASA in December.
A successful flight not only may boost its chances for additional NASA work, but also could attract commercial and scientific customers for both Antares and Cygnus.
Cygnus capsules are not designed to return to Earth, but since they can stay in orbit for extended periods of time, Orbital Sciences envisions secondary missions after the capsules depart the station, as well as dedicated flights for customers beyond NASA.
Antares, a two-stage, medium-lift rocket, made a successful debut test flight in April. For Wednesday's flight, it is expected to place a Cygnus capsule, loaded with about 700 kg of food, clothing and other supplies, into orbit.
Over the next four days, the capsule will demonstrate its ability to maneuver in space and communicate with the station.
If all goes as planned, Cygnus would fly itself to the station on Sunday so astronauts can use a robotic crane to pluck the capsule from orbit and attach it to a berthing port.
