A United Launch Alliance Delta 4 rocket carrying NASA's first Orion deep space exploration craft is poised for launch Thursday on an unmanned test flight. The heavy-lift rocket will boost the Orion capsule to an altitude of 3,600 miles, setting up a high-speed re-entry and splashdown west of Baja California. NASA

NASA is gearing up for a milestone unmanned test flight Thursday, the first launch of the agency's Orion deep space exploration spacecraft intended to one day carry astronauts on missions beyond low-Earth orbit to the vicinity of the moon, one or more nearby asteroids and, eventually, Mars.

Liftoff atop a United Launch Alliance Delta 4 heavy-lift booster from launch complex 37 at the Cape Canaveral Air Force Station is targeted for 7:05 a.m. EST (GMT-5) Thursday, the opening of a two-hour 39-minute window. Forecasters are predicting a 60 percent chance of favorable weather.

The $370 million mission "is absolutely the biggest thing that this agency's going to do this year," said William Hill, deputy associate administrator for Exploration Systems Development. "This is really our first step in our journey to Mars."

While that might seem a stretch considering no one expects astronauts to visit the red planet before the 2030s, Mike Hawes, Lockheed Martin's Orion program manager, said the new spacecraft represents a major milestone in NASA's post-shuttle evolution and its plans to fly astronauts beyond low-Earth orbit for the first time since the Apollo moon landings.

"There's always a danger of over hype, but we have now built a spacecraft that is human rated for the first time in 42 years," he said in an interview with CBS News. "And so from that standpoint, I think it's really significant.

"Granted, it's a stepping stone in the early cadence, it takes longer than most of us would want, but (it gets) people to think about the fact that you have to design a different spacecraft to go out beyond the space station than what we have been doing in low-Earth orbit for so long. So that's where I think it is, maybe, worthy of the hype."

The Orion capsule during final assembly at the Kennedy Space Center.

NASA

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NASA set to launch critical Orion test flight