There are no people on today’s test flight of Orion, the capsule that is planned to take humans once again beyond the confines of Earth into deep space. Whether such a small capsule will ever make it as far as Mars is another question.
Launch weather officer Kathy Winters says conditions “are promising” with a 70 per cent prospect of favourable weather for the opening of the early morning (1205 GMT) launch window.
Heading into the final hours of countdown the mood in Houston mission control is upbeat. “On the vehicle side everything is extremely clean. We're ready to go,” says Mark Geyer, NASA's Orion programme manager.
Flight director Mike Serafin hasn’t experienced this kind of feeling around Nasa since the end of the Space Shuttle programme. “We are launching an American spacecraft from American soil and beginning something new,” he says.
“It’s a new mission and there are some things I'm sure we're going to learn from this unmanned flight test that will enable us to fly humans into deep space.”
With the launch of Orion, Nasa is about to claw back some of the ground it lost after the premature cancellation of the Space Shuttle programme by President Bush when there was nothing on hand to replace it.
The short, unmanned flight of Orion - a conical vessel reminiscent of the Apollo command modules that carried men to the Moon in the 1960s and 1970s - will test key technologies.
Orion is being developed by Lockheed Martin alongside a powerful new rocket that will have its own debut in three or four years’ time. Together, they will form the core capabilities needed to send humans beyond the International Space Station (ISS).
Today’s flight will be on a stand-in Delta IV-Heavy rocket - currently the largest launcher in the world and so the blast off will be spectacular.
Shortly after midnight local time the 330-foot tall mobile service tower was retracted from Cape Canaveral's pad 37B and the wheeled gantry structure moved along rail tracks to its launch position about the length of a football field away from the rocket.
Crews then worked on securing the complex for launch before leaving the danger area around the pad.
All workers had to be clear prior to the start of hazardous operations in the countdown - which include fuelling the Delta IV's Common Booster Cores and the second stage with supercooled liquid oxygen and liquid hydrogen propellants - which began shortly before 3 am.