A ROCKET that aims to replace the ageing space shuttle fleet and carry astronauts into low-Earth orbit is poised for its first test flight, amid deep uncertainty over the program’s future.
Barring bad weather, countdown for the rocket that carries hopes of returning humans to the moon and for the first time to Mars will begin at 1am (17:00 AEST), with a four-hour launch window opening at 8am (midnight AEDT).

“The Ares I-X flight test vehicle is poised on Kennedy Space Centre’s launch pad 39B and is ready to fly,” the US space agency said.

But while NASA scientists said they had “no issues” with the 100m prototype, the world’s largest at present, the weather could still throw a spanner in the works.

The forecast for tonight showed only a 40 per cent chance of favourable weather.

NASA needs 15 minutes of good weather to launch.

If weather concerns cloud the test launch, the next window would be from 1200-1600 GMT (midnight-06:00 AEDT) tomorrow, when the forecast was for 60 per cent “go”.

If that fell through, the world would have to wait until next month to get its first look at the launch vehicle.
NASA will gather data collected by more than 700 sensors placed throughout the rocket during the ascent of the integrated stack.

Only the first stage of Ares I-X – a modified solid-fuel motor from the shuttle program – will be tested, while the upper stage and capsule are mock-ups.

Data obtained during the two-and-a-half-minute flight will help the US space agency determine whether the prototype is safe and stable in flight before the new generation of launch vehicles is used to take astronauts into orbit.

A team of experts has projected that will not happen before 2015, leaving a five-year gap after the shuttle is retired in 2010