Washington - After battling tricky weather conditions off and on all morning, NASA called off a planned Tuesday launch test of the next generation space rocket that is to replace the ageing space shuttle. Engineers were unable to find enough time to launch the Ares I-X rocket when clouds were not affecting the Kennedy Space Centre during a four-hour launch window that began at 1200 GMT.
NASA said it would try again beginning at 1200 GMT Wednesday, but there was still a 40-per-cent chance that weather would force it to scrub the launch.
Less wind was expected and cloudiness was to decrease, but engineers would still have to look for breaks in the cloud cover for a chance to lift off, forecasters said.
NASA kept pushing back the planned launch time throughout the morning, at one point even beginning the final minutes of countdown before being stymied by weather.
A passing ship had also prompted a brief pause. Since pieces of the rocket will fall back into the ocean, NASA was being particularly watchful of maritime traffic.
Ares I is the first of two new rockets planned by NASA for its Constellation programme with the eventual goal of returning humans to the moon.
Ares I would be used to carry astronauts to low-earth orbit, including to the International Space Station, aboard the next- generation Orion crew capsule. A later, more powerful Ares V rocket is to be developed to carry astronauts to the moon and beyond.
NASA will use hundreds of sensors on the rocket to gather information during the 445-million-dollar test flight about how safe and effective the rocket is. It will carry a simulated crew module and travel up to 46 kilometres into the atmosphere on its 369-second flight.
The test simulates the path that an Ares rocket carrying an Orion crew capsule would take and will reach up to four-times the speed of sound. It has a mock-up of an Orion capsule and an extra rocket booster to simulate as closely as possible actual conditions.
The capsule will separate from the rocket at about 40 kilometres above the Earth and will fall back into the ocean.
The Ares rocket will also fall to Earth on a recovery parachute and scientists will then analyse data gathered on a series of sensors attached to the device.
Engineers will use the test to assess the flight control system and to control for roll torque, the force that causes a rocket to rotate as it flies. NASA will also be looking closely at the separation of the rocket and the recovery system.
But the programme itself and Ares could be in jeopardy as US President Barack Obama reviews the US space programme. An independent review commission said earlier this month that NASA would not be ready to send astronauts aloft with the rockets until at least 2017, two years after schedule.
That widens the gap between the retirement of the shuttle next year and implementation of the new vehicle, leaving astronauts dependent on Russian spacecraft to reach the International Space Station.
The review panel also suggested that policy makers should consider using commercial vehicles to carry humans to low-earth orbit rather than Ares I, allowing NASA to focus its attention on longer trips.
But NASA scientists said regardless of the policy decision, the Ares test would allow them to gather valuable data applicable to any high-powered rocket to move the space programme forward.
