Glitch occurs during Nasa shuttle launch rehearsal

MELBOURNE, Florida - The shuttle Discovery crew staged a dress rehearsal today for their planned launch in July, but the practice run suffered problems that would have grounded the spacecraft during takeoff.

Discovery is the first shuttle scheduled to return to flight since 2003, when the shuttle Columbia disintegrated on re-entry and killed all seven astronauts aboard. Columbia's wing was damaged during the launch by a falling piece of insulation foam.

Two issues surfaced during the test of Discovery - poor weather and a communications glitch with Air Force safety and tracking equipment that would have been required during an actual launch.

The exercise concluded with a scripted last-second cutoff of the shuttle's main engines, a fail-safe mechanism designed to prevent an explosion should something go wrong.

The practice countdown was a routine test NASA conducts before each shuttle launch. Rather than heading into orbit, however, Discovery was scheduled to be hauled back to the vehicle assembly building in Cape Canaveral, Florida, for additional work.

Discovery was scheduled to launch in either May or June, but last week managers decided to delay the mission until mid-July so engineers can work on the shuttle's fuel tank.

Managers were debating whether to conduct a second test of the fuel tank before the shuttle is removed from the launch pad, NASA officials said.

An initial test last month revealed problems with sensors that monitor the amount of liquid hydrogen in the tank. The system includes four cutoff sensors, but two of the devices failed repeatedly during the test.

Following today's practice countdown, the Discovery astronauts inspected the launch pad emergency evacuation system and discussed the exercise with managers.

As the launch team practised flight preparations, a suite of photographers oversaw an upgraded network of 20 still and video cameras that will operate on launch day, NASA launch commentator George Diller said.

The cameras are located in a 122km long track along central Florida's Atlantic coast. The imagery is among the requirements imposed by Columbia accident investigators so NASA can have a better view of the shuttle during takeoff.

Columbia was fatally damaged during its launch by a piece of foam insulation that fell off the fuel tank and struck the spacecraft's wing. NASA never knew Columbia's wing had a hole because there were no clear images of that section of the shuttle taken during its ascent.

- REUTERS