(AP) -- A mechanical failure forced a NASA contractor on Thursday to call off the first test firing of the main part of NASA's powerful new moon rocket.
The test wasn't immediately rescheduled as officials scrambled to learn the root cause of the failure.
Alliant Techsystems Inc. called off the rocket burn with just 20 seconds left on the countdown clock. Operators cited failure of a power unit that drives hydraulic tilt controls for the rocket's nozzle. The rocket was anchored to the ground in a horizontal position for the test.
It was a setback for a carefully staged, $75 million event that drew thousands of onlookers. Alliant hoped the routine test would prove the performance of a new program for space exploration that, like the test rocket, may not fly because of NASA budget problems.
There was no indication anything was wrong with the rocket itself, which packs 1 million pounds of chemical propellant, enough to boost a 321-foot-long vehicle 190,000 feet into the atmosphere.
At a news conference in Utah, officials said the power unit for the nozzle controls, which steers a rocket in flight, was robbed of fuel, apparently because of a faulty valve.
That had immediate implications for the space shuttle, which uses a nearly identical system. Officials in Utah immediately notified their counterparts at the Kennedy Space Center in Florida, where NASA has had to twice delay the launch of Discovery for other reasons.
The Ares test problem could introduce a new delay in the launch of Discovery, previously set back because of a shuttle fuel valve and weather.
Shuttle managers said Thursday they will examine what went wrong with Ares and decide by early Friday whether to go ahead with a launch set for 11:59 p.m. EDT Friday.
The Ares rocket is the centerpiece of the plan started by President George W. Bush to send astronauts back to the moon by 2020 and then on to Mars. That plan, and all of NASA's human space program, is under review by a special independent panel, which will make recommendations to President Barack Obama on Monday. Some space experts expect the Ares rocket program to be modified or canceled.
But Thursday's glitch won't be a reason for that, experts said.
Problems, delays and outright failures are common in tests of new rockets and is nothing to worry about, said two former top NASA officials.
"The development of all launch vehicles is spotty and checkered at best," said Scott Hubbard, once director of NASA's Ames Research Center and now a professor of astronautics and aeronautics at Stanford University. "The fact that they are having troubles is not surprising at all."
Even after more than 125 flights, the space shuttle gets glitches like this that causes delays, Hubbard said. The shuttle Discovery has had its launch delayed twice this week. Once was because of a signal problem, the other due to weather.
Former NASA associate administrator Alan Stern, now associate vice president of Southwest Research Institute of San Antonio, said the company was prudent in not pushing with the test.
"This is a big deal, if it goes badly there are serious consequences," Stern said. But a delay in a test isn't necessarily a bad thing and shouldn't effect the White House's decision on whether to continue with the Bush moon program that features Ares rockets.
"This is a normal occurrence," Stern said.
AP Science Writer Seth Borenstein in Washington, D.C., contributed to this report.
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