NASA's new rocket designed to launch astronauts into orbit and eventually the moon passed a key engine test firing Thursday.

The motor, the solid-fueled first stage of NASA's new Ares I rocket, blasted hot flames and plumes of brown smoke and dust into the sky while lying on its side during the brief static test in Promontory, Utah.

NASA contractor Alliant Techsystems (ATK), which is building the rocket stage, conducted the trial at around 3 p.m. EDT (1900 GMT) at its Space Systems facility there. The exercise was the second try to test the motor, after the first attempt was aborted due to a last-minute anomaly on Aug. 27.

"After witnessing what we just saw, it's pretty easy to become speechless," said Alex Priskos, first stage manager for Ares Projects at NASA's Marshall Space Flight Center in Huntsville, Ala.

"With this test, we have taken lessons learned from many years of experience in solid rocket motor development and have built on that foundation," he said.

The motor tested today will drive the first stage of Ares I, a two-stage rocket designed to carry humans into space in the Orion crew capsule, also in development. Orion and Ares are NASA's plan for a next-generation vehicle to replace the space shuttle after it retires in 2010 or 2011.

The system, part of NASA's Constellation Program, is slated to begin operational flight no earlier than 2015. Earlier this week, a White House-appointed committee tasked with reviewing NASA's future plans for human spaceflight released a summary of its findings that stated the space agency cannot afford its current vision of returning astronauts to the moon by 2020.

The committee outlined five human spaceflight options, some of which do not include the Ares I rocket, for consideration by President Barack Obama.

The Ares I rocket's first stage is based on the twin solid rocket boosters, also built by ATK, used to launch NASA shuttles into orbit. The shuttles use four-segment boosters, while Ares I first stage uses a larger, five-segment motor. The segments used in Thursday's test were all previously flown on space shuttle launches.

The $75 million test firing lasted for about 123 seconds - the total time it would fire in an actual launch - giving engineers a chance to monitor 46 design objectives through 650 instrument channels. The burn packed about 22 million horsepower and temperatures of roughly 4,500 degrees Fahrenheit (2,480 degrees Celsius) - hot enough to boil steel, and turn the Utah sand underneath it to glass.

"It's a very humbling experience when you think about harnessing the kind of energy we just unleashed," Charlie Precourt, vice president and general manager of space launch systems for ATK, said in a briefing after the test.

The team said the test went according to plan, with no signs of anything unexpected.

"We are confident we're going to get all the data that we wanted to get out of this test," Priskos said. Although the data so far is preliminary, "it's absolutely consistent with our expectations and what we thought we were going to get."

Engineers will spend the coming days and months poring over the extensive data generated by the firing.

ATK traced the glitch that thwarted the Aug. 27 test back to a component of the ground controller unit, which routes power to the system that moves the motor nozzle. Engineers replaced the failed component, which apparently fixed the issue.

Another significant test is looming for Ares I. On Oct. 31 NASA plans to launch the Ares I-X test flight to try out the rocket concept with a full first stage and simulated second stage.

• Video - NASA's Ares I-X Test Flight Unveiled
• Video - Back to the Moon with NASA's Constellation 
• Video Show - NASA's Vision for Humans in Space