Promontory» The rocket motor roared to life and for just over five seconds it burned as if it were a tiny sun suddenly brought to Earth.

Utah's Alliant Techsystems and NASA on Tuesday held the first ever ground test of a motor that in the event of a launch pad emergency or during an initial ascent will be used to save the lives of astronauts sitting atop an Ares I rocket, part of the nation's next-generation vehicle for human space flight that is now under development.

"It is designed to act just like an escape seat on a jet aircraft," Gary Bates, chief engineer for ATK, explained prior to the test. "If it ever needs to be used, it will propel the crew [inside the Orion space capsule] away in a nice arc so they can return to earth safely."

Alliant, or ATK, already is well known as the maker of booster motors used to launch the space shuttle into orbit. It now is playing a big role in the development of the propulsion system for the Ares I, as well as developing two of the three smaller motors needed for the launch abort system as a subcontractor to the Virginia-based Orbital Sciences Corp.

The motor tested Tuesday represented the main propulsion for the launch abort system. It stood 17 feet high and was 3 feet in diameter. It was fixed into a vertical test stand with its four nozzles pointing skyward, the opposite direction as during an actual launch.

Barry Meredith, NASA's manager of the Orion Launch Abort System, said the current configuration of the motor is capable of producing about a half million pounds of thrust and should be able to safely lift the crew module that will carry as many as six astronauts off the Ares I rocket and fly it about one mile away to safety.

He explained that the motor was developed so the majority of its fuel will be burned in the first three seconds. Should the abort system ever be used, the astronauts suddenly will find themselves experiencing about 15 to 16 G's of pressure.

"That may be enough to cause them to momentarily black out, but they'll only be under that amount of stress for a very brief period -- only a couple of seconds -- so they should recover quickly," said Frank Culbertson Jr., a former astronaut who now serves as the deputy general manager at Orbital Sciences.

Additional testing of the launch abort system will begin next spring at the White Sands Missile Range in New Mexico and continue over the next several years.

"There will be both ground and flight tests," Meredith said, noting those tests will be pointed toward completing development of the abort system in time for the first operational flight of Orion and Ares I now scheduled for 2015.