PROMONTORY — The booster rocket that is to push U.S. manned space flight back on track, to the moon and beyond, passed its first real test firing Thursday in front of the engineers who built it and NASA officials who say it's the only way to fly.

The DM-1 motor, which is the most powerful rocket motor on the planet and will be the business end of the 323-foot Ares I space vehicle, affectionately known as The Stick for its spindly design, ignited shortly after 1 p.m. and burned for more than two minutes.

As the ground rumbled and a heavy plume of smoke rose from the flame, which was literally as bright as the sun and produced a force approximating a dozen 747 airliners taking off at once, a crowd of several hundred ATK employees cheered while NASA and ATK administrators breathed a big sigh of relief.

"It's humbling to witness that much energy being harnessed," said Charlie Precourt, ATK vice president and general manager of ATK Space Launch Systems. "It's hard to describe what 3.6 million pounds of thrust looks and feels like unless you see it. But right now, and given what the immediate readouts are, we're all smiles here."

Those smiles might not last, though.

The Ares I is supposed to take men and women to the moon by 2020. But with budget cutbacks the past several years, and hearings on a review of NASA by a White House commission to begin next week, the only thing the Ares ground crew say it can do is move ahead with the expectation that the details such as funding in Washington will be worked out.

The Augustine Commission reported earlier this week that "the U.S. human spaceflight program appears to be on an unsustainable trajectory because it is perpetuating the perilous practice of pursuing goals that do not match allocated resources."

The Ares takes one perilous aspect out of the situation — it's going to be the safest way up and back of anything out there, said Kent Rominger, ATK vice president for test and research operations. "This rocket is a hundred times safer, it leverages all the infrastructure we've built and contains all the upgrades that will make it the safest space vehicle ever built."

ATK and NASA want to move as quickly as possible to shelve the space shuttle fleet, given two tragedies and its age, not to mention increased interest in commercial companies taking over manned launches. One option under the Augustine report is to keep the shuttle flying. That option would save money, but with each flight comes another risk of launching a vehicle that has a track record of one disaster every 67 flights.