The front hall of the National Air and Space Museum is a temple to man-made wonders. Charles Lindbergh's Spirit of St.. Louis is here, suspended in mock flight near the Bell. X-1 that Chuck Yeager flew to break the sound barrier.

But it's what sits beneath these relics that moves most visitors: nine trophies from NASA's golden years, including the Apollo. 11 capsule that carried Neil Armstrong and Buzz Aldrin to the moon nearly 40 years ago.

But there's something missing from the "Milestones in Flight" display: NASA's current workhorse, the space shuttle. A scale model of the orbiter sits two rooms away, dwarfed by rockets of yesteryear.

The placement is symbolic of NASA's failure to inspire Americans during the past 36. years, since the end of the moon program.

"Where I get depressed is the human- spaceflight program," sighed museum curator Roger Launius, looking at the shuttle mock-up. "Our lead [over other countries] is lessening. Will they overtake us? That's the question for the next 50 years."

With half a century of amazing accomplishments behind it, NASA is entering a second space age beset by uncertainty and searching for a renewal of "the right stuff."

Though its agenda is ambitious -- a return to the moon and an eventual flight to Mars -- the agency is hobbled by a lack of resources and a public that is only mildly interested in its mission.

"It is absolutely feasible that the Chinese will [get to the moon] before we are able to do it because they have the political will to do it," said Joan Johnson-Freese, a security expert at the U.S. Naval War College.

"Space is always about the connotation of the future, and in my mind we are ceding that leadership simply because we cannot get our act together."

It wasn't always like this.

NASA was a creation of the Cold War, intended to inspire the public with dreams of space exploration and assuage fears that the Russians would get there first.

On Oct. 4, 1957, the Soviet Union launched Sputnik. I1, the first satellite to achieve Earth orbit. Though little more than a grapefruit-sized metal ball with trailing whiskery antennas, Sputnik shocked an America already worried about nuclear war -- and kicked off a race for technological superiority in the heavens.

On July. 29, 1958, President Eisenhower signed the National Aeronautics and Space Act after a fierce debate over whether the agency should be under military or civilian control. The civilians carried the day, and NASA opened its doors on Oct.. 1, 1958.

The agency was led by visionaries with larger-than-life personalities, such as rocket legends Wernher von Braun and Robert Goddard. Within a year -- as U.S. rockets blew up on the launchpad and the Soviets prepared to launch the first man into space -- NASA electrified the nation by selecting the first astronauts. Throughout the 1960s, a mesmerized nation halted whatever it was doing to watch NASA launches on live television.

Much has been accomplished since then. Men have walked on the moon; unmanned probes have explored asteroids, planets and the solar system; space telescopes have beamed back dazzling pictures of the heavens, while rovers buzz about the surface of Mars.

There's been a civilian payoff as well: Everything from GPS navigation to cell-phone technology to cordless power tools and much more has spun off from NASA projects.

But it has been 36 years since an astronaut last walked on the moon. And since 1981, America's human-spaceflight program literally has been going in circles -- in low Earth orbit aboard the shuttle and the international space station.

Meanwhile, other nations -- China, Russia, even the European Union -- are advancing their own programs and are threatening U.S. pre-eminence in space.

That concerns NASA Administrator Mike Griffin.