Fifty years after inspiring the nation, many are now wondering whether NASA’s best years are behind it.

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.

There’s something missing from the Milestones in Flight display, however: 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 a half-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.

In circles

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 1, 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.

“Whether America takes part or not, human exploration of space will go forward in this century,” he said recently. “It is only a question of who those explorers are, what languages they speak and what values they hold.”

‘In museums’

China widely is considered the rival to watch. Last week, Beijing sent three “taikonauts” into orbit for their first-ever spacewalk – an important step toward an expected Chinese space station and possible moon landing.

China’s progress comes as NASA sits at a crossroads: eager to retire the shuttle in 2010 but struggling to build the Ares rocket and Orion capsule that will replace it.

This month, NASA had to beg Congress to allow it to buy rides to the international space station on Russian rockets because Ares won’t be ready until at least 2015.

The frustration at the agency is palpable. William Bruner, a NASA assistant administrator, last week wrote on a blog that as China eyes a lunar mission, “our lunar capability sits in museums.”

Griffin, perhaps the most farsighted NASA head since James Webb got the agency to the moon in the 1960s, thinks President Nixon should have followed the moon landings with a drive to send astronauts to Mars.

Instead, the space shuttle launched in 1981. Its stated mission – a reusable space truck – was as prosaic as its appearance.

Martin Rees, president of The Royal Society, Britain’s academy of sciences, recently said the only time the shuttle made news was when it crashed. The losses of Challenger in 1986 and Columbia in 2003 killed 14 astronauts and badly dented NASA’s reputation.

After the second accident, President Bush, acting on the recommendations of a blue-ribbon panel, decided it was time to retire the shuttle and get NASA thinking about sending astronauts back to the moon and ultimately to Mars. In 2005, Bush chose Griffin – himself a rocket scientist – to turn the vision into reality.

Griffin’s aim was to restore NASA’s reputation as a place of cutting-edge engineering and research.

It has not been easy.

In fear of chances

NASA has not successfully built a new rocket in more than a generation – though it has spent billions on projects it never finished. The agency even had to bring back engineers from the Apollo days to show a new generation how it was done.

Bob Sieck is one of those Apollo graybeards advising NASA as it struggles with its new Ares I rocket. Sieck admires the agency’s scientific and engineering talent. The problem, he says, is NASA’s multilevel bureaucracy; too many people and political considerations are involved in making decisions.

And, he says, there’s a great fear of taking chances.

“In my day if you failed, people would say, ‘Nice try. What do you need to make it right?'” recalls Sieck. “Nowadays, they convene commissions to investigate.”

But above all, Sieck and others say, it comes down to money.

During the Apollo era, as much as 4 percent of the federal budget was devoted to NASA; that percentage today would amount to $110 billion. But NASA’s budget is $17 billion – and even that evokes criticism that money spent “up there” should be diverted to more pressing issues “down here.”

For his part, Griffin refuses to abandon the dream. In spite of technical and political problems dogging his new rocket, and the fact that in January a new administration could fire him and rethink his plans, Griffin thinks if NASA stays the course, it could rekindle the fire of the past.

“When we do exciting things, people are excited. When we do boring things, people are bored,” he said. “The new space policy calls on us to do exciting things again … so I am just trying to get us there.”