WASHINGTON (AP) — The signs of a midlife crisis are there: A 50th birthday approaching; a longing for the glory days of youth; a hankering to dump the aging partner of 27 years; and a costly flirtation with a new young thing.

This isn't some balding businessman in a sports car. It's NASA.

The National Aeronautics and Space Administration, which opened its doors on October 1 1958, is struggling with its identity and its future. The agency's angst is Velcroed to the vehicle that NASA has been married to for more than half its life and is seeking to dump — the space shuttle.

The shuttle has kept NASA going to the same place over and over, circling the Earth 18,449 times since 1981. For much of that time, NASA's mission has been to build the international space station, a place to do research and to learn how to live in space.

But the NASA of the future is looking to retire the shuttle in 2010 and build new space vehicles to return astronauts to the moon and, someday, to travel to Mars.

Doing that requires a clean break from the shuttle program. But a combination of pressures — political, economic, engineering and diplomatic — make it difficult, costly and some say unwise to ditch the shuttle as soon as planned. While NASA publicly talks about shuttle retirement, it's also quietly making sure it could postpone those plans. Divorce isn't as easy as it once looked.

Making the break from the shuttle programme would mean five years without an American way to get into space, forcing astronauts to hitch a ride with the Russians to the multi-billion-dollar space station that US taxpayers funded.

That makes many people uncomfortable. The two presidential nominees and many in Congress say they want to keep the shuttle flying past the 2010 retirement date mandated by the Bush administration.

But doing so would be costly, and given the current financial meltdown, big spending on NASA in the future doesn't seem likely...

"There's a lot of problems NASA has at middle age. It's being asked to do too much," said Syracuse University public policy professor Henry Lambright. "It's unrealistic to expect you to carry on this burden of the past, the shuttle and the space station, while you do something new without more money. You can't do it."

Suggesting NASA is having a mere midlife crisis is sugarcoating the situation, said Hans Mark, an aerospace engineering professor at the University of Texas who was a NASA administrator during the Reagan administration.

"It's not a midlife crisis. It's a disaster," Mark said. "We can't possibly give up on the shuttle and let Russians be the only ones get to the space station. We don't have a higher-tech replacement for the shuttle, and we screwed up the space station" by putting it in an orbit that prevents it from being useful for missions to the moon or Mars.

Wayne Hale, NASA's deputy associate administrator, tried to put the situation in the best light.

"We are at a crossroads," Hale said, noting the future could be viewed as dangerous or an opportunity.

"If we had done things the way we wish we could have, we wouldn't be here," Hale said. "But here we are... It's a shame we got in this situation."

John Logsdon, a space policy expert at the National Air and Space Museum, said: "NASA at 50 is still suffering from a decision made when it was 12."

During the race to the moon, NASA got special treatment, essentially getting a blank check during the Kennedy space race era. In 1970, President Nixon ruled it would be treated like all other federal agencies, and "NASA has been in the midst of a perpetual crisis ever since," Logsdon said.

These days a new attitude is called for from an agency that began as risk-taking one that raced the Russians. As Hale put it, NASA must become "more mature."