Sixty years ago, spurred by competition with the Soviet Union, the United States created NASA, launching a journey that would take Americans to the moon within a decade.

Since then, the US space agency has seen glorious achievements and crushing failures in its drive to push the frontiers of space exploration, including a fatal launch pad fire in 1967 that killed three and two deadly shuttle explosions in 1986 and 2003 that took 14 lives.

Now, NASA is struggling to redefine itself in an increasingly crowded field of international space agencies and commercial interests, with its sights set on returning to deep space.

These bold goals make for soaring rhetoric, but experts worry the cash just isn't there to meet the timelines of reaching the moon in the next decade and Mars by the 2030s.

And NASA's inability to send astronauts to space -- a capacity lost in 2011 when the space shuttle program ended, as planned, after 30 years -- is a lasting blemish on the agency's stellar image.