The space shuttle Endeavour is docked at the International Space Station… (NASA TV )
Spare parts were collecting dust in warehouses in Bell, Downey and Palmdale when the urgent call came from NASA: the nation needed another space shuttle.
It was the unusual beginning of the orbiter Endeavour, which will streak across the California coastline at hypersonic velocity one last time Wednesday, carrying its six astronauts and two decades of the nation's human space flight history.
When it was christened in Palmdale in 1991, it was the newest and most capable of the fleet, fawned over by astronauts for its advanced flight electronics, sinuous skins and, eventually, the first toilet that actually worked.
Photos: Endeavour's final flight
"It was a real clean bird," said Robert "Hoot" Gibson, the Navy aviator who flew Endeavour the year it entered service in 1992. "We didn't have any issues with that machine."
But it began its life amid a political scheme to circumvent opponents by squirreling away spare parts in the hope they would someday amount to a real spacecraft.
When the Challenger was lost in an explosion in 1986, the spare-parts plan was vindicated and they suddenly became the starting point for keeping the shuttle program alive.
And now the ship will come back home a museum piece in the county where it was built, destined for a display at the California Science Center in Los Angeles. The last shuttle flight is scheduled to launch July 8, after decisions by the Bush and Obama administrations to end the program.
During Endeavour's 24 previous journeys, which covered more than 103 million miles, astronauts engaged in all kinds of breathtaking, often scientifically incomprehensible and occasionally bizarre exploits.
In its current flight, the orbiter is helping to complete the International Space Station. Over the years, it helped repair disabled satellites, grow proteins and serve as maternity ward for pregnant frogs. In 1996, it flew a Coke machine that malfunctioned.
Endeavour delivered one of the most spectacular space feats short of a moon landing in December 1993, when it flew into high orbit and dazzled the nation with the Hubble Space Telescope repair mission.
The flight took Endeavour to an orbit about 350 miles high, forcing engineers to check whether every piece of its structure could handle the higher stress on reentry, recalled Bill Novak, a Boeing engineer in Huntington Beach who has worked on the program for nearly 39 years.
Without the shuttle's unique architecture, equipment and propulsion system, Hubble would have been left permanently out of focus.
"Every time I see new pictures of the universe from Hubble, it is rewarding," said Ken Bowersox, the Endeavour pilot who grappled Hubble with the orbiter's robotic arm. "It was a big mission, but there were a lot of big missions. You couldn't find the most important one."
Indeed, at the end of its life, there is wide agreement that Endeavour and its sister orbiters served the nation well.
The space shuttle was maligned during much of its history for failing to meet the promise that it could drive down the cost of reaching orbit and serve as a single means of launching defense, commercial and scientific payloads.
The program was dogged for decades by questions over its very purpose. It often had interminable launch delays. Two accidents scarred the program and left the nation mourning the deaths of 14 men and women.
The Challenger accident in 1986 led the Defense Department to abandon plans to use the shuttle to launch military spacecraft. And the Columbia breakup during reentry in 2003 led investigators to conclude that the craft was "inherently risky," a death sentence for the program.
But in hindsight, the shuttle program exceeded by a wide margin the capabilities of any other nation, taught astronauts how to routinely work in space and paved the way for an astounding number of breakthroughs, according to scientists, astronauts, engineers and government officials.
"It gave us the capability to expand our knowledge of the universe," said NASA chief Charles Bolden, a former shuttle commander.
It helped make peace with Russia after the end of the Cold War and brought women and minorities into space for the first time, Bolden said.
Endeavour was the star of the fleet, the one chosen to fly some of the most difficult missions. By the time it was produced at Rockwell International's Downey and Palmdale plants, engineers had already fine-tuned the design and manufacturing process. As a result, it was the lightest and sleekest of the fleet.
"You could look down the belly and see the difference," said Gerald Kinder, a Boeing aerodynamic heating engineer who has worked on the shuttle program for 30 years.