By Jane Sutton
MIAMI (Reuters) - When the United States embarked on its shuttle program decades ago, it set out to build a workhorse vehicle that would make space travel routine and beat the Soviets during the Cold War struggle for dominance in space.
The resulting spaceship had 2.5 million parts and was nine times faster than a speeding bullet as it climbed heavenward. It was the first reusable spacecraft, capable of gliding back to Earth like an airplane.
"It was leading-edge stuff back then," said NASA Chief Historian Bill Barry. "It was seen as a major leap forward."
Other manned spacecraft did not fly home. They were ballistic missiles that splashed down into the sea or used thrusters and parachutes to control their plunge to Earth.
The shuttle program will end next month after three decades and 135 voyages when Atlantis returns from a mission set to launch from the Kennedy Space Center in Florida on July 8.
NASA is consigning its shuttles to museums because they are too old and too expensive to keep flying, and the space agency plans to design and build something new with a farther reach.
To understand what relics the shuttles are, consider:
When the first one, Columbia, made its inaugural flight in April 1981, music was sold on cassette tapes, there were no dot-coms and the United States had no commercial cell phone service.
IBM introduced its first Personal Computer four months later -- a desktop that weighed 21 pounds (9.5 kg), not counting the disk drive or keyboard, and came with a 16-bit operating system called MS-DOS 1.0.
The shuttle design itself is a product of the 1970s. President Richard Nixon signed off on the shuttle program in 1972, a mere 15 years after the Soviet Union launched the first man-made satellite, the beachball-sized Sputnik that marked the dawn of the space age.
TIME TO LET GO
The shuttles have been "pretty darn amazing," Barry said.
"I'm going to be very sad in July when the last shuttle flight ends," he said. "I love the program and I'm sorry to see it go but I think it's time to let it go."
Five shuttles were built, ending with Endeavour in 1992. The design changed a bit with each one and there were steady upgrades over the years. The external fuel tanks were made lighter and stronger. The main engines underwent several overhauls to make them safer.
A crew escape system was added after Challenger exploded in 1986, killing seven astronauts. The toilets and air-scrubbing systems were upgraded so the crew could stay in space longer than the original one-week limit.
But the basic structure stayed the same, Barry said.
"Out of 2.5 million parts, many of them have been replaced but not changed dramatically. I suspect it's not that much different from what it used to be," he said.
The shuttle never lived up to Nixon's dream of a reliable, low-cost space freighter that would fly almost weekly. It was supposed to whisk ordinary people into space in such gentle comfort that they would not need to undergo years of rigorous training -- they would no longer need the Right Stuff, the macho toughness of NASA's original astronaut corps.
"It was going to make access to space easy, cheaper and accessible to average American scientists and engineers, not just NASA test pilots," Barry said.
NASA did put politicians, a Saudi prince and other civilians on shuttle flights, until the Challenger explosion killed Christa McAuliffe, who was to be the first teacher in space.
The shuttles were never as reliable as their planners envisioned. NASA lost seven more astronauts when Columbia was torn apart during re-entry to the Earth's atmosphere in 2003.
The shuttles averaged only four or five flights a year and were not as cheap as envisioned either. The original design was changed in order to keep the construction cost within budget, but that raised the operating costs, Barry said.
The lifetime cost of the shuttle program is hard to calculate, but researchers at the University of Colorado-Boulder estimated it at $196.5 billion (in 2010 dollars), according to a study published in the April 7 issue of the journal Nature.
The shuttles did exceed expectations in some ways, Barry said. They allowed astronauts to not only launch satellites, but to grab and repair them and put them back into service.
Most remarkably, he said, they allowed NASA to regularly rejuvenate the Hubble Space Telescope, which for 21 years has produced images that are transforming astronomers' understanding of the universe.
With their enormous cargo bays, the shuttles also enabled the United States and its partners to build the International Space Station, though not in a way anyone imagined when President Ronald Reagan green-lighted that project in 1984.
The United States' original goal was to one-up the Soviets by building a bigger, fancier space laboratory than the Soviet Mir. Today that competition between the two Cold War enemies is seen as having been good for the entire space program, and leading to the broad international cooperation for the peaceful exploration of space.
"We wouldn't have gone to the moon in the first place if they hadn't been kicking us in the butt every chance they got in the 60s," said Barry, who formerly led the Russia Team in NASA's Office of External Relations.
When the Soviet Union collapsed in 1991, the United States realized its space program was one legacy of communism "that was really good," Barry said.
The former enemies now are now partners in space. Russia will ferry U.S. astronauts to the 16-nation International Space Station in its Soyuz capsules until the next generation of U.S. spaceships are ready to do the job.
(Editing by Philip Barbara)