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updated 7/16/2005 3:03:07 PM ET 2005-07-16T19:03:07

Maybe NASA's managers still view the shuttle as the Cadillac of space technology, but they sometimes make it sound as if it were a cranky old Ford with a few too many miles on it.

Deputy shuttle manager Wayne Hale says its recent on-again, off-again electronics problem "reminds me of an old truck I own."

Delays for safety improvements have repeatedly thwarted the shuttle's comeback from the Columbia catastrophe 2 1/2 years ago. But aging components could eventually add their own setbacks and risks to flying as the shuttles near retirement in just five years, according to authorities on space travel.

"If I have any worries at all, it's a few years from now, down the road, when the hardware gets older," said Bob Sieck, a former shuttle launch director and NASA safety adviser.

Designed in the 1970s, the shuttle was meant to advance space travel by several giants leaps. It was to be named the Space Clipper, in a reference to the speedy American clipper ship that expanded the possibilities of sea travel in the 19th century.

The shuttle would be the first vehicle to travel back and forth to space. Its comparatively comfy quarters for crew and garage-like cargo bay made the old space capsules feel like claustrophobic sardine tins. The shuttle would make trips to space much more routine, more like commercial flying. It would potentially be the first step in putting space within the reach of ordinary business and tourism.

In the end, the shuttle took on its more prosaic name and accomplished more prosaic functions — but still is a marvel of sorts. It has deployed satellites, maintained the Hubble Space Telescope, and helped to build the international space station. It has kept Americans in space while they tried to decide on their next destination after the moon.

But the shuttle's end has come in sight. "The clipper ships were the peak of the sailing art, and we don't see those either. I think there's a lesson to be learned from that," NASA Administrator Michael Griffin said last week at Kennedy Space Center.

Columbia flew the first shuttle mission in 1981. It was quickly followed in the next several years by the shuttles Challenger, Discovery and Atlantis. Challenger was obliterated in its 1986 disaster, and Columbia was lost in 2003, killing a total of 14 astronauts in the two accidents. NASA is left with Discovery and Atlantis, ages 20 and 21, as well as the 13-year-old Endeavour that replaced Challenger.

Aging electronics
People are young at 20, but electronics are well into maturity by then — if not beyond. "I wonder whether I could find a single electronics box in my house that's 25 years old and still works. I don't think I can. It's the same thing with the orbiter," the NASA administrator said of a recent shuttle part breakdown.

It is ostensibly a similar problem in a fuel sensor that ruined the shuttle's long-awaited return to flight last week. A manager said — and not in jest — that they would first try to wiggle the wires. However, NASA did enlist a cross-country team of hundreds of engineers to figure out what went wrong. The agency has indefinitely delayed the launch.

John Muratore, a NASA systems manager working on the sensor fault, acknowledged the problem of fathoming glitches in aging shuttles. "There isn't a lot of experience with aging, with having spacecraft that have had this long an operational life," he said.

To troubleshooters, the shuttle presents a labyrinth of wires, cables, signal boxes, transistors, diodes and capacitors — one of the world's most sophisticated machines. It enfolds 230 miles of wiring and 1,060 valves alone, and about 2.5 million parts in all.

Shuttle parts are regularly inspected and often replaced, especially ones viewed as critical to protect crew, craft and cargo. The shuttle replaces its external fuel tank with each flight.

"We have replaced much of the hardware. Some of the systems ... are more reliable than they were at the beginning of the program," said Michael Wetmore, NASA's director of shuttle processing. However, he acknowledged that some systems might show "a slowly increasing rate" of problems in the future.

Rattled by 180 million horsepower of thrust at liftoff, many shuttle parts do wear over time. They undergo extreme cold and heat during a flight. Some get nicked during maintenance, and others get chafed. Wires slowly crumble.

"We have learned that parts do need replacing more frequently than we would like," said Randy Avera, a former NASA engineer who helped develop the shuttle inspection program.

He said NASA should expand inspection and maintenance to keep the maturing shuttle fleet both efficient and safe. He said that will cost more money and possibly keep shuttles on the ground even longer. He fears the agency won't act quickly enough.

Kathryn Thornton, a former astronaut who has advised NASA on returning to flight, said she worries the agency won't be willing to keep the spacecraft in the best flying condition as it approaches retirement. "You have to keep the people and expertise around to the last flight," she said.

U.S. Sen. Kay Bailey Hutchison, R-Texas, who chairs the Subcommittee on Science and Space, said she believes Congress will provide the money needed to keep the shuttle running safely until its successor is developed. "I think the key is not whether they are getting too old, but whether they are maintaining them properly," she said.

After all, she said, each was designed for 100 trips into space. Discovery, the dean of the fleet, has launched only 30 times. The entire fleet has gone up only 113 times. Its designers envisioned a lot more wear but over a much shorter time. The original design called for a 10-year life span.

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