Safe Landing but Fragile Future

The space shuttle Discovery made a picture-perfect landing Tuesday in the California desert, capping America’s return to manned spaceflight but also reviving the debate over the safety of the decades-old spacecraft.

Jarring the California coast with a pair of sonic booms, Discovery glided to a landing at 5:11 a.m. in the Mojave Desert.

The 14-day mission that returned the shuttle to flight -- 30 months after the Columbia shuttle accident in 2003 -- was hailed by NASA officials and shuttle astronauts as a milestone for the space agency.

“It’s going to be really hard to top this mission,” said NASA Administrator Michael D. Griffin.

But amid the cheers, aerospace experts said the glitches that dogged the flight -- falling foam insulation, faulty sensors, protruding heat-resistant fabric, a torn insulation blanket -- underscored the fragility of the shuttles and NASA’s troubling inability to resolve fundamental safety problems.

They said the space agency had a long way to go before shuttle flights regained their routine status, a necessary hurdle before the nation embarks on President Bush’s far more complex plan to send astronauts to the moon and Mars.

“We’re not back in space,” said Robert L. Park, a physicist and spaceflight expert at the University of Maryland. The Discovery mission “created more public angst and showed how we are just hanging on by our fingertips.”

John Pike, head of GlobalSecurity.org, an Alexandria, Va.-based space and military think tank, said NASA’s jubilation ignored deeper safety problems.

“They are all on happy pills,” he said of the space agency.

Uncertain weather in Florida forced Discovery to land in California instead, where at a news conference after the craft’s return from its 5.8-million-mile journey, shuttle commander Eileen Collins appealed to the public not to give up on a program that was still working to recover from the Columbia disaster.

“Please support us,” she said. “Remember, the Columbia crew believed in this mission.”

Bush, speaking from his ranch in Texas on Tuesday, promised to press forward with his plans to extend manned spaceflight to the moon and Mars.

“It’s an important step for NASA ... as it regains the confidence of the American people and begins to transition to the new mission we’ve set out for NASA.” he said.

To a large extent, Discovery’s in-flight problems came to light only because of new surveillance equipment deployed to examine every nook and cranny of the craft.

In the past, many such problems would have been noticed only once the shuttle was safely home.

Though the scrutiny may help make flights safer, it also forces NASA to face having to fix problems in space -- a risky and cumbersome process that could shake confidence in the space agency’s ability to maintain a safe craft.

“The sad thing is that in the effort to demonstrate that it is being diligent, the agency is undermining popular support for any manned spaceflight,” said Loren Thompson, public policy analyst with the Lexington Institute, an Arlington, Va., think tank. “It enforces the public’s apprehension of human spaceflight.”

NASA has little choice but to continue with the shuttle program if it hopes to complete construction of the International Space Station by 2010, when the shuttles are scheduled to be retired. The space agency needs to make up to 20 more shuttle flights.

“We’ve dug ourselves into a hole,” Park said.

The Discovery mission vividly showed -- in live video images -- that NASA had not resolved the most important safety issue for the shuttle fleet: the shedding of insulating foam from the crafts’ external fuel tanks.

A chunk about half the size of the one that doomed the shuttle Columbia in 2003 came dangerously close to hitting Discovery during its launch.

The shuttle fleet has been grounded until engineers can figure out a way to keep large chunks of foam from peeling away from the fuel tank.

NASA could either find a way to more consistently apply the foam by machine or replace the foam in problem areas.

If either approach works, NASA could still make its next launch window for the follow-up flight of Atlantis, scheduled for no earlier than Sept. 22.

But it would be a tight deadline. Discovery first must be prepped to serve as a backup vehicle -- a process that will be delayed because it will take at least a week to transport Discovery from California back to Florida.

“The American people can have confidence in us to work as hard as we can to understand why [the foam-shedding problem] happened and fix it before we begin flying again,” Griffin said.

Some analysts and engineers believe the foam problem is so systemic to the shuttle that it cannot be completely resolved. They say NASA may have to come up with new operating procedures rather than fix the problem outright.

Though he insisted that the shuttle could be made safe, Griffin himself has said NASA would never again build a manned spacecraft that follows the shuttle design, which exposes the craft to debris from the adjacent fuel tank and rockets.

Even if the foam issue is resolved, many other problems must be overcome before the shuttle can resume regular flights to finish building and equipping the International Space Station.

Discovery’s first launch date, in May, was postponed to July after tests showed that ice could build up on the super-cooled surface of its external fuel tank and then could fall off and damage the shuttle.

Then faulty fuel-level sensors prompted NASA officials to order another delay before the July 26 liftoff.

During the mission, sensors in crucial panels that line the leading edge of the wing indicated potential hits from debris.

The sensor readings raised alarms because of the similarity to the Columbia accident, which stemmed from damage to the same part of the wing. NASA has been unable to explain the readings.

Moreover, so many new rules and safety procedures are being implemented that some analysts believe NASA could become overloaded with information and paralyzed by indecision.

There were more than 100 cameras and sensors monitoring Discovery, compared with three employed for the Columbia launch.

The new cameras showed the fragility of the shuttle’s heat-resistant tiles. And seemingly minor “gap fillers” -- pieces of insulating fabric set between the tiles -- posed enough of a threat to justify a spacewalk for repairs.

Damage to an insulating blanket near the cockpit caused NASA to consider another repair spacewalk. That problem was eventually deemed to pose no significant risk and was left as is.

NASA officials said having too much information was far better than making the “guesstimates” that had effectively doomed Columbia.

Data were insufficient for assessing the potential damage caused by a large chunk of foam that had fallen off the external tank, so NASA engineers cleared the Columbia for reentry even though the 1.6-pound chunk of foam had torn a hole in its wing.

But Pike, of GlobalSecurity.org, said NASA might now be too cautious, as evidenced by the agency’s decision to forgo a landing attempt in Florida early Monday morning because of low clouds.

NASA mission control said that although the weather was technically “go” for landing, the conditions were too unstable to take a chance on landing what is essentially a large glider.

“You can’t take low clouds, because we only have one shot at landing,” reentry director LeRoy Cain said Tuesday.

“We can’t go around for another chance.”

NASA’s intense focus on identifying and fixing problems on the shuttle could delay or even derail completion of the space station by 2010.

With so many new ways to spot damage or other problems as the shuttle fleet shows its age, repairs could chip away at the shuttles’ primary purpose of helping build the space station.

NASA acknowledges that its course for the future is fraught with risk. After more than 24 years of operation, the space agency still considers the shuttle an experimental vehicle.

“You can’t put it on schedule and just fly it,” said William F. Readdy, NASA’s associate administrator for space operations and a veteran of three shuttle missions.

“There isn’t a single part of it that is easy,” he said.

Pae and Johnson reported from Kennedy Space Center in Florida, and Zarembo from Edwards Air Force Base.

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Mission troubles

The space shuttle Discovery’s flight was postponed from May to July because of concerns about ice buildup, and the July 13 countdown was halted because of a faulty fuel sensor. A look at the problems that Discovery’s crew faced:

July 26: A chunk of insulating foam broke off the external fuel tank during launch but did not strike the orbiter. NASA suspended all future flights until the problem could be resolved.

Aug. 3: Two gap fillers glued between tiles on the orbiter’s underside had come loose during launch, posing a danger of excess heat on reentry.

An astronaut removed the gap fillers during a spacewalk.

Aug. 4: A section of thermal blanket had pulled loose near the cockpit during launch. NASA engineers cleared the shuttle for landing after determining that the blanket posed a slim chance of breaking loose and damaging the orbiter during reentry.

Source: NASA