NASA space shuttle officials disputed claims Friday that the space agency had relaxed acceptable risk standards while building toward its first orbiter launch since the Columbia disaster.

"We're not doing anything that moves the risk or tries to hide the risk, or takes it to an unacceptable level," said Wayne Hale, NASA's deputy shuttle program manager, during a teleconference with reporters. "We're sharpening the pencil on how we do our [risk] calculations."

Hale's comments came in response to a New York Times report that suggested the agency had loosened its risk standards in order to meet the new flight safety protocols instituted in the wake of the Columbia accident.

The report, citing internal documents forwarded to Times reporters, indicated that NASA had changed at least some of the statistical methods used to understand the risks of ice, foam insulation or other launch debris impacts. The report also suggested that lesser risk standards were required because NASA could not meet traditional standards for its first post-Columbia launch.

"Everything we're doing is consistent with how we approach risk and safety elsewhere in the program," said John Muratore, NASA's manager for shuttle systems engineering and integration, during the teleconference. "We're not changing the way we calculate risk."

Some of the documents referenced by the Times were written in part by Muratore, the newspaper reported.

Returning to flight

NASA's three remaining shuttles were grounded following the loss of the Columbia orbiter, which was destroyed - and its seven-astronaut crew killed - during reentry on Feb. 1, 2003. Hot gases, investigators later concluded, had penetrated Columbia's left wing through a hole gouged into its heat-resistant skin weeks earlier at launch by a 1.67-pound, briefcase-sized chunk of foam insulation from the shuttle's external fuel tank.

Since then, NASA shuttle managers and engineers have worked to revamp the agency's orbiter launch system in order to minimize risk and increase safety for future astronaut crews.

"This is a risky business," Muratore said of human spaceflight. "But we have done a tremendous amount to mitigate that risk...and there are still some improvements we could put in over time."

NASA's first post-Columbia accident mission, STS-114 aboard the Discovery shuttle, is slated to launch no earlier than May 22. In addition to testing a new orbiter inspection boom and repair methods for patching thermal protection tiles and reinforced-carbon-carbon panels, the mission will deliver vital supplies to the International Space Station (ISS).

Internal dissent

Hale said that he was particularly disheartened that the engineers who sent the internal documents to Times did not go through NASA channels, and that they feared retribution.

NASA's internal culture was found partly at fault for the loss of Columbia because of an apparent feeling that dissenting opinions were frowned upon or punished. The agency has attempted to institute a culture change alongside its return to flight efforts.

"It bothers me that somebody felt they couldn't come up to us during a meeting," Hale said.

Hale added that while the bulk of the Times report was balanced, he took issue with a statement by Paul A. Czysz, emeritus professor of aerospace engineering at St. Louis University, who told the Times he was "amazed at how they were adjusting every test to come out right."

"I find that personally offensive," Hale said. "We're doing our best to find out what the truth is. We're not adjusting our results, though there is some debate about what they mean."

More analysis is still needed before Discovery will be completely cleared for a May 22 liftoff, but NASA officals were confident they would be concluded.

"If I didn't think we were going to come to a conclusion, I don't think we'd be announcing launch dates," Hale said.

         Fixing NASA: Complete Coverage of Space Shuttle Return to Flight