Engineers to Tackle Cause of Foam Shedding

In a report presented at a July meeting of the American Institute of Aeronautics and Astronautics in Tucson, a copy of which was obtained by The Washington Post, engineers from NASA's Aeroelasticity Branch concluded on the basis of wind-tunnel and other studies that the PAL ramps appeared unnecessary. But, in part, because one set of conditions could not be fully modeled, the team encouraged NASA to gather data from an actual flight to confirm their findings.

With those results in hand, mission controllers granted permission to install five sensors on Discovery's PAL ramp, to get real-time measures of the stresses there, according to an internal NASA memo written more than a week after Discovery's launch and examined by The Post.

The memo said preliminary data from the sensors supported the team's contention that the ramp could be eliminated without harm but added that more in-flight testing is needed before taking such a step.

The memo noted that the sensors had been installed on the liquid oxygen section of the tank -- the highest part of the tank and, therefore, the section where breakaway debris would have the highest chance of hitting the orbiter's vulnerable underside -- but that additional useful data could be obtained if sensors were also attached to the liquid hydrogen ramp on future shuttle flights.

Malone said Atlantis is equipped with sensors on the oxygen part of the tank, as Discovery was. But she said she did not know whether additional sensors have been attached to the hydrogen component.

Officials offered no specifics yesterday on how they might deal with the other parts of the tank that shed during Discovery's launch, but they expressed optimism that the problem is solvable.

"Now that we have Discovery back on terra firma, we'll go work those other issues," said William W. Parsons, the shuttle project manager. "In the next week or so we'll get preliminary data and findings about where we're headed."

Gugliotta reported from the Kennedy Space Center in Florida.