"No showstoppers" for July 1 launch

NASA still aims to launch Discovery on its second post-Columbia test flight July 1, and senior shuttle program managers see "no showstoppers" on the horizon.

That was the word today from NASA Shuttle Program Manager Wayne Hale after the agency completed a two-day review considered critical to clearing Discovery for flight.

The so-called Debris Verification Review was carried out at Kennedy Space Center to determine whether the shuttle's redesigned external tank will shed pieces of foam insulation large enough to cause severe damage to Discovery's heat shielding.

Hale said NASA fully expects small chunks of foam to come off the tank during flight. And he acknowledged that there still are parts of the tank that could shed pieces large enough to cause critical damage.

But NASA managers believe the chance of that happening is only about 1 in 100, or about the same probability that problems with other critical systems might cause the loss of an orbiter and its astronaut crew.

Consequently, NASA believes flying the mission without further tank modifications is an acceptable risk, Hale said.

About 100 NASA managers and engineers took part in the two-day review. Hale said some recommended that the agency delay the upcoming flight until additional tank modifications could be made. He characterized the debate as "spirited."

The prime concern is the chance that so-called Ice Frost Ramps could shed foam large enough to cause severe heat shield damage. Particularly vulnerable are fragile thermal tiles that protect an orbiter and its astronauts from intense temperatures encountered during atmospheric reentry.

The ramps are manually applied blocks of foam designed to keep ice from building up on metal brackets that secure pressurization lines to the outside of the tank. Hale acknowledged they are a hazard. Engineers are working on a redesign that would stem foam loss, but it probably won't be ready until later this year or early next year.

A few hurdles still must be overcome prior to a July 1 launch.

NASA must complete routine prelaunch work on the shuttle at launch pad 39B and two more key management reviews are planned.

Managers next Wednesday will hold a review aimed at ensuring changes made to the tank since an initial test flight last summer will work as intended. On that flight, a one-pound piece of foam popped off Discovery's tank and nearly struck the ship's right wing.

The debris came from a long ramp of foam insulation designed to provide a windshield for the pressurization lines and cabling on the outside of the tank. NASA removed the ramp from the tank for the upcoming flight.

Engineers will present the result of analyses done to determine whether aerodynamic pressure during flight might rip the pressurization lines and cabling from the tank, triggering catastrophe. Hale said preliminary analyses indicate it will be safe to fly without the windshield.

Also on tap: A traditional Flight Readiness Review in mid-June.

The upcoming launch window for Discovery's mission extends through July 19. The next opportunity: Aug. 28 through Sept. 13.