Discovery heat shields believed to be OK

NASA this afternoon said shuttle Discovery's heat shields are expected to be in good condition despite four reported events of external tank foam or other debris coming loose during Thursday's climb to orbit.

LeRoy Cain, the deputy shuttle program manager and chair of the Mission Management Team overseeing Discovery's flight, said all four events happened after the period when aerodynamic force can cause dangerous strikes.

Cain presented slides that showed a chunk of foam missing from the tank near a flange where the liquid hydrogen tank meets the intertank section, and the path of what was believed to be the biggest piece of foam shed, three minutes and 51 seconds into flight. 

That area of the tank is known to be susceptible to a phenomenon called "cryo pumping," Cain said, in pockets of cold air heat up during ascent as fuel is burned and pop foam from the tank.

Of the four reported debris events, Cain said one was not confirmed to be foam.

Discovery's crew is wrapping up a day of heat shield inspections using the shuttle's 50-foot robotic arm and a 50-foot boom extension equipped with sensors and cameras. Orbiter systems are performing well.

Analysts on the ground will review images downlinked from today's scans and pictures taken from the International Space Station during tomorrow's approach.

A decision is expected Sunday on whether Discovery's thermal protection system is in good health or if any areas of concern require a more detailed look.