The U.S. space agency NASA has cleared the shuttle Discovery for re-entry Monday with no need for another repair spacewalk. The crew has finished most of its work at the International Space Station and took time Thursday to remember fallen astronauts and cosmonauts.
After a mission fraught with worries about problems with Discovery's fragile heat shield, shuttle officials say the orbiter appears safe to come back to Earth.
The last issue engineers hurried to analyze was a loose piece of thermal blanket below the cockpit window, believed torn during Discovery's launch by debris falling off its exterior fuel tank. NASA feared that if the fabric ripped away during the high-speed descent through the atmosphere, an impact could damage Discovery's tail or braking rudder.
A fourth spacewalk was considered, but Mission Control radioed to Japanese crewman Soichi Noguchi that the venture outside would not be necessary. Wind tunnel tests simulating re-entry had showed the billowing blanket not to be a threat.
MISSION CONTROL: "Soichi, we have good news. The blanket underneath the window is safe for return. We had new analysis that showed that the debris transport would be no issue and we came to the same conclusion with the tunnel test."
NOGUCHI: "That's, I would say, good news."
NASA's engineering analysis showed a very small chance that the blanket flap would tear away during descent. Even if it did, the worst result of a fabric impact might be a 15 centimeter by two meter hole in the shuttle's rudder, which the space agency says would not cause the crew to lose control during re-entry.
Deputy shuttle program manager Wayne Hale says the risk from the fabric is too small compared to that the crew would face during a spacewalk to cut the cloth away.
"The remedy that might be called for to try to make this better would be worse. We would violate the 'first, do no harm' principle. So we believe that the chances of anything untoward happening with this piece of fabric is remote," said Mr. Hale.
President Bush told reporters at his Texas ranch that, although the shuttle has been beset by the need for unplanned repairs, he is confident that mission officials will make the right decision about how to proceed with a safe landing.
Discovery is to undock from the International Space Station on Saturday after an eight-day visit in which the crew restocked the outpost with supplies and performed spacewalk repairs on its gyroscope stabilizers.
As they orbited high above Earth Thursday, the combined U.S., Russian, and Japanese team aboard the two spacecraft paid tribute to space colleagues who have died in accidents over the years, most recently in the shuttle Columbia in 2003.
"To the crew of Columbia as well as to the crews of Challenger, Apollo-1, and Soyuz-1 and 11, and to those who have courageously given so much, we now offer our enduring thanks," said Space Station astronaut John Phillips.
At the end of the nine-minute tribute in three languages, the orbiting complex passed into nighttime.