NASA to postpone additional shuttle tank work

CAPE CANAVERAL, Fla., Apr 29 (Reuters) NASA plans to fly the space shuttle Discovery in July without further changes to the external fuel tank, despite some engineers' concerns that the tank needs more work.

Foam insulation falling off the tank during launch damaged shuttle Columbia's heat shield, causing the destruction of the craft and the deaths of seven astronauts as the ship attempted to return through the atmosphere on February. 1, 2003, officials said yesterday.

The problem area was redesigned, but foam from another part of the tank fell off during the July 2005 launch of sister ship Discovery on the first post-Columbia mission. The debris did not damage Discovery.

NASA is in the midst of testing its second redesign, which removed two wedges of foam that shield cables and pressurization lines on the outside of the tank from buffeting winds during the shuttle's supersonic climb to orbit.

''The question is 'Will the vehicle hold together or not?''' space shuttle program chief Wayne Hale said in a teleconference with reporters. ''If the answer is 'No,' well we're not going anywhere.'' That decision will be made during a preflight review on June 16.

The removal of the 38-foot-long and 14-foot-long foam ramps also raised concerns about 34 small foam wedges which cover metal brackets that anchor the pressurization lines and a tray housing the cables.

While acknowledging the possibility of a catastrophic strike on the shuttle from a piece of flyaway foam, Hale said in the end he decided to postpone additional work until after the tank's new redesign had been tested in flight.

Removing the ramp, said Hale, is ''the largest aerodynamic change that we have made since the shuttle first flew.'' ''We're in a flight test program,'' he added. ''When you make a major change, you should fly that major change and if you have to make additional changes then you make them after the flight.'' In the worst-case scenario, if 3.5-ounce chunk of foam fell off a tank bracket at the most critical time during Discovery's launch, and if it hit the most vulnerable part of the ship's heat shield, the consequences could be catastrophic, Hale said, adding that the risk was extremely small.

''We expect to see foam from the (wedges covering the metal brackets) coming off on the next flight,'' Hale said.

The pieces, however, are not expected to pose a significant threat to the shuttle or its crew.

Upon Discovery's safe return, additional work is planned to reshape the foam insulation over the brackets, Hale said.

NASA plans to fly the shuttle another 16 or 17 times to complete assembly of the International Space Station. The fleet is to be retired in 2010.

REUTERS SRS RK0436