More Changes To External Tank On Tap After Discovery's Flight

A lot has been done... but there's still a lot of work to do. That was the word from space shuttle program manager Wayne Hale Wednesday, as he told reporters that while Discovery is slated to fly into orbit next month with a much-modified -- and hopefully safer -- external fuel tank, scientists have not stopped looking for more ways to reduce the likelihood that insulating foam will break off during launch, and potentially damage the orbiter.

"We are on a road for continuous improvement," Hale said at a news conference. "We are trying to eliminate the biggest hazards and work our way on down."

At the very top of that list of hazards were the old tank's protuberance air load ramps, or PALs, that were originally designed to divert airflow away from plumbing and electrical connections between the tank and the orbiter.

Since the last shuttle flight, scientists have removed the two ramps -- which were 38.5- and 14.5-feet long -- in order to eliminate the source of foam fragment that doomed Columbia in February 2003, and caused many tense moments during Discovery's first Return-to-Flight mission last August.

Although two sources of foam breakage have been eliminated, Hale said there's more work to be done.

"We have found no showstoppers. We believe we have made significant improvements," said Hale. "There will continue to be foam coming off the external tank. What we have done in a very systematic manner is eliminated the largest hazards."

Next on the list of changes to the massive fuel tank will be the elimination of 34 foam fixtures, each weighing 1 to 2 pounds, that insulate a row of metal brackets called "ice frost ramps".

Hale said these pose the biggest challenge to Discovery's upcoming flight, slated to liftoff July 1. However, changes to the ramps aren't expected to fly until later shuttle missions in 2007.

FMI: www.nasa.gov