14 DAY TRIAL // As if it was not enough, NASA engineers have found a third small crack in the aluminum skin of the external fuel tank of the space shuttle Discovery, while they were carrying final repairs before the spacecraft's last spaceflight.
Kennedy Space Center engineers were already analyzing the two 23 centimeters (9 inch) cracks, discovered earlier this week on the same fuel tank.
This new crack, discovered yesterday, was found on the metal skin on an adjacent section of the fuel tank, unlike previous cracks, that were in a metal 'stringer' – a ring around the upper section of the tank, and beneath a layer of damaged foam insulation.
The 'stringers' are aluminum strips that are meant to ensure the structural integrity of a part of the fuel tank called the intertank – the segment between the liquid oxygen and liquid hydrogen tanks.
NASA spokesman Allard Beutel told SPACE.com that “the thinking is, when the original stringer cracked because of stress and pressure loads, it then transferred, and the adjacent stringer on the left hand side got a small crack in it.”
This is not the first time that shuttle technicians have repaired such cracks on external tanks, and they did it by replacing the broken aluminum with a stringer section twice as thick, and replacing the foam afterward.
But in this situation there is however a small difference: it is the first time that they have to work on the shuttle at the launch pad.
Normally, this kind of cracks were taken care of during the external tank production phase at NASA's Michoud Assembly Facility in New Orleans, where the space shuttle fuel tanks are being built.
Beutel specified that this third crack is about 3 inches (7.6 cm) long, and it's located on the left-hand side of the original cracked section.
This weekend will be a very busy one for the shuttle technicians, who will have to analyze all data and find the best way of safely repairing the Discovery, on location.
“They're going to analyze the new data and expand their look for additional cracks,” said Beutel.
“They want to better understand how much stress that area can take, and how the cracks happen in the first place.”
Discovery's next flight will be its last mission before being retired along with the rest of NASA's shuttle fleet, and hopefully everything will go as planned, on November 30.