By Liz White, UT staff
Kennedy Space Center, Florida-Launch of the Space Shuttle Discovery, originally planned for Saturday 1 July, is now scheduled to go ahead today, Tuesday 4 July.
Routine inspection of the polyurethane foam insulation covering the shuttle's external fuel tank found a crack in the foam, but the Mission Management team has analysed the data and decided that this is not a cause of concern.
Saturday's launch was delayed by bad weather, and inspectors working overnight on Sunday, after the tank was drained, found a crack-reported to be 12 cm by 3mm- in the foam.
The Shuttle managers at NASA-National Aeronautics and Space Administration-have been heavily criticised already in the US media for deciding to fly the next Shuttle mission despite acknowledging the risk that foam debris from the tank could break away. NASA, however, says that it has "always made it clear that foam will come off the tank due to the highly dynamic conditions during the early stages of launch." A 750g chunk of foam from the external fuel tank was identified as the cause of the damage to the Columbia shuttle which resulted in its catastrophic break up on re-entry on 1 Feb 2003, killing the seven member crew.
After extensive redesign of the tank and foam, particularly in the area of the protruberance airload (PAL) ramps, Shuttle managers concluded that, while they could not guarantee a total absence of foam debris, any pieces were going to be too small to cause significant damage.
Then, during last July's successful Discovery flight, some foam from the PAL ramps came off the tank. Inspection showed cracks in these ramps, said NASA and the programme managers decided to fly the remaining shuttle missions without the ramps.
Assessing the latest crack, in the foam near a bracket that holds the liquid oxygen feedline in place, NASA identified the probable cause as rain during Sunday's launch attempt. This may have caused water to run down the feedline and form ice near the top of the strut next to the feedline bracket, NASA's statement said.
As the tank warmed and expanded, it is likely that the ice that formed pinched the foam on the top of the strut, causing a crack and eventual loss of a small piece of foam, according to NASA's 3 July statement.
"Extensive analysis showed that the area around the crack is intact and there is no concern for heating as there is adequate foam in place on the strut. Additional borescope inspection of the tank revealed that the bracket has no cracks," the statement concluded.
Pic: the PU-coated external tank used for last July's successful Discovery mission. "
