NASA switched to a Freon-free insulating foam for the external fuel tanks starting with the STS-87 flight of the Shuttle Columbia in 1997. This flight received dramatically more damage then previous flights. Subsequent shuttle flights using the new foam continued to result in up to 11 times more damage then previous flights with the original foam. Click on Read More for the full story.
The switch to the environmentally friendly foam was made as part of a NASA effort to reduce the environmental impact of space flights. EPA regulations banning CFC's including Freon were put in place due to a suspected link to high altitude Ozone layer depletion.
Examination of the extensive inspection photographs of Discovery has found only small damage to the thermal protection system. NASA has admitted that it was simply luck that one piece of foam almost as large as the one blamed for the destruction of Columbia missed the leading edge of Discoveries wing, and has grounded the remainder of the shuttle fleet until a solution is found. If that piece of foam would have fallen off just 30 seconds sooner in the flight it may have hit the shuttle with similar force as the one that doomed Columbia.
A detailed search through the pictures and video taken during Discovery's launch has found a much smaller piece of foam that apparently deflecting off the wing. Other items found during the inspection include a piece of damaged tile on the critical nose wheel door and a piece of gap filler, which insulates between the tiles, which is protruding located slightly farther back on the belly of the shuttle. These areas are being examined in great detail.
Talk about this article in the discussion 
