NASA is considering new options for foam insulation on the space shuttle external fuel tank, according to a contractor involved with the project.
Four pieces of polyurethane foam fell off the space shuttle Discovery during liftoff July 26. Discovery was scheduled to return early on Aug. 8.
PU foam problems with Discovery follow similar problems in 2003, when space shuttle Columbia exploded after a large chunk of foam fell from its external tank and damaged its left wing. After that, NASA engineers redesigned the external tank so it would use less PU, and added four rod-shaped heaters to help the foam keep the tank warm.
New designs for the external tank are not finished, but it would not be surprising if the foam were either better anchored to the tank or partially replaced on future missions, according to an Aug. 4 e-mail from Lockheed Martin Corp. spokesman Harry Wadsworth.
Lockheed Martin manufactures NASA's external tanks, including the foam, at its NASA Michoud facility in New Orleans. The site is government-owned but run by Lockheed Martin.
In the case of Discovery, four pieces of PU fell during liftoff, and one piece struck the wing. The shard was 7 inches long and 2 inches wide and struck the wing with one-tenth the force necessary to cause an accident, according to a NASA statement.
The largest piece of foam to fall was between 24-33 inches long, 10-14 inches wide and 2½-8 inches tall, but it did not touch the shuttle. The foam was jarred when the external tank hit the orbiter during launch.
NASA has declared that there will be no more flights until it finds a satisfying fix to its foam woes.
The PU was initially put on the tank to stabilize temperature, so ice wouldn't form. ``The [PU] foam on the external tank maintains propellant quality and insulates the tank from extreme cold and hot temperatures,'' Wadsworth said.
