NASA concerned over ice hit on underside of Endeavour

William Atkins
Saturday, 11 August 2007 19:27

Science - Space

Tracking cameras on the ground and on the external tank recorded debris hitting the underbelly of the space shuttle Endeavour at about 58 seconds after it was launched into space 8/8/07 for its STS-118 mission.

Nine pieces of mostly foam, but some ice, were seen impacting the shuttle orbiter as it launched to the International Space Station. Two debris hits were especially of concern to NASA mission managers: 24 seconds into the flight debris hit the tip of the shuttle’s body flap, near the underside of the tail; and 58 seconds after liftoff debris hit the underside of the shuttle’s right wing.

The 58-second hit now seems to be the one that most troubles ground controllers at the Mission Control Center in Houston, Texas.

In the photographs, the ice hit shows up as a lightly colored gouge or nick about 4.5 feet (1.25 meters) from the starboard (right) landing gear door, which is covered with black-colored tiles from the shuttle’s thermal protection system (TPS). One major 3-inch (7.5-centimeter) by 3-inch (7.5-centimeter) damaged spot is identified, with lesser spots also being seen.

The ice came from the external tank (ET). Ice forms on the external tank because it is filled with very cold fuel (liquid hydrogen) and oxidizer (liquid oxygen). In addition, foam insulation is applied to the ET, which also has a tendency to break off in fragments during launch of the shuttle.

The STS-118 crew will use the orbiter boom sensor system (OBSS) to investigate further the incident area. If the gouge is deep enough, the astronauts have equipment and materials onboard to perform a spacewalk to repair the area. They have three options for the repair: (1) inject a thick caulky substance into the damaged site and use a trowel-type tool to spread it above the damaged area, (2) apply a black-colored carbon and silicon paint-like fluid to the damaged area, and (3) bolt a heat-resistant plate on top of the damaged area.

On Sunday, August 12, 2007 (beginning at about 12:06 pm EDT [16:06 GMT]), the shuttle astronauts will use the 100-foot (30-meter) robotic arm and extension beam to inspect the damaged area. Lasers located at the end of the extension beam will sense and record the size and depth of the gouge. Additional photographs will be taken. Mission controllers on the ground will then perform additional analysis to determine if the damage is serious enough to perform a spacewalk to repair the damage.