The Hunt for Damage on Endeavour

Aug. 12, 2007 — -- Astronauts are using the shuttle's robotic arm to get a better look at a damaged area on Endeavour.

Video of Endeavour's launch shows a grapefruit-sized piece of foam coming off a bracket on the fuel tank, then bouncing off a strut farther down and ricocheting into Endeavour, said John Shannon, chairman of the mission management team.

The brackets hold the long fuel feed line to the tank, and the struts connect the tank to the shuttle for launch. Ice tends to form near the brackets, and engineers believe ice caused the foam to pop off at liftoff.

Astronaut Cady Coleman, who heads the robotics program for the astronaut office, said while using the robotic arm to inspect the damage is a delicate procedure, the crew knows what they are doing.

"They've practiced this before in their training," Coleman said, "and it has been pre-planned. They know how to get their head ready and proceed safely."

Shannon said foam has come loose from the brackets on at least three of the four previous shuttle flights, and that worries Shannon.

"It's a little bit of a concern to us because this seems to be something that has happened frequently," he said.

The foam hit underneath Endeavour's right wing, and gouged a three-inch-by-two-inch nick in the shuttle's heat tiles, which protect the orbiter from the searing heat of re-entry.

The foam hit was bad luck for NASA, but where it hit may turn out to be good luck, because under the damage is a structural spar that could act as a heat sink and protect the shuttle, which means NASA may not have to send a spacewalker out under the shuttle to repair Endeavour in orbit.

NASA has struggled with foam loss from the external tank since the space shuttle began flying in 1981 -- until Feb. 1, 2003. A 1.67-pound piece of foam broke off Columbia's external tank during launch and smashed into the shuttle's left wing almost 82 seconds in. It punched a hole in the wing, which allowed super-hot gases to penetrate the wing as the shuttle re-entered the atmosphere. Columbia broke up over Texas, killing its crew of seven.

The flight control teams, which worked on missions prior to, and including, Columbia's last mission, had no way to inspect a shuttle for damage. One of the requirements NASA had to meet before returning the shuttle fleet to space was figuring out how to inspect each orbiter for damage.

Each shuttle now flies with an orbital boom outfitted with a camera and a laser, which attaches to the shuttle's robotic arm. During each mission, time is built into the schedule to allow the crew and Mission Control to inspect each shuttle before it is allowed to return home.

Coleman said NASA has to be as diligent as possible.

"We understand that there are risks, risks that we maybe didn't understand as well before Columbia," Coleman said. "We have the tools to do it, and there is no reason not to do the inspection."

The imagery analysis team will pore over the video and photography down linked from the inspection, and hopes to be able to clear Endeavour for a safe return on Monday.

NASA will struggle with foam loss from these brackets for several more flights until a new design for the bracket is implemented for STS 128, which flies sometime in 2008.

Space Shuttle program manager Wayne Hale has long acknowledged the flaws of a foam-covered external tank. When asked once at a press briefing what advice he would give the designers of the space ship that will take astronauts back to the moon, he said, "I would tell them to put the tank under the spaceship."

The drawings that have been released of the Moon-Mars launch system Constellation show that indeed, the tank will go under the spaceship.