by Marcia Dunn
AP Aerospace Writer
Columbia accident investigators hoped to finally fire a piece of foam at space shuttle wing parts, a crucial test to help prove whether the foam is capable of a catastrophic strike.
Late Friday morning, the overcast sky was clearing and the drizzle had stopped, allowing researchers to prepare the giant cannon and wing replica for the impact test.
The experiment was rescheduled after Scott Hubbard, the investigator in charge of the testing, was stuck in Houston on Thursday because of thunderstorms and could not fly to San Antonio.
Also, lightning would have endangered those taking part in the outdoor experiment. And the driving rain would have ruined the picture-taking required for the test.
"It's been several months to get this point, where we're ready to fire a piece of foam at the actual reinforced carbon that represents the leading edge of the shuttle," Hubbard said Friday after arriving in San Antonio.
It will be the first time foam is shot at the panels and seals that form the leading edge of shuttle wings. The key pieces were removed from another shuttle, Discovery.
During Columbia's liftoff back in January, a 1 1/2-pound chunk of foam broke off the fuel tank and smashed into the leading edge of the left wing. The investigation board suspects the debris knocked a hole in the edge that two weeks later let in the scorching gases of re-entry and doomed the ship and its seven-member crew.
Last week at Southwest Research Institute, a similar-size piece of foam was fired at a wing replica made up of fiberglass panels and seals taken from the never-launched shuttle prototype Enterprise. The parts that took the brunt of the impact were deformed by the foam.
Hubbard said he and others expect the upcoming test to result in greater damage because the reinforced carbon is more brittle than fiberglass.
To simulate what investigators believe happened at the launch pad, the foam will be fired at 530 mph through the 35-foot barrel of a nitrogen-pressurized gun normally used to shoot debris at airplane parts. Twelve high-speed cameras will document the test.