SAN ANTONIO ? A chunk of foam insulation fired at shuttle wing parts Monday blew open a gaping 16-inch hole, yielding what one member of the Columbia investigation team said was the “smoking gun” that proves what brought down the spaceship.

The crowd of about 100 watching the test gasped and cried, “Wow!” when the foam hit — the impact so violent that it popped a lens off one of the cameras recording the event.

The foam struck roughly the same spot where insulation that broke off Columbia’s external fuel tank smashed into the shuttle’s left wing during launch. Investigators had speculated that the damage led to the ship’s destruction during re-entry over Texas in February, but Monday’s test offered the strongest proof yet.

“We have found the smoking gun,” Columbia Accident Investigation Board member Scott Hubbard said of the panel’s seventh and final foam-impact test.

The 1.67-pound piece of fuel-tank foam insulation shot out of a 35-foot nitrogen-pressurized gun and slammed into a carbon-reinforced panel removed from shuttle Atlantis.

The countdown boomed through loudspeakers, and the crack of the foam coming out at more than 530 mph reverberated in the field where the test was conducted.

Sixteen high-speed cameras captured the impact, and hundreds of sensors registered movements, stresses and other conditions. The impact was so strong — packing a full ton of force — that it damaged some of the gauges.

“There’s a lot of collateral damage,” said Hubbard, a high-ranking NASA official.

Hubbard said the test results showed it would have been extremely difficult, if not impossible, for Columbia’s astronauts to have repaired such a large hole in orbit. He stressed that the actual gap in Columbia’s wing may have been a bit smaller — or possibly a bit bigger.

NASA investigator Dan Bell examines a 16-inch hole seen in a carbon-reinforced wing panel removed from space shuttle Atlantis after a chunk of foam insulation was shot at it during a test in San Antonio. A member of the Columbia investigation team said Monday's test was the smoking

“We know that almost surely there was a breach on the order of 10 inches in diameter,” he said. “Here we’ve got one 16, so that’s in the same ballpark in my book.”

He added: “The board’s goal was to connect the dots between the foam-shedding event and the proximate or the direct cause of the accident, and that’s what this whole test program has been about. I think today we made that connection.”

Monday’s test at the Southwest Research Institute best replicated the blow from debris that occurred 82 seconds into Columbia’s liftoff in January.