Throw a piece of insulation bigger than you are into your car at 35 mph and tell me it's not that big of a deal.

"even if it was steel...lol" I can tell you don't work around construction materials or around aircraft. Aircraft/spacecraft are made light to get them up...very light. It's easier to bang on a wing with a rubber mallet and make a huge dent in it than it is your car you drive everday.

Remember it doesn't even take a puncture to take down the shuttle, rather a small dent can cause a heat problem when the airflow over it changes suddenly. I'm not sure if the wing was ruptured on the shuttle that came down but possibly just a disruption.

I picked up tons of pieces of the last shuttle on Forest Service land (actually we just tagged and GPS'ed them) in San Augustine and Sabine county Texas two years ago. Peices that were just a little smaller than a person would weigh 20 pounds - maybe less.