"In 1999, the Southwest Research Institute, a non-profit laboratory in San Antonio, Texas, fired insulating foam fragments from a compressed-gas gun into thermal tiles and recorded the results with digital cameras. After the Columbia crash, NASA asked the institute not to release those results. The space agency also has tested the foam in wind tunnels and aboard a research jet."
http://www.bayarea.com/mld/mercurynews/news/5100794.htm