. >> professor larry tanner does research on destruction from tornadoes. >> pictures of damage aftero is aut impact. >> where wind really becomes an issue is the debris opens up the building envelope, the walls the roof. once you have that envelope opened, now you've got double the trouble. the most predominant projectile that we see in these storms is normally something like a two by four. >> so what you tend to see coming out of this cannon is what you tend to see flying around when a tornado is centered? >> absolutely. we did a shelter research for the national science foundation back in maize after the moore tornado. specifically just to look for shelters in the storm path. >> the question now is: not whether to rebuild, but how. >> we're smart engineers. we know how to design for the wind speeds. and now, we know how to design for impact resistance. >> research performed tests on a variety of building materials. some of them failed. through trial and error, innovation came in the form of reinforcement and engineering. >> should we -- load the cannon? >> load the cannon. okay, le