Looks like the experimental designer actually thinks it might have been completely destroyed by friction: http://en.wikipedia.org/wiki/Operation_Plumbbob#Propul

Looks like the experimental designer actually thinks it might have been completely destroyed by friction: http://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap http://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_o...