"Brian Gaff" wrote in message
...
Could some form of radar be used to look at these surfaces, from the tank?
Maybe milimetric scanned repeatedly?

I doubt that foam would reflect radar very well, and I think you'd have to
make quite a bit of room in the belly somewhere for an MMW radar that would
be used only for a little while. A LIDAR System might work better, though,
and it wouldn't take up as much space.