for First
that real proposal by Max Valier in 1929
Unfortunately Valier was killed in 1930, when an alcohol-fuelled rocket exploded on his test bench
second
So called Von Braun "Rocket interceptor"
there were some study but nothing serious.
For my part, this thing is a urban legend
More on this Interceptor
http://www.luft46.com/misc/vbi.html