Why doesn't a certain level (lvl 6) in the "normal" Naval research tree need to be investigated to produce Nuclear BS, Nuclear subs and Nuclear Carriers? now I can produce nuclear carriers without knowing the construction of at least level 1 normal carrier ...?!
For Nuclear Rockets this condition (rocket lvl 4) remained.
That's not very logical ...
I would suggest the need for basic research.
Or, you can research SP Arty without even knowing how to build AC.
The whole research tree was made SO HASTILY and without any serious consideration that is amazing.