An "idea" that's impossible to build (in terms of cost, time, materials, or understanding of physics), and/or has to benefit or reason to exist, isn't much worth discussing in a forum dedicated to discussing science and technology. As a lark in Misc, maybe. Just not here...
I have to disagree with this. There is nothing wrong with discussing something "impossible". The least of which reason is that how do you know it's impossible without discussing it first?
The problem is that the discussion has to be open with both sides (if it degenerates to "sides") being open to talk about the problems with the idea, how it can be improved on, and what the alternatives are.
It seems some of the threads here get sidetracked with the semantic use of words. On both sides of the argument. This to me comes off as pure trolling especially in cases where the intent of a word can be inferred from the post it was used in.