Good crazy ideas revolve around solving one or a handful of extremely hard engineering tasks, which make everything else easier "assuming the crazy thing works."
Bad crazy ideas break any part of that description. The single hard thing is new science/research instead of engineering, or the new hard thing won't make the rest easier, or the new hard thing is supposed to get rid of all the other problems.
Bad crazy ideas break any part of that description. The single hard thing is new science/research instead of engineering, or the new hard thing won't make the rest easier, or the new hard thing is supposed to get rid of all the other problems.