From the N-1's wikipedia page: Each of the four attempts to launch an N1 failed; during the second launch attempt the N1 rocket crashed back onto its launch pa

From the N-1's wikipedia page: Each of the four attempts to launch an N1 failed; during the second launch attempt the N1 rocket crashed back onto its launch pad shortly after liftoff and exploded, resulting in one of the largest artificial non-nuclear explosions in human history. Energia's a more interesting comparison, since it's hard to know if its advertised payload was at all accurate, but it did fly. I'd say that if it could have delivered its advertised payload reliably, the design probably would have flown more than twice and would have survived the fall of the Soviet Union. I have no idea what a half-finished Buran weighs...