One of the weird parts is that this is a solid fuel rocket. The USSR AFAIK never developed big solid boosters like the US.

Which always struck me as weird considering the USSR's ICBM program was supposed to be mobile from the start and it seems a lot easier to load a solid rocket onto a truck than carrying around (and having to pump) hypergolic mixtures that eat though any container, and kill by detonation, burns, poisoning, and cancer, in that order.