Other propellants makes me think- when, exactly, was nitroglycerine invented? I know the official patent date is 1864 or thereabouts, but other bits of chemistry lore floating around suggest it's not that hard to synthesize by accident; may have been discovered on numerous occasions before that, during the age of alchemical nonsense, with two major caveats.
It's a powerful, highly volatile explosive. Anyone who stumbled across it and had no idea what it was or how to treat it...there may be a good rational explanation for all those mediaeval alchemists who "stumbled across something man was not meant to know, and were torn apart by demons." Fluorine in the nineteenth century had a similar reputation; it was said that you could tell who had just managed to isolate elemental fluorine by reading the obituary columns.
So, in the field of developing other propellants then- if you can stop the alchemists blowing themselves up, yes, that will make the basis (with stabilisers, lots of stabilisers) of a successful solid propellant. It's roll of the dice time when it would be safely invented- arguably the official date is 1864 because laboratory procedure had developed to the point where it could at last be safely done. If it could be fluked earlier, well.