Comment by tlavoie

I had (maybe still have somewhere?) a book I'd ordered online as a youth, on how to do exactly that. They were somewhat fiddly, in the sense of being slightly lower-impulse, with clay nozzles and a hollow fuel grain. Never quite got around to making any. I should look for that book though. In any case, it's likely harder than it used to be to get saltpeter, which they just carried in the pharmacy.