rocket stove: a small stove that holds small fast-burning fire that directs heat very efficiently for cooking. I've never made one! I think I'll start with a large coffee can size and experiment.
As I've seen them, in the interior of the coffee can there are other tincans cut and arranged from the bottom (where the fire is lit) to the top (where the pot sits) plus a little chimney to redirect smoke away from the chef.
I'm sure to make some mistakes! But I'll be happy to learn from them. And I'll keep a lookout for a stainless steel pot that will fit on top of a coffee can. It's sure to get sooty and burnt on the bottom, but the bottom of the pot doesn't need to be clean!
I have seen a ceramic Japanese "tea stove" (basically like a bucket with a vent in the bottom for air intake). It burned a special cake of coal with holes in it, but it could have run on wood or charcoal if needed. It fit those cast-iron teapots beautifully, and most other pots as well - it had a wide rim with three little nubby feet for them to stand on, so there was just a slot of clearance under the pot all the way around.
If you don't want black on the pot, we used to leave a film of soap on the bottom of our camping cookware. It scorched a bit, but it was really easy to wash off afterwards.