Hubs and I have used a variety of rocket stoves. When he first heard of them he experimented on several different styles and materials. He even made one with three separate cooking heads so we could prepare more than one dish for dinner at one time. It worked OK but not great. We live in a tiny house off grid. He had started to make a rocket mass heater to heat our home. We have an endless supply of 1.5-2” diameter wood. He took a very old large propane cylinder, put a chimney stack in the center of it, and filled the perimeter with 275# of play sand. That would keep the house warm for hours and if one of us was up during the night, we could refill the wood feed. It could also be used for a cook top if we wanted. Lifus Interruptus happened when one of our kids plus spouse moved out here without access to water. Our small on demand water heater took a dump shortly thereafter. Hubs took the rocket stove he’d made and turned it into a water heater. He placed a non-functioning gas water heater on top of the stove. Sealed it well. Plumbed cold water to fill via the tube in the tank and hot water to release at the top. Voila! A water heater capable of heating 60 gallons of water in 45 minutes in winter and 25 minutes in summer. It kept enough hot water for 4 showers and doing dishes. And it was HOT! I do not have pictures. All the pictures were on a phone that I no longer have access. It was big. It looked ungainly. But it worked flawlessly for three years. To me it was beautiful. This is just one example of the versatility of these stoves. Now ones like this are not portable by any means, but there are several styles that are. A small one can even fit in your BOB. If you are more urban, there will be a huge supply of burnable materials if SHTF. These stoves could come in very handy. https://homesthetics.net/rocket-stove-plans/