Pocket rocket stove. I got this idea from the rocketstoves.com website as an excerpt of Ianto Evans’ rocket mass heater book. The book version is slightly different, but as you can see this version works quite well. It’s a 5 gallon metal bucket with stovepipe through the lid. An 18″ section goes down into the bucket for the feed tube, and two 24″ sections go up for the chimney. It gets VERY hot, burns wood fast and clean, and radiates an absurd amount of heat.