A Rocket Stove is probably so named because the vertical column of flame in it resembles that of a rocket’s. The flame however does not descend as in a rocket, but rise. The updraft thus created, draws ample air to completely burn firewood. The net result is that the stove is smoke free, economic in firewood use and fast to cook with.
It was invented by Dr Larry Winiarski about a decade ago. There is growing interest in it worldwide, among people who have been searching for the ideal cook stove for the poor. It has been found that respiratory diseases among poor women are traceable to long hours spent cooking in unventilated indoors using smoky stoves. The Rocket Stove addresses all these issues with great simplicity. In addition, making do as it does with twigs and slender sticks as fuel, a Rocket Stove has a beneficial impact on the environment. Women are also spared long treks in search of cooing fuel.
Winiarski has stated the principles governing design at this link. If that is too rigourous read, a quick illustrated explanation
is found here. Simply speaking, a Rocket Stove consists of two pipes arranged in a L-shape; the vertical limb, [usually about 400mm or 18″] is longer than the horizontal. The horizontal limb is where the fuel is introduced. Some free space is ensured here for combustion air to be drawn. Fire is begun using an oily rag, paper, straw or pine needles. Slender twigs are then placed over the fire and once they catch, larger sticks may be introduced. Soon the initial smoke ceases and there is a steady brisk column of fire. Heat is controlled by pushing in or pulling out firewood. [This site has a good review of various wood stoves, their merits/demerits and finally a simple Rocket Stove design]
Looking back on the first Rocket Stove project at pointReturn, it is now clear it was both too large for current needs and over ambitious in design. I was building a stove that can cook for a dozen people who are not yet on the horizon. An over creative approach led to incorporation of a two-pot top with a damper control and two baking boxes. It was fun to design and build though. It engaged five of us on a full fun-filled day. You can see the detailed drawings I made at this link. You can also choose to run them as a correctly sequenced instructional slideshow. Caption in each frame explains the step.
But before you build one like that, here is a critical review. The size as I said, is too large. On the day it was inaugurated it did cook for 26 people but such a stove is more efficient when it is used regularly, more or less all day, as in hostels and restaurants. Chunky lengths of firewood are required to sustain a robust vertical flame. In other words the design is for a professional cooking.