Rocket Mass Heater Designs

I've done a lot of research on rocket stoves and rocket mass heaters --- to the point of obsession.Their design is ingenious. They've taken all the principles of all the masonry furnaces and wood stoves and created a marvel.

image cred: http://en.wikipedia.org

The first rocket stoves I saw were made by folks called "bushcrafters" - people who make useful stuff out of stuff they find. They'd use coffee cans or soup cans and arrange them so the fire burns hot and the heat goes directly to the cooking pot - very little heat is wasted. I thought it was a great idea for camping without having to take a camp stove and fuel along -- just use the wood from the surrounding camp - and not a lot of it either. The fire burns so hot you just need a little to get your food cooked.

I like a fire at night when I camp, but sometimes it's nice to just not have a fire at all - just let my eyes get accustomed to the dark and listen. I call it "using my radar" - where I just plop myself on a log and listen as intently and as far away as I can without the noisy crackling of a campfire, picking out all the faint, distant sounds and wondering what made them. Sometimes you hear coyotes, or a sampling of interesting owl songs. I once heard a mouse scurrying and squeaking in the cave I shared with it. These little coffee can rockets stoves burn just enough wood to cook on, so you can still have a hot meal on nights you want to enjoy the quiet.

image cred: http://www.inspirationgreen.com

So I thought these little soup-can stoves were the extent of it, until further investigation into rocket stoves revealed all sorts of designs, some that incorporated heavy insulation around the burn box for hotter fires, leading to an inverted 55 gallon steel drum that can radiate heat into your room like a wood stove. From there the introduction of cob sculpting took the design to amazing new heights! You can run the exhaust stovepipes through gobs of thick thermal mass (in the form of a long cob bench) horizontally - and then out a tall chimney all the way at the other end of the room - and the heat from the exhaust gets stored in the thermal mass bench along the way, releasing slowly into the room for hours after the fire's gone out.

I saw some of these in person -- one at the Mother Earth News Fair at Seven Springs PA and another in use at the Earthship at Blue Rock Station here in Ohio. The concept is simple, effective and the most efficient design in the world. You don't need to split wood and burn logs. You basically heat with kindling, creating fires so hot they don't even leave creosote, storing the heat in the thermal mass for hours. You can literally heat an efficient home (like the one we'll build) using the deadfall from a few acres of woods. Coppicing a willow or even using bamboo growing in old humanure compost can produce a steady supply of wood, too.

Though the fire burns super hot, by the time the heat from the exhaust reaches the other side of the room, it only heats up the vertical chimney to about 120 degrees or so, and there's so little smoke that folks in the city have piped these out their window and the neighbors don't even know there's a wood burning heater in the house. Good way to fly under the radar to avoid paying those nasty heating bills in cities that don't allow wood-burning heaters.

I love this illustration next. It gives you all the necessary proportions so you can tweak it to suit your home.
(compliments of Permies.com). See how you can just toss in long sticks and let them feed themselves into the fire at they burn down? After having heated with a woodstove in Hocking County for a few years, the thought of not having to split wood or constantly feed a fire is a comforting one. I plan to design my stove with a cage over the hot box so I can stack long branches that will self-feed the fire for longer periods of time, so I don't have to.

I'd like to build a small one under our bed so in winter we can burn a few sticks an hour before bedtime and let that heat rise slowly from under our bed.

This is great design for a kitchen stove:

 Soon after we talked together about using a cast iron griddle for a cooking surface, lo and behold a good friend just happened to buy us one for Christmas. This so far is closest to the design I'd like to use for our kitchen.