Hydrogen peroxide, H2O2, is not something most people normally think of as “fuel.” After all, it’s got no carbon in it. Most people know that, as an oxidizer, it can enhance the burning rate of fuels, but the familiar “fire triangle” teaches us that combustion requires both an oxidizer and a fuel, plus a source of ignition, to get started. Turns out, depending on how concentrated it is, hydrogen peroxide can, under the right conditions, explode all on its own. The 3% aqueous solution in your medicine cabinet is completely safe, but the hazards increase rapidly as the amount of H2O2 goes up and the amount of H2O goes down. Up around 85% peroxide, the stuff is literally rocket fuel, and its spontaneous decomposition in the presence of a catalyst like, say, metallic silver or manganese dioxide, happens incredibly fast. The rocket motor in Wendell Moore’s famous Bell Rocket Belt (Wikipedia) operated on this principle.
Shown above is a video of the Dragonfly DF1, an experimental aircraft under development by Swisscopter US. Instead of a traditional gasoline engine, the Dragonfly has peroxide-powered rocket engines on the tips of its main blades, with a mechanical take-off to drive the tail-rotor. Large tanks of high-test peroxide supposedly provide 50 minutes of flight at 40 mph.
So why would anyone want a helicopter that works this way? Turns out an H2O2 rocket motor is vastly simpler than a gasoline engine, mechanically, and thus (at least theoretically) less failure-prone, and therefore safer. All you need to make an H2O2 rocket is a tank of high-test peroxide, another tank of inert gas to pressurize it, and a nozzle with a silver-coated screen to spray the stuff through. [via DVICE]