Rocket Candy: Sugar and KNO3 Rocket Fuel
Rocket Candy is a type of rocket propellant for model rockets made with sugar as a fuel, and containing an oxidizer. The propellant can be divided into three groups of components: the fuel, the oxidizer, and the additive(s). The fuel is a sugar; sucrose is the most commonly used. The most common oxidizer is potassium nitrate (KNO3). A traditional sugar propellant formulation is typically prepared in a 13:7 oxidizer to fuel ratio.
There are many different methods for preparation of a sugar-based rocket propellant. Dry compression does not require heating, only the grinding of the components and then packing into the motor. However, this method is not recommended for serious experimenting. Dry heating does not actually melt the KNO3, but it melts the sugar and then the KNO3 grains become suspended in the sugar. Dissolving and heating the propellant actually melts both of the components and combines them.
Open flame should never be used to melt the propellant, and the mix should always be heated in an oil bath, never over direct heat. Because rocket candy is extremely flammable, it should be prepared in small batches, out of doors or in an outbuilding, and using adequate personal protective equipment (eye protection at the very least). But Do Not Attempt This At Home.