Rocket candy

Rocket Candy, or R-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). Additives can be many different substances, and either act as catalysts or enhance the aesthetics of the liftoff or flight. 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. If you use this way of preparation always melt the sugar, remove heat source and then add the KNO₃ to avoid premature ignitions. Dissolving in water, then heating the propellant to drive off the water eliminates the need to melt the components while still achieving thorough mixing.

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. This is to avoid hot spots causing auto-ignition or caramelization and degradation of the propellant. Preparing rocket candy in a microwave oven is very dangerous because localized hotspots can ignite. 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).

The specific impulse, total impulse, and thrust are generally lower for the same amount of fuel than other composite model rocket fuels, but rocket candy is significantly cheaper.

In the United States, rocket candy motors are legal to make, but illegal to transport without a low explosives users permit. Since they count as amateur motors, a user must launch them at a sanctioned Tripoli Rocketry Association research launch and must have at least a Tripoli Rocketry Association high power level 2 certification. Similar laws apply in Canada, the UK, and Australia.

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