Rocket candy

Rocket candy is a term used to describe the practice of manufacturing rocket fuel from a formulation using sugar as a fuel and binder.

This formulation is used primarily by amateur rocketry hobbyists due to the ease of obtaining the ingredients. The sugar fuel/binder is mixed with the oxidizer potassium nitrate, which is also easily obtainable and reasonably safe to work with. Engines using this type of fuel are sometimes termed "sugar motors" or K/S motors (for KNO₃/Sucrose).

The KNO₃ is commonly mixed with molten sugar and poured into the rocket casing, sometimes using various centre molds to obtain different cross-sections. These cross-sections dictate the burning pattern of the poured grain. Another method is to make a water solution of the two components, in the same manner as making toffee. This mixes the two parts completely, and it occurs at a lower temperature, providing a safer margin below the auto-ignition point. 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, to avoid hot spots causing auto-ignition or caramelization and degradation of the propellant.

Rocket candy is hygroscopic and needs to be sealed from moisture.

Rocket candy was used in the amateur rockets in the book "Rocket Boys" and its film adaption "October Sky". It was also featured on the Mentos and Coke episode of "MythBusters", though it was contained in a paper cupcake wrapper and called a "smoke bomb".

Fuel substitutions

Some sugars can be substituted for sucrose in rocket candy. Sorbitol, a common artificial sweetener, produces a less brittle propellant with a slower burn rate. This reduces the risk of cracking propellant grains. Lactose, corn syrup, and other sugars have also been used with some success.

Ratios

Typically the proportion is 60/40 with the former being potassium nitrate. When iron oxide is used, it is usually used up to 2%. Sulfur is sometimes used up to 10%. Metal powders are used up to 10%. Baking soda is typically used at about 5%, but can be used for up to 30% for extremely slow burning propellants.

Additives

Flame rate increasers: Metal powders, iron oxide (catalyst)Flame rate decreasers: Baking sodaOthers: Corn syrup, carbon black, sulfur

External links

* Amateur Rocketry [http://www.gdescalzo.com.ar/motor_god-1.htm] web page in Spanish language, featuring sorbitol (candy) rockets and rocket motors.

* Richard Nakka's Experimental Rocketry Web Site [http://www.nakka-rocketry.net/] .

* Recrystallized Rocketry [http://www.jamesyawn.com/] .

* Sugar Shot To Space [http://www.sugarshot.org] .