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Rocket candy: Wikis


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Rocket candy or rcandy is a term used to describe the practice of manufacturing solid rocket propellant from a formulation using sugar as a fuel and binder. It is also occasionally known as "Caramel Candy", a term that was popularised by Bertrand R. Brinley, in his pioneering book on amateur rocketry, Rocket Manual for Amateurs, published in 1960. This propellant was used in some of the amateur rockets described by Homer Hickam is his best-selling memoir Rocket Boys.

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. Dissolving the rocket propellant components in water will not work, because this propellant is very hygroscopic. It absorbs water from the air and if its components were dissolved in water, the dry propellant could not be recovered without heating it, which is a very dangerous operation. 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 when stored. The hygroscopicity problem can solved by adding 1% red iron oxide to the mixture of potassium nitrate and sugar. This additive not only prevents water from being absorbed, but also makes the propellant burn more quickly


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.[1] Lactose, corn syrup, and other sugars have also been used with some success.


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.


Flame rate increasers: Metal powders, iron oxide (catalyst).
Flame rate decreasers: Baking soda.
Others: Corn syrup, carbon black,400 Micron Aluminium Powder, sulfur.

External links


  1. ^ Sorbitol propellant instructions


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