Candy/Sugar Rocket Propellant (KNSU) [ENG]

1. Sugar-nitrate rocket propellant(KNSU) is most often a mixture of potassium nitrate and sugar or sorbitol 00/00 or 00/00 by mass, respectively.  It often referred to as candy propellant or R-candy, since the sugar and nitrate are cooked and cast into a hard cylinder resembling hard candy.  Interestingly, the sugar is can be acquired from actual candy products such as gummy bears and pixie-stix®.1 Large motors are always cast in re-crystallized grains; while smaller motors can be dry-pressed using confectioners sugar and milled KNO3.  Most R-candy enthusiasts prefer using high fructose corn syrup in addition to regular sugar, which provides a much longer curing time at low temperatures, similar to using sorbitol. The long, low temperature curing time makes it easy to hand load into molds, as well as reducing many cracking and grain boundary issues that will almost certainly arise in larger grains using table sugar only.  However, some amateurs have had success casting large grains with only table sugar and KNO3 by adding water and boiling the water out.  Almost all sugar/nitrate motors are core burners, due to the slow burn rate of sugar propellant.  Red iron oxide powder or sulfur powder can be added as a catalyst to increase the burn rate of sugar r-candy propellant.  Usually, the catalyst constitutes between 0.5% to 3% of the final mass.

More recently, other sugar alcohols similar to sorbitol, are being assessed in sugar rocketry.  Erythritol and Xylitol are two sugar alcohols that have been used with potassium nitrate to manufacture amateur propellants.  Known as KNER and KNXY respectively, results appear successful but not without issues.  KNER can be harder to ignite and slower burning but easier to cast than sugar-nitrate.  KNXY(Xylitol sugar) is also slower burning but can be hard to cast and cool properly.

2. Basic ratio:

potassium nitrate..........................................00%

sugar or sorbitol............................................00%

3. Advantages:

• Non-toxic or poisonous (it's almost food)

• Easy to buy

• Inexpensive

• Nice smoke trail

• Lots of information available

4. Disadvantages:

• Lower performance (less energy-dense) than APCP or ANCP

• Hygroscopic

• Slow burn rate

5. Cautions:

Mixes with fast burn rates can rupture the motor in an explosive manner if the casing strength is insufficient or the pressure and rate are incorrectly calculated.

Severe burns can result from contact with melted R-candy.

Never microwave R-candy or cook it on the kitchen stove indoors.

6. Interesting Facts:

Some sugar/nitrate users like to add a small amount of aluminum powder, magnalium powder or magnesium powder to the mix for a nice sparkly tail.

A small amount of sodium bicarbonate (baking soda) can be added to slow the burn rate.