This type of rocket fuel is commonly referred to as “R-Candy”
The main components of this composition are a brand of stump remover, which is 100% potassium nitrate (KNO3), and plain white table sugar.
When mixed together in ratios of 60% KNO3/40% Sugar by weight, and placed on medium heat, they melt into a creamy brown liquid. This is because the sugar caramelizes and absorbs the KNO3. The smell is similar to that of making candy, and that’s why this is sometimes referred to as “Rocket Candy” or “R-Candy”.
The mixture is volatile, and will violently ignite if brought in contact with a flame, so extreme caution needs to be used at this point.
“Mix everything by weight. 30% sugar, 60%potassium nitrate and 10% sulfur for the best rocket fuel. Melt slowly and pour into tube. Nozzle should be 60 degrees entering side (converging) and 30 degrees leaving (diverging) and the hole should be 1/3 the dia. of the motor tube. Tubing should be seamless steel. Nozzle..cold rolled. Bulkhead…cold rolled. To give it an intitial pulse put a rod up through the nozzle about 1/3 the length of the motor. Pour the liquid propellant over this rod. Pull the rod out when cooled.”