I would like to preface this Instructable with some brief remarks about safety. While these materials are all relatively safe by themselves, when put together they form an incredibly dangerous compound. Utmost caution should be taken when following these instructions. Always wear goggles and gloves and do not use an open flame. While this is a safe way to create a successful rocket engine, it is still very dangerous and should be treated as so, you assume all risk involved by proceeding.

image from:jerryjdavis.com

Step 1: Gathering Materials

To make this rocket engine you will need:

- a scale

- Potassium nitrate (stump remover depending on the type will work; look at the ingredients on the package to determine the percentage of potassium nitrate)

- sugar

-corn syrup

-water

- a spatula

-graduated cylinder

-clay

-paper

-cotton string

- a few BIC pens

-a wooden hammer

- a portable stovetop or hot plate

- a drill

- tape

-scissors

-blowtorch

Step 2: Making the Casing

The casing is the outer shell of the engine. To make the casing, cut an 8 x11 piece of paper into 1 inch strips and roll them around the BIC pen to form a tight paper cylinder. Tape the cylinder throughly to be sure that the cylinder is tight. Note: bigger casings may be created by cutting larger strips and wrapping them around a thicker cylinder than a BIC pen. After the casing has been taped tightly(maintaining the structure of the cylinder) roll a small amount of clay into a small ball and place it into one end of the casing. After this has been done place the casing vertically on a table with the end with the clay in it touching the surface of the table, then jam the BIC pen into the casing pushing the clay at the bottom into a flat surface about an 1/8 of an inch thick. Note: You may want to make multiple of these because depending on the size of your mixture you will have enough to make plenty of these.

Step 3: Measuring

To make this mixture you will need

2 parts potassium nitrate: 1 part sugar: 25/9 corn syrup: 25/36 water

I have found that for most rockets the best size mixture is: 33 grams of Potassium nitrate: 17 grams of sugar: 6 grams of corn syrup: 27 millliters of water.

Measure out these substances and place them in cups

Step 4: Mixing

Once these quantities have been measured. Set the portable stovetop to 300 degrees F.

Once the stovetop reaches 300 degrees, add the corn syrup

20 seconds or so later add the water,potassium nitrate and sugar simultanously

After the ingredients have been added, begin mixing them together immediately. Quickly stir the ingredients together with the spatula.

At first the mixture will look watery, but with continued stirring it will solidify.

You will know the mixture is done when it turns sticky, gooey and all the water has evaporated. While you will have to sort of eyeball it should look something like the last picture above (may be slightly whiter).

Step 5: Packing

Once the mixture has solidified, scrape it up off the pan with the spatula and then scrape it into the casing.This step needs to be done quickly because the mixture will cool rapidly and becomes difficult to pack.This part is messy and you need to be very careful not to burn yourself. Push the mixture into the casing using the but end of one of the BIC pens (or something with a slightly smaller diameter than the casing) get as much as you possibly can into the casing; it should be filled to the brim. To do this you will need to place the butt end of the pen inside the casing and pack the mixture in by hitting the top of the pen with a wooden hammer. This will ensure that there are no air bubbles in the casing.

Step 6: The Fuse

Allow the hot pan to cool and then clean it with a little soap and water.

To make the fuses you will need a new mixture of 60% potassium nitrate 40% sugar and 30 milliliters of water.

Dissolve the potassium nitrate and sugar into the water in a beaker and stir.

Next, cut multiple 1 inch or so pieces from the cotton string

Once the ingredients have dissolved place the cotton strings in the beaker and let them soak for about a minute or so.

Then, place the wet strings on to the stovetop at 300 degrees and turn them around with the spatula.

Allow them to cook until the are stiff then remove them from the pan and set them aside to let them cool.

Step 7: Drilling

Allow about 5 minutes for the casing to cool, then take a drill with a medium sized bit and drill a hole through the clay end halfway down. This part will allow for the fuse to ignite the engine.

Once the hole has been made, take one of the wicks and place is into the hole. It may not be very secure but wiggle it around and try to get it to stay. To test to see if your wick is secure, turn the engine upside down and see if it falls out.

Step 8: Launching Your Rocket Engine

There are countless ways to put your newly made rocket engine to work. Perhaps the simplest way is to simply tape a small dowel rod to the side of your engine, stick it into the ground (away from anything important like people, houses, cars) and light the fuse with a blowtorch and back at least 10 feet away. However you can get more creative with your launch technique, like creating another separate body for your rocket. This can be a lot of fun and I encourage you to consult other instructables and report your results.