Rocket candy

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Rocket candy is a type of fuel that pushes model rockets. The fuel burns and pushes air out of the rocket's nozzle (the narrowest part of the motor), which pushes the rocket in a forward direction. Rocket candy is not really a type of candy. It is made of sugar, but it is used to power rockets. Rocket candy is made of three different parts. The three parts are the fuel, the part that uses oxygen (air) to make the fuel burn more completely, and the extra chemicals. The fuel is made of a sugar. Sucrose is the most commonly used type of sugar. Sucrose is known as table sugar. The most common part that uses oxygen to make the fuel burn more completely is potassium nitrate (KNO3). This part is also called an oxidizer. The extra chemicals can be many different things. They can change the speed of the fuel burning. Extra chemicals can also make the liftoff and flight more exciting and interesting to watch. A normal rocket candy ‘recipe’ is made of 65% oxidizer and 35% fuel.

Rocket candy is made in different ways. One of these ways is ‘dry compression’. For dry compression, the rocket candy does not need to be heated. The parts need to be ground into small particles. Then the mixture is packed into the motor.[1] Another way to make rocket candy is called ‘dry heating’. Dry heating does not actually melt the KNO3 (chemical used as the oxidizer), but it melts the sugar and then the KNO3 is mixed into the sugar. There is also a third way of making rocket candy called ‘dissolving and heating’. In dissolving and heating, the mixture of fuel ingredients is heated, and both the oxidizer and the fuel are melted and then combine together.

Rocket candy should never be made right above a flame. This is for safety reasons. If the mixture of ingredients is heated over direct heat, it could explode. It could also cause the fuel to be weaker.[2] Making rocket candy in a microwave oven is also dangerous. This can cause the fuel to catch on fire. Rocket candy catches on fire very easily. Therefore, it should be made in small amounts. It should also be made outside or in another safe place. One should also use safety eye glasses.

Rocket candy does not perform as well as some other kinds of fuel used in model rockets. The total amount of power is lower. The amount of power based on the amount of fuel is also lower. However, rocket candy costs a lot less to make than many other fuels.

Components[change | edit source]

Rocket candy is made of three main parts. It is made out of the fuel, the oxidizer, and the extra chemicals. The fuel is the part that burns. When it burns, it makes hot gases that move quickly out of the rocket motor. These quickly moving gases push the rocket as they exit the motor. The oxidizer helps to add oxygen, which the fuel needs to burn. The extra chemicals can do a few things. Some can speed up the burning. Some can also make the fuel burn more completely. Some extra chemicals make the rocket look better when it is launched. They can add sparks and flames to liftoff. They can also add smoke when the rocket flies.

Fuels[change | edit source]

Many different sugars can be used as the fuel for rocket candy. Sucrose, which is the sugar used in home kitchens, is the most common type of sugar used. Sorbitol, a common sugar substitute, is also used. Sorbitol makes the rocket candy break less easily. It also causes the fuel to burn more slowly.[2] Fructose and glucose are harder to use. They make the rocket candy more likely to explode.[3] Fructose and glucose do not have to be heated as much. This makes preparation easier. There are more sugars that can be used. They are not as well known, including erythritol, xylitol, lactitol, maltitol, or mannitol.

Oxidizers[change | edit source]

The oxidizer helps there be more oxygen in the rocket candy when the fuel is burning. The most common oxidizer is a chemical called potassium nitrate. Its chemical formula is KNO3. Other oxidizers can be used instead.[4] Potassium nitrate can be bought from stores that carry garden supplies.

There are two problems that people often have when they use potassium nitrate. The most important thing is to make sure that the potassium nitrate used is pure potassium nitrate. It is possible to buy potassium nitrate. However, potassium nitrate for sale may not be pure potassium nitrate. Another important thing about the oxidizer is the size of the particles. Many people who make rocket candy have an exact size that they want the potassium nitrate to be. This can be done using a coffee grinder.[1]

Extra chemicals[change | edit source]

Extra chemicals are often added to rocket candy. They are used to change the way the fuel burns. These extra chemicals can make the rocket candy burn faster or slower. Some are used to change the color of the flame. Other chemicals are used to make smoke when the rocket flies. Some extra chemicals are used to change the way the fuel feels and acts. They can make the fuel less likely to break. They can also make the fuel more like a flowing liquid. This can make it easier to put the rocket candy into the motor.

People use many different extra chemicals. These are just the ones that are used the most. Metal oxides are one group of extra chemicals. These make the rocket candy burn faster. Metal oxides work best at levels from 1 to 5 percent.[2] This means between one and five grams of extra chemical for every one hundred grams in the fuel. The most common metal oxide is called iron oxide. The most common type of iron oxide is red iron oxide. There are also other colors. Red is the most easy to buy. There is also yellow, brown, and black iron oxide.

Another extra chemical that is sometimes added to rocket candy is carbon. Carbon is found in charcoal or graphite. It is sometimes used as a fuel. It is used more often as an extra chemical. It makes the rocket leave a smoke trail in the sky. When the fuel burns, it makes heat. The heat usually goes to the case of the motor. The carbon keeps some of the heat in the fuel instead.

A metal called titanium is sometimes used as an extra chemical. It is added in flakes to the rocket candy. Titanium makes the rocket make sparks and flames when it is launched.[3]

What is in rocket candy?[change | edit source]

Rocket candy is normally made with 65% oxidizer and 35% fuel. This has a little more fuel than one needs.[3] This way allows the rocket candy to be more liquid when it is melted. Extra chemicals can take the place some of the fuel. When extra chemicals are added the recipe can change. It might change to 65% oxidizer, 25% fuel, and 10% extra chemicals. These are not the only combinations that work. There are many different combinations that will still make a rocket fly.

Preparation[change | edit source]

There are a number of different ways to make rocket candy. Most of the ways include heating the rocket candy. The different ways to make rocket candy are called: dry compressed, dry heated, and dissolved and heated.

In dry compression, the sugar and potassium nitrate are chopped. They should be ground as small as possible. Some people use a mortar and pestle to grind them. Others use a coffee grinder. Then they are mixed. They can be mixed in something called a ball mill or a tumbler. These machines make sure that the two are mixed completely. Then the mixture is pressed into the motor tube. Most people who are serious about experiments do not use this method. People should think carefully before they choose this method.[1]

Another way to make rocket candy is called dry heating. This is more common than dry compression. First, the potassium nitrate is ground or milled. It needs to be made into a powder. Then the potassium nitrate is mixed with powdered sugar in a pot. When the heat is turned on, the sugar melts. However, this method does not actually melt the potassium nitrate. Potassium nitrate needs to be very hot before it melts. Its melting temperature is 613 degrees Fahrenheit. So instead of melting, the grains of potassium nitrate are coated with the melted sugar.

Dissolving and heating is another way to make rocket candy. James Yawn is a well known person who experiments on rockets. He uses dissolving and heating.[5] This method completely combines both the sugar and the potassium nitrate. First, the potassium nitrate and sugar are placed in a pot. Then a little bit of water is added. The sugar and the potassium nitrate combine with the water and make a liquid. When this happens, you cannot see the particles anymore. This is called dissolving. Then the pot is heated. It is heated until the water is hot enough to become a gas and leave the mixture. The mixture will go through several steps. First it will boil. Then it will bubble and ‘spit’. Spitting means that the fuel might splatter. After that it becomes creamy. Dissolving and heating is good for several reasons. The potassium nitrate and sugar do not have to be powder. This is because they both end up together as part of a liquid. This way to make rocket candy also means that the person preparing the fuel has more time to pack it into the motors.

Performance[change | edit source]

Performance of a model rocket is shown by two or three things: 1. Highest force: How much force the gases make when they move out of the rocket motor is different at different times. People often want to know what is the highest force a rocket motor makes. Highest force is measured in Newtons (N). 2. Impulse: Impulse is a measurement of how much force a rocket motor makes, and for how long. A motor that makes a low force for a long time can sometimes have a higher impulse than a motor that makes a high force for a short time. Impulse is measured in Newtons times seconds (N*s). 3. Specific Impulse: If a motor has more fuel, then it will have a higher impulse. There is a way to find out if one fuel makes the same impulse as another fuel. When the number for impulse is divided by the number for the weight of the fuel that was burned, it is called 'specific impulse.' To find out how much fuel was burned, the rocket motor must be weighed before and after firing. The specific impulse can be compared for different fuels and different sizes of rocket motors. Specific impulse is measured in seconds (s). Sugar based rocket fuels have an average Isp(specific impulse) of between 115 and 130 seconds. Compare that to the average Isp of an APCP (Ammonium perchlorate composite fuel), which is 150 to 180 seconds. The most force that sorbitol and KNO3 based fuel with a typical 65:35 ratio can make is 110 N, an Isp of between 110 and 125 seconds, and may have an average force of about 40 N.[3] However, sorbitol and KNO3 rockets with extra chemicals have been recorded as having average forces of up to 100N, total impulses of up to 735 Ns, and specific impulses of up to 128 seconds.[3]

Xylitol and KNO3 based rocket fuels can make a specific impulse of ~ 100 seconds and can have a total impulse of up to 230Ns.[3]

Dextrose and KNO3 based fuels can make an average force of about 80N, a total impulse of 144 Ns, and an Isp of 118 seconds.[3]


Applications[change | edit source]

Rocket candy is also sometimes called “caramel candy”. Rocket candy was used in some of the model rockets created by Homer Hickam. He describes these in his best-selling, true book, Rocket Boys.

Rocket candy might have been made well known to beginning rocket enthusiasts by Lt. Col. Charles M. Parkin in a long magazine (Electronics Illustrated) article. It continued over several issues. The article was published in July 1958. Parkin wrote about how to make rocket candy by using an electric frying pan. Parkin also wrote a book. It was called The Rocket Handbook for Amateurs. It was published in 1959.

Today there is a program called the Sugar Shot to Space Program. This program is trying to make a very powerful rocket powered by rocket candy. The goal is to get this kind of rocket into space.[6] Space is defined as 100 kilometers high. This is the same as 60 miles from the earth’s surface. One of the rockets is called the “Double Sugar Shot rocket”. It has reached 33 kilometers, or twenty miles from the earth’s surface. This means that it is one third of the way to space.[6] The “Mini Sugar Shot rocket” is another rocket. It is a smaller version of the “Extreme Sugar Shot rocket”. The “Mini Sugar Shot Rocket” reached a height of about seven miles. Then it exploded. The “Extreme Sugar Shot rocket” is the rocket that might get into space. It is not yet finished being built.[6]

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