Rocket candy facts for kids

Rocket candy is a special type of fuel used to power model rockets. It helps push the rocket into the sky! Even though it's called "candy," it's not something you eat. It's made from sugar, but it's used to make rockets fly.

This fuel works by burning and creating hot gases. These gases shoot out of the rocket's engine nozzle, which is the narrowest part. This push makes the rocket move forward.

Rocket candy has three main parts:

• The fuel: This is the part that burns. It's usually a type of sugar.
• The oxidizer: This part helps the fuel burn better by adding oxygen.
• Extra chemicals: These can change how fast the fuel burns or make the launch look more exciting.

The most common sugar used as fuel is sucrose, which is regular table sugar. The most common oxidizer is a chemical called potassium nitrate (KNO₃). A typical rocket candy mix is about 65% oxidizer and 35% sugar fuel.

How to Make Rocket Candy

There are different ways to make rocket candy. Most ways involve heating the ingredients. The main methods are: dry compression, dry heating, and dissolving and heating.

Dry Compression

In this method, the sugar and potassium nitrate are ground into a very fine powder. People might use a special tool like a mortar and pestle or a coffee grinder for this. After grinding, the powders are mixed together very well. Sometimes machines called ball mills or tumblers are used to make sure they are perfectly mixed. Finally, this powder mix is pressed tightly into the rocket motor tube. This method is not often used by people who do many rocket experiments.

Dry Heating

This way of making rocket candy is more common. First, the potassium nitrate is ground into a fine powder. Then, it's mixed with powdered sugar in a pot. When the pot is heated, the sugar melts. The potassium nitrate doesn't melt because it needs to be very, very hot (over 600 degrees Fahrenheit!). Instead, the tiny pieces of potassium nitrate get coated with the melted sugar.

Dissolving and Heating

This method fully mixes both the sugar and potassium nitrate. It's used by many experienced rocket builders. First, the potassium nitrate and sugar are put into a pot with a little bit of water. They mix with the water and turn into a liquid. This is called "dissolving." Then, the pot is heated. The water heats up and turns into a gas, leaving the mixture. As it heats, the mixture will boil, then bubble, and might even splatter a bit. After that, it becomes creamy. This method is good because the sugar and potassium nitrate don't have to be powders to start. It also gives the person making the fuel more time to put it into the rocket motors.

Safety First!

Making rocket candy needs to be done very carefully because it can catch fire easily.

• Never make rocket candy directly over an open flame. It could explode or make the fuel weaker.
• Never use a microwave oven to make rocket candy. This can cause the fuel to catch fire.
• Always make rocket candy in small amounts.
• Work outside or in another very safe place.
• Always wear safety glasses to protect your eyes.

What's Inside Rocket Candy?

Rocket candy is made of three main parts: the fuel, the oxidizer, and extra chemicals.

Fuels (The Burning Part)

Many different sugars can be used as the fuel.

• Sucrose: This is common table sugar and the most popular choice.
• Sorbitol: This sugar substitute makes the rocket candy stronger and helps it burn slower.
• Fructose and glucose: These are harder to use because they can make the rocket candy more likely to explode. However, they don't need as much heat to prepare.
• Other sugars: Less common sugars like erythritol, xylitol, lactitol, maltitol, or mannitol can also be used.

Oxidizers (The Oxygen Helper)

The oxidizer adds oxygen to the rocket candy, which the fuel needs to burn.

• Potassium nitrate (KNO₃): This is the most common oxidizer. You can sometimes buy it at garden supply stores.
• Purity is key: It's important to make sure the potassium nitrate is pure.
• Particle size: Many rocket builders like to grind the potassium nitrate into a very specific size, often using a coffee grinder.

Extra Chemicals (For Speed and Show)

Extra chemicals are often added to change how the fuel burns.

• Speed control: Some chemicals make the fuel burn faster or slower.
• Color and effects: Others can change the color of the flame, add sparks, or create smoke trails when the rocket flies.
• Texture: Some chemicals make the fuel less likely to break or more like a liquid, which makes it easier to put into the motor.

Here are some common extra chemicals:

• Metal oxides: These make the rocket candy burn faster. They work best when they make up 1% to 5% of the fuel mix. Iron oxide (often red iron oxide) is the most common metal oxide used.
• Carbon: Found in charcoal or graphite, carbon can make the rocket leave a smoke trail. It also helps keep heat in the fuel.
• Titanium: Added in small flakes, titanium makes the rocket create bright sparks and flames when it launches.

Typical Rocket Candy Mix

A common mix for rocket candy is 65% oxidizer and 35% fuel. This mix has a little extra fuel, which helps it stay more liquid when melted. If extra chemicals are added, they might replace some of the fuel. For example, a mix could be 65% oxidizer, 25% fuel, and 10% extra chemicals. Many different combinations can still make a rocket fly!

How Rocket Candy Performs

When we talk about how well a model rocket performs, we look at a few things:

• Highest Force: This is the strongest push the rocket motor makes. It's measured in Newtons (N).
• Impulse: This measures how much force a motor makes and for how long. A motor that pushes with a small force for a long time might have a higher impulse than one with a big force for a short time. Impulse is measured in Newtons times seconds (N*s).
• Specific Impulse (I_sp): This helps compare different fuels. It's the impulse divided by the weight of the fuel burned. It's measured in seconds (s).

Rocket fuels made with sugar usually have a specific impulse between 115 and 130 seconds. Other fuels, like APCP (Ammonium perchlorate composite fuel), can have a higher specific impulse, from 150 to 180 seconds.

Even though rocket candy might not perform as powerfully as some other fuels, it costs much less to make! For example, a common mix of sorbitol and potassium nitrate can have a specific impulse of 110 to 125 seconds. If extra chemicals are added, the force and impulse can be even higher.

Who Uses Rocket Candy?

Rocket candy has been used by many people interested in rockets.

• Homer Hickam: He was a famous rocket builder who used rocket candy in some of his model rockets. He wrote about his experiences in his popular book, Rocket Boys.
• Lt. Col. Charles M. Parkin: In the late 1950s, he wrote magazine articles and a book called The Rocket Handbook for Amateurs that helped make rocket candy popular among new rocket fans.

Today, there's a project called the Sugar Shot to Space Program. Their goal is to build a very powerful rocket using rocket candy and send it into space! Space is usually defined as 100 kilometers (about 60 miles) above Earth.

• The "Double Sugar Shot rocket" reached 33 kilometers (about 20 miles) high, which is a third of the way to space.
• The "Mini Sugar Shot rocket" reached about seven miles high before it exploded.
• The "Extreme Sugar Shot rocket" is still being built, and it's hoped to be the one that finally reaches space!

See also

In Spanish: Combustible de caramelo para niños