What Is The Difference In Model Rocket Engines?

model rockets

A model rocket engine is what makes your rocket take flight. It plays an important role in terms of experience and expense. The engines are safe as long as you use long to sense. And it is one of the reasons that it one of the safer hobbies to take part in.

Most model rockets are bought are pre-made solid propellant engines that are used once. There are other engines that available that are reusable but some do require some assembly.

In this post, we will go through what is the difference between model rocket engines so you can go launching rockets with confidence. Let’s get started!

What Are Model Rocket Engines?

A model rocket engine is what makes the model rocket take flight.  The engines are made up of two ingredients that give them the necessary thrust. These are made up of fuel and an oxidizer.

The most common model rocket engine is the black powder that has three ingredients which are charcoal, potassium nitrate, and sulfur.

Model rocket engines come in a variety of sizes and weights, with different amounts of propellant, with different burn patterns which affect the thrust profile, and with different values of the delay time.

model rocket launch

Are Model Rockets Safe?

Model rockets are generally safe but it does require you to use common sense. The greatest risk from model rockets is a human-rocket collision, causing damage, or causing a fire.

It is important to have permission from the landowner and the public rules where you plan to launch the rocket

What Fuel Do Model Rockets Use?

There are 2 main types of rocket motors. These are as follows.

Black Powder

A black powder used in rocket motors is also called gun powder. Black powder is made of charcoal, sulfur, and potassium nitrate.

The black powder is cheaper and ignition is relatively easy comparing to other alternatives. But it burns very fast, it’s volatile and shipping requires HAZMAT shipping.


Composite used in rocket motors is simply that the propellant is a mixture of ingredients such as fuel and oxidizer substances together. Just creates a chemical reaction.

Composite is more expensive than black powder and harder to ignite but it performs better.

Rocket Launch

What Is A Single Use, Loadable, And Reload Motors?

You will notice on the model rocket engine description that an engine is a single-stage engine. There are three types of motors that are available.


As the name suggests these motors are used once and then are discarded. The main advantage is a cheaper initial setup as you don’t have to buy casing but can work out expensive in the long run.


This is another type of single-use motor. The difference is that you must assemble the rocket motors before flying them.


Reloads require you to purchase casing but overtime reloads are far more cost-effective than single-use motors.

What Do Model Rocket Engine Numbers mean?

Each engine has a letter-number code that indicates the size and power of the engine. An example of a rocket engine code would be B4-4 or A8-3.

Taking B4-4 as an example. The letter which in this case is B indicates total impulse. This is the total power produced by the engine.  Each letter has up to twice the total power of the previous letter. So for example, a ‘B’ engine has twice the power of an ‘A’ engine.

The first number which in this case is 4. Refers to the average thrust of the engine. This is simply how fast the engine powers the rocket. So The higher the number, the faster the speed.

The last number which in this case is 4. This is the time delay in seconds between the end of the thrust phase and the ignition of the ejection charge.

You can read more information here on the model engine codes.

rocket launch

What Is The Difference In Model Rocket Engines?

The main types of rocket motors are black powder and composite, with the key differences as follows.

  • Composite propellant has more power by weight than black powder. This can be up to 3 times.
  • A reinforced plastic case is used in a composite model rocket motor instead of a wound paper case.
  • Composite model rocket motors are much louder than black powder model rocket motors.
  • Rockets powered by composite model rocket motors will fly much higher and faster than black powder model rocket motors.

Final Thoughts​

Finally, there are two main engine fuel types with black powder been the most popular and cheaper. By familiarizing yourself with engine codes and engine types with help you to make a better decision when buying a model engine.

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Difference In Model Rocket Engines

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