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Model Rocket Engines


In this article we take a look at the thing that propels a rocket upward. It is called an engine and it is a neat little device.


Model Rocket Engine

This is the engine from a model rocket and it is of course the thing that makes it all go. It is a wonder of modern technology in that in such a small package it can generate enormous force and launch a model rocket well over a 1,000 feet into the sky.

End view of rocket engine

If you look at the end of the engine you can see the orifice that the pressure will come out of. The other end of most engines also will blow a small charge to pop the parachute.


The beautiful thing about these rocket engines is that they are disposable and they can be used in many different rockets.

You simply slide an engine into the rocket.


And the rocket is ready for launch. After launch to remove the engine and you can re-use the rocket by installing another engine.


If you are looking to purchase engine rockets here is a link to Estes Rocket Engines at Amazon I also have a selection of rocket engines at the bottom of this page for quick purchase.

There are a few things about model rocket engines you should know and this is a short tutorial on what they, are, what the different types are and how they work.

Safety Note: These are powerful little devices and can cause bodily harm. Always follow all safety rules that are recommended by the manufacturer when you are handling, using, or disposing of these rocket engines.

Model Rocket Engine Packs

About Model Rocket Engines

There are three basic types of Engines and lots of small variations.

Type 1: Standard Size (A thru D) in a variety of different strengths. This is the most common size engine and it is what you use with most rockets. I will explain the different strengths.

Type 2: E size engine - This is a larger size engine and fits only in certain size rockets. This is also a much more powerful engine and requires an older person to purchase and use.

Type 3: Multi-stage engines - This type of engine doesn't just fire once. It fires the rocket off the pad then after a certain amount of time another stage fires off. Much like real NASA rockets do.

The Numbering system for Rockets

Here is a common number for a rocket engine: B6-4 and this is how the numbers breakdown: The first digit (in this case "B") indicates the impulse strength of the engine, the second digit ("6") indicates the average thrust in newtons of the engine and the third digit ("4") indicates the delay in seconds before the secondary charge fires to eject the parachute.

So, How Powerful are they?

The most commonly used engines are lettered from A thru E and the A is the weakest, B is a little stronger, C even more stronger, D stronger yet and finally E is the strongest. They are usually characterized as B being twice as strong as A and so on. While this isn't exactly true because the power is measured in a range it is a reasonable rule of thumb when considering strength of engines.

The second number

The average thrust is important when considering the weight of a model rocket. The higher the average thrust the faster the liftoff acceleration which means you can lift a heavier rocket. So, the higher the number the heavier the rocket it can launch.

The Third Number

If you are using a typical rocket the engine manufacturer has planned this number out for you. Generally the more powerful the engine the longer the delay before parachute ejection charge. This allows the rocket to climb higher before parachute. But there are some variations, particular when using multi-stage rockets. In a multi stage rocket the first engine typically has a 0 delay which enables it to immediately fire off the next stage. Sometimes this digit will have a "P" which means the rocket is plugged and has no ejection charge. Used sometimes in smaller rockets or gliders that have no parachute.

Fractions of the A Engine

There are also much less powerful engine variations for the A size engine and it is shown as a fraction. a 1/2 A will be about half as strong as the A and a 1/8 will be about one eighth as strong.

There are many different types of engines but for the average hobbyist making his or her own rockets the standards range from 1/8-A to E. Although there are much larger and more powerful engines available.

A Look Inside a Rocket Engine showing how it works

Rocket engine diagram

This diagram shows a typical rocket engine and how it works.

The Clay nozzle is where the exhaust exits the engine. The propellant is what propels the engine (and rocket) forward. the delay charge will burn with a lot of smoke. The purpose of this charge is to delay a certain amount of time before the ejection charge is set off. The ejection charge is what shoots out the top end of the engine and this deploys the parachute.




A3-4T Model Rocket Engines (4)

A8-5 Standard Engine (3) HAZ

B6-6 Engine

C6-5 Standard Engine (3) HAZ

Estes D12-3 (3 ea) Model Rocket Motors - 1666

E9-8 Engine Pack 3 Pk