Engine F.A.Q.'s




How does an engine work? 

When an engine is ignited, it produces thrust and boosts the rocket into the sky. After the propellant is used up, delay is activated, producing tracking smoke and allowing the rocket a brief coast. After the delay, the ejection charge is activated, which activates the recovery system.


What do the engine codes mean?

Each engine has a letter-number-number code (e.g., B6-4). 

The letter indicates total impulse. This is the total power (in Newton-seconds) produced by the engine. Each succeeding letter has up to twice the total power as the previous letter. For example, a ‘B’ engine has twice the power of an ‘A’ engine. 

The first number in the code refers to the average thrust of the engine. Average thrust is the engine’s average push, or how fast the engine powers the rocket to go. The higher the number, the faster the speed. Higher thrust engines may be the best choice for heavier models or models with higher drag factors such as a larger diameter. 

The final number in the code gives you the time delay in seconds between the end of the thrust phase and the ignition of the ejection charge.  Selecting the correct delay allows your rocket to reach apogee which is most instances is the best time for the recovery system to be activated.   Engine types ending in ‘0’ have no time delay and are used for booster stages and special purposes only. Engines ending in ‘P’ have no time delay or ejection charge and the forward end is “Plugged” so that no hot gases are released from the forward end. 

For more detailed information from Estes Educator, Click Here! 


Can I use old engines?

Engines do not have a shelf life, so if they have always been stored in a cool dry place, and not exposed to excessive humidity,  and temperature cycling [extreme heat or cold (140 degrees to 32 degrees Fahrenheit)] the engines should perform properly.  However, you will have to watch for erosion of the clay cap and the dark propellant  showing on the sides.  If the engines appear to be damaged, such as bulging, loose or unwrapping of the casing, crumbling nozzle or if they have been subjected to temperature cycling, you should dispose of them in accordance with the instructions below.

Disposal of Estes Pro Series II composite motors

Any Estes Pro Series II composite engine (motor) may be safely disposed of by digging a small hole in the ground, placing the Pro Series II composite motor vertically in the hole, nozzle up and packing the soil back around it.  The composite engine or motor should then be ignited in the normal fashion using an igniter and an electrical launch controller with 30 feet of cable.  When ignited, all pyrotechnic components of the motor will be consumed.  Never place any part of your body above the motor during the disposal process.  You and all others should remain at least 30 feet away during the process.  Do not approach the motor for 1-5 minutes.  The casing may be very hot.  Protect your hands with gloves or other appropriate tool when handling a Pro Series II motor after firing.  The spent Pro Series II motor casing may be disposed of in any outside trash receptable and provides no additional harm to the landfill.

Disposal of standard Estes engines

Soaking a small quantity of model rocket engines in water until they disintegrate will render the engines harmless.  The non-colored paper casings will become unwound. The glue with which they are held together is organic and non-toxic.  The intimate mixture comprising the propellant, delay and ejection charge will separate and fall to the bottom of the water as will the natural clay material comprising the nozzle and cap.  These remnants can be safely disposed of in an outside trash receptacle.  Each of the components is basically harmless alone and is not dangerous to people or the landfill in small quantities.  If the components are left together to dry completely, the remnants are likely to be very flammable but should not pose a great hazard so long as they are not “remixed”. 


What is engine clustering?

Engine clustering is using two or more engines (or the simultaneous ignition of more than one engine in a model) in a cluster to provide greater thrust for single or first stage lift-off and acceleration of rockets and rockets with payloads. NASA used this technique to launch the Saturn I and Saturn V among others. Generally, a model rocketeer should use a maximum of 4 engines in a cluster, since more engines make ignition less reliable.

A successful engine cluster must be carefully set up. The thrust of the engine arrangement must be balanced around the centerline of the rocket, or the rocket will veer off course. Similarly, all engines away from the centerline should have the same thrust. Also, all engines should be located fairly close together.

Ignition is the most important part of clustering. All engines must ignite at once or within fractions of a second of each other. The only ignition system proven safe and reliable is direct ignition using standard igniters. This is done by linking igniters together in a parallel manner so that each engine is ignited at the same time without igniters burning one by one.

Unusual engine arrangements should be developed carefully. If the thrust is out of balance, or ignition fails, the rocket may fly off course making it unsafe.

For more detailed information on clustering from Estes Educator, Click Here! (pages 21-24 of "The Classic Collection")


What is multi-staging?

Multi-staging is when two or more engines coupled together are used in stages (or ignited consecutively or one after another) to propel a rocket higher and faster. Lower and intermediate stages always use engines that have no delay and tracking charge and no recovery system ejection charge. There is no delay so that the next engine can receive the maximum velocity from its booster. The engines which are suitable are those ending in zero, such as C6-0.

In the upper stage, an engine with a delay and tracking charge and recovery system ejection charge is used. An engine with a long delay should be used as the rocket must lose velocity before activating the recovery system. This will give you greater altitude and avoid damage to the recovery system.

Before attempting to build a multi-stage rocket, the rocketeer should build and fly several single stage rockets to familiarize themselves with the principles involved. The reliability of a two stage rocket is always less than a single stage rockets, and as more stages are added the reliability drops even farther. Hence, more building and flying skill is required as the rockets become more complex.

For more detailed information on multi-staging from Estes Educator, Click Here! (pages 3-6 of "The Classic Collection")


To learn more about model rocketry visit the Estes Educator website. There you’ll find tons of educational resources and publications!



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