Model Rocket Engines Explained: Choosing the Right Estes Engine

Reading an Estes Engine Code

Estes model rocket engines are labeled with a code such as A8-3 or C6-7. Each part of the code describes a specific performance characteristic:

Letter: Total Impulse Class

The letter indicates the engine's total impulse class. Each letter class roughly doubles the total impulse of the class before it (for example, a C-class engine delivers about twice the total impulse of a B-class engine, which delivers about twice that of an A-class engine).

First Number: Average Thrust

The number immediately after the letter is the engine's average thrust in Newtons. A higher number means a stronger push off the pad.

Second Number: Delay Time

The number after the dash is the delay, in seconds, between engine burnout and recovery-system ejection (when the parachute or streamer deploys). A longer delay gives a lighter or faster rocket more time to coast to its highest point (apogee) before ejection fires.

Matching an Engine to Your Rocket

The correct engine for a given rocket depends on the rocket's weight, recommended engine list, and the altitude or flight style you want. Every rocket kit lists its compatible engines and recommended delay times in its instructions. Based on current listings in our Model Rocketry collection, here is how three common Estes engines are typically used:

• 1/2A6-2: An 18mm engine intended for rockets under 2 oz (57 g), such as beginner kits, with a 2-second delay.
• A8-3: An 18mm engine for lightweight rockets under 3.0 oz (85 g), with a 3-second delay.
• C6-7: An 18mm engine with 10.00 Newton-seconds of total impulse and a 7-second delay, suited to lighter rockets that keep climbing after burnout or to upper-stage use in multi-stage builds.

Always confirm the manufacturer-recommended engines for your specific kit before flight; the engine list varies by rocket design and weight.

Flying Safely

Model rocketry is regulated by a published safety code. Before launching, review and follow the Estes Rockets safety information and the National Association of Rocketry model rocket safety code, and follow all instructions included with your specific rocket and engine. Key practices generally covered by these safety codes include using only factory-made engines as intended by the manufacturer, launching from a clear open area away from structures, dry vegetation, and low-flying aircraft, using a stable launch system with an electrical ignition system and a switch that returns to \"off\" when released, and keeping spectators at a safe distance during ignition and flight.

Local laws, launch site rules, and land-use restrictions vary by location. Check with your local government and any launch site operator before flying, and confirm any age or supervision guidance printed on the specific product packaging.

Shop Model Rocket Engines and Kits

Browse Estes engines, starter kits, and accessories in our Model Rocketry collection, and see our Beginner Rocketry: How to Choose Your First Model Rocket guide for help picking your first kit.

WARNING: This product can expose you to chemicals known to the State of California to cause cancer. For more information, visit www.P65Warnings.ca.gov.