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 liftoff 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 four 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 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 if ignition is not successful in every engine, the rocket may fly off course making it unsafe.