From Apogee email that arrived today. Quoting Tim VanMulligan
Cluster rockets fire multiple motors at the same time, creating one of the most fascinating launches you can experience in model rocketry."
Instead of one motor pushing the rocket skyward, Cluster Rockets have several motors that ignite at the same moment. The result is a launch that produces more flame, more smoke, and a much louder liftoff.
For many builders, flying a cluster rocket is one of the most exciting milestones in the hobby.
Beyond the visual spectacle, clustering also teaches valuable rocketry skills. Builders learn how to wire igniters correctly, manage simultaneous ignition, and design rockets that remain stable with multiple thrust sources working together.
Once you understand the process, cluster rockets open the door to a whole new level of experimentation.
And Curtis said, "amen".