Mich. Comp. Laws § 259.781: Model rockets; definitions.

Sec. 1.

As used in this act:

"Model rocket" means an aero-model that ascends into the air without use of aerodynamic lifting forces against gravity and is propelled by means of a model rocket engine.

"Model rocket engine" or "engine" means a device or combination of devices which provide the necessary force or motive power to cause the model rocket to move through the air.