Michigan Compiled Laws, Chapter 259. Aviation § 259.784

(a) It shall be a commercially manufactured device or combination of devices wherein all chemical ingredients of a combustible nature are pre-mixed and ready for use.

(b) The force or motive power shall be created by a rearward discharge of gas generated by the combustion or other operation of materials contained solely within the device or combination of devices.

(c) The device or combination of devices shall have been tested by the federal bureau of explosives and shall qualify as a “toy propellant device” under title 18, section 11 of the United States code.

(d) An engine constructed wholly or partly of metal shall be equipped with an adequate blowout disc or other safety release, as an integral part of the engine, for the purpose of preventing rupture of the engine casing in the event of internal over-pressure.

(e) It shall be so designed and constructed as to be incapable of spontaneous ignition or combustion in air, water, under pneumatic or hydraulic pressure, as a result of motion or jarring, when subjected to a temperature of 170 degrees Fahrenheit or less, or in glycerine.