An improved reaction wheel assembly and method is provided whereby a reaction wheel assembly contains a safing mechanism for securing the assembly. A rotor shaft assembly and bearings are provided whereby a reaction wheel assembly selectively may be either safe or operational, and the safing assembly provides for application of stabilizing force longitudinally along the axis of rotation of a rotor shaft. Further, a method of providing momentum stabilization to a vehicle using this apparatus is provided. A safing mechanism for releasably securing a reaction wheel rotor assembly of a satellite during launch is disclosed.