717. Balancing Tolerances as Related to Space Vehicles

Paper

Abstract

Dynamic balancing a space vehicle presents problems that normally are not encountered with other rotating bodies or components. The attachment of journal and supporting bearings occurs when the space vehicle is mounted on the turn-table of the balancing machine. The turn-table, spindle, drive pulley and any other parts which are rigidly attached to and rotate with the space vehicle become an integral part of the rotor during the balancing operation and may affect the specified balancing tolerance. In effect, the configuration of the space vehicle has changed in order to make it conform to the definition of a rotor. It is assumed that all of the rotating parts of the balancing machine, including the fixturing, are prebalanced to a tolerance considerably below the level to which the payload is to be balanced. It also must be pointed out that any attachment of accessory parts, such as slip-rings, to the balancing machine or shifting of components, such as adaptor and drive pulley, can affect the unbalance readout since all rotating components become part of the rotor being balanced. When the space vehicle is rotating on the turn-table a dynamic balancing operation can be carried out precisely about the spin axis which was provided for the space vehicle. If a dynamic or two-plane balancing correction is performed, the inertia axis of the entire rotating body is adjusted by adding, removing or shifting masses so that the inertia axis becomes co-incident to the spin axis of the balancing machine journals.