Thermal Vacuum Accelerated Life Test on a Prototype Teldix Single-Gimballed Momentum Wheel

摘要

A prototype TELDIX single-gimballed momentum wheel (SGMW) has been tested in vacuum at isothermal temperatures and with various thermal gradients. The mechanism consists of a momentum wheel which is oscillated in one plane through + or - 5 deg angular motion by a stepper motor giving a nominal step size of 0.031 deg. During the accelerated life tests a total of 1.5 x 10 to the 7th power steps were carried out which represents more than 150 times the number of steps which would occur in a 7 year lifetime of operation in a communications satellite. Detailed measurements on the motion of the stepper motor were taken at intervals during the test and the distribution of step sizes presented as a histogram evaluation. Several minor variations in step size distribution occurred during the various tests which did not correlate with temperature level. The electrical performance of both the momentum wheel motor and stepper motor showed no change during the tests. The amount of wear on the teeth of the stepper motor was found to be consistent with the low torque exerted by the gimbal system and was insufficient to alter the tooth profile. Steel balls had been fitted to the gimbal bearings. Duroid cages were used and the transfer of lubricant from these cages had minimized steel wear in the bearings.