of the actuator components, Penzane 2001-3PbNp Oil was utilized in the motor bearings and Rheolube  2004 grease was chosen for the lubricant throughout the harmonic gear. Other flight applications with the  same material combinations for the harmonic gear components had also used Braycote@ because of a  much lower operating temperature requirement than MRO. Since the required operating temperature  range did not necessitate the use of bray oil or grease, the Penzane lubricant family was chosen since it  tends to demonstrate more life capability over the Bray series when the operating temperatures are  moderate.  Table 1. Commercially Available Materials for  Note: The Melonite process is a Nitrocarburizing case hardening per SAE-AMS-2753B  Hardware Verification  The motor and gearbox assembly was the same for all of the six axis applications on MRO, allowing one  life verification 6 be performed on the worst case loaded design that would encompass all of theother  five axis applications on MRO. The life verification program for these actuators consisted of operating a  harmonic drive assembly alone in ambient environment with standard lubrication, followed by operation of  an assembled flight-like actuator assembly in a vacuum with thermal cycling and a representative wiring  harness for loading of the output gear.  The lone harmonic drive gear assembly was operated in a standard gear test fixture used at the harmonic  drive vendor. This was performed at ambient pressure and temperature in a bath of low viscosity  commercial oil at an input speed of 1750 RPM and with an applied load on the output that matched the  cable loading from harnesses. The wave generator was driven for 32 million revolutions with no sign of  unusual wear or failure of the bearing or the gear teeth. This was done without incident to a rotational life  of five times the flight requirement of 6.2 million input revolutions, indicating harmonic gear rotational  lifetime was a low risk.  Next an Engineering Development Unit (EDU) actuator was operated in a flight-like configuration. The  EDU actuator used the flight housings with output hardware that supported the High Gain Antenna cable  management system. The cable management system was incorporated to cycle the cabling as well as  provide flight like output loading to the harmonic gear. The High Gain Antenna application was chosen  because it has the largest number of cables across any of the gimbal axes. The EDU actuator was  operated over a total output angle of 340 degrees. The EDU actuator was run in a thermal/vacuum  environment, with the temperature slowly cycled from -25°C to +40°C at the rate of one thermal cycle  every 18 hours. The actuator was driven at a motor rate of 125 RPM for approximately 3.8 million input  revolutions, and then run at 65 RPM for the remainder of the time. The EDU motor was driven with an  industrial stepper motor driver, severely limiting visibility into the performance of the actuator. The stepper  motor driver was used for this operation for several reasons: flight actuator drivers were not available for  the start of the running, the motor is a two-phase brushless dc (not three phase), and the rotary life was  believed to be low risk so the limited visibility was not considered to be significant. The EDU life setup is  shown in Figure 6.  41