A pillow block assembly, turnbuckle, and grounded load cell string were attached to the driveshaft to  apply a known moment on the pivot assembly during testing. This known moment produced reaction loads on the bushings roughly equivalent to those expected during vehicle traverse on Mars. The DC servomotor rotated the driveshaft and cylindrical housing through a specific dithering angular  motion profile during bushing testing. This motion profile was developed to replicate the oscillating motion  of the Flight Main Differential Pivot.  The pivot assembly, comprised of the bushing pair, central pivot shaft and cylindrical housing, was  mounted inside a temperature chamber that was used to drive the assembly through a specific  temperature profile. The chamber also provided a humidity-controlled, dry nitrogen environment throughout testing. During test planning the option of testing in a CO 2 environment was discussed.  Although the CO 2 environment would have been preferred as the Martian atmosphere is predominantly  CO 2, the cost and schedule impact associated with that testing was prohibitive. The team also felt that  testing in dry Nitrogen would yield acceptable results based on test data from the Phase One Testing at GRC. Bushing Material / Lubrication Description  Seven different bushing material / bushing lubricant combinations were evaluated as part of the test  series. Two MoS 2-based bonded film lubricants were selected for the test series, a bonded film with a  “phosphate-like” binder and a bonded film with a silicate binder. These lubricants were coupled a stainless steel alloy based on its anti-galling characteristics in the event of coating failure. Polyamide-imide and polyimide samples were added to the test series after initial testing of the first bonded film sample revealed less than ideal bushing wear behavior. These two polymeric bushing materials were selected based on their suitability for the low temperature, dry running flight pivot environments. All bushing samples were run against either 7075-T7351 Aluminum or Ti6Al4V shafts and housings that  matched potential flight pivot materials. The aluminum shafts and housings were coated with a PTFE infused hard anodized coating. All titanium parts were coated with a PTFE infused anodic coating. Both of these coatings were applied to provide a hard, low friction, wear resistant bearing surface. Table 2 summarizes the bushing material and lubricants used for each test in the series:  Table 2:  Phase Two Testing Material Matrix  Test Date Housing & Shaft Material Bushing Material Bushing Coating  6/29/06Al 7075-T7351 with PTFE infused  hard anodized coating Stainless steel MoS 2 based bonded film  lubricant with silicate binder  9/18/06Al 7075-T7351 with PTFE infused  hard anodized coating Stainless steel MoS 2 based bonded film  lubricant with “phosphatelike” binder 9/25/06Al 7075-T7351 with PTFE infused  hard anodized coatingPolyamide-imide None 10/24/06Al 7075-T7351 with PTFE infused  hard anodized coatingPolyimide None 12/12/06Al 7075-T7351 with PTFE infused  hard anodized coatingPolyamide-imide Braycote 601 Greaseplate  1/29/07Ti6Al4V with PTFE infused anodic  coatingStainless steel MoS 2 based bonded film  lubricant with “phosphatelike” binder  2/7/07Al 7075-T7351 with PTFE infused  hard anodized coatingStainless steel None 86