impacts on the design should be done, and if necessary, a life test should be conducted. The program did  not have the time or funds to conduct a life test on the second bellows coupling used and the program  accepted that risk. This has been borne out by the fact that the BAPTA has so far seen over 40 million  revolutions to date without a failure.  Manv Commercial Slip Rina Vendors Can Use Help When Desianina For Space. Especiallv When it  Comes To Thermal Desian 81 Bearinas  There several slip ring vendors being used for space in the USA. All of the slip rings vendors are primarily  “commercial” slip ring vendors wherein space is a sideline business. As such, it is recommended that  special attention/oversight be given to the slip ring vendor to ensure the unique design and reliability  aspects related to space are satisfied. For instance, none of the slip ring vendors have special expertise  in bearing design, or detailed thermal analysis that is typically required for long-life high reliability space  applications. As such, NRL and Ball assisted the slip ring vendor with the bearing design and purchased,  lubricated, screened, and helped install the bearings. NRL also performed a detailed thermal analysis and  provided the information to the slip ring vendor to assist in temperature and thermal expansion/brush  alignment analyses. The detailed thermal analvsis NRL Performed on the Windsat slip rinas was critical in  ensurina adeauate performance from the slip rinas as well as enablina us to understand and recover from  the Windsat BAPTA on-orbit anomalv. This will be discussed further in the next section “On-Orbit  Anomaly Lessons Learned.”  Slip Rinas - “Devil is in the Details”  Slip rings are a fairly ‘low tech” device. However, for high reliability, long-life space applications “the devil  is in the details” to ensure proper performance and reliability. When passing high-frequency signals  across slip rings this problem is multiplied greatly. On the Windsat slip rings many “detail problems” were  encountered such as the following:  1) As mentioned previously the Windsat slip rings were solid “soft” gold with a thin hard gold flash  top coating. The slip rings were sent to Ball Aerospace for cleaning and lubrication. After cleaning  a microscopic inspection was performed wherein it was noticed that several of the slip rings were  cracked (Figure 8). After the first cracks were discovered a 100% microscopic “mapping” of the  slip rings were performed and other cracks were found. The rings were also eddy current  inspected, which also uncovered a few faint cracks. None of the cracks affected the ring  resistancehmpedance, and the brush wear actually tended to smear over the cracks in a  beneficial manner so it was decided that the cracks were acceptable. Finding cracks on solid  “soft” gold slip rings was surprising. It was determined that the cracks were caused by plating with  a current density that was “in-spec” but at the high end of the spec. Subsequently the current  density tolerance was revised and the second, flight spare slip ring was plated with no cracking.  While the crackina was not desirable, no problems were ever caused bv the cracks.  Figure 8. Cracked Slip Rings  21 5