NASA-LLIS-1336

Abstract

<strong>Description of Driving Event:</strong> <br>During integration of the Genesis spacecraft, many flight and ground support equipment (GSE) cables were found to be electrically incompatible with spacecraft systems although they matched the cable wiring diagrams. Several times, testing had to be halted and the system analyzed for possible electrical overstress caused by power having been applied to the wrong pins. Eventually, spacecraft testing was stopped long enough to perform a pin-by-pin comparison of the cable wiring diagrams to the latest unit and system schematics. Once this was completed, errors were identified, the cables were reworked, and the problems were resolved. <br>The accuracy of cable wiring diagrams was a continuing problem on Genesis. Typically, cables are built by cable harness shops to the specifications provided by cable drawings and cable wiring diagrams. Cable design and fabrication may take place concurrently with the design of spacecraft black boxes. As a system design evolves and pin-out requirements change, there is a time lag before the interface control drawing (ICD) is updated and the changes flow back to the cable design and documentation. Should the cables be built to an outdated document, the first powering of a given spacecraft may cause major damage. Since the connectors still mate with their assigned receptacles, the electrical mismatches may not be apparent. Validating the cable harness configuration against unit and system schematics is a very time-consuming activity. If it is delayed until integration and test has already commenced, the task can impact the project schedule.