8. 4. 2 ON-ORBIT MAINTENANCE SAFETY A preliminary safety analysis has been performed for several identifiable mission and task phases associated with constructing and servicing the SPS. The phases cover fabrication, assembly, preoperational checkout, and maintenance. Potentially hazardous situations were identified in virtually all phases. In view of the limited actual experience data base available in the assembly and maintenance of large spacebome structures under zero gravity conditions, a large portion of the analysis relies on engineering judgment; further analyses are required to identify additional potentially unsafe conditions that may exist. The following assumptions are made on astronaut participation in the previously mentioned mission phases: 1. Astronaut skills are at a monitor and maintenance level. 2. Equipment used to fabricate structural members and the antenna is automated. 3. The SPS is assembled essentially by sophisticated assembly jigs supported by a few free-flying teleoperators. 4. Pre-operational checkouts are automated, and malfunctions are corrected by free-flying teleoperators. 5. Maintenance is performed by free-flying teleoperators and robot trucks. This analysis was performed assuming that assembly operations are based in an orbiting construction facility and that maintenance operations are based in a space station attached to the SPS. The investigative effort consisted of determining the degree of crew involvement in the mission phases in order to gain an overview of astronaut participation and man-machine-structure relationship. Then, gross potential hazards were identified. This information is listed in Table 8-1. Where astronaut participation is listed as a monitoring function, he will take the required corrective action in case of equipment malfunction. This may involve extravehicular activity or the reprogramming or manual control of a teleoperator. As hazards become better defined, special safety procedures and equipment will be evolved to protect the crew.
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