including the operation of the RMS retention latches, its ability to withstand launch and landing loads, payload capture and release and orbiter/payload collision avoidance. These items are verified over a series of flights. SAFETY IN THE PRESENCE OF MALFUNCTIONS Intentional malfunctions of the RMS are not part of the flight test program and are an aspect that is only simulated. Prior to each mission, however, malfunctions are produced for the particular payload and mission operations. The pass/fail criteria is the ability of the crew and the system software to avoid orbiter collision. To date the RMS has successfully flown four flights, and has accomplished unloaded arm tests, software and hardware performance tests, operation in all primary and backup modes of control, thermal testing, and loaded arm validation using 180 kg and 360 kg payloads. Initial analyses of the flight data shows very close correlation between on-orbit test results and the simulation predictions. ROBOTICS IN SPACE With the RMS a proven operational arm, it is now appropriate to consider the directions of its future evolution. Plans for space require that the 1981-1984 time frame will be used to develop all shuttle systems to operational status. This period will include enhancement of all systems towards evolving the technology base for a permanent space presence, and will allow intermittent manned/sortie experience. The next six years will see on-orbit servicing and assembly and the development of unmanned, then manned construction facilities in low Earth orbit (LEO). The last decade of the century will see the development of manned geosynchronous facilities. During the next two years, very little RMS system modification is expected. The requirement is primarily for attachments to the existing system. Applications will include the development of spin tables for the deployment and retrieval of spin stabilized satellites and the development of special purpose end effectors. The 1984-1990 period in space is mainly characterized by the development of spacecraft servicing techniques. Initially this will be achieved by use of the module interchange technique as the means to repair, changeout or redefine the mission. Such missions will use the universal service tool (UST) hand-held or attached to the arm and is seen as a key demonstration of the capability of the RMS/Shuttle to service spacecraft. The UST (see Fig. 5) is an adaptable modular multipurpose tool. The system comprises a control module, a drive module and a working module, the latter for spacecraft subsystem changeout would be a specially developed hexagonal socket wrench with torque reaction and locking posts. For servicing it is visualized that a spacecraft will be berthed to the shuttle. The berthing interface would hold the payload and maintain it in a predetermined position whilst reacting the applied forces and torques and a manipulator system will be developed to accomplish this. This arm could be manoeuvred to allow access to the payload for either RMS mounted tools, changeout mechanisms or an RMS mounted work station for extra vehicular activities. For this payload handling arm, an initial Spar study determined that a nondextrous five degree-of-freedom arm is satisfactory. An important requirement is that the arm always maintains position relative to the orbiter and will not backdrive under orbiter
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