Solar electric propulsion technology is currently being used for geostationmT satellite station keeping. Analyses show tint electric propulsion technologies can be used to obtain additional increases in payload mass by using them to perform part of the orbit transfer. Three electric propulsion technologies are examined at two power levels for geostationary insertion of an Atlas HAS class spacecraft. The onboard chemical propulsion apogee engine fuel is reduced in this analysis to allow the use of electric propulsion. A numerical optimizer is used to determine the chemical burns that will minimize the electric propulsion transfer times. For a l&_-kg Atlas HAS class payload, increases in net mass (geostationary satellite mass less wet propulsion system mass) of 150--8N kg are enabled by using electric propulsion for station keeping, advanced chemical engines for part of the transfer, and electric propulsinn for the remainder of the transfer. Trip times are between one and four months.

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The successes of the Cassini/Huygens mission have heightened interest to return to the Saturn system with focused robotic missions. The desire for a sustained presence at Titan, through a dedicated orbiter and in-situ vehicle, either a lander or aerobot, has resulted in definition of a Titan Explorer flagship mission as a high priority in the Solar System Exploration Roadmap. The discovery of active water vapor plumes erupting from the "tiger stripes" on the moon Enceladus has drawn the attention of the space science community. The NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system is well suited to future missions to the Saturn system. NEXT is used within the inner solar system, in combination with a Venus or Earth gravity assist, to establish a fast transfer to the Saturn system. The NEXT system elements are accommodated in a separable Solar Electric Propulsion (SEP) module, or are integrated into the main spacecraft bus, depending on the mission architecture and performance requirements. This paper defines a range of NEXT system configurations, from two to four thrusters, and the Saturn system performance capability provided. Delivered mass is assessed parametrically over total trip time to Saturn. Launch vehicle options, gravity assist options, and input power level are addressed to determine performance sensitivities. A simple twothruster NEXT system, launched on an Atlas 551, can deliver a spacecraft mass of over 2400 kg on a transfer to Saturn. Similarly, a four-thruster system, launched on a Delta 4050 Heavy, delivers more than 4000 kg spacecraft mass. A SEP module conceptual design, for a two thruster string, 17 kW solar array, configuration is characterized. Nomenclature

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Abstract:Adequate economic justification is a key requirement for the implementation of robotic systems in the construction industry. In the present work the concept of off-line simulation is used to provide the user with a rational approach for economic decision making with regard to the use of robotics. The proposed off-line simulation process helps the user in planning, scheduling and costing the whole job. With the aid of a graphical simulation package, the user can estimate the whole job time that reflects the cost of the individual tasks. A simple criterion is developed to estimate the task cost based on the task simulation time. The criterion takes into account the individual costs of the robotic system components, labour, transportation, site preparation and office work. This work is applied to Starlifter, a heavy tool deployment manipulator.