electronics, thermal control requirements, effluent contamination of spacecraft surfaces, launch vehicle integration, operations and safety requirements, attitude control, electromagnetic interference, and power control and distribution. The impact on spacecraft design philosophy of these constraints and criteria are explored. Several NEP spacecraft are characterized and discussed with respect to the electric propulsion system used. The electric propulsion categories are electrothermal (resistojet, pulsed electrothermal thruster, arcjet), electromagnetic (magnetoplasmadynamic, pulsed inductive thruster), and electrostatic (ion). A brief description of the nuclear power source and mission application will be given for each NEP spacecraft concept within each electric propulsion category. The NEP design philosophy for each spacecraft concept will be described with respect to the identified constraints and criteria. (Paper number IAF-ICOSP89-2-3.) Note: ★ The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. 2-4. Overview of CNES-CEA Joint Programme on Space Nuclear Brayton Systems F. Carre, E. Proust, S. Chaudoume, P. Keirle, Z. Tilliette & B. Vrillon Commissariat a 1'Energie Atomique, Centre d'Etudes Nucleaires de Saclay, 91191 Gif-sur- Yvette Cedex, France (Tel: 33 (1) 69 08 54 04). A cooperative program between the French Centre National d'Etudes Spatiales (CNES) and the Commissariat a 1'Energie Atomique (CEA) was initiated in 1983, to investigate the possible development of 20 to 200 kWe Brayton nuclear space systems. After the completion of the preliminary design of a reference 200 kWe turboelectric power system in 1986, a new 3-year study phase was initiated with the aim of assessing the various reactor candidate technologies and system design options applicable to 20 kWe power level, which meets the projected electric needs of the first European space missions from year 2005 onward. All considered 20 kWe power system concepts employ a single or dual recuperated Brayton conversion system, using He-Xe (40 g/mole) as working fluid and exchanging the waste heat with a heat pipe radiator. Two of the three candidate reactors make use of the available technologies of the Liquid Metal Fast Breeder Reactors (LMFBRs) and the High Temperature Gas Cooled Reactors (HTGRs) to not only minimize the cost of developing new technologies but also reduce the uncertainties associated with deploying new technologies with no flight experience. The third reactor concept incorporates the very high temperature materials and advanced fuel technologies considered for the design of the reference 200 kWe power system. Near optimum operating conditions for minimizing the total mass of each candidate power system, have been determined by a fairly detailed numerical modeling of the entire system. Normal and accidental operating transients have been simulated in liquid metal cooled systems. The about equivalent mass performances evidenced by the optimization studies of all considered 20 kWe power systems (2100 kg±5%), validate a development strategy of a first European 20 kWe space nuclear power source, based on the LMFBR or the HTGR derivative technology for minimizing the development risks. The final decision about the design options and the development strategy will be taken on the basis of evaluation criteria including launch safety, lifetime and operational reliability, complexity of the start-up scenario, extrapolation potential and required development effort. The next phase of the project, subject to commitment in 1989, will be dedicated to detailed design studies of the selected system. (Paper number IAF-ICOSP89-2-4.)
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