Radiators Radiator panel concepts were evaluated to identify that tube/fin arrangement producing maximum power dissipation per unit mass while providing a baseline level of resistance against meteoroid penetration. The resultant panels were included in a computer model which provided the total radiator system mass (for panels, manifolds, pumps, and pumping power penalty). Manifold mass was found to be extremely critical, requiring a change from a linear radiator arrangement to a more compact ''halo" which more closely clusters the radiator area around the heat source. Freezing of the liquid metal fluid of the radiator was found to occur during solar occultation. Radiators with heat pipe panels may be resistant to manifold freezing. Solar Concentrators The concept baselined for high concentration ratio (over 200) systems involves a large number (5000 or more) of individual steerable reflectors which form an approximately paraboloidal surface. A relatively light structure, which is somewhat compliant to stresses from thermal transients, gravity gradients, attitude control system operation, etc., is used to support these steerable facets. The facets are composed of metallized plastic film tensioned by a support frame. A computerized model of these solar concentrators was used to determine the sensitivity of the following variables: 1. Geometric concentration ratio (concentrator area 4 aperture area) 2. Number of facets 3. Rim angle (angle between concentrator plane and aperture) 4. Facet pointing error 5. Sun angle relative to concentrator axis. A range of concentrator types was also analyzed for use with solar cells, including both two-dimensional (strip) and three dimensional types. Mass estimating relationships were developed for these concentrators.
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