The refined flux-mass model, taking into account the directional flux concentration, is shown in Table 4-27. It was derived from the graphs in Figure 4-41. The left hand graph was divided into 10° wide increments or strips. The first column of the table is the mean angle of each strip. The second column is the relative number of observations represented by each strip. The third column is the percentage of the total number of observations; i.e., of the total flux, represented by each angular strip. Column four transforms the directional flux to the flux normal to the radiator plane; i.e., the ecliptic plane. It is the flux of column three multiplied by the sine of the appropriate angle. Column five is column four multiplied by the omnidirectional flux for meteoroid particles .001 gm (.0000022 Ibm) or greater. Each line represents the proportion of the total flux contributed by each angular strip to the total flux normal to the ecliptic plane. Since the radiator tubes are spaced, the weighted flux of column five must be modified by a view factor to account for particles which are included in the flux, but which pass harmlessly between the tubes. These view factors are different for each angle. They are tabulated in column six for tubes spaced at 50 mm (2 inches) and in column eight for tubes spaced at 75 mm (3 inches). The final derived flux is the weighted flux multiplied by the view factor. 4.10.2 Tube/Fin Radiator 4.10.2.1 Panel Design Analysis and Modeling The tube/fin radiator panel consists of a multitude of small diameter tubes joined to headers or manifolds at each end. The tubes are spaced 50 mm (2 inches) to 75 mm (3 inches) apart and are connected to each other by fins. Heated fluid (gas or liquid) is pumped through the tubes and waste heat radiated from the fins. It is a provisional requirement that 70% of the system must still be operative after a 30-year life without repair or replacement. Applying this philosophy to the radiator, it means that no more than 30% of the tubes must be penetrated and that the damaged tubes must be isolated to prevent loss of coolant. The radiator must be divided into subpanels such that in combination with a barrier against an appropriate particle size, a minimum weight is achieved. A suitable size of subpanel for transportation into orbit in one piece is 20 m x 20 m (65.6 ft. x 65.6 ft.). This will require subdividing Table 4-27. Derived Directional Meteroid Flux
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