into smaller or mini-panels to achieve a radiator degradation of not more than 30% in 30 years. Using the total derived flux, from Table 4-27, for a particle of .001 gm (.0000022 ibm) or greater, the subpanels will require subdividing into 5 minipanels for the 50 mm (2 inches) tube spacing and 4 mini-panels for the 75 mm (3 inches) tube spacing. As shown in Figure 4-44, each mini-panel will require an inlet and outlet valve for isolation in the event of tube penetration. tion of tube pitch, tube diameter, and fin thickness. Figure 4-46 was used in determining the dimensions of Configurations B and C of Figure 4-45. The first barrier is the radiator fin and the second is the armor around the tube. The main meteoroid flux is at a shallow angle to the radiator and increases the effective distance between the first and second barriers. Figure 4-46, taken from Reference (3) enables a minimum weight two-sheet aluminum barrier to be chosen for protection against a certain meteoroid particle. Fig. 4-46. Minimum Weight Two-Sheet Aluminum Barrier A segment of radiator structure (Figure 4-47) was divided into a nodal network and a steady-state energy balance was calculated at each node by a digital computer program. The Beta Computer Program solves steady-state and transient thermal problems when radiative, convective, and conductive thermal paths are defined. Fig. 4-44. Meteroid Shielding Philosophy A computer analysis was conducted of radiator panel configurations designed to withstand the predicted meteoroid environment. Three basic configurations were studied. Figure 4-45 shows a section view and the thermal analysis nodal networks for each configuration. Fig. 4-45. Radiator Configurations Configuration A relies on increased armor thickness around each tube for meteoroid protection; whereas Configurations B and C utilize fin structure as a bumper to fragment the meteoroids. Forty-five parameter runs were conducted for each configuration to evaluate the optimum combinaFig. 4-47. Beta Program Solves Thermal Network Modeling of Radiator Structure The heat rejection of a unit area of radiator surface was calculated as a function of radiator fluid temperature and the results were then integrated
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