antenna centerline perpendicular to the mast and therefore only half the structure had to be idealized. Symmetrical and anti-symmetrical models were then run using both methods of solution. Ground rules and assumptions used in both models are presented below: • Structure symmetrical about antenna centerline perpendicular to mast. • Analysis uses only half structure. • Antenna is included as rigid body and lies at centerline of mast. • Antenna has 5 degrees of freedom, no rotation about X-axis. • Mast idealized as consisting of multiple beams having bending stiffness, but no torsional capability. • Mast moments of inertias based on six current elements per polarity. • All other support structure idealized as axial loaded struts. • Areas of mast and solar array buses based on power distribution system operating temperature of 38°C (100°F). • Solar array elements lie in plane of blankets. • Total cross-sectional area of non-conductive struts is 0.27 in.2 • Tension-only wires replaced by single tension/compression struts; cross section area is 0.01 in.2 • Model representing half structure consists of 684 members and 232 nodes. • Satellite weight distributed as lumped masses at node points. Table 3 gives a summation of the weights and inertias used in the structural analysis. Dynamic Mathematical Model - A dynamic analysis was performed on the symmetrical and anti-symmetrical structural models using both ASTRAL/COMAP and NASTRAN. Both methods are normal-mode solutions using large digital computer programs. Solution consists of the natural ■ frequencies of the system, relationship between the degree of freedom displacements or mode shapes, and generalized model masses and stiffnesses. The solution using the NASTRAN method retained virtually all the degrees of freedom associated with the 232 grid points, with each grid point having 3 degrees of freedom. The ASTRAL/COMAP solution had to be reduced to about 250 degrees of freedom because of the limitation of the size of the problem that the program can handle. For checking purposes, solutions using both ASTRAL/COMAP and NASTRAN were
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