Figure 2.1-19. Compression Frame Girder Configuration Subelement "b" is the triangular beam element that is fabricated on-orbit in the same manner as the solar array structure. The dimensions of this element (2.54 meters) were Established by an anticipated need for internal personnel access either during assembly or for maintenance activities during the operational life cycle. Figure 2.1-20 depicts a concept for a tribeam personnel transporter. Analysis indicates the dimensions of subelement "b" are more than adequate to assure compressive stability under its anticipated loading (Pcr + 3). The overall dimension "w" of the compression frame cross-section is dictated by general stability moment of inertia, I, requirements, where A valve of "w" = 43.3 meters satisfies the. above equation. The dimensions and characteristics of the six (6) compression frame columns are tabulated in Table 2.1-1. The catenary rope and tension web design and analysis details are summarized in Figures 2.1-21 and 2.1-22. Table 2.1-2 is the preliminary weight statement for the complete compression frame - tension web antenna structure concept. As indicated, the weight estimate is superior to both the earlier Grumann/Raytheon and Martin-Marietta estimates. If the compression frame material were graphite/polyimide composites rather than aluminum a further weight savings of approximately 20 percent would be realized.