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Fig. 25h The eighth vibration mode from the STAGS model. The modal vibration frequency predicted by STAGS is 19.82 Hz. The situation here is analogous to that depicted by the STAGS model in Fig. 25d (n = 3 circumferential waves + some tank lateral motion) and compared with Fig. 25a (n = 3 circumferential waves + some tank lateral motion). This mode is analogous to that displayed in Fig. 25e: a combination of shell deformation with n = 4 circumferential waves and rolling motion of the propellant tank approximately as a rigid body with significant tension and compression in the supporting struts. While the two superficially similar STAGS vibration modes that are orthogonal to each other shown here and in Fig. 25e can exist, there is no analogous situation in which there exist multiple modes with primarily tank rolling motion in the decoupled GENOPT/BIGBOSOR4 model. As with Fig. 25e the two components of total motion from STAGS shown here should be compared with the predictions from GENOPT/BIGBOSOR4 shown in Figs. 16a(B) and 16b(G).
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