404 N. Abraham et al. Fig. 34.5 HIAD configuration without straps Table 34.1 Test configuration matrix Test article Configuration ID Inflation pressure Six-meter with Tri-Torus and Straps 1 8 psi all toroids 2 15 psi all toroids 3 20 psi all toroids 4 15 psi T1/T2/T6.5, 8 psi all others Six-meter without Tri-Torus and with Straps 5 8 psi all toroids 6 15 psi all toroids 7 20 psi all toroids 8 15 psi T1/T2/T7, 8 psi all others Six-meter without Straps and Tri-Torus 9 8 psi all toroids 10 15 psi all toroids 11 20 psi all toroids 12 15 psi T1/T2/T7, 8 psi all others (SOCIT) which utilizes a system identification process to calculate the mathematical representation of a physical system using experimental free decay time records [3]. The step relaxation technique was only performed for the configurations with the tri-torus (Configurations 1–4). The difference in the modal frequencies between the shaker and step relaxation test techniques were seen to range from 0.1 to 3 %, without any significant trends. This percent difference was acceptable for this study. It should be noted that all the results given in this paper are from the shaker tests. 34.3 Modal Test Results The modes obtained from the experimental results are shown in their respective order in Fig. 34.9. With reference to Fig. 34.1, the brown quadrilateral represents the bottom plane of the center body assembly. The black quadrilateral represents the baseplate. The gray quadrilateral represents the four tri-axial accelerometer assembly locations for the center body. Finally, the joints of the orange quadrilaterals represent the 14 tri-axial accelerometer assembly locations on the inflatable.
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