# Development of a Novel Deployable Solar Panel and Mechanism for 6U CubeSat of STEP Cube Lab-II
## 5 Experimental Validation
### Launch Vibration Environment Test  
The launch vibration tests of the proposed solar panel module were performed at ambient room temperature (20 \({}^{\circ}\)C) under the qualification-level sinusoidal vibration [34] and random vibration [35] launch loads to verify the damping performance and structural safety in a launch environment. Figure 13 illustrates an example of the launch vibration test setup of the VMLSA on a vibration shaker (J260/SA7M, IMV Corp., Osaka, Japan). To monitor the input vibration loads on the specimen, accelerometers were mounted on the test jig of the solar panel and the slip table of the vibration shaker. During the test, the output acceleration responses of the solar panel module were obtained using an accelerometer attached to the middle of the solar panel. The structural safety of the solar panel under vibration loads was validated by comparing first eigenfrequencies in low-level sine sweep (LLSS) tests executed before and after full-level vibration tests; the variation of first eigenfrequency in the LLSS tests must be within 5%. Additionally, after performing all vibration tests, a solar panel deployment test was executed to determine mechanism reliability. A modal survey test was conducted before and after the aforementioned full-level vibration tests to determine the first eigenfrequency of the solar panel by a low-level sinusoidal vibration excitation on the specimen with an amplitude of 0.5 g. The \(z\)-axis LLSS response of the solar panels in the same axis excitation conducted prior to the full-level vibration tests is shown in Figure 14. The first eigenfrequency of the VMLSA in the launch stowed configuration was 75.0 Hz, which is higher than that of a typical PCB solar panel by a factor of 1.53. Figure 14: Low-level sine sweep test results in \(z\)-axis excitation. Figure 13: An example of launch vibration test setup of VMLSA on a vibration shaker. The VMLSA's corresponding axis sine vibration test results during the \(x\)-, \(y\)-, and \(z\)-axis excitations are shown in Figure 15. The qualification level of full-level sinusoidal vibration loads for small satellites, as preferred by the QB50 System requirements and recommendations [34], was applied along the axis of the solar panel, but the \(z\)-axis was the most important axis because it produced the highest dynamic deflection in comparison to the others. The solar panel's corresponding \(x\)-, \(y\)-, and \(z\)-axes maximum acceleration responses under a sinusoidal vibration input load of 2.5 g in each excitation axis were 2.5, 2.5, and 10.26 g, respectively. A maximum 10.26 g resonance response was observed at 75 Hz on the \(z\)-axis of the VMLSA during the same axis excitation. The VMLSA's corresponding axis random vibration test results for each excitation axis are shown in Figure 16. The Grms values in each corresponding axis calculated from the PSD acceleration profiles under the \(x\)-, \(y\)-, and \(z\)-axis excitations were 16.57, 16.36, and 13.51, respectively. Compared to the input level random vibration profile of 14.1 Grms, the Grms of VMLSA was lower by a factor of 1.04 in the \(z\)-axis owing to the high damping achieved by the attached stiffeners. Figure 15: The results of VMLSA’s corresponding axis sine vibration tests in the \(x\)-, \(y\)-, and \(z\)-axis excitations. The results of the LLSS tests conducted before and after the full-level sinusoidal and random vibration tests are summarized in Table 8. The first eigenfrequency shift of the VMLSA was within 4.85% throughout the test sequences, which is within the 5% criterion. The visual inspection of the solar panel module performed after all the vibration tests did not report dissociation and plastic deformation of the stiffeners. Thus, the structural safety of the solar panel under launch vibration loads was validated at the qualification level. Furthermore, in the middle of the VMLSA, the maximum relative dynamic displacement under the random vibration load calculated by the 3-sigma value of acceleration G\({}_{\text{rms}}\) response was 0.12 mm.