Session: 01-12-03: Spacecraft Structures 3

Paper Number: 162344

162344 - Experimental Studies of Dynamic Scaling of Deployable Composite Structures 

As space missions require structures of increasingly size for solar sails, reflector antennas and solar arrays, the dynamics of these systems become ever more important, since large deflections can result in efficiency loss in performance, as well as damage or even failure, and the specter of overall instability becomes ever more real. The first step to address such problems is the accurate identification of the system dynamics, most notably the vibration mode shapes, natural frequencies, and damping ratios. However, these systems cannot be tested at full size prior to deployment in the space environment. Numerical simulations may overlook some key components of the dynamics, such as the correct damping mechanisms. To address this problem, structural scaling methods can be used to gain knowledge on full scale systems without directly performing experiments on them.

There are multiple scaling methods, such as Dimensional Analysis (Buckingham, 1914) and Energy Distribution (De Rosa, 2012), each with its own advantages and limitations. A specific challenge of composite structures is non-homogeneity and multiple components such as stiffeners or battens with varying length. The proposed scaling method combines the STAGE scaling method (Casaburo, 2019), which derives the system scaling laws based on the dynamic equations of motion in combination with a Rayleigh quotient approximation, which exploits the mode shapes to approximate the natural frequency. The Rayleigh quotient is expressed in terms of different energy components, related to specific characteristics of the system, for which a scaling law can be individually formulated. The scaling laws that correspond to each component are obtained from a scaling map containing the dynamic properties of the system for different nominal sizes of the component. Thus, the natural frequencies, mode shapes, and damping laws are derived from the scaling map, and can be approximated as a function of the size of each component. This allows for non-homogeneous scaling, i.e. changing the dimensionality of some of the components, while leaving other components unchanged.

The proposed method is validated both numerically and experimentally using a deployable strip from the Caltech Space Solar Power Project (CSSPP) structure (Sommer, 2025). The goal of the CSSPP is to send foldable solar arrays into space for energy harvesting. Since the full system requires 60 m by 60 m structures, testing of scaled systems will prove valuable in analyzing the dynamics of the full system.

The results of this study demonstrate the ability to predict the dynamics of large-scale structures, by executing a set of scaled experiments and developing a scaling law which is comprised of the key dynamic components of the system. It is believed that this method can utilized to identify and control the dynamics of large scaled systems.

References

De Rosa, S., Franco, F., Li, X., & Polito, T. (2012). A similitude for structural acoustic enclosures. Mechanical Systems and Signal Processing, 30, 330-342.‏

Casaburo, A., Petrone, G., Franco, F., & De Rosa, S. (2019). A review of similitude methods for structural engineering. Applied Mechanics Reviews, 71(3), 030802.‏

Buckingham, E. (1914). On physically similar systems; illustrations of the use of dimensional equations. Physical review, 4(4), 345.

Sommer, C., Truong, A., Wen, A., Gdoutos, E., Madonna, R., & Pellegrino, S. (2025). On-Orbit Demonstration of the Deployable On-Orbit Ultra-Light Composite Experiment (DOLCE) on the Caltech Space Solar Power Demonstration 1 (SSPD-1) Mission. In AIAA SCITECH 2025 Forum (p. 1007).‏

Presenting Author: Eyal Baruch Caltech

Presenting Author Biography: Dr. Eyal Baruch is a postdoctoral researcher specializing in structural dynamics at the Space Structures Laboratory at Caltech. He previously conducted research in the dynamics laboratory at the Technion. His master’s thesis focused on the identification and control of mistuned cyclic symmetric systems for Structural Health Monitoring, while his Ph.D. research explored model-based Atomic Force Microscopy. During his master's studies, he published three papers on the subject, and he also authored a paper based on his Ph.D. research.
Throughout his master's and Ph.D. programs, Dr. Baruch served as a teaching assistant for multiple courses, including Dynamics and Vibration, Hybrid Robotics, and Microprocessors.
Currently, as a postdoctoral researcher, Dr. Baruch investigates the dynamics of ultralight, foldable composite space structures. His work aims to model and control the dynamic behavior of these innovative structures to enhance their efficiency and mitigate potential failure.