Traveling to space requires a great deal of energy. This then limits the size of spacecraft accessible to transport to space. An optimization of a flexible tube that could be used as a satellite deployable structure was conducted by varying the cross section of the tube and its composite material properties. The material properties manipulated include the selection of a fiber, matrix, filler volume ratio, and orientation. HEEDS, a commercially available software, conducts the optimization process using the SHERPA algorithm. In the optimization, the finite element code, ABAQUS, iteratively performs two simulations. First, ABAQUS determines the stress distribution along the tube when wrapping the tube in its stored configuration. Second, ABAQUS finds the first natural frequency of the deployed structure. The objective function driving the optimization process is minimizing the weight and strain energy of the tube to create a light but highly flexible tube. This provides benefits of avoiding a violent deployment and lowering the dynamic response of the spacecraft during deployment. Three optimizations were performed with 1000 iterations each, using different initial geometries. While all three produce very similar results, one design converges to a clear best result. Using the best design, a series of deployment simulations are performed, using different boundary conditions to represent various scenarios. These boundary conditions include a free body dynamic response to deployment, a restricted response to only allow for rotation about the direction of deployment, and an increased damping deployment. Energy is dissipated differently comparing the results, showing that the most realistic case, being a free body deployment, has the lowest effect on the system. The spacecraft can dissipate energy by oscillating in the other axis. While damping does reduce the settling time for the deployed tube, there is notable oscillation in the middle of the tube seen in the transient state. / Master of Science / The size and weight of a spacecraft is important when considering its feasibility to launch to space. By creating a spacecraft that can be stowed in a small configuration and deploy, new parameters arise, thus new designs can be created. This paper observes using different shapes and materials to create an expandable tube, providing a support structure for a satellite or spacecraft. HEEDS, an optimization software, uses the SHERPA code to select the shape of the cross section and create a composite material. Composite material selection is comprised of a fiber, a matrix, a filler volume ratio, and an angle for the fibers to lay at. After selecting these parameters, HEEDS calls a finite element software, ABAQUS, to perform two simulations. The first simulation wraps the tube around a central hub and observes stress at each timestep. The second simulation finds the first mode of natural frequency of the deployed model. Using user defined constraints that revolve around the safety factor of the stress and minimum frequency, each iteration is marked as feasible or infeasible. An objective function is used to evaluate the best design. This paper focuses on minimizing the weight of the tube and the strain energy inside of the objective function. By minimizing the strain energy, the tube will deploy less violently and cause less rotation due to deployment. HEEDS performs 1000 iterations on three different initial geometry. While there are similar defining factors of each final design, there is one design that is better than the other two. Using the best design, ABAQUS runs three different deployment simulations to observe the deployment behavior. These scenarios encompass different dynamic simulations and show that a realistic deployment where the spacecraft is free to rotate on all axis is safe.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/110393 |
| Date | 01 June 2022 |
| Creators | Fink, Zachary Adam |
| Contributors | Aerospace and Ocean Engineering, Kapania, Rakesh K., Artis, Harry Pat, Inoyama, Daisaku |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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