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Case Bradford, Samuel

Publications and source records attributed to Case Bradford, Samuel.

Detection and Mitigation of Transient Instabilities in Deployable Booms

Deployable space structures offer versatile uses in many space applications, as they can create very large space structures from a single space launch. However, they usually present important dynamical challenges during the critical deployment phase. In this paper, we focus on the dynamical behavior of deployable booms and the important challenge of avoiding collisions between boom’s structural elements or with other parts of the spacecraft, that can potentially have serious consequences. We define this kind of collisions as “transient instabilities” in deployable booms. A new paradigm to tackle these issues is presented in this paper, using techniques from multi-agent/swarm literature like transient instability prevention methods that avoid inter-agent collisions. We have adapted these techniques to deployable booms to guarantee safe deployment of booms and avoid collisions. We also present computational simulations of boom deployment in order to validate our techniques and demonstrate its use for future space missions.

Balas, Mark↗

Design of Flexures for Deployable Reflectarrays Using High Strain Composites

This paper presents a novel flexure design for small scale refelectarrays, specifically CubeSats, that requires high level of deployment precision. Advantages of using a HSC flexure includes additional thermal stability, lesser part count and passive deployment mechanism using the stored strain energy. The proposed design is to use two flat HSC strips of thickness ℎ, length 2𝐿ℎ, width 𝑊ℎ that attach to the core-reflector panel interface. The flexure satisfies two main requirements: ability to fold to a specific compaction 𝑑 without material failure and sufficient stiffness in the deployed configuration. The elastica analysis was implemented to identify the maximum strains in the flexure when folded and provide relations that combine Δ, ℎ, 𝐿ℎ with the maximum allowable strain. A simplified analysis was performed of the vibration of a panel-flexure combination using a two degree of freedom system. The vibration analysis reveals a dimensionless length parameter 𝛽 = (𝐿ℎ/𝐿𝑃) (Δ/ℎ) that determines the transition between bending and shear modes. A non-dimensional relationship was obtained between the natural frequency and 𝛽 that captures the impact of each parameter on the response of the structure. Our current work involves fabricating and testing of the proposed flexures using High Strain Composite materials, with plans to build a prototype for a deployable reflectarray.

López Jiménez, Francisco↗