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Dynamic Analysis of Additively Manufactured Tensegrity Structures
Get PDFHerein, we present an analysis, design, and experimental testing of modular prestressed pin-jointed structures constructed from bistable units and inspired by the classical triangular tensegrity prism. Tensegrity structures, characterized by a combination of tension members (cables) and compression members (bars) in a self-equilibrated state, have gained significant attention in engineering over the past two decades due to their unique nonlinear mechanical behavior. The discontinuity of the compression members in tensegrity structures leads to a slightly different failure behavior compared to their lattice structure counterparts, with unprecedented applications. However, traditional fabrication and assembly methods have posed challenges for their widespread adoption. This research benefits from a recently introduced innovative approach for designing and fabricating bistable “tensegrity-like” units where there exists no flexible element in its structure. Vat photopolymerization technology was utilized to create compliant mechanisms based on a triangular tensegrity prism. Two types of structures, namely a double tensegrity-like unit cell and a lattice structure incorporating the triangular tensegrity prism, were fabricated. Quasi-static compression tests were conducted along with high strain rate experiments were conducted using a specialized direct-impact Hopkinson pressure bar setup. Compression tests at both low and high strain rates confirmed the reliable activation of the designed bistable twisting mechanism, even under large displacements, without the need for self-stress. Experimental results at low and high strain rates demonstrated that these low-density units (relative density of 20%) with bistable characteristics are well-suited for applications requiring highly customizable multistable metamaterials. Here, a sudden transition event (snapping), was clearly seen in both quasi-static and dynamic tests. This, indeed, shifts the structure into a secondary stable configuration while maintaining the twisting mechanism throughout the loading cycles. Overall, this study presents a promising avenue for the design and application of tensegrity-like units in various engineering contexts, demonstrating the effectiveness of tensegrities to carry external loads across a wide range of strain rates
Analytical Solution for Transient Thermal Behavior of Two Semisolids With Contact Resistance and Interfacial Heat Generation
No full textHigh-Fidelity CFD Simulation of Supersonic Flow Over a Forward-Facing Step
No full textA forward-facing step was analyzed in supersonic flow at a free-stream Mach number of 1.5 using structured, overset CFD methods with a hybrid RANS/LES turbulence model to assess shock-boundary layer interaction effects. Grid refinement was analyzed using automated multigrid cycling, and results indicate further grid refinement may be warranted. General flow features, boundary layer separation location, and shock unsteadiness match those found in the literature. A correlation study was conducted, and it was determined that the spanwise dimension of the grid system is appropriately sized for periodic boundary conditions
Harnessing the Fourth Dimension Through Nonlinear Damping in Optical Fiber Flow Sensing
No full textIn this study, nonlinear damping is introduced as a critical enhancement in the operation of a fiber tip optomechanical flow-sensor. The flow sensor, is integrated onto the cleaved face of an optical fiber and features a three-dimensional (3D) rotor fabricated using a two-photon nanomachining process. By infusing a polydimethylsiloxane hydrocarbon stabilizing agent via integrated microfluidic channels into the sensing element, the device achieves consistent periodic measurement of gaseous nitrogen flow rates between 10 and 20 LPM. This paper presents a comprehensive characterization of the fiber tip flow sensor and highlights the advantages of nonlinear damping in enhancing the sensitivity and reliability of flow measurements
Statistical reliability estimation of space launch vehicles: 2000–2022
No full textExcerpt: This research examines the reliability of space launch vehicles (SLVs) performing commercial, civil, and military space lift missions through trend analysis and a variety of statistical methods. Data sets obtained from the Seradata database are analyzed for trends by examining data subsets including launch date, sector (commercial, civil or military), launch country, intended mission orbit, SLV family, and failed subsystem
Variable-fidelity sensors and observer uncertainty using touring multi-body periodic orbits to conduct cislunar SSA: preliminary study
No full textAn accelerating interest in cislunar space and lunar orbit for civilian, commercial, and scientific missions requires a space situational awareness (SSA) architecture extending beyond geosynchronous orbit to promote space traffic management and safety. Space-based SSA in cislunar space is challenging due to difficulties associated with accurately estimating the position of the surveillance satellite, which is a foundational requirement for effectively performing the general SSA mission. Using multiple surveillance satellites with lower-fidelity sensors helps alleviate these concerns by aggregating multiple data sets with higher variance to achieve the same level or potentially improved accuracy as compared to fewer higher-quality sensors. A subset of Earth–Moon periodic orbits, herein identified as “touring” orbits, are used for an optical surveillance constellation with a target resident space object (RSO) in a L 1 Halo orbit. Angles-only measurement data are processed utilizing an extended Kalman filter to estimate the position of the RSO. The analysis focuses on assessing the effectiveness of different numbers of surveillance satellites using touring cislunar periodic orbits for conducting the SSA mission relative to L 1 . Overall, this study finds that the use of an SSA constellation with low-fidelity sensors can match the performance achieved by a constellation featuring higher-fidelity sensors and reduced observer uncertainty for the observer orbits examined
Influence of Environmental Barrier Coatings on the Overall Effectiveness of a Film Cooled Ceramic Matrix Composite Plate
Get PDFSilicon carbide ceramic matrix composites, a promising new potential upgrade over the conventional metals currently used for jet engine turbine blades, have a propensity to oxidize in a combustion environment. Engine manufacturers often apply environmental barrier coatings to prevent the composites from oxidizing. What is unclear, however, is how environmental barrier coatings effect underlying composite temperatures. This research examined the coatings’ effects by first characterizing the influence of environmental barrier coatings on the underlying temperature of a protected ceramic, then evaluating the significance of lateral conduction for cooling a coated ceramic, and finally comparing cooling results for coated and uncoated ceramics at low and high temperature conditions. The results showed that the coatings have little to no influence on overall cooling effectiveness, that lateral conduction in both the ceramic and the coating was an important factor in the overall cooling effectiveness, and that conventional scaling techniques must be modified to more accurately scale low temperature film cooling experiments for ceramics up to high temperature conditions
Preliminary Assessment of Cislunar Disposal Orbits
Get PDFThis thesis investigates the disposal of end-of-life spacecraft from key orbits with a focus on minimizing delta-v expenditure and preventing debris propagation. Simulated Lyapunov and halo orbits around the L2 Lagrange point are analyzed for disposal feasibility. Both impulsive and continuous thrust methods are explored to achieve disposal trajectories. Continuous thrust will be modeled after a Hall thruster utilizing electric propulsion. Leveraging the Circular Restricted Three Body Problem framework, low delta-v cost trajectories are computed, with a multi-level correction algorithm optimizing total delta-v via heteroclinic connections. The study assesses various delta-v amounts for Earth-Moon system escape and evaluates the potential for reaching the Earth\u27s sphere of influence and Hill sphere. Results indicate a successful selection of disposal trajectories for both Lyapunov and halo orbits, offering insights into effective space traffic management strategies. This research establishes a foundational framework for future cislunar disposal operations, contributing to sustainable space traffic management practices
Rapid Passive Safety Determination Using Backward Reachability for Spacecraft Rendezvous and Proximity Operations
Get PDFAs the prevalence of autonomous space systems rise, there is an urgent demand for robust and precise safety analysis. The future of RPO necessitates coordination of satellites in a dynamic and congested space environment while avoiding collisions. Passive safety in RPO refers to the implementation of strategies that minimize the collision risk in the event of orbital or control deviations. This multifaceted problem includes maintaining KOZ, utilizing predictive modeling to anticipate collision scenarios, and designing spacecraft with robust GNC systems allowing for timely course corrections. The current literature’s focus has been on the separation distance between spacecraft as a primary safety consideration. However, a more comprehensive approach is required that considers thrust malfunctions paired with RTA, a monitoring algorithm that evaluates the safety implications of primary controller commands. RTA then allows the command to proceed or triggering the implementation of a backup controller. This paper conducts a comprehensive survey of the literature on passive safety in RPO and presents a RTA solution addressing a wider range of safety violation issues