Reduced-Order Modeling for Flexible Spacecraft Deployment and Dynamics

The present work investigates reduced-order modeling for ultralight, packageable, and self-deployable spacecraft where reduced-order models (ROMs) are required to simulate deployment, structural dynamics during spacecraft maneuvers, and for real-time applications in trajectory optimization and control. In these contexts, ultralight, flexible spacecraft dynamics are characterized by geometrically nonlinear structural deformations combined with large rigid body motions. An approach based on proper orthogonal decomposition (POD), energy-conserving sampling and weighting (ECSW), and a floating frame of reference (FFR) is proposed to construct accurate and efficient ROMs. The proposed approach is then tested on a benchmark problem that involves geometrically nonlinear deformations, large rigid body motions, and strain energy release during dynamic snap-back, the last of which is analogous to the energy release during deployment. The resulting ROM for this benchmark problem is approximately 20% the size of the original full-order model with no appreciable loss of accuracy

Power-Optimal Guidance for Planar Space Solar Power Satellites

This paper presents power-optimal guidance for a planar space solar power satellite (SSPS). Power-optimal guidance is the attitude trajectory that maximizes the solar power transmitted by the SSPS. Planarity is important because it couples the orientations of the SSPS’s photovoltaic and antenna surfaces. Hence, the transmitted power depends on the relative geometry between the SSPS, the sun, and the receiving station. The orientation that maximizes power transfer changes as this relative geometry changes. Both single- and dual-sided SSPS architectures are considered. A single-sided SSPS has one photovoltaic surface and one antenna surface. A dual-sided SSPS is a single-sided SSPS with at least one additional photovoltaic or antenna surface. Geometric arguments show that a dual-sided SSPS has superior performance to a single-sided SSPS. Power-optimal guidance is then presented for the special cases of SSPSs in geostationary Earth orbit, medium Earth orbit, and low Earth orbit transmitting to an equatorial receiving station at the time of Earth’s vernal equinox. These examples emphasize important solution properties, including the need for large slew maneuvers, and they show that, even though system efficiency decreases as orbit altitude decreases, reduced path losses actually increase the amount of received energy per unit aperture area. This has significant system implications for future space solar power missions

Attitude maneuver design for planar space solar power satellites

This paper investigates the attitude dynamics of a planar space solar power satellite (SSPS) by formulating the power-optimal guidance problem as a nonlinear trajectory optimization problem. The power-optimal guidance problem determines the orientation of an SSPS throughout its orbit that maximizes the amount of power transmitted to Earth. This transmitted power is a function of the relative geometry between the SSPS, the Sun, and the receiving station. Hence, it is inherently coupled to the attitude of the SSPS, i.e., the orientation that maximizes power transmission changes as the relative geometry changes. We first approximate the discretized trajectory optimization problem as a quadratic program (QP). We then solve the QP to obtain attitude trajectory designs for various orbits. These solutions highlight how maximizing transmitted power typically requires large slew maneuvers. Ultimately, by quantifying control and propellant requirements for various orbits, we emphasize how maneuver dynamics play an important role in SSPS design

Design and evaluation of a unique RT-qPCR assay for diagnostic quality control assessment that is applicable to pathogen detection in three species of salmonid fish

BACKGROUND: The detection of pathogens at early stages of infection is a key point for disease control in aquaculture. Therefore, accurate diagnostic procedures are a must. Real-time PCR has been a mainstay in diagnostics over the years due to its speed, specificity, sensitivity, reproducibility and throughput; as such, real-time PCR is a target for improvement. Nevertheless, to validate a novel diagnostic tool, correct setup of the assay, including proper endogenous controls to evaluate the quantity and quality of the samples and to detect possible sample degradation, is compulsory. This work aims to design a unique RT-qPCR assay for pathogen detection in the three salmonid species reared in Chile. The assay uses elongation factor 1 alpha as the single endogenous control, thus avoiding the need for multiple endogenous controls, as well as multiple validations and non-comparable quality control parameters. RESULTS: The in vivo and in vitro analyses of samples from Salmo salar, Oncorhynchus mykiss and Oncorhynchus kisutch showed that when primers were accurately selected to target conserved regions of the elongation factor 1 alpha (ELF1α) gene, a single novel RT-qPCR assay yielding similar and reproducible Ct values between the three species could be designed. The opposite occurred when an assay originally designed for Salmo salar was tested in samples from the two species of the genus Oncorhynchus. CONCLUSIONS: Here, we report the design and evaluation of an accurate trans-species RT-qPCR assay that uses the elongation factor 1 alpha (ELF1α) gene as an endogenous control and is applicable for diagnostic purposes in samples obtained from the three salmonid species reared in Chile

Scheherazade

The Utah State University Symphony Orchestra presents its annual spring concert, this year being Rimsky-Korsakov\u27s Scheherazade . Rimsky-Korsakov based the music of his symphonic suite on the Arabian Nights stories, with the orchestra depicting moods and representing characters from the tales.https://digitalcommons.usu.edu/music_programs/1065/thumbnail.jp