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Reconstructing ancient clothing has a long tradition in Scandinavian archaeology and during her professional career as a hand weaver, Anna Nørgård has produced many items of prehistoric clothing and sails for various museums in Denmark and abroad. For her, a reconstruction is a tool, a way to gather new knowledge. Nevertheless, only on rare occasions has she been asked to produce a report and document her work. This implies that most museums are not aware of the scientific potential that the reconstruction process itself offers. In this article, she shares some of her thoughts and experiences with Scandinavian Iron Age textile technology gathered while working on reconstructions of finds such as the Lønne Hede and Huldremose clothing, the Skærsø textile and multiple metres of sail cloth. [ABSTRACT FROM AUTHOR]

Several standardized and validated information literacy (IL) tests have been developed for use in U.S. post-secondary contexts, but fewer choices exist for schools outside of the U.S. In an earlier study (Cowan, Graham, & Eva, 2016) the authors explored IL testing at a Canadian university using the international version of the SAILS Cohort test. This article describes a second study that used the Build Your Own Test (BYOT)—a customizable version of the SAILS Individual Scores test—to evaluate undergraduate students’ IL learning. Pros and cons of using the Cohort and BYOT versions of SAILS are discussed, with the aim of providing guidance for other schools interested in pursuing such testing. The authors found the BYOT allowed them to better gauge the extent to which individual students’ IL ability levels changed over the course of one term.

The propulsive characteristics of an Electric Solar Wind Sail are usually evaluated using a simplified model in which all the sail tethers are coplanar and form a sort of rigid disk. However, the three-dimensional arrangement of the tethers is fundamental information in the study of the spacecraft performance, and must be accounted for in refined mission analyses. In this paper, a Finite Element approach is chosen to estimate the deflected shape of the tethers, thus allowing important information on the structural response of the sail to be obtained. A parametric code is developed to perform a static analysis of an Electric Solar Wind Sail, whose requirements are given in terms of payload mass and spacecraft characteristic acceleration. In particular, the tether structural response is investigated using three different beam models, which are compared in terms of accuracy and computational efficiency. The analysis is specialized to the noteworthy case of a Sun-facing sail that is placed at a distance of one astronomical unit from the Sun. The numerical results, which concern a set of possible sail configurations, are compared with those taken from analytical models. • The paper analyzes the E-sail deformed shape using a finite element approach. • A parametric procedure is proposed to perform the E-sail static analysis. • The tether structural response is investigated using three different beam models. • The numerical results are compared with those taken from analytical models. [ABSTRACT FROM AUTHOR]

Physics based methods have been developed to obtain accurate design estimates for the performance of relativistic interstellar laser sails and to identify technologies to mitigate losses inherent in the physics. The physical principles that are applied include those of the Special Relativity and Quantum Mechanics. Special Relativity is especially difficult to apply consistently. A method is summarized which makes the application of the Special Relativity straightforward, reducing the possibility of errors generated by neglecting important effects and by reducing mathematical difficulties. Once launched, the spacecraft design must remain fixed, and this dictates a design for the sail that must be able to respond to a broad range of possible events. Although physics-based losses cannot be eliminated, or even reduced, technologies can be applied at the source to help reduce their effect at the sail. These losses include: 1) the decrease in frequency, and hence energy, due to Doppler effects and 2) decreases in the intensity due to delays in the arrival of the photons. Including relativistic effects amplifies these losses at the velocities necessary for interstellar flight. When the sail reaches one fifth of the speed of light the losses become significant. Some losses can be mitigated while others cannot. For example, free electron lasers can be used to keep the frequency (and hence the energy of the photons) constant at the sail and a phased array can be expanded in area to narrow the beam width. Both can be used keep the momentum transferred constant at the sail. A phased array will also allow the beam direction to be controlled. Mathematical models and results will be presented for Doppler and intensity losses, beam width and direction control. A straightforward method to include effects of relativity has been applied to aid in performance estimates for relativistic interstellar laser sails. Although losses based on the physics remain the same their effects at the sail can be reduced significantly. Phased arrays will help with direction control, beam spreading, and intensity adjustments while free electron lasers can help mitigate Doppler effects. Sail structural dynamics, an important consideration not previously discussed, is introduced and methods to lessen the effects are discussed. • A straightforward method to include fully relativistic effects in the dynamics of laser sails. • A spacecraft that accelerates at a constant rate cannot be contacted by any means after a finite time. • The vibrations of the sail during the acceleration will produce dynamic instabilities that will have to be avoided. [ABSTRACT FROM AUTHOR]

Light sailing is the only existing in-space propulsion technology that could allow us to visit other star systems in a human lifespan. In order to best harness radiation pressure, light sails need to be highly reflective, lightweight and mechanically robust. This is traditionally achieved by the use of nanometer-thin reflective layers supported by a micrometer-thick substrate that endows them with the necessary sturdiness. This combination usually results in a sail mass that is too high to be efficiently used for extrasolar exploration. Here, we propose a potentially scalable sail design that combines a hollow substrate with an atomically-thin 2D material which, thanks to its ultimately low surface density, allows reducing the mass contribution of the substrate. To demonstrate the potential of such sails, we have studied the laser-induced displacement of graphene-on-copper sails in vacuum and in microgravity. In these conditions, 0.25 mg samples are accelerated by using lasers of different wavelengths (450 and 655 nm) and power (0. 1 – 1 W). The measured thrust is one order of magnitude larger than the theoretical calculations for radiation pressure alone. This calls for further theoretical studies and attracts interest on graphene as light-sail material. • Light sails based on graphene have a reduced mass density that boosts their thrust. • Graphene sails were accelerated with a laser in vacuum and microgravity. • Microgravity enables sail release with reduced clamping effects during take off. • Delays on the light-induced displacement may be caused by material desorption. • 2D sails pave the way for reaching other star systems in a human lifespan. [ABSTRACT FROM AUTHOR]

The research presented in this paper is part of a more extensive research on possibly diverse velarium systems. At the beginning of this brief description of the velaria, it is necessary to list the main parts and elements that make up a velarium system. Each of the 23 complex catenaries was stretched over 4 masts connected to 4 pilasters by means of 8 backstays: 4 lower backstays that carry the sails and 4 upper tensioning backstays by means of tackles tied up to the top of the mast in order to elevate their middle parts and create a bell above the auditorium with a slope towards the main deck so that rainwater could be directed to the grooved cornice and waterspouts. A total of 92 lower backstays + 92 upper backstays = 184 backstays: 68 masts 30'30 cm and 16 masts 18'20 cm making up a total of 84 masts, 84'2 = 168 shrouds and 84 cippi. [ABSTRACT FROM AUTHOR]

Premise: Adaptive seed dispersal mechanisms are fundamental to plant fitness, but dispersal advantage is scale‐dependent. We tested the hypothesis that informed dispersal in response to an environmental cue enables dispersal by wind on a local scale for Astragalus holmgreniorum, a desert species restricted to swales and wash skirts with overland flow, but prevents longer‐distance dispersal by water into unfavorable wash habitats. Methods: Pod biomechanics in A. holmgreniorum lead to major shape modifications with changes in moisture content. We performed laboratory experiments to examine the interaction of pod shape with wind and water, and conducted field experiments in A. holmgreniorum habitat evaluating the roles of wind, water, and seed predators on dispersal. Results: Dry pods exhibit a flattened crescent shape with partial dehiscence that facilitated wind dispersal by ground tumbling and seed scattering in laboratory experiments. Rain simulation experiments showed that even small precipitation events returned wetted pods to their cylindrical shape and opened the dorsal suture, exposing the seeds. In the field experiments, dry pods were moved locally by wind, whereas rain caused pod opening and washing out of seeds in place. Seed predators had minimal effect on pod movement. Conclusions: Astragalus holmgreniorum exhibits pod structural remodeling in response to environmental change in a striking and novel demonstration of informed dispersal. Wind‐driven movement of dry pods facilitates local seed dispersal, but rain causes pods to open and release seeds, ensuring that they are not transported out of suitable habitats and into active washes where they would be lost from the seed bank. [ABSTRACT FROM AUTHOR]

This article unveils the geometric characteristics of boats with sails of many sizes, covering the range 102–105 kg. Data from one hundred boat models are collected and tabulated. The data show distinct trends of convergent evolution across the entire range of sizes, namely: (i) the proportionality between beam and draft, (ii) the proportionality between overall boat length and beam, and (iii) the proportionality between mast height and overall boat length. The review shows that the geometric aspect ratios (i)–(iii) are predictable from the physics of evolution toward architectures that offer greater flow access through the medium. [ABSTRACT FROM AUTHOR]

The concept of green energy means the activity of generating the electrical or thermal energy required for a diverse range of consumers, from renewable and non-polluting energy sources, such as: photovoltaic or solar panels, wind turbines, biomass/biogas/biodiesel, hydrogen, batteries of combustion, wave / tidal energy, geothermal or hydroelectric etc. By choosing such sources, consumers will be able to support the development of more environmentally friendly hot water for hygienic / household use, electricity or heating the house. Given that the cost of depreciation of the investment is not too long, then for us all, the implementation of green technologies can be a profitable investment not only for the industrial consumers but also for the domestic energies, thereby increasing energy independence but at the same time, reducing the cost of bills for certain utilities such as ones. [ABSTRACT FROM AUTHOR]

This research studies the characteristics of ocean current meanders from the viewpoint of power generation engineering and the potential of maximizing ocean current power generation capacity by making generator turbines to track the meanders applying a recently proposed Cross-stream Active Mooring concept. The current meanders will hurt capacity factor of marine turbines moored at fixed locations, somewhat like the issue of wind availability for wind farms. The new mooring concept features a hydro sail system that can deploy generator turbines transversely across streams in a marine current. The hydro sail system can further adjust the horizontal position of the turbines, by changing sail angle of attack, to actively track fast streams in an ocean current. This paper first reviews and discusses the characteristics of short-term track variations of the Florida Current and the Kuroshio near Taiwan and then analyzes potential improvement in power generation using measured and simulated current velocity data in the two ocean currents, suggesting a potential increase of 10–40 % power generation achievable by tracking the meanders. Operations of the hydro sail were demonstrated by tests using remote controllable and passive scale models. Control methods are discussed. Approaches to observe, predict and track the meanders are conceptualized. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical three-dimensional propulsion process of electric sail considering constant thrust angle. Due to the small characteristic acceleration of electric sails, its dimensionless form is defined as a perturbation parameter. For an electric sail with a determined initial state, an analytical approximate three-dimensional trajectory consisting of a primary term and perturbation terms can be derived by considering a reasonable approximation in the equation of motion. Furthermore, rectification steps are introduced to minimize approximation error caused by reasonable approximation and continuous changes in elements of osculating orbit. Despite the addition of fixed step rectification, the analytical estimation time is much shorter than the integration time, as the entire approximation process, including the rectification step, is analytical. The time required for analytical approximation is much lower than that for integration. Significantly, the parking orbit of the electric sail required for analytical approximation can be arbitrary. Based on the characteristics, the proposed analytical approximate three-dimensional trajectory is suitable for fast trajectory prediction of various complex deep-space exploration missions, especially for splicing trajectories with different pitch angles to solve problems with fixed targets. [ABSTRACT FROM AUTHOR]

Rapid performance prediction tools are required for the evaluation, optimization, and comparison of different wind propulsion systems (WPSs). These tools should capture viscous aerodynamic flow effects in 3D, particularly the maximum propulsion force, stall angles, and interaction effects between the lift-generating units. This paper presents a rapid aerodynamic calculation method for wing sails that combines a semi-empirical lifting line model with a potential flow-based interaction model to account for 3D interaction effects. The method was applied to a WPS that consisted of several wing sails with considerable interaction effects. The results were compared to CFD RANS simulations in 2D and in 3D. For the evaluated validation cases, the interaction model improved the prediction considerably compared to when the interaction was not accounted for. The method provided acceptable driving force, moments, and stall predictions, with negligible computational cost compared to 3D CFD simulations. • Aerodynamic sail–sail interaction effects the performance of wind propulsion systems • Presenting a rapid potential flow-based method (ISILL) for interacting sails • Viscous 2D input to the method generated by Reynolds-averaged Navier-Stokes CFD • Wing sail validation study with varying sheeting at different apparent wind angles • Predictions of the total driving force, the center of effort, and the point of stall [ABSTRACT FROM AUTHOR]