5,277 research outputs found
Shape-changing solar sails for novel mission applications
In order to increase the range of potential mission applications of solar sail technology, this paper introduces the
concepts of shape change and continuously variable optical properties to large gossamer spacecraft. Merging the two
concepts leads to the idea of solar sails as multi-functional platforms that can have potential benefits over conventional
solar sails by delivering additional key mission functions such as power collection, sensing and communications. To
this aim, the paper investigates the static deflection of a thin inelastic circular sail film with a variable surface reflectivity
distribution. The sail film is modelled as a single surface framed by a rigid supporting hoop structure. When changing
the reflectivity coefficient across the sail surface, the forces acting on the sail can be controlled without changing the
incidence angle relative to the Sun. In addition, by assigning an appropriate reflectivity function across the sail, the
load distribution due to solar radiation pressure can also be manipulated to control the billowing of the film. By an
appropriate choice of reflectivity across the sail, specific geometries can be generated, such as a parabolic reflector,
thus enabling a multi-functional sail. This novel concept of optical reconfiguration can potentially extend solar sail
mission applications
Multi-step self-guided pathways for shape-changing metamaterials
Multi-step pathways, constituted of a sequence of reconfigurations, are
central to a wide variety of natural and man-made systems. Such pathways
autonomously execute in self-guided processes such as protein folding and
self-assembly, but require external control in macroscopic mechanical systems,
provided by, e.g., actuators in robotics or manual folding in origami. Here we
introduce shape-changing mechanical metamaterials, that exhibit self-guided
multi-step pathways in response to global uniform compression. Their design
combines strongly nonlinear mechanical elements with a multimodal architecture
that allows for a sequence of topological reconfigurations, i.e., modifications
of the topology caused by the formation of internal self-contacts. We realized
such metamaterials by digital manufacturing, and show that the pathway and
final configuration can be controlled by rational design of the nonlinear
mechanical elements. We furthermore demonstrate that self-contacts suppress
pathway errors. Finally, we demonstrate how hierarchical architectures allow to
extend the number of distinct reconfiguration steps. Our work establishes
general principles for designing mechanical pathways, opening new avenues for
self-folding media, pluripotent materials, and pliable devices in, e.g.,
stretchable electronics and soft robotics.Comment: 16 pages, 3 main figures, 10 extended data figures. See
https://youtu.be/8m1QfkMFL0I for an explanatory vide
Shape-changing Collisions of Coupled Bright Solitons in Birefringent Optical Fibers
Wecritically review the recent progress in understanding soliton propagation
in birefringent optical fibers.By constructing the most general bright
two-soliton solution of the integrable coupled nonlinear Schroedinger equation
(Manakov model) we point out that solitons in birefringent fibers can in
general change their shape after interaction due to a change in the intensity
distribution among the modes even though the total energy is conserved.
However, the standard shape-preserving collision (elastic collision) property
of the (1+1)-dimensional solitons is recovered when restrictions are imposed on
some of the soliton parameters. As a consequence the following further
properties can be deduced using this shape-changing collision. (i) The exciting
possibility of switching of solitons between orthogonally polarized modes of
the birefringent fiber exists. (ii) When additional effects due to periodic
rotation of birefringence axes are considered, the shape changing collision can
be used as a switch to suppress or to enhance the periodic intensity exchange
between the orthogonally polarized modes. (iii) For ultra short optical soliton
pulse propagation in non-Kerr media, from the governing equation an integrable
system of coupled nonlinear Schroedinger equation with cubic-quintic terms is
identified. It admits a nonlocal Poisson bracket structure. (iv) If we take the
higher-order terms in the coupled nonlinear Schroedinger equation into account
then their effect on the shape-changing collision of solitons, during optical
pulse propagation, can be studied by using a direct perturbational approach.Comment: 14 pages, ROMP31, 4 EPS figure
Shape changing and accelerating solitons in integrable variable mass sine-Gordon model
Sine-Gordon model with variable mass (VMSG) appears in many physical systems,
ranging from the current through nonuniform Josephson junction to DNA-promoter
dynamics. Such models are usually nonintegrable with solutions found
numerically or peturbatively. We construct a class of VMSG models, integrable
both at classical and quantum level with exact soliton solutions, which can
accelerate, change their shape, width and amplitude simulating realistic
inhomogeneous systems at certain limits.Comment: 6 pages, 4 figures, revised with more physical input, to be published
in Phys. Rev. Let
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