Deployable Space Research Articles

Thermomechanical properties and deformation behavior of a unidirectional carbon‐fiber‐reinforced shape memory polymer composite laminate

ABSTRACTA shape memory polymer (SMP) demonstrates large reversible deformation functionality upon exposure to heating stimuli. In this study, the thermomechanical properties and deformation behavior of a unidirectional carbon‐fiber‐reinforced SMP composite (SMPC) laminate were studied. The findings can be used as a basis to design angle‐ply laminated plates, woven laminated plates, or special laminated structures used for space deployment. The fundamental static and dynamic mechanical properties of SMP and SMPC were characterized. The fiber‐reinforced SMPC exhibited local postmicrobuckling behavior and obtained a high‐reversible macroscale strain of 9.6%, which enabled the high‐reversible deformation to be used for foldable structures in space. The state of critical failure of bending deformation was determined through microscale morphology observations and provided the upper limit in the design of SMPC structures. The evolution of the key shape memory properties (e.g., recovery speed and recovery ratio) during deformation cycles was characterized, and it offered the general recovery performance of a space deployable structure. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48532.

Latest modification of the deployable space reflector structure with V-folding bars

In this paper, a new modification of the mechanical load-bearing ring structure is considered. It is shown that due to the appropriate changes made to the ring, its structure possesses obvious advantages as compared with the previously proposed variant. The projecting tips of the struts to which the central flexible shaping system is attached are replaced by paired levers with torsion springs of new design, which guarantee the smooth deployment of the ring and keep the cables in permanently tensioned condition. In the new modification, the central flexible shaping system is directly attached to the upper and lower hoops of the ring, thereby preventing the bending of struts when the reflector is completely deployed. The new multi-stage deployment scheme of the structure considered in the paper operates without synchronization mechanisms—the upper and lower kinematic chains get deployed not simultaneously as in the previous ring variant but in alternating order. The validity of design computations is confirmed by the FEM mathematical models for which deformations of structural elements, displacement of nodes, and eigenfrequency values are determined. The optimization of structural elements makes it possible to design the mechanical characteristics and strength margin of the ring with a minimal number of elements and minimal cross-sectional values, which simplifies the ring structure on the whole, and reduces its weight.

A possible analysis for failure of U.S. SMAP satellite

The Soil Moisture Active-Passive (SMAP) satellite is the only satellite with a large deployable space eccentric rotating ring truss antenna clamped along a generatrix and rounding a parallel axis. However, the active radar of SMAP satellite stopped working within months of its launch. What are the reasons leading to so dramatic consequences? It is a possibility that the satellite damage is caused by vibration. In this paper, the nonlinear breathing vibrations of the large deployable space eccentric rotating composite laminated ring truss antennas with the large radius are studied from a theoretical analysis of view. Referring to the equivalent model of the continuum circular cylindrical shell clamped along a generatrix, we propose a dynamic model of the eccentric rotating composite laminated circular cylindrical shell subjected to the lateral and the temperature excitations. Considering an eccentric rotating composite laminated circular cylindrical shell clamped along a generatrix and rounding a parallel axis, the nonlinear partial differential governing equations of motion are established by using Donnell thin shear deformation theory, von Karman-type nonlinear relation and Hamilton’s principle. The nonlinear ordinary differential governing equations of motion are obtained by using Galerkin discretization. Based on the theoretical model, the nonlinear breathing vibrations of the equivalent model are studied for the SMAP satellite antenna subjected to the lateral and the temperature excitations for the first time in this paper. Firstly, the effects of different parameters on the toggle condition of 1:2 internal resonance are studied. The effects of the radius and the eccentricity ratio on the natural frequencies are not obvious for the eccentric rotating composite laminated circular cylindrical shell. Furthermore, it is also found that the influence of the thickness and the eccentricity ratio on the resonant rotating speeds cannot be ignored for the eccentric rotating composite laminated circular cylindrical shell. Then, based on the case of 1:2 internal resonance and principal parametric resonance-1/2 subharmonic resonance, the parametric excitation T is selected as the controlling parameter to discover the nonlinear breathing vibrations of the eccentric rotating composite laminated circular cylindrical shell. The periodic and chaotic motions of the equivalent model for the SMAP satellite antenna are found when the rotating speed corresponds to the internal resonant point at the certain excitations for different lateral and temperature excitations. Therefore, the chaotic motions of the SMAP satellite antenna occur under the combined action of temperature parameter excitation and lateral excitation in the space environment. According to the research results of this paper, the active radar of the SMAP satellite may be damaged by severe nonlinear vibrations. We reasonably speculate that the failure of the active radar for the SMAP satellite antenna is caused by the nonlinear vibrations in 1:2 internal resonance. Thus, this paper not only provides a possible analysis for the failure of the SMAP satellite, but also provides the theoretical guidance for study of similar ring truss antennas. This research has important theoretical significance and engineering value.

Design and form finding of cable net for a large cable–rib tension antenna with flexible deployable structures

Cable net structures are important in the construction of large deployable space antennas. The shape and tension of a cable net must be properly designed for the operating requirements of a reflector in orbit. The application demand for large-scale space antennas highlights the problem of the flexible deformation of deployable structures. Thus, such deformation, which has a significant effect on surface accuracy, should be considered in the form finding design of cable nets. In this study, an approach considers the flexible deformation of deployable structures for identifying the desired shape for a cable net is proposed. First, the dimension of the triangles used for dividing the cable net of a cable–rib tension antenna is designed for the required accuracy, and the shape of the cable net is determined by introducing the sag effect in the design of boundary cables. Then, an approach that is based on force density and nonlinear finite element methods and ensures the appropriate node position and uniform tension of the cable net is proposed for the form finding problem. A feature of the developed method involves an optimization model that calculates the deformation of the deployable structure and iteratively modifies the node position to form the cable net. The genetic algorithm is employed for the acquisition of a set of optimal tensions with constraints. Finally, numerical examples and experimental test results are presented to validate the veracity and effectiveness of the proposed approach.

Design and evaluation of a shunted flexible piezoelectric damper for vibration control of cable structures

In this work a shunted flexible piezoelectric damping system is designed and numerically evaluated for the purpose of vibration attenuation of large deployable space cable structures. We propose a design of a tube-shaped flexible piezoelectric energy absorber consisting of multilayered PVDF sectors, which could be shunted with two types of passive electric circuits, i.e. the series resistance-inductance (LR) shunt and the series resistance-negative capacitance (NC-R) shunt. The compatible stiffness of the PVDF tube ensures an effective transformation of deformation from the vibrating cable to the energy absorber. For best performance we carried out optimization on the geometric parameters of the PVDF tube. By analysis we found that the optimal thickness of the PVDF tube is roughly 0.4 times of the inner tube radius. We optimized the shunt circuits and selected the appropriate distribution position of the damper in the flexible cable structures. The performance of the design was numerically evaluated based on three problems, namely the longitudinal vibration of a single-cable structure, the transverse vibration of a single-cable structure and the vibration of a cross-cable structure. Based on the results, we confirm the remarkable performance of the design. Being highly frequency dependent, the design with the LR shunt only works for one deformation mode at a time, e.g. bending or stretching. In contrast, the design with the NC-R shunt works for both modes as it has a much wider frequency band. The design with the LR shunt has better performance than the NC-R shunt when dealing with the stretching deformation mode only. For vibration with combined stretching and bending, however, the performance of both designs is equally good. This is because the NC-R shunt can work for both deformation modes simultaneously, and hence it shows great adaptability and application potential in vibration control of complex flexible space structures.

Double-Layer Cable-Net Structures for Deployable Umbrella Reflectors

The umbrella cable-net structure is one of the most popular forms for deployable space reflectors and has been successfully applied to many in-orbit deployable antennas. The umbrella ribs only provide open support for the cable net, so designing the geometric shape and the internal tension of the umbrella cable-net structure is complex. This paper suggests several double-layer cable-net structures for a deployable umbrella reflector. First, a typical composition of the umbrella reflector was introduced and the design basis of its geometric topology was further discussed. Then, two methods for the static equilibrium analysis of the cable-net structure were introduced for the mechanical calculation of the cable-net structure. Next, three types of the cable-net structure—wedge-shaped/wedge-shaped (W/W), triangular/triangular (T/T), and triangular/wedge-shaped (T/W)—were put forward. The three cable-net types were applied to a reflector and their performances were analyzed and compared with each other to demonstrate their feasibility and applicability.

Plasma parameters and discharge characteristics of lab-based krypton-propelled miniaturized Hall thruster

The lowered costs for operational deployment in space, as well as the ability to implement sophisticated peripherals with integrated systems on-board satellites in orbit has catalysed the recently seen rapid growth in space industry. This growth has been driven mainly by the proliferation of miniaturized space systems, which include satellites, rockets and other payloads, with expanded our ability to acquire and analyse data in orbit. Of great interest to the community working on the continued miniaturization of satellites and other components for space is the provision of micro-propulsion modules for in-orbit manoeuvres. In this work, we report performance parameters of lab-based Kr propelled miniaturized Hall effect plasma thrusters developed at SPC-S, which include thrust, efficiencies, and specific impulse, made possible through a bimodal quadfilar suspended thrust measurement system. Additionally, the plume profiles are studied through a spatially actuated Faraday probe system. Finally, non-invasive plasma diagnostics through analysis of discharge current oscillations as well as optical emission spectroscopy is presented to give a holistic overview of possible diagnostic methods for real-time measurements pertaining to the evaluation of plasma thruster systems. This work explicitly evaluates the effect of the propellant flow rate on the data obtained through the aforementioned diagnostic methods.

Carbon Fibre Reinforced Shape Memory Polymer Composites for Deployable Space Habitats

Intelligent material shape memory polymers (SMPs) and their composites are capable of memorizing and recovering the original shape upon exposure to a particular external stimulus. This paper presents the mechanical properties, thermomechanical behaviour and the shape memory characteristics of 0/90 woven carbon fibre reinforced shape memory composite. The results revealed that the superlative mechanical properties of carbon fibres as a reinforcement has enhanced the strength of the SMP composite (SMPC) to be applicable for space engineering innovations. Furthermore, the recovery behaviour of 90o bended SMPC specimens have been investigated by exposing to heated air and near infraredradiation. Both stimulus methods have shown almost 98% shape recovery. In addition, a model of a cubic deployable structure has been fabricated and respective shape programming and recovery behaviours have been investigated based on the enclosed volume. Interestingly, the deployable structure has been programmed in to almost three times smaller volume and very nearly recovered to its original shape under vacuumed conditions. Accordingly, the carbon fibre reinforced SMPCs can be used to produce deployable space habitats to fabricate on earth, compress and pack in a spacecraft, transport to an outer space location and ultimately deploy in to the original shape.

Preliminary test and analysis of an ultralight lenticular tube based on shape memory polymer composites

Shape memory polymer composites (SMPCs) demonstrate the advantages of light weight, high strain rate, high strength, high stiffness, self-locking and self-deployment. In this study, the mechanical properties and deformation performance of SMPC-based lenticular tube are studied. Dynamic mechanical analysis (DMA) tests and three-point bending tests were carried out to determine thermomechanical properties, and +45°/−45° fiber layout was chosen as the optimum layout. Tensile tests were conducted to investigate the mechanical properties of SMPC at different temperature. The strain distribution during recovery process was obtained by digital image correlation (DIC) experiment. Bending and recovery process were simulated by finite element analysis, the stress distribution of curved state of lenticular tube were obtained. Comparing with traditional lenticular tube, SMPC-based lenticular tube exhibits the advantages of controllability and stability in deploying process, and they still work well after folding 30 deformation cycles. Due to its above advantages, several potential applications are proposed for deployable space structures and will be validated in near future.

Preparation of epoxy-based shape memory polymers for deployable space structures using diglycidyl ether of ethoxylated bisphenol-A

To develop epoxy-based shape memory polymers (ESMPs) with a high switching temperature and good mechanical and shape memory properties for deployable space structures, the crosslink density and chain flexibility of the conventional epoxy resin, diglycidyl ether of bisphenol-A, were controlled by adding a flexible epoxy resin, diglycidyl ether of ethoxylated bisphenol-A with six oxyethylene units (DGEEBA-6). With increasing DGEEBA-6 content, the crosslink density of the ESMPs increased, but their glass transition temperature (Tg) decreased. The ESMPs with suitable switching temperatures (120–135 °C) for deployable space structures showed enhanced toughness, modulus, tensile strength, elongation at break, and shape memory properties. The ESMPs had fast full recovery times of only 80 s at Tg + 20 °C. DGEEBA-6 was shown to be a good modifier of ESMPs for deployable space structures.

Design, fabrication, and evaluation of a passive deployment mechanism for deployable space telescope

This article presents a high precise deployment mechanism for a deployable space telescope to facilitate satellite miniaturization. It is designed with a passive deployment mechanism utilizing a spring hinge. In particular, the customized modules and an assembly jig are specifically designed to reduce alignment errors. To confirm the feasibility of the designed mechanism, three alignment errors that influence the optical performance of the structure—tilt, de-center, and de-space—are theoretically analyzed for quarter, half, and full model, respectively. In the case of quarter model, significant results are obtained as a tilt of 21.12 µrad, a de-center of 2.20 µm, and a de-space of 1.71 µm. Based on the theoretical analysis, a deployment mechanism of the quarter model is fabricated, and the alignments of the deployment mechanism are experimentally investigated with a measurement platform consisting of five non-contact-based laser displacement sensors. In addition, the influence of gravity on the alignment error is analyzed and compensated by investigating the tendency of the alignment error according to the rotation degree of the measurement model for the direction of gravity. As a result of the gravity compensation, the proposed mechanism gives acceptable alignment errors as a tilt of 30.04 µrad, de-center of 8.92 µm, and de-space of 4.03 µm, which are controllable by employing the conventional focusing mechanism.

Deployment of flexible space tether system with satellite attitude stabilization

This paper focuses on the complex dynamics and control of deploying a payload using a long flexible tether from a spacecraft. Two different system models are involved, one for detailed dynamics study and the other for control design. Both the flexibility and extensibility of tether and the attitude motion of spacecraft have been incorporated into the system dynamics. In addition, the orbital dynamics of the tethered system are modeled using a set of modified equinoctial elements and considering the J2 perturbation forces. A two-stage mission design has been proposed to divide the deployment into two parts. The first is an ejection separation stage for the payload to be ejected away from the spacecraft to a predetermined position, and the second is a deployment control stage for active tether deployment by regulating tether tension. The attitude motion control of the spacecraft is performed during deployment based on an optimal fuel control method. A closed-loop feedback controller is developed to achieve the deployment by tracking an open-loop optimal trajectory of tether libration states and control input. Finally, numerical simulations have been performed to demonstrate the feasibility of conceptual mission design and effectiveness of the synthetic control scheme.

On-demand deployment of multiple aerial base stations for traffic offloading and network recovery

Unmanned aerial vehicles (UAVs) are being utilized for a wide spectrum of applications in wireless networks leading to attractive business opportunities. In the case of abrupt disruption to existing cellular network operation or infrastructure, e.g., due to an unexpected surge in user demand or a natural disaster, UAVs can be deployed to provide instant recovery via temporary wireless coverage in designated areas. A major challenge is to determine efficiently how many UAVs are needed and where to position them in a relatively large 3D search space. We first consider a discrete set of possible UAV locations distributed in a given 3D space and formulate the problem as a mixed integer linear program (MILP). Owing to the complexity of the MILP problem, we present an effective greedy approach that mimics the behavior of the MILP for small network scenarios and scales efficiently for large network scenarios. Afterwards, we propose and evaluate a more practical approach for multiple UAV deployment in a continuous 3D space, based on an unsupervised learning technique that relies on the notion of electrostatics with repulsion and attraction forces. We present performance results for the proposed algorithm as a function of various system parameters and demonstrate its effectiveness compared to the close-to-optimal greedy approach and its superiority compared to recent related work from the literature.

A Pair of NiCo2O4 and V2O5 Nanowires Directly Grown on Carbon Fabric for Highly Bendable Lithium‐Ion Batteries

AbstractMechanically bendable and flexible functionalities are urgently required for next‐generation battery systems that will be included in soft and wearable electronics, active sportswear, and origami‐based deployable space structures. However, it is very difficult to synthesize anode and cathode electrodes that have high energy density and structural reliability under large bending deformation. Here, vanadium oxide (V2O5) and nickel cobalt oxide (NiCo2O4) nanowire‐carbon fabric electrodes for highly flexible and bendable lithium ion batteries are reported. The vanadium oxide and nickel cobalt oxide nanowires were directly grown on plasma‐treated carbon fabric and were used as cathode and anode electrodes in a full cell lithium ion battery. Most importantly, a pre‐lithiation process was added to the nickel cobalt oxide nanowire anode to facilitate the construction of a full cell using symmetrically‐architectured nanowire‐carbon fabric electrodes. The highly bendable full cell based on poly(ethylene oxide) polymer electrolyte and room temperature ionic liquid shows high energy density of 364.2 Wh kg−1 at power density of 240 W kg−1, without significant performance degradation even under large bending deformations. These results show that vanadium oxide and lithiated nickel cobalt oxide nanowire‐carbon fabrics are a good combination for binder‐free electrodes in highly flexible lithium‐ion batteries.

User Preference Aware Caching Deployment for Device-to-Device Caching Networks

Content caching in the device-to-device (D2D) cellular networks can be utilized to improve the content delivery efficiency and reduce traffic load of cellular networks. In such cache-enabled D2D cellular networks, how to cache the diversity contents in the multiple cache-enabled mobile terminals, namely, the caching deployment, has a substantial impact on the network performance. In this paper, a user preference aware caching deployment algorithm is proposed for D2D caching networks. First, the definition of the user interest similarity is given based on the user preference. Then, a content cache utility of a mobile terminal is defined by taking the transmission coverage region of this mobile terminal and the user interest similarity of its adjacent mobile terminals into consideration. A general cache utility maximization problem with joint caching deployment and cache space allocation is formulated, where the special logarithmic utility function is integrated. In doing so, the caching deployment and the cache space allocation can be decoupled by equal cache space allocation. Subsequently, we relax the logarithmic utility maximization problem, and obtain a low complexity near-optimal solution via a dual decomposition method. Compared with the existing caching placement methods, the proposed algorithm can achieve significant improvement on cache hit ratio, content access delay, and traffic offloading gain.

A Novel Sub-regional Key Distribution Scheme for Distributed Wireless Sensor Networks

Security is critical to any networks, including WSNs. The packets are transmitted hop by hop in WSNs over a broadcasting medium, which makes them vulnerable. So, data encryption should be employed. Due to the resource-limited nodes in WSNs, the producing, distribution, and management of keys, needful for encryption, become challenging research issues. Among them, key distribution is the most complicated because of nodes’ random deployment and poor memory space. In this paper, a novel key distribution scheme of bivariate symmetric polynomials based on sub-region is proposed for distributed WSNs. With reasonable division of sub-regions, the process of keys distribution goes on without nodes’ location information. It is extremely different from location-based or grid-based key distribution schemes. More obvious advantage is that the number of polynomials stored in each node is much less than E–G scheme and poly&&q-composite scheme. The simulation result shows our scheme far outperforms the poly&&q-composite scheme with much less energy overhead.

Shear-induced buckling of a thin elastic disk undergoing spin-up

The stability of a spinning thin elastic disk has been widely studied due to its central importance in engineering. While the plastic deformation and failure of an annular disk mounted on a rigid and accelerating circular shaft are well understood, shear-induced elastic buckling of the disk due to this ‘spin-up’ is yet to be reported. Here, we calculate this buckling behavior within the framework of the Föppl–von Kármán equations and give numerical results as a function of the disk’s aspect ratio (inner-to-outer radius) and Poisson’s ratio. This shows that shear-induced elastic buckling can dominate plastic failure in many cases of practical interest. When combined with existing theory for plastic failure, the results of the present study provide foundation results for a multitude of applications including the characterization of accelerating compact disks and deployment of space sails by centrifugal forces.

Indoor multiple human targets localization and tracking using thermopile sensor

Thermal sensors have been widely applied for human targets in battlefield surveillance and smart housing. A low-resolution thermopile sensor—GridEye is used to localize and track indoor multiple human targets. Interpolation is introduced to increase the resolution of sensor data and Gaussian filter is designed to smooth the data. An adaptive threshold method is designed to remove non-human thermal targets and background image. The human targets are located by considering the space deployment and the viewing angle effect of GridEye. Depending on target positions and the heat signatures of human targets, the targets are associated with their respective trajectories. The experimental results have shown that multiple humans can be tracked well in the indoor environment.

Iterative Unreplicated Parallel Interference Canceler for MDL-Tolerant Dense SDM (12-Core × 3-Mode) Transmission Over 3000 km

We propose a novel multiple-input multiple-output (MIMO) detection scheme based on iterative unreplicated parallel interference cancelling (UPIC) technique for mode dependent loss (MDL)-impaired few-mode fibre (FMF) transmission. An optical MIMO channel over an FMF exhibits a mode-dependent property where each mode division multiplexed signal is passed through a different lossy channel, known as an MDL phenomena. One challenging issue for realising future deployable space division multiplexing (SDM) systems is establishing reliable and robust signal transmission techniques in the presence of MDL. The main contributions of this paper include first, a proposal of newly developed iterative interference cancellation technique with parallel processing for MDL-impact mitigation, second, a comparative study on performance of MIMO detection schemes, and third, a demonstration of the longest dense SDM transmission over multicore (MC)-FMF. The proposed UPIC with iterative processing is experimentally shown to improve Q-factors by more than 3 dB, and record-long dense SDM transmission reach exceeding 3000 km over 12-core × 3-mode MC-FMF was achieved.

Development of a Ground Prototype Test System for Deployable Space Structures by using Multi Robots

Development of a Ground Prototype Test System for Deployable Space Structures by using Multi Robots