Lightweight Space Research Articles

A Light Space Manipulator with High Load-to-Weight Ratio: System Development and Compliance Control

In order to meet the requirements of the space environment for the lightweight and load capacity of the manipulator, this paper designs a lightweight space manipulator with a weight of 9.23 kg and a load of 2 kg. It adopts the EtherCAT communication protocol and has the characteristics of high load-to-weight ratio. In order to achieve constant force tracking under the condition of unknown environmental parameters, an integral adaptive admittance control method is proposed. The control law is expressed as a third-order linear system equation, the operating environment is equivalent to a spring model, and the control error transfer function is derived. The control performance under the step response is further analyzed. The simulation results show that the proposed integral adaptive admittance control method has better performance than the traditional method. It has no steady-state error, overcomes the problems caused by nonlinear discrete compensation, and can facilitate analysis in the frequency domain, realize parameter optimization, and improve calculation accuracy.

Fundamental characteristics of self-deployable convex shells using shape memory polymer

This study proposes a concept for self-deployable shell structures made of connected shape memory polymer (SMP) shells, which are configured to a convex shape. In this research, the convex SMP shell is deformed from a flat configuration to convex one by heating it. The concept aims to realize deployment without impact to the structure in the course of deployment by applying thermal control, and to offer higher stiffness of the deployed structure due to the convex configuration of the shells. In addition, the shape recovery process of the SMP convex shell realizes self-deployable and highly stable deployment capabilities because the shape recovery of SMP utilizes material response to recover the memorized convex shape rather than the release of an elastic hinge. Experiments were performed for two-dimensional deployable structures with SMP convex shells to examine the fundamental deployment characteristics of the proposed concept. The shape recovery process of the shell from the given stowed shape to the flat state was shown to be very stable, and the experimental results indicated that the mechanical properties of the tape connecting each convex shell is significant in obtaining demanded deployed states. The deployment characteristics observed in the experiments demonstrated the achievement of complete deployment and the gradual decrease in the deployment speed, implying that low-impact deployment can be realized by this concept. Moreover, the bending stiffness after deployment increased due to the shape recovery of the convex shape. The design flexibility of the convex shell was also considered by introducing another layer to vary the deployment process. All these fundamental characteristics demonstrate the potential of the proposed concept for the self-deployment of the next generation light-weight space structures.

Optimization Design of the Spaceborne Connecting Structure for a Lightweight Space Camera

For a lightweight space camera installed vertically with a satellite platform, due to the different conditions between ground and orbit, the relative deformation between the camera and the satellite platform results in a drift of the camera line of sight (LOS), which affects the imaging quality. This paper proposed an optimization method for the spaceborne connecting structure considering the camera LOS drift. By using a variable density topology optimization method, the configuration of the connecting structure was obtained. Based on the configuration, the sensitivity of its size parameters to the system’s performance was analyzed. Analysis data showed that the size parameters have an obvious influence on the camera LOS shift. In order to obtain the optimal combination of size parameters, a multi-objective parametric optimization model was established. Finally, engineering analysis of the optimized structure showed that the system performances meet the design requirements of the satellite, and the lightweight ratio of the connecting structure reaches 54%. This study provides a reference for the design of other similar structures for space cameras.

Optimal Geometry for Cable Wrapping to Minimize Dynamic Impacts on Cable-Harnessed Beam Structures

Abstract Power and cable carrier systems have been shown to significantly impact the dynamic behavior of lightweight space structures. The goal of this paper is to obtain an optimal cable placement geometry for cable-harnessed beam structures by minimizing the impact of added cables on the system dynamics. The cable is harnessed to the beam in a periodic pattern, which forms several repeating fundamental elements within the structure. An analytical model for the cable-harnessed beam, using an energy-equivalence homogenization method, is employed for the purpose of optimization. The natural frequencies of the cable-harnessed beam are then matched with the bare beam (when no cables attached) using an optimization algorithm to find the optimal cable placement solution for the given system parameters. Subsequently, the system parameters’ effects on the optimal solutions are investigated and discussed. Experimental modal analysis is then performed to further validate the optimal solutions found using the model. The test results further validate findings from the model, and the frequency response functions from the bare and optimally wrapped beams align really well.

A Review on the Seismic Performance of Assembled Steel Frame-precast Concrete Facade Panels

Assembled steel structure housing has the advantages of low cost, light weight and flexible space arrangement, which has been largely used in government-subsidized housing in China. Meanwhile with the rising of assembled steel structure housing, precast concrete facade panels have been widely used. In this paper, the research on the seismic performance of assembled steel frame with precast concrete facade panels in China is summarized and discussed, including the influence of precast concrete facade panels, flexible connections and the seismic performance of steel frame influenced by precast concrete facade panels. According to the research status, the mechanical characteristic of the precast concrete facade panels following the deformation of steel frames; the seismic performance influence of the main structure in rare earthquakes because of the flexible connections are analysed. This paper provides a reference for seismic theory establishment of assembled steel structure housing envelope system.

Experimental study on imaging and image deconvolution of a diffractive telescope system.

Diffractive telescopes are one of the most promising solutions to build lightweight space telescopes with a diameter over 10 m. However, the performance of the imaging systems is inevitably degraded by the high-order diffractive light from the diffractive system. To address this problem, in this paper we mathematically deduce the imaging model, including multiple-order diffraction, by the scalar diffraction theory. After the imaging characteristics analysis, an adaptive Wiener filtering algorithm based on the principal component analysis method is proposed. The broadband imaging and deconvolution experiments are performed by the 80 mm diffractive optical telescope systems. Results demonstrate that this method increases the average gradient by at least 8.2 times and improves imaging quality and contrast. It could be a useful exploration for high-performance imaging of large-aperture and lightweight telescopes.

Reliability and loading-following studies of a heat pipe cooled, AMTEC conversion space reactor power system

During the progress and development of the space technology, the space reactor power system (SRPS) is one of the best options for providing high power density, long-term life, light weight, and high reliability space power for civil or military space missions. The heat pipe cooled SRPS (HPS) equipped with the static conversion technology Alkali Metal Thermal-to-Electric Conversion units (AMTEC) has good inherent dynamic characteristic for frequent change load following of the space mission power, with high safety and reliability. This paper analyzed the system safety and reliability of an AMTEC conversion HPS, the load following characteristics of the AMTEC conversion and the HPS's performance in response to partial surface area loss of potassium heat pipe radiator. The results show the following. (1) As the external load resistance increases, the AMTEC thermoelectric conversion efficiency and electric power output both increase to the maximum, and then decrease. The maximum thermoelectric conversion efficiency and electric power output correspond to different critical external load values. The load following capacity of the AMTEC HPS exists only when the external load demands exceed a critical value. (2) When the potassium heat pipe radiator's surface area is partially lost because of the impact of a meteorite, the reactor thermal power, the AMTEC conversion efficiency and the electric power output also decrease, except the radiator temperature due to the radiator area loss. The waste heat rejection, the conversion efficiency and electric power output of the system decrease proportionally to the radiator's surface area loss. To ensure the safety and reliability of the SRPS, the reactor thermal power will run down after the loss of the radiator's surface area.

Flexible IGZO TFTs and Their Suitability for Space Applications

In this paper, low earth orbit radiation (LEO), temperature, and magnetic field conditions are mimicked to investigate the suitability of flexible InGaZnO transistors for lightweight space wearables. More specifically, the impacts of high energetic electron irradiation with fluences up to $10^{12}\,\,{\mathrm{ e}}^{-}$ /cm2, low operating temperatures down to 78 K and magnetic fields up to 11 mT are investigated. This simulates 278 h in LEO. The threshold voltage and mobility of transistors that were exposed to $e^{-}$ irradiation are found to shift by +(0.09 ± 0.05) V and $-(0.6\pm 0.5)\,\,{\mathrm{ cm}}^{2}{\mathrm{ V}}^{-1}{\mathrm{ s}}^{-1}$ . Subsequent low temperature exposure resulted in additional shifts of +0.38 V and $-5.95\,\,{\mathrm{ cm}}^{2}{\mathrm{ V}}^{-1}{\mathrm{ s}}^{-1}$ for the same parameters. These values are larger than the ones obtained from non-irradiated reference samples. Conversely, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiated, cooled down, and exposed to the magnetic fields. If these notions are considered during the systems design, these devices can be used to unobtrusively integrate sensor systems into space suits.

Dynamic modelling and control of a Tendon-Actuated Lightweight Space Manipulator

The Tendon-Actuated Lightweight Space Manipulator has advantages such as a large range of motion and lightweight when compared with conventional space manipulators. In this paper, dynamic modelling and controller design of a tendon-actuated manipulator are investigated. First, nonlinear coupling dynamic equations of the central body spacecraft and a four-degree-of-freedom tendon-actuated manipulator mounted on it are derived based on Kane's equation, and their controllers are then designed while considering the dynamic coupling. In addition, a tension analysis method is proposed that is subject to the tension constraints, and the actuators of the tendon-actuated manipulator are analysed. Numerical simulations indicate that the designed controller can achieve attitude stability of the central body spacecraft and endpoint trajectory tracking of the tendon-actuated manipulator. A feature of the tendon-actuated manipulator is its enlargement of the joint actuated torque, and a long link, tendon-actuated manipulator has more benefits relative to a conventional space manipulator.

Double Donut Schmidt Camera, a wide-field, large-aperture, and lightweight space telescope for the detection of ultrahigh energy cosmic rays.

A wide-field, large-aperture, and lightweight Schmidt configuration has been studied for a space mission proposal named Extreme Universe Space Observatory free flyer (EUSO-FF). EUSO-FF will be devoted to the study of ultrahigh energy cosmic rays, i.e., with energy >5×1019 eV, through the detection of UV fluorescence light emitted by air showers in the Earth's atmosphere. The proposed telescope has a field of view of about 50° and an entrance pupil diameter of 4.2m. The mirror is deployable and segmented to fit the diameter of the launcher fairing; the corrector is a lightweight annular corona.

English

English

Stray light characteristics of the diffractive telescope system

Diffractive telescope technology is an innovation solution in construction of large light-weight space telescope. However, the nondesign orders of diffractive optical elements (DOEs) may affect the imaging performance as stray light. To study the stray light characteristics of a diffractive telescope, a prototype was developed and its stray light analysis model was established. The stray light characteristics including ghost, point source transmittance, and veiling glare index (VGI) were analyzed. During the star imaging test of the prototype, the ghost images appeared around the star image as the exposure time of the charge-coupled device improving, consistent with the simulation results. The test result of VGI was 67.11%, slightly higher than the calculated value 57.88%. The study shows that the same order diffraction of the diffractive primary lens and correcting DOE is the main factor that causes ghost images. The stray light sources outside the field of view can illuminate the image plane through nondesign orders diffraction of the primary lens and contributes to more than 90% of the stray light flux on the image plane. In summary, it is expected that these works will provide some guidance for optimizing the imaging performance of diffractive telescopes.

Image degradation characteristics and restoration based on regularization for diffractive imaging

The diffractive membrane optical imaging system is an important development trend of ultra large aperture and lightweight space camera. However, related investigations on physics-based diffractive imaging degradation characteristics and corresponding image restoration methods are less studied. In this paper, the model of image quality degradation for the diffraction imaging system is first deduced mathematically based on diffraction theory and then the degradation characteristics are analyzed. On this basis, a novel regularization model of image restoration that contains multiple prior constraints is established. After that, the solving approach of the equation with the multi-norm coexistence and multi-regularization parameters (prior’s parameters) is presented. Subsequently, the space-variant PSF image restoration method for large aperture diffractive imaging system is proposed combined with block idea of isoplanatic region. Experimentally, the proposed algorithm demonstrates its capacity to achieve multi-objective improvement including MTF enhancing, dispersion correcting, noise and artifact suppressing as well as image’s detail preserving, and produce satisfactory visual quality. This can provide scientific basis for applications and possesses potential application prospects on future space applications of diffractive membrane imaging technology.

Design and optimization of the CFRP mirror components

As carbon fiber reinforced polymer (CFRP) material has been developed and demonstrated as an effective material in lightweight telescope reflector manufacturing recently, the authors of this article have extended to apply this material on the lightweight space camera mirror design and fabrication. By CFRP composite laminate design and optimization using finite element method (FEM) analysis, a spherical mirror with φ316 mm diameter whose core cell reinforcement is an isogrid configuration is fabricated. Compared with traditional ways of applying ultra-low-expansion glass (ULE) on the CFRP mirror surface, the method of nickel electroplating on the surface effectively reduces the processing cost and difficulty of the CFRP mirror. Through the FEM analysis, the first order resonance frequency of the CFRP mirror components reaches up to 652.3 Hz. Under gravity affection coupling with +5°C temperature rising, the mirror surface shape root-mean-square values (RMS) at the optical axis horizontal state is 5.74 nm, which meets mechanical and optical requirements of the mirror components on space camera.

Security Isolation Strategy Mechanism for Lightweight Virtualization Environment

For cloud service providers, lightweight virtualization is a more economical way of virtualization. While the user is worried about the safety of applications and data of the container, due to the container sharing the underlying interface and the kernel, therefore the security and trusted degree of lightweight virtualization container isolation mechanism is critical for the promotion of lightweight virtualization service. Because the user cannot directly participate in the process of the construction and management of container isolation mechanism, it is difficult for them to establish confidence in the security and trusted degree of container isolation mechanism. Based on the research and analysis of system credible and virtualization isolation mechanism, this paper puts forward a set of lightweight virtualization security isolation strategy mechanism, divides lightweight virtualization container storage address space into several parts, puts forward the definition of lightweight virtualization security isolation, gives the formal description and proof of container security isolation strategy, and combines with related technology to verify the feasibility of lightweight virtualization security isolation strategy mechanism. The mechanism has important guiding significance for cloud services providers to deploy container security isolation.

Novel Concepts for High-Efficiency Lightweight Space Solar Cells

One of the key issues in the design and development of a satellite Photovoltaic Assembly (PVA) is the trade-off to be made between the available volume located to the PVA, its mass and the total amount of power that the solar panels have to guarantee to the spacecraft. The development of high-efficiency, flexible, lightweight solar cells is therefore instrumental to the design of future satellites providing enhanced missions and services. Based on the consolidated development of GaAs-based single junction and lattice matched triple-junction solar cells, several research efforts are being pursued worldwide to further increase the efficiency and reduce mass. Promising approaches include thin-film technologies such as Inverted Metamorphic and Epitaxial Lift-Off (ELO), and the use of nanostructures or highly mismatched alloys grown by MBE. We propose here an alternative path towards the development of lightweight GaAs-based solar cells with the potential to exceed the Shockley-Queisser (SQ) limit of single junction cells. Our approach is based on the synergistic combination of thin-film design, quantum dots (QDs) absorption, and photonic nanostructures. Challenges and opportunities offered by the use of QDs are discussed. A cost-effective and scalable fabrication process including ELO technology and nanoimprint lithography is outlined. Finally, a proof-of-concept design, based on rigorous electromagnetic and physics-based simulations, is presented. Efficiency higher than 30% and weight reduction close to 90% - owing to the substrate removal - makes the proposed device to rank record power-to-weight ratio, with the potential to become a cost-effective, attractive option for next generation space solar cells.

Analytical solutions of the torsional mechanism for a new hybrid fiber-reinforced polymer–aluminum twin-trackway space truss bridge

For emergency purposes, a lightweight space truss bridge was designed. The bridge is composed of twin triangular deck-truss beams incorporating new structural forms and advanced fiber-reinforced polymer profiles. As a new structure, the structural properties of its triangular deck-truss beam have been studied in detail; however, a design-oriented study facilitating the application of the entire twin-trackway bridge under pure torsion remains to be undertaken. The objective of this article is to analytically explore the torsional mechanism of the twin-trackway bridge, which is characterized by torsional angle and torsional stiffness. To verify the derivation procedures and formulae, the pure torsion test and numerical analysis are conducted on a full-scale specimen. The results indicate that the analytical solutions compare well with the experimental and numerical results. The torsional moment is primarily resisted by the vertical bending of twin triangular deck-truss beams. The simplified analytical model can be used with sufficient accuracy for the design of the bridge.

Integrated Optimization Design of Carbon Fiber Composite Framework for Small Lightweight Space Camera

A Carbon Fiber Composite (CFC) framework was designed for a small lightweight space camera. According to the distribution characteristics of each optical element in the optical system, CFC (M40J) was chosen to accomplish the design of the framework. TC4 embedded parts were used to solve the low accuracy of the CFC framework interface problem. An integrated optimization method and the optimization strategy which combined a genetic global optimization algorithm with a downhill simplex local optimization algorithm were adopted to optimize the structure parameters of the framework. After optimization, the total weight of the CFC framework and the TC4 embedded parts is 15.6 kg, accounting for only 18.4% that of the camera. The first order frequency of the camera reaches 104.8 Hz. Finally, a mechanical environment test was performed, and the result demonstrates that the first order frequency of the camera is 102 Hz, which is consistent with the simulation result. It further verifies the rationality and correctness of the optimization result. The integrated optimization method mentioned in this paper can be applied to the structure design of other space cameras, which can greatly improve the structure design efficiency.

Comprehensive structural analysis and optimization of the electrostatic forming membrane reflector deployable antenna

The electrostatic forming membrane reflector antenna (EFMRA) is a promising scheme to construct large-size, high-precision and lightweight space deployable reflector antennas. A set of comprehensive structural optimization design procedures is presented for EFMRA in this paper. This procedure consists of four steps: Firstly, a synthesized form-finding method is introduced for the AstroMesh structure which is the structural foundation of the EFMRA. Based on the nonlinear force density method, a fast iterative format is derived, using which we can get a initial state in which the tensions of the front rear cable networks and one electrode membrane are completely uniform, and all the nodes of the front networks are on the ideal paraboloid. Secondly, based on the finite element theory, a structure-electrostatic coupled analysis model is established to take the coupled field problems into consideration. Thirdly, a technique is proposed to optimize the initial reflective membrane geometry. The shape of the membrane is expressed by a set of polynomials, and the polynomial coefficients are optimized to obtain optimal geometry of the reflective membrane. Moreover, the controlling voltage adjustment model is established, which is solved by sensitivity analysis. At length, these proposed methods are applied to the structural optimization design of an EFMRA. The results validate the effectiveness of this comprehensive optimization procedure and the feasibility of designing the EFMRA to compensate the errors introduced from manufacturing process and environmental changes.

Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiCx:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiCx:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiCx:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc.