Spacecraft Structures Research Articles

Quantitative characterisation of debris cloud-induced pitting damage in AL-Whipple shields of spacecraft using infrared thermography

ABSTRACT Quantitatively evaluating the debris cloud-induced pitting damage in the AL-Whipple structure of spacecraft, is still a challenge, let alone microstructural plastic deformation usually accompanied by geometric cratering defects, which may decrease material stress-carrying capacity and structural life. With this motivation, a dedicated modelling technique is proposed to gain an insight into various modalities (i.e., geometric and plastic defects) of pitting damage-induced thermal modulation for infrared inspection. Then, a sequence of infrared images is obtained and analysed using the gap smoothing algorithm and naive Bayes classification methods. On this basis, a quantitative characterization framework is proposed to characterize the damage modalities and their morphologies. This method is validated using a 3D numerical model which contains pitting damage acquired from the real-world structure. Modality classification and morphology evaluation results are well consistent with the artificial defects, in terms of the modality, diameter, and depth. Then they‘re experimentally corroborated, in which the severity and distribution of pitting damage are precisely characterized, in terms of the crater number and morphologies, as well as the size of plastic regions around these craters, which are consistent with the actual observations. This work proposes a non-destructive strategy for pitting damage evaluation, which is engineering-friendly.

Development and Prospect of Space Debris Protection Structures for Spacecraft

Background: As the pace of human conquest of space continues to accelerate, the number of spacecraft carrying out various activities in space continues to increase, so that the available orbital space continues to decrease, the amount of space debris continues to increase, and thus the probability of orbiting spacecraft being impacted by space debris is also increasing. Research on the development of protective structures in the current state is conducive to improving the protection performance of spacecraft protective structures against space debris, reducing the occurrence of spacecraft disintegration events and spacecraft collision events, and may also promote the development of many fields through the development of new technologies. Aim: Through the latest application and development of spacecraft, the advantages and disadvantages of various protection structures are summarized, and the development trend of academic and aerospace protection engineering is analyzed. Methods: Through the latest representative patent research methods for spacecraft space debris, research content, and creative structure, the principle and characteristics of the protective structure are demonstrated. Results: By comparing the application of different spacecraft space debris protection structures, the existing problems of the current protection structures are listed, and the potential development paths and research topics are put forward Conclusion: The development of aerospace, military, and other industries benefit from the development of protective structures, and the composite spacecraft space debris protection structures have broad development prospects.

A shakedown oriented topology optimization algorithm utilizing second-order cone programming (SOCP) and its application in spacecraft structure design

A shakedown oriented topology optimization algorithm utilizing second-order cone programming (SOCP) and its application in spacecraft structure design

Development of linear bearing equipment for modal testing of low-frequency weakly damped spacecraft structures

This article presents the results of a study of the bearing capacity and dissipative properties of an aerostatic linear bearing developed at JSC RESHETNEV for modal testing of complex structures. When selecting equipment for modal testing, the main condition is the requirement to minimize the distortions introduced into the determined dynamic characteristics: frequencies of natural vibration modes, the vibration modes themselves, as well as modal masses and damping coefficients. In other words, all equipment used for ground-based modal testing should ideally have zero added mass, stiffness and friction. The main systems containing elements that create dissipative forces that affect the determination of damping coefficients are systems for weight compensation and vibration excitation on natural modes. The weight compensation system usually contains either elastic elements or a system of guides with rolling or sliding bearings. If the former bring additional rigidity and mass to the test object, the latter bring mass and friction (dry or viscous), which increases the error in determining the dynamic characteristics. The excitation of vibrations on natural modes, in most cases, is carried out by electrodynamic vibrators consisting of a magnetization coil (or permanent magnet) and a movable coil moving in a magnetic gap. The movable coil is oriented in the magnetic gap using a special system containing either elastic elements or a linear guide bearing. Vibrators with elastic coil suspension elements cannot be used for modal tests of extended structures with low rigidity. The problem of creating an ideal bearing to replace classic linear (sliding or roller) ones arose during preparation for modal tests of the wing of a solar battery of a spacecraft (SC). Aerostatic bearings (supports) have virtually zero friction and sufficient load-bearing capacity, in which compressed air acts as a lubricant, eliminating physical contacts of the interacting surfaces. To confirm the possibility of using aerostatic bearings in equipment for conducting modal tests of extended structures with low frequencies of natural oscillations, comparative tests of a roller and aerostatic bearing were carried out. During the tests, optimal air flow parameters (nozzle diameter, operating pressure and gap) were selected, which ensure the required load-bearing capacity for radial forces and torques (bending and torsion). A comparative assessment of dissipative properties was carried out when measuring the attenuation parameters of single-mass harmonic oscillators, which include aerostatic and roller linear bearings. With a nozzle diameter of 0.6 mm, a working gap of 40 μm and a bearing input pressure of 1.0 bar, the logarithmic decrement of oscillations of the harmonic oscillator with an aerostatic bearing was 0.084, which is more than 28 times lower than the logarithmic decrement of oscillations of an oscillator with a roller bearing. The conducted studies confirmed the possibility of using the developed aerostatic bearing in test systems used in modal tests of large-sized transformable spacecraft structures.

Shape of fragments cloud behind heterogeneous screen by a space debris particle impact

Technogenic pollution of near-Earth space poses a threat to the functioning of spacecraft. Collisions between space debris (SD) and spacecraft (SC) structures can have catastrophic consequences or cause localized damage, leading to the loss of SC operability or the failure of certain functions. The SC body must effectively protect the internal equipment from various external impacts, be technologically feasible to manufacture, and have as little mass as possible. As a result, the task of designing spacecraft bodies and protective screens for low-orbit SC is particularly relevant due to the large concentration of SD in low Earth orbits.A comparative numerical study was conducted to evaluate the effectiveness of various thin shields in protecting against impacts from space debris particles. The study examined homogeneous shields made of A356 aluminum alloy and 316L stainless steel, as well as volumetrically reinforced composite shields produced using additive manufacturing with steel inclusions, and shields with a gradient distribution of steel throughout the thickness of an aluminum matrix, all with the same areal density. In all the heterogeneous plates considered, the volumetric concentration of steel was 36 %. The study covered an interaction velocity range of 2–9 km/s. Numerical modeling results indicated that the structure of the thin heterogeneous plate does not affect the shape of the debris cloud formed behind the protective shield. The findings of this study can serve as a basis for selecting materials for the development of more effective protection for spacecraft against high-velocity impacts.

Cross-sectional zero-dimension temperature model for thin-walled circular tubes in space environment

A sufficiently accurate, yet computationally efficient prediction of temperature field is essential for design of spacecraft structures. This paper presents a model dimension reduction method for thermal analysis of thin-walled circular tubes in space environment, which takes into account radiation heat transfer among the internal surfaces besides heat conduction along the circumferential direction and radiative emission from the external surface. Temperature distribution on the tube cross section is approximated by a series of harmonic functions, so that a one-dimensional problem is reduced to that of zero dimension. The relation between average and perturbation temperatures that depend only on time is broadened to fully coupled one. By comparison to the previous model and the plane finite element model, the accuracy and economy of the new model are illustrated. The results show that internal radiation exchange plays an important role in thermal analysis of thin-walled circular tubes used extensively in spacecraft appendages. Furthermore, differences between present and previous models are analyzed and a two-way analysis of variance is performed to determine the effect of various physical and geometric parameters on the temperature distribution and response of the tubes. The work can be further developed to analyze thermally induced deformation and vibration of spacecraft structures.

Experimental and Numerical Investigation on Attitude Adjustment Characteristics of Spacecraft with Impulse Thruster

AbstractThe spacecraft serves as an effective tool for the space exploration. The present study is devoted to investigate the yaw attitude adjustment motion of the spacecraft influenced by the reaction-jet control system. A novel spacecraft device with impulse thrusters is designed for the vacuum test. And a synchronous test system, equipped with high-speed cameras, is established to record the motion process of the spacecraft under the various initial setting conditions. Subsequently, a six degrees of the freedom exterior ballistic model is calculated considering the interior ballistic process in the impulse thruster. The experimental results confirm that the position change of the designed device’s center of mass aligns with expectation, and the prediction error of final attitude angle remains below 2%. Based on this foundation, the change rule of the impulse thrust under different main charge loads is explored. The non-linear impulse thrust needs to be coupled with the rotation motion to enhance calculation accuracy. And the position of the center of mass is investigated to illustrate the advantage of the designed spacecraft structure. Finally, the calculation of the ignition interval time required for each target attitude angle is conducted, providing the essential data for further optimization design research. The outcomes from this paper can offer valuable technical means for advancing studies on the spacecraft attitude control.

Prediction method for re-damage behavior of the repaired CFRP bolted joint

Composite materials are widely used in various aircraft due to their high specific strength, stiffness, corrosion resistance, and robust design flexibility. However, when subjected to complex loading conditions, composite structures are susceptible to damage, necessitating prompt repair upon aircraft return. Analyzing the re-damage process of repaired structures is crucial for assessing aircraft structural reliability, lifespan, and determining whether a repeat flight is warranted. In this study, a prediction method was proposed for re-damage behavior through meso-modeling and energy analysis of the repaired composite bolted joint. First, this article established a meso-mechanical model for composite laminates, analyzed force transfer characteristics at the fiber − matrix interface, and derived equations for stress field. Additionally, a strain energy distribution model was developed for composite bolted repaired joint near fibers and repaired area, proposing a damage prediction method based on the strain energy criterion. This method could anticipate the location, type, sequence, and magnitude of damage. Finally, simulation calculations yielded mechanical characteristics of the repaired area under typical load conditions, while loading tests verified the feasibility of the prediction method. This study offered an effective means of predicting performance degradation in composite structures and provided a vital direction for optimal spacecraft structure repairing methods and parameters.

Calculation of the coupling loss factors for the angle connected beams

The use of the statistical energy method for the analysis of dynamic systems assumes knowing coupling loss factors of the subsystems. Coupling loss factors show how much energy transfers from one subsystem to another. They are included in the system of power-balance equations and must first be determined analytically, experimentally or numerically. The most promising of the listed methods is numerical. In particular, this article uses the finite element method. The purpose of this study is to determine the coupling loss factors of two subsystems in two versions of their relative position. The basis is the model of an L-shaped connection of two beams, which is quite common in such studies. L-shaped connections of structural parts are prevalent in building structures, but in other areas, such as the development of space and aviation technology, structural elements with an angle other than 90° between them. Since energy methods can also be applied to the aerospace industry, when developing approaches to structural analysis using such methods, it will be useful to know how the energy system parameters, in particular the coupling loss factors, depend on the coupled angle. The paper considered two configurations of the system: in the first, the beams connected at a right angle, in the second, at an angle of 45°. We calculate the coupling loss factors of the beams for both system configurations. Conclusions of this paper draw about the possibility of extending the result to more complex structures, namely the spacecraft structures.

Acoustic emission source localization for complex structure with multi-holes based on heuristic adaptive pathfinding and gradient descent method

Space debris poses a safety hazard to the operation of spacecraft, and the study of impact localization for spacecraft structures is of significance for the timely discovery of the impact location and the safeguarding of spacecraft and personnel safety. However, existing studies have mainly focused on continuous structures, and discontinuous structures of spacecraft with portholes and orifice-containing valves have been understudied. Therefore, in this article, the shortest propagation path algorithm of the signal and the acoustic emission source localization method applicable to multi-holes discontinuities structures are proposed. After calculating the signal arrival time difference, the localization method calculates the shortest propagation path of Lamb wave in complex multi-holes structure by the heuristic adaptive path-finding algorithm, which calculates distance differences traveled by the signal propagation to each sensor. The heuristic adaptive path-finding algorithm first constructs a map set based on the geometrical features of the structure, after which it searches for each partial path in the final path by heuristic computation to identify the shortest signal propagation trajectory. The objective function is established based on the target structural characteristics and sensor position parameters, of which the parameters of the equations are optimized based on the new travel difference-of-distance values generated from the results of the heuristic adaptive pathfinding calculation. Finally, the acoustic emission source coordinates are updated with a gradient descent strategy, which has an average localization error of 0.956 cm in 252 experiments and can effectively realize the impact localization calculation of multi-holes complex structures.

Mathematical simulation of ionospheric plasma diagnostics by electric current measurements using an insulated probe system

The goal of this work is to theoretically substantiate the possibility of determining the charged particle density in the ionospheric plasma by separately measuring the electric currents of an insulated probe system in the electron saturation region. The ionospheric plasma composition is modeled by two ion species with significantly different masses and electrons to keep the plasma quasi-neutrality. The probe system, which is electrically insulated from the spacecraft structure, consists of cylindrical electrodes: a probe and a reference electrode. The reference electrode to probe current-collecting area ratio can be significantly less than required by the single cylindrical probe theory. The electrodes are oriented transversely to a supersonic flow of a collisionless plasma. In addition to the main plasma with two ion species, a model plasma with a single ion species is considered. The mass of the model ions is such that the ion saturation current to the cylinder is the same for both plasma models. Based on a previously obtained asymptotic solution for the electron saturation current in a plasma with a single ion species, computational formulas are found for determining the ion mass composition and the electron density by probe current measurements. The errors of the formulas are estimated numerically and analytically as a function of the probe system geometry, the bias potential of the probe relative to the reference electrode, and the accuracy of potential and current measurements. It is shown that a proper choice of the probe system settings and the accuracy of probe measurements assures a reliable determination of the charged particle densities in a plasma with two ion species. A priori estimates are presented for the effect of the current bias potential measurement errors on the reliability of determining the ion mass composition and the electron density of the ionospheric plasma.

Mathematical Modeling of Multi-Physics Phenomena in Smart Materials and Structures

Smart materials and buildings show interesting multi-physics effects, where the interaction of different physical fields like mechanics, electromagnetics, thermodynamics, and sound is very important. This essay gives an in-depth look at different mathematical modeling methods used to understand and predict how smart materials and buildings will behave in various situations. At its core, the modeling framework combines guiding equations from various physical fields. This calls for a comprehensive method that takes into account how these events interact with each other in complex ways. The basis is mechanics, which includes fundamental equations that show how materials react to mechanical forces, including elasticity, viscoelasticity, and flexibility. Electromagnetic effects are very important in materials like magnetostrictives and piezoelectrics, where the way electrical and mechanical fields combine determines how they work. To correctly describe this electrical connection, Maxwell's equations are linked to mechanical equations. This lets devices like sensors, motors, and energy harvesters be designed and improved. Thermodynamics is used for shape memory metals and phase change materials, whose behavior is controlled by changes in temperature. Adding heat transfer equations to mechanical and electromagnetic equations helps us fully understand how these materials interact with heat, motion, and electricity, which is important for many uses, from medical devices to spacecraft structures. Structures with active shaking control systems that use piezoelectric materials have interesting acoustic effects. With the help of mechanical and electrical algorithms and acoustic wave transmission models, it is possible to study and create smart structures that can reduce noise and shocks while also improving their performance and integrity. The study also talks about numerical methods, like finite element methods and multiphysics modeling tools, that can be used to quickly solve the linked equations. These tools help us learn more about how complicated materials behave in various working situations.

SpaceLight: A Framework for Enhanced On-Orbit Navigation Imagery

In the domain of space rendezvous and docking, visual navigation plays a crucial role. However, practical applications frequently encounter issues with poor image quality. Factors such as lighting uncertainties, spacecraft motion, uneven illumination, and excessively dark environments collectively pose significant challenges, rendering recognition and measurement tasks during visual navigation nearly infeasible. The existing image enhancement methods, while visually appealing, compromise the authenticity of the original images. In the specific context of visual navigation, space image enhancement’s primary aim is the faithful restoration of the spacecraft’s mechanical structure with high-quality outcomes. To address these issues, our study introduces, for the first time, a dedicated unsupervised framework named SpaceLight for enhancing on-orbit navigation images. The framework integrates a spacecraft semantic parsing network, utilizing it to generate attention maps that pinpoint structural elements of spacecraft in poorly illuminated regions for subsequent enhancement. To more effectively recover fine structural details within these dark areas, we propose the definition of a global structure loss and the incorporation of a pre-enhancement module. The proposed SpaceLight framework adeptly restores structural details in extremely dark areas while distinguishing spacecraft structures from the deep-space background, demonstrating practical viability when applied to visual navigation. This paper is grounded in space on-orbit servicing engineering projects, aiming to address visual navigation practical issues. It pioneers the utilization of authentic on-orbit navigation images in the research, resulting in highly promising and unprecedented outcomes. Comprehensive experiments demonstrate SpaceLight’s superiority over state-of-the-art low-light enhancement algorithms, facilitating enhanced on-orbit navigation image quality. This advancement offers robust support for subsequent visual navigation.

Irregular ANCF model and experimental investigations of the irregular membrane structures with variable cross-section

The membrane spacecraft structures are widely used for deep space exploration and on-orbit operation, but the dynamic responses of them is more complex. To advance the state of membrane structures, in this paper, a new ANCF membrane element is established to model dynamic equations of the membrane structure precisely and efficiently. Firstly, the irregular ANCF membrane element is studied by considering anomalistic boundary and variable cross-section. The mapping relations between the sub-ANCF element and the parent-ANCF element are illuminated by the Jacobian matrix, which makes the strain of each irregular element accurately calculated with the same shape functions. It is helpful to improve the description accuracy of inherent attributes and reduce the element number of dynamic systems. Further, the nonlinear dynamic model for membrane spacecraft system is established by the virtual work principle. Finally, the numerical examples and experiments are analyzed to verify the correctness of the proposed method and discuss the influence of nonlinear geometry and distortion on the dynamic behaviors. The results from the time domain and frequency domain analyses demonstrate that the distinct irregular geometric boundary of the irregular spacecraft can be more accurately modeled using the presented method. However, the difference becomes more pronounced when the distortion is too large. The research outcomes of this paper can provide theoretical guidance for the irregular spacecraft system, which is of great significance and urgently needs to be studied.

Internal Nuclear Propulsion System for Future Space Applications

Internal nuclear pulse propulsion (INPP) represents a novel approach to space propulsion, where controlled nuclear detonations occur within the spacecraft itself, offering potential advantages in safety and propulsion control compared to conventional external detonation designs like Project Orion. INPP relies on the same fundamental principles of nuclear pulse propulsion, utilizing the momentum generated by nuclear explosions to propel the spacecraft forward. Proposed INPP designs involve strategically placing small nuclear devices within the spacecraft's structure, detonating them in sequence to produce controlled impulses for propulsion. However, significant engineering challenges, such as radiation shielding, precise detonation control, and safety considerations, must be addressed to realize the full potential of INPP. Despite these hurdles, ongoing research and development efforts aim to harness the transformative capabilities of INPP, promising to revolutionize space exploration by enabling efficient and rapid interstellar travel while ensuring the safety of spacecraft and crew.

Distributed angle‐only orbit determination algorithm for non‐cooperative spacecraft based on factor graph

AbstractBayesian filtering provides an effective approach for the orbit determination of a non‐cooperative target using angle measurements from multiple CubeSats. However, existing methods face challenges such as low reliability and limited estimation accuracy. Two distributed filtering algorithms based on factor graphs employed in the sub‐parent and distributed cluster spacecraft architectures are proposed. Two appropriate factor graphs representing different cluster spacecraft structures are designed and implement distributed Bayesian filtering within these models. The Gaussian messages transmitted between nodes and the probability distributions of variable nodes are calculated using the derived non‐linear Gaussian belief propagation algorithm. Gaussian messages propagate from the deputy spacecraft to the chief spacecraft in the sub‐parent spacecraft architecture, demonstrating that the estimation accuracy converges to the centralised extended Kalman filter (EKF). Simulation results indicate that the algorithm enhances system robustness in observation node failures without compromising accuracy. In the distributed spacecraft architecture, neighbouring spacecraft iteratively exchanges Gaussian messages. The accuracy of the algorithm can rapidly approach the centralised EKF, benefiting from the efficient and unbiased transmission of observational information. Compared to existing distributed consensus filtering algorithms, the proposed algorithm improves estimation accuracy and reduces the number of iterations needed to achieve consensus.

Development of Anisogrid Lattice Composite Structures for Fighter Wing Applications

This paper presents research on the use of anisogrid lattice structures in fighter wing applications. While the anisogrid lattice structure has been widely used in spacecraft structures, its implementation in main aircraft structures is still limited. The study is aimed at investigating the feasibility of utilizing an anisogrid lattice structure in fighter wing design. The analysis and optimization focus on determining the optimal weight of the composite wing structure, considering static, buckling, and flutter failure constraints. Various lift distributions, including triangular, Schrenk, and constant, are applied to evaluate the structure’s response to static failure caused by aerodynamic loads. The anisogrid structure design incorporates inclined lattice elements between ribs and spars, with spar arrangement in the wing box featuring an anisogrid configuration. The anisogrid lattice structure is expected to produce higher bending and torsional stiffness compared to conventional orthogonal structures, producing better flutter and buckling characteristics. The optimized wing structure successfully meets static, buckling, and flutter load requirements at speeds below 500 m/s. The study showcases triangular, Schrenk, and constant load distributions resulting in half-wing masses of 504, 571, and 707 kg, respectively. The results show that flutter and buckling loads are no longer the critical loads in wing structural design but static load.

Deployment Simulation of Foldable Membranes Using Absolute Nodal Coordinate Formulation and Validation

It has become a trend to use foldable membranes to construct large spacecraft structures such as solar sails, antennas, and drag sails with the advantages of being lightweight and having high packing efficiency. To enhance the existing numerical simulation of membrane deployment, the nonlinear behavior of the crease is finely described based on experiments and integrated into the numerical model via the principle of virtual work. Specifically, a foldable membrane is modeled as a multibody system (MBS) based on the absolute nodal coordinate formulation (ANCF), where the flexible facet is meshed with both ANCF triangular and quadrilateral thin shell elements and the crease is treated as a virtual torsional spring with special constraints along the fold line. The MBS modeling method is validated via the deployment experiment of a Z-folding membrane. The deployment of a four-unit Miura-ori membrane is further analyzed to show the capability of the approach in modeling foldable membranes with complicated configurations. Good agreement is obtained on the membrane-deformed configurations between the simulation and experiment. Additionally, the driving force at the corners is obtained. This research is expected to provide a more accurate simulation to facilitate the design and optimization of the space deployable membrane structure.

Three-dimensional deformation measurement techniques in space multi-physical fields based on digital image correlation

Aiming at the three-dimensional deformation measurement requirement of the high-stability structure of spacecraft in space multi-physical fields, a comprehensive instrument protection device in a vacuum high-low temperature environment is developed using ultra-low temperature anti-condensation and vacuum heat insulation technology. This ensures that the digital image correlation (DIC) measurement camera always remains in a constant temperature and pressure environment and can stably exert its original efficiency in space multi-physical field environments. Subsequently, a path-dependent DIC method based on a graphics processing unit computing parallel acceleration is proposed by combining a pre-interpolation strategy and integrated image technology, which realizes high-precision matching of digital images before and after deformation in a spatial multi-physical field environment and improves the computing efficiency. To address the problem that a common reference point may deform significantly in a space environment with a large temperature change, which leads to inaccurate system accuracy, combined with a random sampling consistency algorithm and singular value decomposition method, the optimal registration of the coordinate system and the solution of deformation were realized by setting the threshold of the reference point margin screening. Finally, a three-dimensional deformation measurement system in high- and low-temperature vacuum environments was built, and the three-dimensional deformation measurement of the satellite antenna in high- and low-temperature vacuum environments was verified, which proves the effectiveness and accuracy of the above method.

Multi-sensor data fusion reconstruction method for vibration dynamic responses of aerospace structures

The dynamic responses of key locations are important inputs for the life and reliability assessment of spacecraft structures. Due to the limited sensing resources, most critical responses are difficult to measure directly. A structural dynamic response reconstruction method is necessary. The responses of target locations can be reconstructed based on the empirical mode decomposition (EMD) of measured signals and the modal superposition. However, the structural modal information contained in the measured signal of a single sensor is limited, affecting the reconstruction accuracy. In this paper, a response reconstruction method based on multi-sensor data fusion is proposed. It is applied to a main load-bearing structure of a spacecraft and its typical components to verify its strain response reconstruction effect under random vibration loads. The experimental results show that multi-sensor data fusion improves the strain reconstruction accuracy. The maximum reduction in reconstruction error is from 8.7% to 1.3%. The reconstruction accuracy is further improved with the increase in the number of sensors. The optimal weighted fusion strategy for this problem is the weights defined by the Euclidean distance (EUC) or the dynamic time warping distance (DTW). The fusion results show a better performance with the increase in the power of the defined distance. The proposed multi-sensor fusion method improves the reconstruction accuracy via supplementing structural information to each other and eliminating the instability of single measured signals. More accurate dynamic responses via reconstruction reduce the large input uncertainty in life prediction and lay the foundation for building structural digital twins and managing structural health more effectively.