Space Vehicles Research Articles

KAJIAN KEBUTUHAN DAN PENDAPATAN PARKIR PADA KAWASAN OBJEK WISATA PANTAI KELAN KABUPATEN BADUNG BALI

Badung Regency is one of the largest contributors to regional economic income, namely in the world of tourism, especially the South Badung area which is famous for its many beach tourism objects which attract many foreign and local tourists. Availability of parking spaces, of course, must have good parking services in order to optimally utilize the available parking space capacity. This research focuses on planning the need for parking space and parking revenue for two-wheeled vehicles and four-wheeled vehicles in the Kelan Beach tourist area, because parking is one of the supports for tourism so that visitors can feel comfortable and can realize an adequate parking pattern. The planned land area for parking two and four-wheeled vehicles at Kelan Beach is 2097.30 m² in total. The survey method used is the cordon count and patrol method. Characteristics of parking for two-wheeled vehicles include the highest volume, namely 461, accumulation of 141 vehicles, duration of 1.63 hours, capacity of 173, turnover rate of 0.18, index of 0.68 less than (<) 1.00, which means the need for parking is below capacity/sufficient, and four-wheeled characteristics include volume maximum of 163, accumulation of 33 vehicles, duration of 1.48 hours, capacity of 49, turnover rate of 0.23, index of 0.57 less than (<) 1.00 which means parking needs are below capacity and do not need expansion. The parking space requirements for two-wheeled and four-wheeled vehicles are 63 and 20 slots respectively. The parking layout at Kelan Beach tourist destination adopts a 90° angle pattern for both two-wheeled and four-wheeled vehicles, with respective parking space dimensions of 0.75 m x 2.00 m and 2.50 m x 5.00 m. The projected annual parking revenue is estimated at IDR.499,441,667.00, calculated based on fixed rates. Paving blocks are chosen for the parking surface, with a cost of IDR.441,345,000.00.

A New Double-Step Process of Shortening Fibers without Change in Molding Equipment Followed by Electron Beam to Strengthen Short Glass Fiber Reinforced Polyester BMC.

It is vital to maximize the safety of outdoor constructions, airplanes, and space vehicles by protecting against the impact of airborne debris from increasing winds due to climate change, or from bird strikes or micrometeoroids. In a widely-used compression-molded short glass fiber polyester bulk-molded compound (SGFRP-BMC) with 55% wt. CaCO3 filler, the center of the mother panel has lower impact strength than the outer sections with solidification texture angles and short glass fiber (SGF) orientations being random from 0 to 90 degrees. Therefore, a new double-step process of: (1) reducing commercial fiber length without change in molding equipment; followed by a (2) 0.86 MGy dose of homogeneous low-voltage electron beam irradiation (HLEBI) to both sides of the finished samples requiring no chemicals or additives, which is shown to increase the Charpy impact value (auc) about 50% from 6.26 to 9.59 kJm-2 at median-accumulative probability of fracture, Pf = 0.500. Shortening the SGFs results in higher fiber spacing density, Sf, as the thermal compressive stress site proliferation by action of the CTE difference between the matrix and SGF while the composite cools and shrinks. To boost impact strength further, HLEBI provides additional nano-compressive stresses by generating dangling bonds (DBs) creating repulsive forces while increasing SGF/matrix adhesion. Increased internal cracking apparently occurs, raising the auc.

A combination of “Inner - Outer skeleton” strategy to improve the mechanical properties and heat resistance of polyimide composite aerogels as composite sandwich structures for space vehicles

Low density aerogels with high fatigue resistance are widely used in the manufacturing of core material structures in aircraft fuselage to be able to tolerate the extreme environment of aerospace. However, most organic aerogel materials have poor energy absorption of external impact forces, and are prone to irreversible deformation, such as contracture and collapse in the process of long-term service. In order to solve this problem, a new type of thermosetting-thermoplastic polyimide composite aerogel was prepared, with its microstructure presenting the coexistence of the inner and outer skeletons. The intermolecular forces promoted the assembly of the soft thermoplastic layer and the strong thermosetting layer in the thermodynamic process with 4.63–6.55 μm range. The hard-soft layer structure improved the compressive and the shear load bearing capacities by bending of the panel (Compressive modulus is 1.60 MPa–3.52 MPa, tensile modulus is 1.04 MPa–1.45 MPa). Its permanent degradation less than 1.5 % after 500 cycles at 30 % strain. C–CPIAs also exhibited excellent heat resistance and thermal insulation performances, with a T5% value of 612 °C (C-CPIA-2), Tg of 458 °C (C-CPIA-3). The sandwich materials can be used as outer protective composite material of aircraft fuselage for future deep space missions.

A Branch-and-Price Algorithm for an Integrated Online and Offline Retailing Distribution System with Product Return

This study identifies critical inefficiencies within a dual-channel operation model employed by a fast fashion company, particularly the independent operation of three logistics distribution systems. These systems result in high operational costs and low resource utilization, primarily due to redundant vehicle dispatches to meet the distinct demands of retail store replenishment, online customer orders, and customer return demands, as well as random and scattered return requests leading to vehicle underutilization. To address these challenges, we propose a novel integrated logistics distribution system design and management method tailored for dual-channel sales and distribution businesses. The approach consolidates the three distribution systems into one cohesive framework, thus streamlining the delivery process and reducing vehicle trips by combining retail and customer visits. An optimization algorithm is introduced to factor in inventory and distribution distance, aiming to achieve global optimization in pairing retail store inventory with online customer orders and unifying the distribution of replenishment products, online products, and returned products. The paper contributes to the field by introducing a new variation of the Vehicle Routing Problem (VRP) that arises from an integrated distribution system, combining common VRP issues with more complex challenges. A custom Branch-and-Price (B&P) algorithm is developed to efficiently find optimal routes. Furthermore, we demonstrate the benefits of the integrated system over traditional, segregated systems through real-world data analysis and assess various factors including return rates and inventory conditions. The study also enhances the model by allowing inventory transfers between retail stores, improving inventory distribution balance, and offering solutions for scenarios with critically low inventory levels. Our findings highlight a significant reduction in total operating cost savings of up to 49.9% and vehicle usage when using the integrated distribution system compared to independent two-stage and three-stage systems. The integrated approach enables the utilization of vacant vehicle space and the dynamic selection and combination of tasks, preventing unnecessary mileage and space wastage. Notably, the integration of inventory sharing among retail stores has proven to be a key factor in generating feasible solutions under tight inventory conditions and reducing operational costs and vehicle numbers, with the benefits amplified in large-scale problem instances.

A novel molecular structure design of liquid silicone rubber modified by ceramic precursors for high-performance flexible ablation

High ablation-resistant silicone rubber exhibits a significant role in the thermal protection of space vehicles. However, its limited by the low mechanical strength in practical heat protection applications. Herein, a novel molecular network structure is proposed, which links polycarboxysilane (PCS) rigid molecules onto polydimethylsiloxane molecular chains. The use of PCS rigid chains enhances the heat resistance while reducing the material's mass ablation rate. The addition of a small quantity of PCS (0.406 mmol) increases the tensile strength of the material by 10.4 % and augmentes the static ablation residual weight by 32.8 % compared with polydimethylsiloxane. Additionally, PCS molecular modification of polydimethylsiloxane is beneficial for maintaining the stability of the char layer after oxygen acetylene ablation, making the char layer denser, and improving the interface bonding between the ceramic layer, pyrolysis layer and matrix, ultimately improving the ablation performance of polydimethylsiloxane. This work provides a new approach for development of high-performance flexible ablative materials.

Constructing lightweight ternary interpenetrating network of carbon fabric/siloxane/phenolic aerogels for long-time high-temperature thermal protection

Lightweight ablative material has served the critical role of protecting space vehicles upon hypersonic entry. However, low oxidation resistance hinders its long-time high-efficiency service in a high-temperature oxidizing atmosphere. Herein, we prepared a lightweight ternary interpenetrating network of three-dimensional carbon fabric, siloxane aerogel, and phenolic aerogel, which are structurally interpenetrating in macro-, micron-to nanoscale and chemically crosslinking at the molecular scale, resulting in a unique combination of low-density (∼0.3 g/cm3), good thermal stability and oxidation resistance, outstanding mechanical properties, and ultralow thermal conductivity. More intriguingly, long-time thermal protection performance (zero surface recession and temperature below 60 °C at 38 mm in-depth after being exposed to 1300 °C for 20 min). The findings of this work provide not only a great potential candidate material for long-time thermal protection in aviation and aerospace applications but also a simple but efficient approach to fabricating multifunctional binary, ternary, and even multiple interpenetrating networks.

Enhanced Visual Performance for In–Vehicle Reading Task Evaluated by Preferences, Emotions and Sustained Attention

The proliferation of electric and hybrid vehicles has made it possible for people to read and work in a stationary vehicle for extended periods. However, the current commonly used in–vehicle lighting design is still centered around driving and driving safety. Following recommendations from the literature, a neutral white color band (4000 K–5000 K) with 50–100 lx at the vehicle table area is favored. Whether this lighting environment can meet the needs to enhance the reading performance in a modern vehicle was investigated in this presented study. Therefore, in total, 12 lighting settings were designed based on combinations of four illuminance levels (50 lx, 100 lx, 150 lx and 200 lx) and three correlated color temperatures (3000 K, 4000 K and 5000 K); we recruited 19 subjects (12 females, 7 males) and let study participants evaluate each condition based on electronic and paper reading. Next, subjective preferences, positive and negative emotions, feeling of fatigue and sustained attention were tested. We found that higher illuminance and higher CCT (Correlated Color Temperature) can significantly improve the performance of in–vehicle readers in most aspects following Kruithof’s law (p < 0.05). Among them, we recommend the combination of 150 lx and 4000 K as the light parameters for in–vehicle reading as a new development guideline. In addition, we also discovered the inconsistency of people’s lighting preferences between in–vehicle spaces and conventional spaces. For indoor lighting, illuminance values up to 1000 lx are still favored. For an in–vehicle function, starting with 200 lx, the preference level and reading performance already declined. In comparison between electronic and paper reading, both were similarly evaluated. These results show that a neutral white light color should be chosen with a horizontal illuminance of maximal 150 lx for a reading light function independent of the reading device. Interdisciplinarily speaking, our findings can be applied in similar small spaces or transportation modes with gentle acceleration and deceleration such as small space hotel rooms, trains, airplanes or ships.

Analysis and improvement of characteristics of power supply systems for the small space vehicle of the AIST-2 type

Analysis and improvement of characteristics of power supply systems for the small space vehicle of the AIST-2 type

Simulations and experimental study on imaging of thick defect in reusable thermal protective system using microwave NDT

Reusable thermal protective system (TPS) plays a key role for protecting space vehicles against the aerothermal heating. Thus the characterization of TPS performance becomes an important issue in their production, processing and applications. This paper demonstrates the detection and imaging of inner disbond and thick defect, which considerably compromises the performance of TPS materials within a two-layer TPS configuration (a special designed thick heat insulation tile backed by an aluminum alloy plate). The methodology employed for this investigation is a near-field microwave non-destructive testing (NDT), encompassing both simulations and experimental study. A 3D microwave model for the two-layer TPS structure containing the specified defects was established, and the magnitude and phase of the waveguide input impedance (i.e. S11 parameters) for each node within the X-band (8.2 ∼ 12.4 GHz) frequency range were obtained in the work. The simulation results reveal distinct featured amplitude and phase images of defects at various frequencies. Correlation processing algorithms were employed to make the images dimensionally reduction and featured enhancement. Finally, the results were verified by experimental measurements using an open-ended rectangular waveguide. Interestingly, the disbond defect between the two layers could be clearly identified by the phase information after correlation processing algorithms. The proposed method appears to offer a contactless, intuitive, and effective approach for characterizing defects within TPS materials.

Incorporating Driving Behavior Metrics Derived from Naturalistic Driving Data into Macroscopic Safety Modeling

This research leveraged datasets from the Strategic Highway Research Program 2 (SHRP2) Naturalistic Driving Study (NDS) to explore the potential benefits of incorporating macroscopic measures derived from NDS into traditional safety modeling. Large datasets with traversals from more than 1,700 unique drivers were used to extract driving behavior on freeway segments. New sets of time series totaling over 1,600 h of driving were developed, including vehicle dynamics exclusively during car-following, while also tracking the spacing between the instrumented vehicle and the vehicle being followed. This paper focuses on the statistical modeling of crash frequency incorporating macroscopic metrics derived from the new time-series datasets as regards the mean, median, variance, and 85th percentile of vehicle spacing, vehicle speed, and traffic density. Results of this exploration indicate that an increase in the traffic density variance, an increase in the speed variance, and a decrease in the mean vehicle spacing had significant effects associated with increases in multi-vehicle crash frequencies. These results can be used to estimate the safety effect of countermeasures that may change speed, density, and or spacing, along with changes in annual average daily traffic (AADT).

Fundamental problems of safety in space flights

The tenth Space Flights Safety Symposium discussed the problems of Space flight safety, protective measures for space structures and the future strategies aimed at conducting safe and peaceful Space missions. The following topics were under discussion: protection of Space structures from space debris collisions and micrometeoroids; fire safety of Space vehicles; propulsion systems modeling and simulations; supercomputer predictive modeling for ensuring Space program safety; safety at launch and during landing or splash down.

Effects of moving vehicles and running lane on the dynamic response of a long-span floating suspension bridge

ABSTRACT Long-span floating bridges are not as robust as bottom-fixed bridges under moving vehicle loads due to weaker foundation stiffness. Understanding the effect of vehicles on the vehicle-induced dynamic response is essential for structural and operational safety assessments. This paper developed a dynamic analysis framework for floating bridges under moving vehicles, including different running lanes. The effects of moving vehicle speed, weight, running lane, vehicle number, spacing in the fleet, and vehicle fleet arrangement on the dynamic response of the example floating suspension bridge were investigated. The primary research outcomes include the following: 1) The developed framework can efficiently compute the dynamic response of the example floating bridge under moving vehicles. Compared with the bottom-fixed bridge scheme, the floating bridge under the same moving vehicle has larger dynamic responses, especially the lateral vibration response of the girder. 2) The vertical response of the floating bridge is mainly affected by the vehicle weight. The offset distribution of vehicle running lanes exaggerates the lateral vibrations of the bridge, of which the magnitude is similar to the vertical response. 3) Increasing the vehicle spacing in the fleet and implementing two-way opposing fleet traffic can effectively reduce the vehicle-induced lateral vibrations of the long-span floating suspension bridge. The design of the floating bridge can benefit from a better understanding of its dynamic response under moving vehicles.

A method of reconstruction of anisotropic fluxes of geomagnetically trapped particles from in-flight measurements of high precision

High anisotropy of geomagnetically trapped particles’ fluxes requires utilization of a complex methodology for their reconstruction from in-flight measurements. For precise position-sensitive instruments operating in the event-by-event mode, a standard approach is the one originally developed for the SAMPEX/MAST experiment. It consists in calculation of the instrument’s effective areas averaged over gyro-phase angle as a function of pitch angle of detected particles for detector’s different orientations relative to the geomagnetic field vector. This orientation normally changes as the instrument moves in space. Moreover, some space vehicles bearing a measuring instrument may and do change their orientation during flight by rotation of the instrument or as a whole. Each possible orientation needs an independent calculation of effective areas for each possible pitch angle, which is usually done by means of Monte-Carlo simulation. Therefore, especially for sophisticated devices, the calculation of an accurate and representative response function (consisting of a set of effective areas) may involve a vast amount of computation.In this paper, we propose a simplified approach, which is based on the assumption that for an anisotropic flux, the angular sphere the particles come to the detector from can be split into solid angle domains, within which the flux can be treated as isotropic. This allows one to use much easier computed geometrical factor or acceptance of the instrument as the proportionality factor. This method suggests that it can be calculated with respect to registration of the particles from these domains (we call it partial acceptance). The main advantage of the presented method is that the whole set of partial acceptances for each instrument orientation relative to the geomagnetic field vector and for all available values of (equatorial) pitch-angle for this orientation can be obtained from one simulation sample (for the given energy) of isotropic flux.

Bioinspired and Multifunctional Tribological Materials for Sliding, Erosive, Machining, and Energy-Absorbing Conditions: A Review.

Friction, wear, and the consequent energy dissipation pose significant challenges in systems with moving components, spanning various domains, including nanoelectromechanical systems (NEMS/MEMS) and bio-MEMS (microrobots), hip prostheses (biomaterials), offshore wind and hydro turbines, space vehicles, solar mirrors for photovoltaics, triboelectric generators, etc. Nature-inspired bionic surfaces offer valuable examples of effective texturing strategies, encompassing various geometric and topological approaches tailored to mitigate frictional effects and related functionalities in various scenarios. By employing biomimetic surface modifications, for example, roughness tailoring, multifunctionality of the system can be generated to efficiently reduce friction and wear, enhance load-bearing capacity, improve self-adaptiveness in different environments, improve chemical interactions, facilitate biological interactions, etc. However, the full potential of bioinspired texturing remains untapped due to the limited mechanistic understanding of functional aspects in tribological/biotribological settings. The current review extends to surface engineering and provides a comprehensive and critical assessment of bioinspired texturing that exhibits sustainable synergy between tribology and biology. The successful evolving examples from nature for surface/tribological solutions that can efficiently solve complex tribological problems in both dry and lubricated contact situations are comprehensively discussed. The review encompasses four major wear conditions: sliding, solid-particle erosion, machining or cutting, and impact (energy absorbing). Furthermore, it explores how topographies and their design parameters can provide tailored responses (multifunctionality) under specified tribological conditions. Additionally, an interdisciplinary perspective on the future potential of bioinspired materials and structures with enhanced wear resistance is presented.

3D Galileo Reference Antenna Pattern for Space Service Volume Applications.

There is an increasing demand for navigation capability for space vehicles. The exploitation of the so-called Space Service Volume (SSV), and hence the extension of the Global Navigation Satellite System (GNSS) from terrestrial to space users, is currently considered a fundamental step. Knowledge of the constellation antenna pattern, including the side lobe signals, is the main input for assessing the expected GNSS signal availability and navigation performance, especially for high orbits. The best way to define and share this information with the final GNSS user is still an open question. This paper proposes a novel methodology for the definition of a high-fidelity and easy-to-use statistical model to represent GNSS constellation antenna patterns. The reconstruction procedure, based on antenna characterization techniques and statistical learning, is presented here through its successful implementation for the "Galileo Reference Antenna Pattern (GRAP)" model, which has been proposed as the reference model for the Galileo programme. The GRAP represents the expected Equivalent Isotropic Radiated Power (EIRP) variation for the Galileo FOC satellites, and it is obtained by processing the measurements retrieved during the characterization campaign performed on the Galileo FOC antennas. The mathematical background of the model is analyzed in depth in order to better assess the GRAP with respect to different objectives such as improved resolution, smoothness and proper representation of the antenna pattern statistical distribution. The analysis confirms the enhanced GRAP properties and envisages the possibility of extending the approach to other GNSSs. The discussion is complemented by a preliminary use case characterization of the Galileo performance in SSV. The accessibility, a novel indicator, is defined in order to represent in a quick and compact manner, the expected Galileo SSV quality for different altitudes and target mission requirements. The SSV characterization is performed to demonstrate how simply and effectively the GRAP model can be inserted into user analysis. The work creates the basis for an improved capability for assessing Galileo-based navigation in SSV according to the current knowledge of the antenna pattern.

Non-equilibrium and anisotropy in Titan atmosphere entry

Titan is the largest moon of Saturn. It is the only moon in our solar system provided with atmosphere. Therefore, exploration of Titan demands aerodynamic computations aimed at a proper design of space vehicles that will bring instruments to its surface. To this purpose, the aerodynamic computing methodologies are Computational Fluid Dynamics (CFD) for the solution of continuum flow fields and Direct Simulation Monte Carlo (DSMC) method for the solution of rarefied flow fields. The failure of the Navier-Stokes equations at high altitude is due to non-equilibrium (different translational, rotational and vibrational temperatures) and to anisotropy (different components in the x, y and z direction of the translational temperature). The limitations in using DSMC at low altitudes are due to technical limitations of the computer, i.e. memory capacity and processing speed. In the present work, non-equilibrium has been quantified by the relative differences between translational and rotational (θt-r), translational and vibrational (θt-v) temperatures. Similarly, the relative differences between the translational temperature component along x and those along y (θx-y) and z (θx-z) quantified anisotropy. For each test condition, the maximum values of θ are representative of non-equilibrium and anisotropy. Computations have been carried out considering the Huygens capsule in axial-symmetric flow, along Titan atmospheric entry in the altitude interval 100–470 km by means of the commercial codes: 1) Fluent v18.1 in the interval 100–295 km, 2) DS2V-4.5 64 bits in the interval 295–470 km. The present computations stated that in the Titan entry of a capsule of dimension comparable with that of Huygens, the altitude of about 182 km should be the limit altitude for a proper use of a CFD code.

Berthing proximity maneuvers and trajectory planning of a space manipulator via Kane’s formulation

On-orbit servicing is one of the most challenging tasks of the recent space era. Space Manipulator Systems (SMS) can represent viable technological solutions for several space operations, such as in-situ refueling, repairing of operating spacecraft, or debris grappling. Regardless of the specific task, SMS must approach the target object and then establish a physical connection with it using a single or more robotic arms. This work considers a space vehicle equipped with a pair of two-link robotic arms, with the intent of efficiently designing and simulating the overall spacecraft dynamics until contact takes place. The links that compose each arm are modeled as rigid bodies, assuming relatively slow dynamics. Instead, flexibility is introduced in the model of the rotary joints. The overall dynamics is investigated using Kane’s methodology, which is general, highly systematic, and joins the advantages of both the Newton/Euler and the Lagrange formulation. Both SMS and the target, assumed as noncooperative, are placed in low Earth orbit, in close proximity. Trajectory planning of the robotic arm is investigated, while considering the effect of the arm motion on the overall attitude dynamics. Precise attitude maneuvering is mandatory in order that grappling be successfully completed. To do this, a quaternion-based, globally stable attitude feedback law is designed, implemented, and tested. Actuation is demanded to an arrangement of control momentum gyroscopes. These devices are modeled with the inclusion of gyroscopic coupling effects, and are driven by means of suitable steering laws, for the purpose of pursuing the desired attitude control action. Accurate modeling of SMS, with also the inclusion of disturbances due to joint flexibility, in conjunction with the use of suitable feedback attitude control and steering laws for both the robotic arms and the actuation devices, allows obtaining the desired variables, i.e. (i) the motor torques (for steering both the joints and the attitude devices) and (ii) the constraint actions (forces and torques). A Monte Carlo analysis points out effectiveness of the control architecture proposed in this study in the challenging mission scenario of interest.

Fused deposition modelling of dense complex-shaped SiCp/Al composites with excellent properties

SiCp/Al composites are widely used in space vehicles, electronic packaging, automobiles, rail vehicles and other fields due to their excellent mechanical and thermal properties. Complex-shaped SiCp/Al parts are usually manufactured by mechanical processing, which is expensive and time-consuming due to the high hardness of SiC phase. As a highly effective 3D molding method, Fused Deposition Modelling (FDM) of the complex-structure SiCp/Al composites was reported for the first time in this paper. SiCp/Al composites was densified by pressureless infiltration after FDM, and as-acquired bulk possessed high densification of 92.67 % and the SiC volume fraction of 43.2 %. Moreover, excellent performances were also presented, including flexural strength of 211 MPa, thermal conductivity of 112(W/m·K), and the thermal expansion coefficient of 8.67 × 10-6K−1.

An analysis of polymer material selection and design optimization to improve Structural Integrity in 3D printed aerospace components

This paper presents an analysis of material selection and design optimization techniques to enhance the structural integrity of 3D printed aerospace components. The study highlights the importance of considering material characteristics and design factors such as shape, orientation, and support structures in order to achieve reliable and high-performance components. Various materials, including metals and polymers, commonly used in aerospace applications are evaluated, along with their properties and limitations in the context of 3D printing. Furthermore, the impact of different printing parameters on the structural integrity of the components is discussed. The study identifies optimization strategies such as topology optimization, lattice structures, and infill patterns, which can significantly improve the strength and durability of 3D printed parts. The results demonstrate the potential of these techniques to optimize the design and material selection of aerospace components, leading to lighter, more efficient, and reliable parts for air and space vehicles.

Overview of Bridge Crane Control

This paper summarizes the research hotspot of underactuated mechanical system in nonlinear control field, and emphasizes its wide application in practical engineering, including space vehicle, inverted pendulum and navigation system. The Chinese government has supported the construction crane industry through a series of policies and regulations, providing guidance for its safe production and technical specifications. In the context of social development, the application demand of bridge gantry cranes in narrow environments is increasing, and the future development trend will focus on the direction of intelligence, science and technology and humanization. In recent decades, the research results on the positioning and pendulum of bridge crane at home and abroad are divided into open loop and closed loop control methods, and the control methods are described in detail in this paper.