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Abstract: Abstract Distributed propulsion UAV is an aircraft configuration in which cross-flow fan is used in close conjunction with the fixed-wing at the leading edge. This generates good amount of lift and lowers the stalling speed as compared to that of conventional wing aircraft. This UAV does not stall at higher angle of attack. The distributed propulsion UAV offers many merits of both fixed-wing aircraft and helicopters as the fan’s tip speed is extremely low in this UAV as compared with the conventional aircraft propellers or helicopter rotors thereby increasing the propulsive efficiency and reducing the noise. In this present study, an attempt has been made to design and develop the distributed Propulsion UAV. Design is done using Solidworks and CFD analysis is carried out using Ansys. Thus, the distributed propulsion UAV that is developed will be able to take-off and land in a shorter runway at low-speed conditions and has better stalling characteristics as compared to that of conventional aircraft. A different mechanism is used to run the cross-flow fan in this study, different airfoil as well as a working model is developed. PubDate: 2022-05-10
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Abstract: Abstract This paper reviews and presents a trade-off study between three new concepts to study the presence of water on the Moon. The concepts are all different concerning the method of application. The first concept confirms the presence of water on the Moon through a comparative ratio study of water formation by hydrogen bombardment at varying intensity. The second concept studied is the Moon Orbiter which confirms the presence of water by studying the spectrum of radio waves from faraway stars over the permanently shadowed regions of the Moon. The third concept is the close site study in which the presence of water is confirmed by heating the surface of the Moon with the help of a reflector array. A trade-off study is conducted between various factors for example feasibility, application location of the experiment on the surface of the Moon, cost-effectiveness, and timeline. These are the basic factors that the concepts are studied on, but the trade-off between other critical factors is also done to select and present the best as well as a feasible method to check the presence of water on the surface of the Moon. Study is conducted to set a base level for standardizations for all future space missions to be conducted in this or any other domain. The efficiency of the mission can be studied through the projections and metrics carried out in this paper. PubDate: 2022-04-30
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Abstract: Abstract Forecasting of collisions between resident space objects (RSOs) is becoming critical for the future exploitation of near-Earth space. A constellation of 28 spacecrafts (plus in-orbit spares) in sun synchronous orbits is proposed as a solution for improving the current space situational awareness capabilities. Each satellite uses an optical payload to track target RSOs, with the satellite's position precisely determined. Multiple pictures of the RSO are taken, and the spacecraft attitude used to calculate the target's position relative to the spacecraft. The target's orbit is then determined from the movement of the target through the field of view over time. The system outputs orbit state vectors of the tracked object, allowing precise orbit characterisation and collision forecasting to be delivered. The constellation's design allows high temporal resolution, so reliable information can be supplied to end-users. The paper shows the results of the system design of a demonstration mission meant to verify the feasibility of the concept, performed by a team of students of Cranfield University. The exercise addresses all the aspects of the preliminary design, including the definition of the mission and system requirements, the selection of the overall mission architecture, operations, and mission phases. A cap on the overall cost allows for the realisation of the platform within a university budget. The outline of the design includes not only the selection and sizing of all the subsystems and payload but also suggests a new strategy for deploying the constellation if the demonstration mission is successful. The utilisation of high TRL and COTS components, as well as mass, power, and link budgets, demonstrate the feasibility of the overall mission concept. PubDate: 2022-04-23
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Abstract: Abstract This paper focuses on the locomotion planning for a quadruped robot walking on the lunar rough terrain. Firstly, the detailed terrain data of the explorable area acquired by the navigation camera is filtered. The terrain is afterwards triangular meshed and reconstructed as a simplified triangular grid model with terrain features retained. Then, the reinforcement learning method is used to plan the path of the robot in the grid-based environment. It employs terrain relief and roughness as the rewards, therefore intelligently determining the optimal detection route with maximum cumulative reward. Finally, gait planning is carried out to make the legs actuate adaptively to the path. Particularly, the step sequence is adjusted with different steering angles, and the footsteps are decided based on the robot mechanism constraints and uneven terrain conditions. Numerical simulations illustrate the walking process of the quadruped robot. The results show that the robot can learn the optimal path with fewer trunk undulations, and generate continuous, stable, and safe gaits. It proves that the locomotion planning method can effectively improve the mobile stability, efficiency, and adaptability of the quadruped robot when walking on the lunar surface. PubDate: 2022-04-21
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Abstract: Abstract The main research question that this study tries to answer is how to produce and install a geostationary crane in space for raising and lowering payloads with the focus on how to install the counterweight, which will be presented the concept of an orbital loom factory to reach the geostationary stability. The strict objective of this study is to answer how to stabilize the space crane with the same Earth rotation that requires a counterweight at 36,000 km altitude. This study presents a proposal to solve this problem, by means of an orbital loom factory satellite in space to manufacture the cable in sections. Through the method of producing little by little, and at each section, a set of tests would be carried out, mechanically analyzed to safety, structural, commissioning, and maintenance. The study found that with this method, it is possible to install the space crane, which means to be an economic interface between Earth and space. Another question was answered on materials requests for engineering strategies, above the strength of materials limits. It was found that it is possible to work to increase this structural capacity using academically the crane model project to analyze the engineering of materials strategically, in addition to the available capacity, formulating a methodology through a suspended cable to withstand extreme mechanical conditions. Finally, will be presented why it is worth building this structure, and how to use the spatial crane as a greener way to access the space. PubDate: 2022-04-19
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Abstract: Abstract Microwave power transmission (MPT) technology has been proposed to supply power to the long-reached systems, such as high altitude airships, unmanned vehicles, and far-reached wireless sensor networks, etc., and it is also the key technology of the solar power stations (SPS). Rectenna array, receiving the microwave (MW) and convert it into the direct current (DC) power, is one main component of an MPT system. In this paper, the development of rectenna arrays are reviewed. Second, the recent research work of rectennas and rectenna arrays at C-, X- and Ka-bands at Shanghai University are illustrated. Thirdly, based on the experimental results and reasonable evaluation, the designs of rectenna arrays for 1 kW DC power at different bands are evaluated and analyzed. Finally, prospects and challenges of rectenna array and MPT technology are discussed. PubDate: 2022-04-18
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Abstract: Abstract Accurate failure prediction is a sharp focus issue in engineering application and advanced science. In it, the most important technique is to properly define the failure criteria. This work presents the critical stress intensity factor and the critical defect size in serving environment, both of which are essentially connected with the environmental surface energy and the environmental plastic deformation work. The defect is further identified as a unified feature to predict serving lifetime of the systems and quantitatively evaluate structural properties in theory and in engineering. Also, a case of defect analysis in aerospace safety is listed at the final. PubDate: 2022-04-04
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Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Space Power Satellite (SPS) is a huge spacecraft to utilize solar energy in space. Because of the huge size, immense mass and high power, there exist many technical difficulties. For a GW SPS system, the generated electric power in space will be over 2 GW, and the whole area of the solar array will be several square kilometers. The high-power electricity generation, transmission and management in space becomes a huge challenge. In the paper, the primary scheme of MR-SPS concept is presented and two important sub-systems, Solar Energy Collection and Conversion (SECC), Power Transmission and Management (PTM) are introduced. The SECC sub-system includes fifty solar sub-arrays. Each solar sub-array is composed of twelve solar array modules. The area of each solar sub-array is about 0.12 km2. The solar sub-arrays transmit electric power to the cables installed on the main structure of MR-SPS by 100 middle power rotary joints. PTM sub-system converts, transmits and distributes the output electric power of SECC sub-system. Most of electric power is transmitted to the antenna and is distributed in the antenna. The remaining electric power is transmitted and distributed to the service equipments for the operation of SPS. The mix of distributed and centralized high-voltage PTM is adopted to meet the requirement of electric power supply of the electric equipments on SPS. Typical space environment influencing high-power electric system is analyzed. The key technologies need to be researched and solved including high-efficient, long-life thin-film GaAs PV cell, ultra-large–high-voltage (500 V) solar array module, high-power conductive rotary joint, ultra-high-voltage (20 kV) cables, high-power converter, high-power switch, etc., and assembly and maintenance of the sub-systems. PubDate: 2022-03-23
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Abstract: Abstract Light weight and flexible III-V multi-junction thin film solar cells play an important role as power energy supplying in space solar power satellites. In this work, we fabricated 3 J GaInP/GaAs/InGaAs solar cells on 30 μm thick polyimide film using temporary bonding and epitaxial layer lift-off via selective wet chemical etching. The thin film solar cells with an average conversion efficiency of 30% (AM0) were connected together in series to increase the module’s voltage up to 500 V. Increasing module’s voltage allows to reducing the resistive losses during long distance current transportation and is enable inverter simplification leading to more efficient. We investigated the influence of the electrostatic discharging on the flexible thin solar module with 500 V ultra-high voltage and the results were discussed. PubDate: 2022-03-19
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Abstract: Abstract In this work, a single-layer reflectarray antenna design operating at the center frequency of 5.8 GHz for microwave power transmission is proposed. The reflectarray unit embodies a slotted circular patch loaded with four symmetrical resonant phase delay lines. By adjusting the length of the phase delay lines, a reflection phase compensation range of about 400° is achieved. The reflectarray uses the low-cost F4B material as the substrate. The feed horn antenna adopts an offset angle of 15°, and the focal diameter ratio (F/D) is 1.2. Based on the reflectarray unit design, a 361-unit reflectarray antenna is designed with the desired pitch angle and azimuth of the reflected wave to be (0°, 0°). The measured gain is 27.3 dBi at the center frequency of 5.8 GHz. The aperture efficiency and 1 dB reflectarray bandwidth are 51% and 20.4% (5.01–6.15 GHz) respectively. In addition, at the center frequency of 5.8 GHz, the side-lobe level and cross-polarization level are lower than − 18 dB and − 30 dB, respectively. PubDate: 2022-03-07
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Abstract: Abstract There will be serious thermal problems in the photovoltaic system of sunlight-concentrating space solar power station (SSPS), which will reduce the conversion efficiency of the photovoltaic system and overall energy transmission of the whole system. In this paper, based on the thermal problems in the optoelectronic system of SSPS via Orb-shape Membrane Energy Gathering Array (SSPS-OMEGA), a thermal management strategy of full-spectrum selective photonic thin-film based on the photoelectric characteristics of photovoltaic cells and pump-driven fluid flow loop is proposed with combination of passive and active cooling methods. Simulation results indicate that the full-spectrum selective thin film can significantly reduce the parasitic heat source in ultraviolet band and sub-band gap, from 205 to 72.8 W/m2 and from 46 to 4.5 W/m2, respectively. Meanwhile, it can effectively increase the emissivity from 0.84 to 0.938. On the other hand, the pump-driven fluid flow loop is designed and the temperature of the PV cell array is well controlled below 50 ℃ for ground-based demonstration validation system of the SSPS-OMEGA project. Finally, a simple experiment investigation is carried out demonstrate the thermal control performance of pump-driven fluid flow loop for photoelectric system. PubDate: 2022-02-23 DOI: 10.1007/s42423-022-00097-6
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Abstract: Abstract Rectifiers and rectennas have been receiving great attention for the applications of wireless power transmission and energy harvesting. This paper describes the challenges and solutions of the rectifiers and rectennas in enhancing conversion efficiency at low and high input power levels for the applications of space solar power station (SSPS). We reviewed the developments of the rectifiers for the applications of wireless power transmission, described the SSPS system, retrospect the history of SSPS, and presented the requirements of rectifiers and rectennas in SSPS systems. Key technologies of high-efficiency rectifiers and rectennas at various input power levels are also proposed. In high power levels, reducing harmonic loss and diode loss is valid to enhance rectifying efficiency. When the input power is low, using booster-voltage technology with low turn-on voltage diodes can improve rectifiers’ performance. To keep a high efficiency in low and high power levels, rectifiers with wide input power dynamic ranges are proposed with various structures. PubDate: 2022-02-11 DOI: 10.1007/s42423-022-00096-7
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Abstract: Abstract Electromagnetic formation flying technology makes use of the inter-satellite electromagnetic force and torque to control the relative position and attitude of the satellites. It has the advantages of no propellant consumption, long lifetime, and high flexibility. Since the electromagnetic formation dynamics is nonlinear and strongly coupled, the magnetic dipole assignment is difficult. This paper studies the electromagnetic formation capability and dipole assignment of double satellites. The feasible engineering constraints are given based on the overall energy consumption optimization goal, which significantly simplifies the electromagnetic model and reserves a certain degree of freedom to assign electromagnetic dipoles. The relationship among electromagnetic force, torque, and dipole is illustrated by the diagram method. We also calculate the envelope of electromagnetic formation capability. The analytical solution of the dipole with the optimal energy consumption and the numerical solution of the dipole with the least angular momentum is given via the typical dipole assignment strategies. The results of the calculation example show that the approaches of dipole assignment are effective. PubDate: 2021-11-29 DOI: 10.1007/s42423-021-00088-z
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Abstract: Abstract In this paper, intelligent materials for flexible actuators are reviewed, including fiber knitted fabric, elastic polymer, electroactive polymer, shape memory alloy and shape memory polymer. This paper will discuss the current challenges in the development of flexible actuators, and analyze its future development. PubDate: 2021-11-23 DOI: 10.1007/s42423-021-00092-3
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Abstract: Abstract A novel photonics-based RF reception approach is proposed as a competitive solution to meet the current challenges of photonics-based approaches and to realize high performances at the same time. The proposed approach adopts the superheterodyne configuration by a combination manner of electronic techniques and photonic techniques, including the ultra-wideband generation of optical LO, the two-stage photonic superheterodyne frequency conversion and the real-time IF compensation. An engineering prototype has been developed and its performance has been evaluated in the laboratory environment. The experiment results preliminarily verify the feasibility of the proposed approach and its engineering potential. The typical performances are as follows: 0.1 GHz ~ 45 GHz operation spectrum range (> 40 GHz), 900 MHz instantaneous bandwidth, 101 dB·Hz2/3 SFDR and 130 dB·Hz LDR, image rejections of ~ 80 dB for 1st frequency conversion and > 90 dB for 2nd frequency conversion. PubDate: 2021-11-17 DOI: 10.1007/s42423-021-00089-y
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Abstract: Abstract The rapid development of space technology has made it increasingly important to use space robots for on-orbit services. Space crawling robots can perform extravehicular condition monitoring, spacecraft fault location and diagnosis, repair and maintenance by carrying different payloads and traversing the spacecraft surface, which has received wide attention from researchers. A prototype of space crawling robot has been designed in this work, which is a quadrupedal insect-like configuration with integrated bionic adhesion material on the bottom of the four feet, and can walk on the satellite surface in a gravity-free space environment. The design and implementation of the crawling robot control system is carried out based on Robot Operating System, including hardware system construction and software architecture design. The tripod gait was also designed to enable the robot to crawl more stably in space. At last, the basic capabilities of the designed space crawling robot are tested in the ground environment, and the results demonstrate the robot’s body control capability, omnidirectional walking capability, and obstacle crossing and avoidance capability. PubDate: 2021-11-15 DOI: 10.1007/s42423-021-00090-5
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Abstract: Abstract To design a gigantic microwave power transmitting array for space solar power station, modular design procedure is discussed. Besides microwave power channels, radiating array and thermal control, functions such as DC power source and beam steering should also be included in the design of the microwave power transmitting array. Smart composite structures integrate electronics, structures, thermal control and other functions into a module, providing an advanced design and integration paradigm. Modular smart composite structure antenna is an ideal candidate for its light weight and other performance. PubDate: 2021-10-26 DOI: 10.1007/s42423-021-00087-0
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Abstract: Abstract Laser wireless power transmission (LWPT) is one of the effective ways to provide long-distance convenient and perpetual energy supplies to electronics. Especially in space power satellite (SPS), LWPT can be used to transfer energy not only to ground, but also to other spacecrafts, which applied for satellite rescuing, spacecraft maintaining in orbit. In space application, LWPT system has characteristics of long distance, higher power, precisely aiming accuracy and better adaptability to space environment. In this paper, we propose a long distance LWPT system in SPS. Firstly the system diagram, composition and key technologies are described, which include the selection of laser, the collimated and expanded module of laser beam, the principle of the optical-to-electrical conversion efficiency of InGaAs photovoltaic cell for the high intensity laser with different laser wavelengths, the Acquisition Pointing and Tracking (APT) system and the Maximum Power Point Tracking (MPPT) technology. Then the LWPT system in SPS is designed, which composed of laser transmitting subsystem, laser receiving subsystem, APT platform and energy managing subsystem. Finally, we evaluate the power conversion performance of LWPT by simulation, which illustrates that the system can achieve better energy transmission effect under the condition of transmission distance of 400 km (space to ground) and beam pointing accuracy of 5 μrad. PubDate: 2021-10-19 DOI: 10.1007/s42423-021-00086-1
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