Advances in Astronautics Science and Technology最新文献

Lightweight structures composed of a closed shell and internal lattice infill are highly desirable in satellites on account of their superior specific stiffness and buckling strength, which are brought about by the sandwich effect. These lattice structures can be fabricated by various additive manufacturing techniques, such as selective laser melting (SLM). However, the sub-millimeter-scale shell thickness and lattice strut diameter of the fabricated structure often deviate from the designed dimensions and lead to noteworthy discrepancies between the resonance frequencies of the fabricated structure and those of the initial design model. In this work, a bracket structure for a satellite is designed via topology optimization-based lattice infill approach and fabricated using SLM. A resonance frequency prediction approach based on X-ray micro-computed tomography and the stiffness equivalence is then proposed. Vibration tests are conducted to obtain the resonance frequencies of the fabricated structure. The prediction errors of resonance frequencies for the first three modes are less than 1%, whereas that of the traditional approach based on finite element analysis is as large as 14%.

Lunar Zebro’s mission is heading the race for deploying the world’s smallest and lightest swarm of nanorovers on the surface of Moon. The concept validation of a single nanorover is of crucial importance, as it will be the launching pad for deploying a swarm of those nanorovers thereafter. Then, they will get connected in a network, acting as a single device and performing scientific missions analyzing data from remote points on the Moon’s surface. In the current study, the complete set of thermo-mechanical-radiation analyses for Lunar Zebro nanorovers are carried out. These range from the Ground Segment to the Moon environment, taking also into account the extreme mechanical and thermal environment at launch-transit conditions when the nanorover is attached to the lander. An innovative ray tracing method to evaluate the effect of the thermal environment on the Lunar Zebro nanorovers is explained in this paper. Material choices, structural design, and mechanical/thermal strategies for the nanorover to overcome the launch, space and Moon’s conditions are shown. The different analyses methods used, expected loads and results obtained should serve as a baseline for evaluating the behaviour of other small devices attached to a lander when aiming for any space mission. More specifically, for those aiming to go to the Moon, the environmental and mechanical expectations here can also be implemented. The ultimate outcome of the paper is the environmental survivability assurance from an analytical perspective of these nanorovers when being sent to the Moon. The validation of the survivability of a single nanorover will be a breakthrough in the space swarm robotics’ field, resulting in the successful performance of the lightest swarm of nanorovers ever deployed on the Moon’s surface.

The periodic lattice structure has obvious advantages in lightweight and multi-functional design. With the development of manufacturing technology, especially the development of selective laser melting, the periodic lattice structure has been more extensively used, and attracts more attention in studying its structural behavior. According to the characteristics of periodic lattice structure, ABAQUS is used to establish its geometric model, and the mechanical properties are simulated and analyzed under compression. Considering three kinds of cantilever beams with solid, periodic lattice and rubber-filled periodic lattice as examples, and comparing with the theoretical results of modal frequencies, the simulation method of the periodic lattice structure is improved. The simulation analysis method is used to analyze the change of mechanical parameters and the change of the damping characteristics of the three types of cantilever beams caused by the dimension difference in different directions. The simulation results can provide a basis for the performance test of the periodic lattice structure and provide a reference for the design of the periodic lattice structure which meets the performance requirements.

Bolt connection in-situ measurement refers to the field measurement of bolt preload without changing the original bolt connection state. At present, the technologies that can be applied to bolt connection in-situ measurement mainly include piezoelectric impedance method, acoustic emission method, ultrasonic method, optical fiber sensing method, etc. This paper summarizes the research status of these measurement methods, analyzes their measurement principle, key technologies, advantages and disadvantages and scope of application, and finally gives the development trend of threaded connection in-situ measurement technology.

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.

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.

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.

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.

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.

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.