Future trends in space photovoltaics

The Air Force, NASA, NRL and the commercial sector are all using small spacecraft to a greater extent in order to provide more cost-effective access to space. This paper discusses the generic photovoltaic technologies which are being studied and/or developed to support these smaller spacecraft, and identifies several specific examples. The unique requirements of these mission types include lower power arrays, arrays with lower mass and stowed volume which will be more compatible with small launch vehicles, and power systems with lower fabrication costs     

Future trends in space power technology

The status of the US Air Force Space Power Research and Development Program is summarized. Generic issues and requirements affecting the strategic planning of space power advances for the 1990s and beyond are described. The major thrusts of the Air Fore part of the Strategic Defense Initiative Office Space Power Program are highlighted, with emphasis on the ongoing advanced component technology development program. The status of these component technologies in the areas of power sources, energy storage, power management and distribution, and thermal management is described. Technology projections for the full range of envisioned technology options for the foregoing are used as the basis for a series of point designs for deriving the subsystem- and system-level benefits of the technologies. The primary focus is on baseload (CW) power systems operating in the range from 100 W for small satellites to 50 kW for potential large surveillance satellites. The secondary focus is on large, multimegawatt pulsed power systems and related components for potential applications such as directed energy. Potential `trump card' technologies related to energy conversion, storage, power electronics, and thermal management are identified     

Air traffic management design considerations

An air traffic management system (ATMS) is a network-centric system being used to manage another network-centric system, namely, an air transportation system. We are developing a design language for network-centric systems and design guidelines for the development system of engineers and domain specialists involved in designing and integrating systems. Note: this development system with today's technology is also a network-centric system. An outline of the design language under construction and the design guidelines being studied is provided. Specifically we discuss ATMS mission objectives (e.g., average yearly throughput of people and freight for a high demand scenario); ATMS sample usage scenarios (e.g., ATMS reroutes air traffic in time and space in reaction to major weather deviation along the northeast coast); and system objectives for an ATMS (e.g., timelines of a specific high volume of messages from aircraft, weather sensors, and airports). We lay out some key design decisions associated with both the development system of engineers and domain specialists and the operational ATMS. Examples of key design decisions for the engineering system are: 1) appropriate partitioning of functional/physical architectures of the engineering system; 2) appropriate degree to telecollaboration and collaboration among design/integration groups; 3) appropriate incremental delivery packages for an incremental delivery schedule of ATMS elements; and 4) appropriate levels and thrusts of the risk management program. Examples of key design decisions for the operational ATMS are: 1) throughput and security trades of the ATMS and 2) throughput and resiliency to weather changes. Finally, we relate network-centric architecture issues to both of the above sets of design decisions.     

Variable-fidelity optimization with design space reduction

Advanced engineering systems, like aircraft, are defined by tens or even hundreds of design variables. Building an accurate surrogate model for use in such high-dimensional optimization problems is a difficult task owing to the curse of dimensionality. This paper presents a new algorithm to reduce the size of a design space to a smaller region of interest allowing a more accurate surrogate model to be generated. The framework requires a set of models of different physical or numerical fidelities. The low-fidelity (LF) model provides physics-based approximation of the high-fidelity (HF) model at a fraction of the computational cost. It is also instrumental in identifying the small region of interest in the design space that encloses the high-fidelity optimum. A surrogate model is then constructed to match the low-fidelity model to the high-fidelity model in the identified region of interest. The optimization process is managed by an update strategy to prevent convergence to false optima. The algorithm is applied on mathematical problems and a two-dimen-sional aerodynamic shape optimization problem in a variable-fidelity context. Results obtained are in excellent agreement with high-fidelity results, even with lower-fidelity flow solvers, while showing up to 39% time savings.     

A cost effective critical space systems design approach

NASA-ISC requires avionics platforms capable of serving a wide range of applications in a cost-effective manner. In part, making the avionics platform cost effective means adhering to open standards and supporting the integration of COTS products with custom products. Inherently, operation in space requires low power, mass, and volume while retaining high performance, reconfigurability, scalability, and upgradability. The Universal Mini-Controller (UMC) project is based on a modified PC/104-Plus architecture while maintaining full compatibility with standard COTS PC/104 products. The architecture consists of a library of stackable building block modules, which can be mixed and matched to meet a specific application. A set of NASA developed core building blocks, (e.g. processor card, analog input/output card, high level analog card, and a Mil-Std-1553 card) were constructed to meet critical functions and unique interfaces     

高原直升机电气系统设计的几点思考

针对高原地区特殊的气候和大气环境,通过对直升机电源、配电、发动机起动等系统的分析,提出对高原直升机电气系统改进的办法和措施。     

Risk-based technology portfolio optimization for early space mission design

The successful design, development, and operation of space missions requires informed decisions to be made across a vast array of investment, scientific, technological, and operational issues. In the work reported in this paper, we address the problem of determining optimal technology investment portfolios that minimize mission risk and maximize the expected science return of the mission. We model several relationships that explicitly link investment in technologies to mission risk and expected science return. To represent and compute these causal and computational dependencies, we introduce a generalization of influence diagrams that we call inference nets. To illustrate the approach, we present results from its application to a technology portfolio investment trade study done for a specific scenario for the projected 2009 Mars MSL mission. This case study examines the impact of investments in precision landing and long-range roving technologies on the mission capability, and the associated risk, of visiting a set of preselected science sites. We show how an optimal investment strategy can be found that minimizes the mission risk given a fixed total technology investment budget, or alternatively how to determine the minimum budget required to achieve a given acceptable mission risk.     

基于粗糙度敏感性研究的风力机专用翼型设计

对几个具有代表性的风力机常用翼型的几何特性和气动特性进行分析研究,详细探讨了各种翼型的前缘粗糙度敏感特性情况。基于一种新的翼型几何形状表征形式,以设计攻角工况下光滑条件和粗糙条件下的升阻比加权值为目标,优化设计得到了一种相对厚度为24.7%的风力机专用新翼型。对新翼型在主要工作攻角范围的升力特性、阻力特性及升阻比特性进行了研究,并详细分析了新翼型在不同工况下的气动特性情况,研究结果表明:新翼型具有低前缘粗糙度敏感性和低湍流敏感性;在设计和非设计运行工况下都具有很好的气动性能;雷诺数的升高和三维旋转效应对风轮叶片新翼型的气动特性具有促进作用。     

基于概率方法的航天器姿态控制系统参数设计

针对传统航天器控制系统参数设计方法中存在的设计保守、主观经验性较强等缺点,使用概率分布对参数不确定性进行量化描述,采用概率指标代替确定性指标,对参数随机分布的系统进行概率分析,并使用可行域图对设计空间进行表征。在此基础上,应用概率优化方法对控制器参数进行优化设计。最后,通过实例对提出的方法进行仿真验证。仿真结果表明,概率分析方法能够放宽参数的设计空间,通过概率优化方法可以得到满足概率指标要求的设计结果,提高了设计效率。     

空间目标逆轨网捕拦截停泊轨道的优化设计

为了提高对空间目标的拦截成功率,可采用拦截器从停泊轨道转移进入拦截轨道逆轨网捕拦截的方式。利用椭圆弹道理论,讨论和分析了该拦截方式停泊轨道优化问题的描述、模型的建立及优化的方法。计算结果表明,对该拦截方式所建立的模型和采用的优化方法满足逆轨拦截对轨道设计的要求,可为空间快速拦截应用提供理论借鉴和参考。     

Optical design and testing of a fast,large aperture,infrared space telescope

An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minium aperture 2.5 metre with an F/1.2 primary and wavelength coverage from = 2 to at least 40 m, and possibly to 100 m. Compactness, low thermal emission from the optics and structure, diffraction limited imaging at = 2 m, and sensitivity to misalignment aberrations and manufacturing errors were the main considerations for this study. Ray tracing results are presented showing the characteristics of the various designs considered. A preliminary investigation of stray light properties is also given. Special emphasis has been placed on the testing of such a fast primary, and optical systems using a lateral shearing interferometer are described for testing both the primary and the primary/secondary combination.     

An approach for formation design and flight performance prediction based on aerodynamic formation unit: Energy-saving considerations

The performance improvement of swarm drones through aerodynamic shape optimization may be challenging due to folded size constraints imposed by the specific launch approach.However, fixed-wing aircraft swarms can benefit from formation flight in terms of energy consumption. This study introduces the concept of the ‘‘aerodynamic formation unit”, which consists of two or three aircraft that form an inseparable unit of the formation. Considering the Unmanned Aerial Vehicle(UAV) distribution and wingtip vortex interference in the formation, two typical aerodynamic formation units are optimized by the variable-fidelity aerodynamic optimization method based on space mapping. The aerodynamic characteristics of the formation UAVs that affect flight performance, such as lift-to-drag ratio(L/D ratio) and static stability are analyzed by Computational Fluid Dynamics(CFD) simulations. The L/D ratio(cruising condition) of the following aircraft can be increased by 22.8% and 57.5% in the optimal units that involve two and three aircraft respectively. Moreover, this study conducts several CFD simulations for multi-aircraft formations formed by the units, which show that the average L/D ratio of the formation can be improved by more than 19%. These results verify the feasibility and effectiveness of the ‘‘aerodynamic formation unit” concept and the optimization framework for formation parameters.     

Predefined-time controller design for a multiple space transportation robots system based on Lp-Norm-Normalized Sign Function

This paper presents a predefined-time controller for Multiple Space transportation Robots System(MSRS), which can be applied in on-orbit assembly tasks to transport modules to pre-assembly configuration quickly. Firstly, to simplify the analysis and design of predefinedtime controller, a Predefined-time Stability Criterion is proposed in the form of Composite Lyapunov Function(CLF-PSC). Besides simplicity, the CLF-PSC also has the advantage of less conservativeness due to utilization of initial state information. Secondly, a concept of LpNorm-Normalized Sign Function(LPNNSF) is proposed based on the CLF-PSC. Different from traditional norm-normalized sign function, the Lp-norm of LPNNSF can be selected arbitrarily according to practical control task requirements, which means that the proposed LPNNSF is more generalized and more convenient for calculation. Thirdly, a predefined-time disturbance observer and predefined-time controller are designed based on the LPNNSF. The observer has the property of predefined-time convergence to achieve quicker and more accurate estimation of the lumped disturbance. The controller has less control input and chattering phenomenon than traditional predefined-time controller. In addition, by introducing the observer into the controller, the closed-loop system enjoys high precision and strong robustness. Finally, the effectiveness of the proposed controller is verified by numerical simulations. By employing the controller, the MSRS can carry assembly modules to the desired pre-assembly configuration accurately within predefined time.     

GPS autoland considerations

It is pointed out that fully automatic hands-off landing (autoland) capability for commercial aircraft, using the Global Positioning System (GPS), has not been demonstrated, and that ground multipath errors limit vertical positioning accuracy. An evolving integrated-sensor-based architecture for approach and landing, called the tunnel concept, is examined. The precise velocity information available could substantially reduce the vertical accuracy requirement for autoland     

A methodology for aircraft mission effectiveness evaluation and design space exploration based on virtual operational test

The early involvement of test and evaluation can significantly reduce the cost of modifying issues and errors found in the later stages of aircraft development and design process.This paper presents a methodology for aircraft mission effectiveness evaluation and design space exploration based on Virtual Operational Test (VOT),incorporating Virtual Open Scenario (VOS) and User in Scenarios (UIS) concepts.By employing modeling and simulation technologies in the early stages of aircraft development and design,a virtual environment can be constructed,allowing aircraft users to participate more closely and conveniently in the design process.Virtual tests conducted by users within the mission context provide data on mission effectiveness and critical user feedback.This paper outlines the main components of the virtual operational test process and related conceptual methods,and discusses an open support system framework that supports VOT.The effectiveness and adaptability of the method are demonstrated through two case studies:a beyond-visual-range air combat scenario and a helicopter ground attack scenario.These case studies demonstrate the evaluation of aircraft mission effectiveness and the sensitivity analysis and optimization of design and operational parameters based on VOT.     

未来工厂

系统仿真、虚拟制造、无纸化生产这些信息时代的新型生产制造模式已经逐渐成熟,并在制造企业中得到了越来越广泛的应用,未来工厂的发展将更加趋向于集成化、数字化、虚拟化、全球化、标准化和智能化。     

未来测量

随着计算机技术、传感器技术和自动化技术的蓬勃发展,先进测量技术已经成为工业发展的支柱技术之一。航空领域方面,随着航空结构和设计对测量技术要求的不断提高使得测量精度不断升级,测量手段更加多样化。     

未来测量

计算机技术、传感器技术的迅猛发展,使得测量技术更加日新月异。随着航空结构和设备对测量技术要求的不断提     

未来工厂

柔性制造、全数字化工厂、智能车间这些全新的制造理念已经逐渐被人们所重视,并逐渐在制造企业中得到应用。未来工厂的发展必将引领制造业又一次新的跨越。