多点压力扫描阀测量系统在激波／湍流边界层干扰实验中的应用

多点压力测量是航空气动力研究及高性能流体机械研究中的重要测试手段。利用计算机和多点压力扫描阀系统，可以高效地完成这项任务，并可能在实验中实现数据采集及整个实验过程的自动化。我们利用ＨＰ１０００／Ａ７００计算机－ＨＰ２２５０－测控装置－压力传感器－高速扫描阀组成的测量控制系统，在超音速风洞内对激波／湍流边界层干扰产生的流场进行了快速多点压力数据采集，并取得了可靠的结果。本文对测试和校正过程中的程序设计、测试方法和应用经验进行了介绍。     

Appearance of neutron stars in the state of subsonic propeller

The state of subsonic propeller is intermediate between the states of supersonic propeller and accretor in the evolutionary tracks of magnetized compact stars. The rotational rate of a star at this stage decelerates due to the interaction between its magnetosphere and the surrounding hot, quasi-static plasma envelope. The magnetospheric radius is smaller than the corotation radius and the boundary of the magnetosphere is stable with respect to interchange instabilities. The rate of the mass flux from the inner radius of the envelope to the stellar surface is limited by the rate of plasma diffusion into the magnetic field of the star. As a result, the subsonic propeller would appear as a low-luminosity accretion-powered pulsar with a soft X-ray spectrum.     

基于径向基函数神经网络的自由曲面重构

根据径向基函数神经网络（RBFNN）具有很强的非线性逼近能力的优点，本文采用RBF网络模型进行自由曲面重构，建立了适应于曲面重构的径向基函数网络模型，讨论了基函数对重构曲面连续性的影响，并与多自由曲面重构，建立了适应于曲面重构的径向基函数风络模型，讨论了基函数对重构曲面连续性的影响，并与多层感知器神经网络的性能进行对比。理论分析和仿真实验结果表明：常用的几种径向基函数重构的曲面都具有很好的连续性，径向基函数网络用于曲面重构，不论是在拟合精度，还是网络的训练速度都明显优于多层感知器网络，具有一定的实用价值。     

Designing to MIL-STD-2165: Testability

The V-22 avionic hardware is the first to be designed under MIL-STD-2165 testability program requirements. This paper presents an overview of the avionics design-for-testability approach and lessons learned to date relative to the application of MIL-STD-2165. The paper will discuss incorporation of testability requirements up front in the avionics design which will drive the supportability philosophy at both the Organizational and Depot levels of maintenance. The paper will compare previous avionics hardware testability requirements versus those applied to the V-22 avionics and highlight areas of improvement. A discussion of testability design impacts on reduced level of testing (i.e. WRA/SRA/System) will be included. In addition, the paper discusses an innovative approach to meeting the user requirements for a man-portable forward deployed maintenance capability that forms the basis for a two level support scenario (Organizational and Depot). The innovation comes from the fact that the on-board Central Integrated Checkout system will provide data as well as fault isolation and will use this data as a mechanism to reduce the size and complexity of the stimulus and measurement hardware at either the Organizational or Depot level depending on the deployment requirements.     

磁悬浮框架飞轮磁轴承技术研究与发展现状

对磁悬浮框架飞轮(MSGFW)和高精度磁轴承研究现状及其未来发展进行了详细阐述。根据转子悬浮力类型，将磁悬浮框架飞轮分为磁阻力构型、洛伦兹力构型和混合力构型，并结合三种构型论述了国内外框架飞轮的发展过程。在此基础上，对球面磁阻力磁轴承和洛伦兹力磁轴承进行了详细介绍，并结合磁路图分析其工作原理，比较了同类磁轴承的优劣。展望了磁悬浮框架飞轮与高精度磁轴承的未来发展方向，指出高动态响应检控共位平动球面磁阻力磁轴承，标准磁悬浮动量球和磁悬浮控制敏感球是磁悬浮框架飞轮的研究重点。     

The Radarsat Antarctic Mapping Mission

The Radarsat Earth-observation satellite was launched on November 4, 1995 aboard a Delta 2 rocket. Equipped with a sophisticated synthetic aperture radar (SAR), Radarsat can produce images of extraordinary clarity even through clouds, smog, haze, smoke, and darkness. The SAR has a variety of operating modes. It can be adjusted to produce swathes between 35 and 500 km in width, with ground resolutions from 100 m to as low as eight. In addition, the beam can be steered at angles up to 49° from the satellite's nadir vector, giving it the unique ability to image areas it is not directly overflying. In exchange for the launch, CSA agreed to provide NASA with access to the SAR data, and to execute a 180° yaw-around of Radarsat twice during its lifetime to map the Antarctic continent. Preliminary results from the first of these Antarctic Mapping Missions, dubbed AMM-1, are presented     

Singularity avoidance of control moment gyros by one-step ahead singularity index

A steering law of control moment gyros for spacecraft attitude control by using one-step ahead singularity index is addressed in this paper. In some recent studies, the null motion approaches or singularity robustness steering laws have been extensively investigated to avoid singular configurations for a control momentum gyro (CMG) cluster. As a novel approach different from them, the proposed approach is based on optimization technique by minimizing the one-step ahead singularity index. Modified approaches are also presented in this paper. The proposed one-step prediction method ultimately gives an optimized solution of gimbal rates with advanced ability to avoid a singularity. A singularity index for reliable computation of a gradient vector is also introduced. Finally, performance of the proposed algorithm is demonstrated by numerical simulations.     

Hybrid optimization for multiple-impulse reconfiguration trajectories of satellite formation flying

A hybrid optimization method is developed for fuel-optimal reconfigurations of a group of satellites flying in formation. The genetic algorithm performs a global search to find two-impulse trajectories, and primer vector analysis finds multiple-impulsive local optimal trajectories with the two-impulse trajectories as initial guesses. Hybrid optimization finds globally optimal trajectories for formation reconfigurations, including formation resizing, reassignment and reorientation maneuvers. Multiple-impulse trajectories reduce the fuel consumption from the two-impulse trajectories by up to 4.4% for those maneuvers. In real missions, satellites can follow two-impulse trajectories to gain the advantage of a smaller number of impulses, with the cost of slightly more propellant. The qualitative characteristics of the optimal trajectories are analyzed from the number of optimal trajectories found by hybrid optimization.     

The impact of US export controls on the Canadian space industry

The International Traffic in Arms Regulations (ITAR) govern the export of defense-related technologies and services from the USA. In 1999 Canada's exemption to ITAR was suspended because of American objections over some Canadian companies retransferring US technology to third countries. This paper is a first attempt to quantify the impact of ITAR on the Canadian space industry. Thirty-two space-related companies were contacted and a total of nine responses were received, representative of around 60% of the Canadian space industry in terms of workforce and revenue. According to the results, the Canadian space industry has been relatively effective in meeting the challenges imposed by ITAR. However, these workarounds do not diminish its negative impacts, particularly with respect to cost and schedule. It is expected that ITAR will continue to affect the Canadian space industry, as no near-term relief from the current regulatory environment is on the horizon.     

Attitude control of a bias momentum satellite using moment ofinertia

Analysis on the attitude controller based upon moment of inertia distribution for a bias momentum satellite is discussed. Spacecraft moment of inertia distribution is represented in the form of product of inertia terms in the system inertia matrix. The product of inertia between orthogonal body axes of the satellite is used to build a controller which controls the nutational motion caused by the angular momentum of the wheel. The attitude controller in the pitch axis controlling the pitch motion as well as nutational dynamics in the roll/yaw planes is analyzed in detail. Analytic expressions using linearized equations are derived providing further insight into the dynamic coupling effect among orthogonal body axes