用于空间探测飞行时间质谱仪的真空系统和取样系统设计

文章介绍了可用于空间探测飞行时间质谱仪的真空系统和取样系统设计,并建立了该TOFMS原理样机的地面试验系统。为适应空间探测和地面试验2种不同工作模式,设计了2套不同的真空系统。根据文章建立的气体样本进样的理论分析模型进行理论分析计算,并通过地面适应性试验测定了质谱室的真空度、空气的Voltage-Amu谱图、Kr样本Voltage-Amu谱图及进样时间。试验结果表明:真空系统和取样系统设计合理,能够满足试验需求;理论分析模型正确,能够用于指导试验。     

The effective temperatures of O-type stars from UV spectroscopy

We present an analysis of high resolution spectra in the far-UV – UV range (∼905–2000 Å) with non-LTE, spherical, hydrodynamical, line-blanketed models, of three O-type Galactic stars, and derive their photospheric and wind parameters. These data extend previously analyzed samples and fill a gap in spectral type coverage. The combined sample confirms a revised (downward) T_eff scale with respect to canonical calibrations, as found in our previous works from UV and optical spectra, and in recent works by other authors.     

New trade tree for manned mars missions

Recent studies on human missions to Mars suggest revisiting the parameters that have the most important impact on the complexity, the initial mass in low Earth orbit, the risks and the development costs for the first journey to the red planet. In the last NASA reference mission, a trade tree is proposed.     

Applications of tuned mass dampers to improve performance of large space mirrors

In order for future imaging spacecraft to meet higher resolution imaging capability, it will be necessary to build large space telescopes with primary mirror diameters that range from 10 m to 20 m and do so with nanometer surface accuracy. Due to launch vehicle mass and volume constraints, these mirrors have to be deployable and lightweight, such as segmented mirrors using active optics to correct mirror surfaces with closed loop control. As a part of this work, system identification tests revealed that dynamic disturbances inherent in a laboratory environment are significant enough to degrade the optical performance of the telescope. Research was performed at the Naval Postgraduate School to identify the vibration modes most affecting the optical performance and evaluate different techniques to increase damping of those modes. Based on this work, tuned mass dampers (TMDs) were selected because of their simplicity in implementation and effectiveness in targeting specific modes. The selected damping mechanism was an eddy current damper where the damping and frequency of the damper could be easily changed. System identification of segments was performed to derive TMD specifications. Several configurations of the damper were evaluated, including the number and placement of TMDs, damping constant, and targeted structural modes. The final configuration consisted of two dampers located at the edge of each segment and resulted in 80% reduction in vibrations. The WFE for the system without dampers was 1.5 waves, with one TMD the WFE was 0.9 waves, and with two TMDs the WFE was 0.25 waves. This paper provides details of some of the work done in this area and includes theoretical predictions for optimum damping which were experimentally verified on a large aperture segmented system.     

Strong geomagnetic activity forecast by neural networks under dominant southern orientation of the interplanetary magnetic field

The paper deals with the relation of the southern orientation of the north–south component _Bz$B_z$ of the interplanetary magnetic field to geomagnetic activity (GA) and subsequently a method is suggested of using the found facts to forecast potentially dangerous high GA. We have found that on a day with very high GA hourly averages of _Bz$B_z$ with a negative sign occur at least 16 times in typical cases. Since it is very difficult to estimate the orientation of _Bz$B_z$ in the immediate vicinity of the Earth one day or even a few days in advance, we have suggested using a neural-network model, which assumes the worse of the possibilities to forecast the danger of high GA – the dominant southern orientation of the interplanetary magnetic field. The input quantities of the proposed model were information about X-ray flares, type II and IV radio bursts as well as information about coronal mass ejections (CME). In comparing the GA forecasts with observations, we obtain values of the Hanssen–Kuiper skill score ranging from 0.463 to 0.727, which are usual values for similar forecasts of space weather. The proposed model provides forecasts of potentially dangerous high geomagnetic activity should the interplanetary CME (ICME), the originator of geomagnetic storms, hit the Earth under the most unfavorable configuration of cosmic magnetic fields. We cannot know in advance whether the unfavorable configuration is going to occur or not; we just know that it will occur with the probability of 31%.     

低雷诺数下离心压气机性能及流动影响的数值研究

对高空低雷诺数条件下低压离心压气机进行了全三维数值模拟,分析了雷诺数对其内部流场的影响.结果表明:随着雷诺数降低,离心压气机的效率、裕度和流通能力下降;影响叶片表面负荷分布,使得转子叶片的做功能力下降;叶片前缘分离区范围增大,二次流增强,分流叶片叶尖泄漏损失增大,主叶片吸力面通道的低速区明显增大,起始位置也向前移动,对展向的影响区域也随之增加.      

Flow Stability Model for Fan/Compressors with Annular Duct and Novel Casing Treatment

A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time. It is shown that under some assumptions, the stability equation can be obtained yielding from a group of homogeneous equations. The stability can be judged by the non-dimensional imaginary part of the resultant complex frequency eigenvalue. Further more, based on the analysis of the unsteady phenomenon caused by casing treatment, the function of casing treatment has been modeled by a wall impedance condition which is included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system. Finally, some experimental investigation and two numerical evaluation cases are conducted to validate this model and emphasis is placed on numerically studying the sensitivity of the setup of different boundary conditions on the stall inception of axial flow fan/compressors. A novel casing treatment which consists of a backchamber and a perforated plate is suggested, and it is noted that the open area ratio of the casing treatment is less than 10%, and is far smaller than conventional casing treatment with open area ratio of over 50%, which could result in stall margin improvement without obvious efficiency loss of fan/compressors.     

星上控制力矩陀螺群隔振平台的动力学特性

为能够给星上有效载荷提供一种超静环境,提出一种星上控制力矩陀螺群(CMGs,Control Moment Gyroscopes)的隔振方案,并对所使用的隔振平台的动力学特性进行研究分析.首先介绍了不同参数模型的隔振元件工作原理和参数特性;其次利用牛顿-欧拉法对含有隔振平台和CMGs的卫星进行动力学建模;最后通过频域和时域的方法分析并对比了各个参数模型下的隔振平台力衰减特性以及对星体姿态稳定度的改善程度.结果表明:两参数加调谐质量阻尼器模型下的隔振平台对共振峰值有一定的衰减作用,三参数模型下的隔振平台在力衰减和对姿态稳定度的改善程度上要明显优于其他2种模型.     

Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas–liquid transfer in microgravity conditions

In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas–liquid transfer with, for instance, the necessity to provide CO₂ (carbon source, pH control) and to recover the evolved O₂ in photobioreactors used as atmosphere bioregenerative systems.     

旋转激光陀螺惯导系统误差传播特性分析

设计旋转式惯导系统(INS, Inertial Navigation System)最重要的工作是理清旋转调制误差自动补偿机理、掌握补偿前后误差的传播特性,在此基础上设计合理的转位方案,并对其进行仿真和试验验证.结合单轴旋转式惯导系统工作原理和误差传播方程,解释了旋转调制误差自动补偿的机理,利用理论和仿真两种手段分析了单轴旋转惯导系统中惯性元件常值误差、随机误差、标度因数误差和安装误差的传播特性,得到了旋转调制对惯性器件误差的调制效果,验证了单轴正反转停方案的有效性和应用的合理性.研究结果为旋转式激光陀螺(LG, Laser Gyroscope)惯导系统的设计提供了理论参考和设计依据.