Ares V launch vehicle: An enabling capability for future space science missions

NASA's planned Ares V cargo launch vehicle offers the potential to completely change the paradigm of future space science mission architectures. Future space science telescopes desire increasingly larger telescope collecting aperture. But, current launch vehicle mass and volume constraints are a severe limit. The Ares V greatly relaxes these constraints. For example, while current launch vehicles have the ability to place a 4.5 m diameter payload with a mass of 9400 kg on to a Sun-Earth L2 transfer trajectory, the Ares V is projected to have the ability to place an 8.8 m diameter payload with a mass of approximately 60,000 kg on to the same trajectory, or 180,000 kg into Low Earth Orbit. Also the Ares V could place approximately 3000 kg (13,000 kg with a Centaur upper stage) on to a trajectory with a C3 of 106 km²/s², arriving at Saturn in 6.1 years without the use of gravity assists. This paper summarizes the current planned Ares V payload launch capability.     

Numerical analysis of broadband noise reduction with wavy leading edge

Large Eddy Simulation(LES) is performed to investigate the airfoil broadband noise reduction with wavy leading edge under anisotropic incoming turbulence. The anisotropic incoming turbulence is generated by a rod with a diameter of 10 mm. The incoming flow velocity is 40 m/s and the corresponding Reynolds numbers based on airfoil chord and rod diameter are about 397000 and 26000, respectively. The far-field acoustic field is predicted using an acoustic analogy method which has been validated by the experiment. A straight leading edge airfoil and a wavy leading edge airfoil are simulated. The results show that wavy leading edge increases the airfoil lift and drag whereas the lift and drag fluctuations are substantially reduced. In addition, wavy leading edge can significantly change the flow pattern around the leading edge and a pair of counter-rotating streamwise vortices stemming from each wavy leading edge peak are observed.An averaged noise reduction of 9.5 dB is observed with the wavy leading edge at the azimuthal angle of 90°. Moreover, the wavy leading edge can mitigate noise radiation at all the azimuthal angles without significantly changing the noise directivity. The underlying noise reduction mechanisms are then analyzed in detail.     

Very large space structures: Non-linear control and robustness to structural uncertainties

Very Large Space Structures (VLSS) are challenging systems to be controlled, due to their high flexibility. In particular, rapid attitude maneuvers can determine great oscillations on the flexible elements of a spacecraft (solar wings, antennas, booms). On account of this, in the last decades many researchers have developed different strategies to effectively damp the elastic vibrations by means of active vibration devices (such as piezo-electric patches) or by means of robust control algorithms. The approach suggested in this paper is different, since neither additional devices nor complex control laws are introduced. In fact, the complete model of the system (including rigid, elastic and orbital dynamics, coupled with control actions) is controlled by the non-linear attitude controller named state dependent Riccati equation, which will be based on a simplified version of the spacecraft model. The task to reduce the mutual interaction between rigid attitude and flexible dynamics is entirely transferred to a modification of the desired trajectory that must be tracked. This command shaping technique is based on the knowledge of the parameters (inertial and elastics) of the VLSS. Unfortunately these parameters are not always exactly known and, however, they may change over the time. On account of this a Monte Carlo analysis has been also performed, showing the robustness of the proposed control strategy to the structural uncertainties. The numerical simulations prove that this strategy, based on the joint application of two well-known yet simple techniques, produces accurate and robust results.     

一种基于三维到达角的无偏伪线性卡尔曼滤波

为了解决大场景下基于三维到达角的目标跟踪问题，提出了一种具有无偏性的伪线性卡尔曼滤波。首先，基于三维到达角信息对目标运动模型与量测模型进行建模；之后，对量测模型进行了伪线性化处理，得到了线性形式的目标量测模型。为了解决伪线性卡尔曼滤波存在的有偏性问题，提出了一种结合EKF（extend Kalman filter）的三维伪线性无偏卡尔曼滤波。仿真实验表明，该模型能够对非机动目标与机动目标有效跟踪，对于百公里级别的目标，当角测量误差从0.1°变化到0.5°，算法在仿真时间结束时均能将绝对位置误差降低至10 km以内，且算法的运行速度与EKF为同一个量级，同时兼顾了抗干扰能力、定位跟踪精度、运行效率的要求，能够为大场景下的目标跟踪提供有效方法。     

射频识别卡读写模块的设计

射频识别卡读写模块是射频卡读写器的核心.根据ISO14443协议,运用现代通信与信号处理的方法,采用最新的RISC指令单片机,设计了射频识别卡的读写模块.该模块没有使用专用的硬件ASIC和功率放大管,纯粹采用软件实现了硬件ASIC的功能.同时它性能稳定、价格低廉,对卡的读写距离在0~10cm.      

大尺度空气舵超声速烧蚀热结构试验

针对全尺寸大尺度空气舵热环境参数,对地面试验的流场参数进行了计算,设计了测试探头,进行了流场校测。将校测结果与计算结果进行了比较分析,结果表明二者吻合较好,最大偏差在30%以内。校测后的流场已成功应用于试验。     

An introduction of mountain-based GPS radio occultation experiments in China

The mountain-based GPS radio occultation is a novel approach to lower atmospheric profiling. The experiments of the mountain-based GPS radio occultation were conducted on the top of Mt. Yaogu (29.38°N, 113.68°E, ∼1240 m) on December 17, 2003, and on the top of Mt. Jiugong (29.39°N, 114.65°E, ∼1550 m) on July 24, 2004. Based on these observation data, the scientific data processing software has been developed and is used to retrieve successfully the atmospheric refractivity profiles. The validation experiment was performed on the top of Mt. Wuling (40.60°N, 117.48°E, ∼2118 m) during August 1–29, 2005. Collocated automatic weather station and the radiosondes nearby were operated simultaneously for the comparison campaign. Results show that the radio occultation technique obtained about 40 profiles every day with the receiver antenna pointing to the south. Comparisons show that the refractivity measured by occultation agree well with those by the radiosondes, but not well with those by the automatic weather station due to their much different geographic locations of measurements. Results of these experiments suggest that the mountain-based GPS radio occultation is an economic reliable novel technique monitoring temporal and spatial variations of local lower atmospheric environments.     

一种新颖的RFID多标签防碰撞算法

在标签运动较规律的无线射频识别(RFID, Radio Frequency Identification)系统中,读写器按照一般的算法不会优先读取即将离开可读范围的标签,而使系统出现较高的漏读率.针对这种场景,提出一种新的防碰撞算法——先到先服务 (FCFS, First Come First Served) 算法.读写器首先按照到达顺序对标签进行分组,先识别紧迫性高的时间分组标签;其次,算法通过新增一个参数有效避免了一些可预测的碰撞时隙.在识别时间分组的过程中设置了总时隙的上限,从而避免系统阻塞.仿真结果表明,在保持漏读率小于0.01的情况下,系统所能承受的标签运动速度比前缀随机化算法提高了50%.当标签到达率为0.45时,系统的通过率改善最明显,比前缀随机化算法提高了13%左右.      

复杂环境下的A/C模式信号处理算法及其实现

本文基于软件无线电的思想,提出一种复杂环境下的A/C模式信号处理算法,该算法从脉冲识别,A/C模式框架判决以及信息代码提取三个方面进行了研究,在识别多目标混叠、拒绝目标幻影,避免异步串扰方面,达到了较好的效果,并在FPGA上实现了该算法.     

短波电台主控制器单元的研究与发展

介绍了短波电台中主控制器单元的发展过程及相应的技术实现,研究了相关软硬件技术,提出了研制主控制器单元的一种新思路。