Transforming solar system exploration: The origins of the Discovery Program, 1989–1993

The Discovery Program is a rarity in the history of NASA solar system exploration: a reform program that has survived and continued to be influential. This article examines its emergence between 1989 and 1993, largely as the result of the intervention of two people: Stamatios “Tom” Krimigis of the Johns Hopkins University Applied Physics Laboratory (APL), and Wesley Huntress of NASA, who was Division Director of Solar System Exploration 1990–92 and the Associate Administrator for Space Science 1992–98. Krimigis drew on his leadership experience in the space physics community and his knowledge of its Explorer program to propose that it was possible to create new missions to the inner solar system for a fraction of the existing costs. He continued to push that idea for the next two years, but it took the influence of Huntress at NASA Headquarters to push it on to the agenda. Huntress explicitly decided to use APL to force change on the Jet Propulsion Laboratory and the planetary science community. He succeeded in moving the JPL Mars Pathfinder and APL Near Earth Asteroid Rendezvous (NEAR) mission proposals forward as the opening missions for Discovery. But it took Krimigis's political skill and access to Sen. Barbara Mikulski in 1993 to get the NEAR into the NASA budget, thereby likely ensuring that Discovery would not become another one-mission program.     

辅助空间遥操作的虚拟管道设计与实现

针对复杂空间环境下进行遥操作的安全性问题,提出一种基于路径点的光滑虚拟管道快速生成算法,改进深度优先算法对虚拟管道进行静态规划,并给出动态修正算法,实现管道的动、静态避障。虚拟管道可为操作者提供视觉、触觉等反馈信息以调整自身操作。操作对象在管道内运动,能安全、快速地达到目标。相对于路径规划方式按指定轨迹避障,该方法提高了操作灵活性和效率。在CHAI 3D仿真平台下进行多组避障实验,验证了算法的有效性。     

Designing method of acceleration and deceleration control schedule for variable cycle engine

Studies show that different geometries of a Variable Cycle Engine (VCE) can be adjusted during the transient stage of the engine operation to improve the engine performance. However, this improvement increases the complexity of the acceleration and deceleration control schedule. In order to resolve this problem, the Transient-state Reverse Method (TRM) is established in the present study based on the Steady-state Reverse Method (SRM) and the Virtual Power Extraction Method (VPEM). The state factors in the component-based engine performance models are replaced by variable geometry parameters to establish the TRM for a double bypass VCE. Obtained results are compared with the conventional component-based model from different aspects, including the accuracy and the convergence rate. The TRM is then employed to optimize the control schedule of a VCE. Obtained results show that the accuracy and the convergence rate of the proposed method are consistent with that of the conventional model. On the other hand, it is found that the new-model-optimized control schedules reduce the acceleration and deceleration time by 45% and 54%, respectively. Meanwhile, the surge margin of compressors, fuel–air ratio and the turbine inlet temperature maintained are within the acceptable criteria. It is concluded that the proposed TRM is a powerful method to design the acceleration and deceleration control schedule of the VCE.     

A novel virtual material layer model for predicting natural frequencies of composite bolted joints

A novel virtual material layer model based on the fractal theory was proposed to predict the natural frequencies of carbon fiber reinforced plastic composite bolted joints. Rough contact surfaces of composite bolted joints are modeled with this new proposed approach. Numerical and experimental modal analyses were conducted to validate the effectiveness of the proposed model. A good consistence is noted between the numerical and experimental results. To demonstrate the necessity of accurately modeling the rough contact surfaces in the prediction of natural frequencies, virtual material layer model was compared with the widely used traditional model based on the Master-Slave contact algorithm and experiments, respectively. Results show that the proposed model has a better agreement with experiments than the widely used traditional model (the prediction accuracy is raised by 8.77% when the pre-tightening torque is 0.5 N∙m). Real contact area ratio A* of three different virtual material layers were calculated. Value of A* were discussed with dimensionless load P*, fractal dimension D and fractal roughness G. This work provides a new efficient way for accurately modeling the rough contact surfaces and predicting the natural frequencies of composite bolted joints, which can be used to help engineers in the dynamic design of composite materials.     

基于Creator和Vega的SAR成像仿真研究

以虚拟现实技术为背景,使用软件平台Visual C＋＋、Multigen Creator和Vega,设计实现了合成孔径雷达（SAR）实时成像仿真系统。文章介绍了SAR成像原理,论述了使用虚拟现实技术设计雷达仿真系统的流程及关键技术,并给出了实际仿真效果。仿真结果表明,该系统能够较好地模拟各种参数下的SAR成像,对雷达系统仿真评估有一定的辅助作用。     

级间开缝间隙传感器动态测试方法研究

针对某型号分离面间隙传感器的测试要求,提出了一种间隙位移传感器的动态测试方案,设计了测量系统,通过激光测试法测量并记录级间开缝间隙传感器CI1-27在自由弹出状态下的输出响应。经应用,该方法操作便捷,数据可靠,为间隙传感器的动态测试提供了一种新的参考。     

小区管道工程的施工管理与组织

小区管道工程在施工过程中受天气和其它工种材料、设备运输的影响比较大,给施工、施工管理和施工组织带来不便。施工过程中要根据施工内容的具体情况制定有效的管理措施和组织方法,在保证施工的质量、安全和进度的前提下,提高施工效益。     

基于虚拟仪器的便携式舰载导弹舰面测试监控系统设计

为实现舰载导弹弹舰协同作业时协同信号的在线监控，设计了一种便携式舰载导弹舰面测试系统。系统的总体设计方案采用虚拟仪器的思想，硬件设计选用PXI架构，软件设计采用层次化结构，并使用数据库技术对数据进行统一管理。系统功能强大、结构合理，且具有很强的可扩展性。     

维修人为差错控制方法探讨

利用类似MSG-3的逻辑、分类方法,借鉴风险评估的思想构建人为差错控制模型。根据人为差错基本理论以及维修管理经验,通过减少维修机构工作载荷及维修机构人为差错概率,构建“维修机构人为差错控制框图”和方法。结果证明,本文建立的模型（方法）基本覆盖了一般维修单位的人为差错控制环节,并具有系统性、预前性、持续性,在笔者所在的维修单位应用良好。     

AOS虚拟信道链路控制器和VCDU合路器的设计实现

在深入研究高级在轨系统(AOS)标准和对星载数据系统进行分析的基础上,设计实现了AOS虚拟信道链路控制器和虚拟信道数据单元(VCDU)合路器。该设计采用现场可编程门阵列(FPGA)实现高级在轨系统虚拟信道链路控制(VCLC)子层的位流业务和虚拟信道存取(VCA)子层的VCA业务,完成了位流协议数据单元(B_PDU)的构造,VCDU的组装、调度、填充和定界等功能,实现了对整星数据流的统一管理。在卫星的星载数据系统设计中,将有效载荷数据和航天器平台数据合一,形成统一数据流,可以节约频率资源,支持宽带数据传输、实现整星数据流的统一管理,使整个系统更灵活、更开放、更有效,提高卫星的自主管理能力。