超级军网转帖[大翻吐血]澳洲军事专家库珀：成都歼20原型机隐身性 ...
来源：百度文库 编辑：超级军网 时间：2024/04/30 11:17:09
支持原创翻译 可以访问 [大翻吐血]澳洲军事专家库珀：成都歼20原型机隐身性能初步评估（上）
http://www.ltaaa.com/bbs/forum.php?mod=viewthread&tid=7857&fromuid=844
本文是由澳大利亚军事专家卡罗·库珀和迈克尔·佩洛西联合撰写的一篇关于歼20隐身性能的初步评估的军事技术论文。由于篇幅过大，译者分上下两篇发表。上篇主要介绍了歼20的外形特点和隐形飞机的一些基本知识，包括隐身材料，并提出了估算RCS的方法。下篇将会进行具体的实验过程和图表分析，以及对歼20隐身性能的数值结果，并做以总结。附录部分没有进行翻译，其中的一些专业术语、理论、概念等均在译文中夹杂介绍。
鉴于译者在此之前对于航空航天及相关学科基本一窍不通，花费两周时间一边查资料一边完成翻译。文中对于一些常识的解释，一方面对外行们进行科普，另一方面也算自己的理解，希望懂行的大牛们勿嫌繁琐。另外还有一些艰深难懂的理论，译者也做了尝试性地解读，为了不影响篇幅，省略了大量的演算公式，只说结论，目的在于把原文所提到的每个参数的意义告诉读者。囿于译者能力所限，对于翻译错误或不准确的地方，欢迎提出批评，定会在第一时间予以修正，还望大家不吝赐教。
原文：http://www.ausairpower.net/APA-2011-03.html
译者：病中乃知
A Preliminary Assessment of Specular Radar Cross Section Performance in the Chengdu J-20 Prototype
成都歼20原型机隐身性能初步评估
Air Power Australia Analysis 2011-03
4th July 2011
A Monograph by
Dr Michael J Pelosi, MBA, MPA,
Dr Carlo Kopp, SMAIAA, SMIEEE, PEng
Text, computer graphics © 2011 Michael Pelosi, © 2011 Carlo Kopp
澳大利亚空中力量分析 2011-3
2011年7月4日
论文由
迈克尔·J·佩洛西 博士/MBA/MPA
卡罗·库珀 博士/MSAIAA/SMIEEE/PEng
文字，电脑绘图©2011 迈克尔·佩洛西，© 2011 卡罗·库珀
半小时前 上传下载附件 (824.05 KB)
First public flight of the Chengdu J-20 prototype, 11th January, 2011 . The shaping design of the J-20 presents no fundamental obstacles to its development into a genuine Very Low Observable design (Chinese Internet).
2011年1月11日，成都歼20原型机首次公开试飞。歼20的造型设计表明，不会对其改进型的超低可探测性（简称VLO，也就是隐身技术Stealth Technology）。设计造成实质影响。
--------------------------------------------------------------------------------------------------------------------------------------------------
Abstract
摘要
--------------------------------------------------------------------------------------------------------------------------------------------------
This study has explored the specular Radar Cross Section of the Chengdu J-20 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe. In addition, the performance of a range of Chinese developed radar absorbers was modelled, based on a reasonable survey of unclassified Chinese research publications in the area. None of the surveyed materials were found to be suitable for use as impedance matched specular radar absorbers. Modelling has determined, that if the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector. Conversely, if the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector. This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.
本课题探讨了成都歼20原型机隐身性能的造型设计，运用物理光学仿真算法在没有隐形涂层情况下分别进行了频率为150兆赫兹、600兆赫兹、1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹、16.0千兆赫兹和28千兆赫兹的模拟，以及在敷设了隐身涂层的情况下，进行了频率为1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹和16.0千兆赫兹的模拟，覆盖了整个机身的角度位面。此外，中国研制的雷达吸波材料的一系列性能已经建模，基于一份非机密的中国该领域研究发行的调查报告。调查表明，材料不适合作为匹配镜面雷达吸收剂的阻抗。在模型已经确定的情况下，如果歼20的生产保留轴对称喷口和符合面积律的平滑截面，飞机最多只能为机头部分提供强劲的超低可探测性能。反之，如果歼20的生产引进矩面喷口设计，改进侧面机身造型，强劲的超低可探测性能将会在S波段及以上范围展现出巨大的潜力，机头部分和机尾以及侧向也会有良好的性能。本课题是通过物理光学模拟穿越九个无线电波段，在歼20原型机的外形设计不存在根本缺陷的情况下，确保改进型达到真正的超低可探测设计。
注释：Radar Cross Section（RCS），雷达散射截面是目标的一种折算面积，用来度量在雷达波照射下所产生的回波强度大小。RCS越小，说明反射越小，越不容易被发现，从而达到“隐身”的效果。RCS减缩有两种途径：一种是外形隐身，通过改变机身造型，把雷达波反射到雷达无法接收的方向上；一种是材料隐身，通过对机身敷设吸波涂层，把雷达波的能量损耗掉。通常外形隐身占到整个RCS减缩的90%左右，也就是说，衡量一架飞机隐身性能的优劣，主要看造型设计是否合理。同时，造型设计关乎到飞机的气动布局，所以如何兼顾隐身和气动的性能，成为了隐身设计的一大课题。
阻抗匹配：当飞行器受到雷达波的照射时，飞行器本身将产生一个散射场，如果雷达吸波材料的阻抗负载合适，则可以使阻抗产生的电磁场与飞行器产生的散射场的场强矢量振幅相当，相位相反，从而相互干涉，使两个场的合成场强减弱，降低飞机的RCS。
·Introduction
·J-20 Prototype Very Low Observable Airframe Shaping Design Features
Chinese Absorbent Materials Technology
·Radar Cross Section Simulation Method / Simulator Design and Capabilities
Aircraft Model Features and Limitations
What the Simulation Does Not Demonstrate
What the Simulation Does Demonstrate
·Specular Radar Cross Section Simulation Results
Analysis of Shape Related Specular Radar Cross Section
Analysis of Specular RCS with a Representative RAM Coating
·Conclusions
·Endnotes, References and Bibliography:
·Annex A Scales, Bands, Geometries, and Representative Threats
·Annex B Basic Concepts in Absorbent Coatings Technology
·Annex C Axisymmetric Nozzle RCS Performance
·Annex D Viewing RCS Plots
·Annex E Glossary of Terms
·介绍
·歼20原型机超低可探测机身外形设计特点
中国的吸波材料技术
·RCS的模拟方法/模拟设计和功能
飞机模型的特点和局限性
什么是非论证模拟
什么是论证模拟
·镜面RCS的模拟结果
外形RCS的相关分析
涂抹典型雷达吸波材料的隐身性能分析
·结论
·附注、参考文献和参考书目：
·附录一 减缩、波段、几何和典型威胁
·附录二 吸收材料技术的基本概念
·附录三 轴对称喷口的隐身性能
·附录四 查看RCS图解
·附录五 术语
--------------------------------------------------------------------------------------------------------------------------------------------------
Introduction
介绍
--------------------------------------------------------------------------------------------------------------------------------------------------
There has been extensive media speculation about the Radar Cross Section [RCS] of the J-20 stealth fighter, since the PLA-AF first exposed the prototype to the public in late December, 2010. Sadly much of this speculation has no valid scientific basis, yet appears to be regarded seriously enough to have influenced public statements by numerous senior officials in Western defence departments.
自从2010年12月份中国空军首次公开透露了原型机以来，很多媒体都在猜测歼20隐形战斗机的RCS。这种猜测虽然没有科学依据，却似乎被认为是一份足以影响到许多西方国防部门高级官员的公开声明。
Performing a full assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft is not a trivial task, as due consideration needs to be given to all major and minor RCS contributors in the design.
进行任何低可探测（LO / -10到-30 dBSM，参见 表格A.1） 或者超低可探测（VLO / -30到-40 dBSM，参见 表格A.1）飞机的全面评估不是一项简单的任务，需要考虑到设计之中所有主要和次要的RCS贡献。
注释：RCS用σ（Sigma）表示，常用单位为㎡（平方米）或dBSM（分贝平方米），公式为σ=4π *（目标处单位立体角内的散射功率/目标处单位面积上的入射功率），两个单位之间的转换关系是：1000㎡=30dbsm，100㎡=20dbsm，10㎡=10dbsm，1㎡=0dbsm，0.1㎡=-10dbsm，0.01㎡=-20dbsm，也就是说，如果RCS的值是0分贝，那么目标的有效照射面积便是1平方米。（显然，目标的真实面积肯定比1平方米大的多）RCS的“贡献”越大，其值越高。
Moreover, such an assessment, if it is to be useful, must consider the RCS from a range of different angular aspects, this encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].
另外，要使评估有效，必须考虑一系列不同角度位面的隐身效果，包括旨在挫败LO/VLO设计的地面和空中威胁系统在各个方位面以及俯仰角的典型特征。（参见 图表A.3和A.4）（威胁系统指能够搜索、捕获、攻击飞机的雷达、导弹等军事设施）
The assessment of RCS must also be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].
对RCS的评估也必须建立在旨在挫败LO/VLO设计的地面和空中威胁系统的工作波长典型特征之下。（参见 表格A.2）
注释：RCS的大小取决于：目标的物理特性（电特性）、目标的几何特性、目标被雷达波照射的方位、入射波的波长、入射场极化方式和接受天线的极化方式。这里先谈谈几何形状对RCS的影响。1、角反射器：雷达波会在两三个平面相交构成的尖锐折角上折射放大，产生很强的回波信号，尤其是正交直角。2、凹腔效应：雷达波在凹腔内经过多次反射、叠加放大之后返回雷达。3、平行原则：对飞机上的边缘进行平行设计，从而将照射的雷达波集中反射到雷达接收不到的方向。（下文中提到的回波的主瓣和副瓣，就是指把电磁波集中反射的几个方向）4、隐藏强散射源：比如弹仓内挂武器或者S型进气道设计，防止雷达波直接照射发动机叶片。5、用一个部件遮挡住另一个强散射部件，比如背负式进气道（进气道在机身上方）或者用垂尾来遮挡尾喷口。6、结构细节处理：包括对铆钉、台阶等处理，防止次级散射；以及把舱门盖口的边缘和缝隙设计成锯齿形状，这样一来可以加剧散射，降低回波方向的强度。
Definitions of these and other terms employed in this document are summarised in Annex E. Reference data for RCS scales, radio-frequency bands, engagement geometries, and representative threat systems are summarised in Annex A.
这些定义和文章中引用的其它术语见附录E。参考资料来源于RCS减缩、无线电波段、接触几何和典型威胁系统见附录A。
If the RCS assessment does not consider angular and wavelength dependencies properly, it will be almost meaningless, in terms of providing a means of determining or estimating the survivability of the LO/VLO design. The common practice of providing a single RCS value for a single aspect at a single frequency yields little information about the actual effectiveness of the design. Such a single point figure permits at best a detection range estimate for a known radar operating at the specified wavelength and aspect.
如果RCS评估不考虑角度和波长的适当关联，只是按照某种方法来确定或估算LO/VLO设计的生存能力，这是毫无意义的。通常在单一频率下的单个面给定一个单一的RCS值，几乎不能印证真实的设计效果。这种单个点阵图所表示的最大范围只是一个已知雷达在规定波长和位面的探测距离。
The PLA's J-20 prototype is an important development in terms of grand strategy, as well as technological strategy, and basic technology. It shows that PLA thinking at the strategic level is focussed on defeating opposing IADS [Integrated Air Defence System] and fighter forces. In the domain of technological strategy, it shows a robust grasp of the limitations of Western technology deployed in Asia. In terms of basic technology, it shows that China's academic research and industrial base has mastered advanced LO/VLO shaping techniques.
解放军的歼20原型机是国家战略、科技战略和基础技术方面的重大进步。这表明了解放军在战略层面的考量已经对准了挫败IADS（综合防空系统）和空军力量。在科技战略领域，表明了PLA强有力地抓住了西方科技在亚洲部署的局限性。在基础技术方面，表明了中国的学术研究和工业基地已经掌握了先进的LO/VLO成形技术。
The intent of this study is to perform a preliminary assessment of the RCS of the J-20 prototype, to establish the potential of the aircraft to be fully developed as an LO/VLO combat asset.
本课题的目的是对歼20原型机的RCS进行初步评估，以确定飞机是否具有成为最先进的低可探测/超低可探测战斗王牌的潜能。
The assessment cannot be more than preliminary for a number of good reasons:
1. The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve
aerodynamic performance, operational characteristics, and LO/VLO performance;
2. The state of Chinese Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent
coatings technology is not well understood in the West;
3. The state of Chinese technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well
understood in the West;
4. The state of Chinese technologies for RCS flare spot reduction, in areas such as navigation/communications antennas,
seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
评估只能是最低级别的几个理由：
1、最终机身造型仍然未知，研发环节可能出现变数，进一步提高空气动力性能、操作特点和LO/VLO性能；
2、西方并不十分清楚中国的雷达吸波材料（RAM），雷达吸波结构（RAS）和雷达吸波涂层技术。
3、西方并不十分清楚中国的传感器（雷达、光电、被动射频）孔径的结构模式和RCS减缩技术。
4、西方并不十分清楚中国的RCS光斑减缩技术，还有导航/通信天线、封条、面板连接、排水孔、散热孔和紧固件等。
注释：雷达吸波材料（RAM）是照射到飞机上的电磁能量被吸收并转化为热能，使反射出去的电波能量越少越好。雷达吸波材料分为涂敷型吸波材料与结构型吸波材料两种。雷达吸波结构（RAS）是一种结合飞机外形的曲面和部位，由RAM、透波材料及其它材料构成独特的吸波-承载复合结构。也就是说，一部分复合材料既可以起到吸波的作用，又可以充当承载和减重的作用。
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these
categories.The relative importance of the respective categories should be discussed.
在所有类别中，使其具有RCS特性的设计，是为了达到可靠的LO/VLO性能。我们要讨论的是相对重要的分类。
Sound airframe shaping is a necessary prerequisite for good LO or VLO performance. If shaping is poor, no amount of credible materials application and detail flare spot reduction will overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be unattainable.
合理的机身造型是良好的LO/VLO性能的先决条件。如果造型很差，即便使用再可靠的材料和细微光斑减缩，也无法比拟机身外形对于减少RCS的贡献。
If airframe shaping is sound, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reductions techniques will yield a VLO design.
如果机身造型合理，只要谨慎地使用雷达吸波材料（RAM）、雷达吸波结构、雷达吸波涂层、孔径RCS减缩和较为次要的光斑减缩技术，就会凸显超低可探测设计。
As a result, modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect.
因此，与外形建模有关的任何VLO设计对于RCS贡献都具有非常高的价值，因为这不仅决定了飞机是否能达到可靠的隐身性能，同时也会使设计师致力于研究RAS、RAM和涂层的应用所产生的效果。
This paper will focus mostly on shape related RCS contributions, due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures. Some tentative modelling of published Chinese RAM coatings will be performed.
本文将重点关注与外形相关的RCS贡献，对RAS、RAM、涂料、孔径RCS减缩和次要的光斑减缩等未知技术性能进行估算时，其固有的不确定因素是无法避免的。在适当情形下，合理的假设可以推算出RCS减缩措施相关的吸波材料的性能。同时，对一些中国已公开的RAM涂料的实验性模拟也会展开。
--------------------------------------------------------------------------------------------------------------------------------------------------
J-20 Prototype Very Low Observable Airframe Shaping Design Features
歼20原型机超低可探测机身造型设计特点
--------------------------------------------------------------------------------------------------------------------------------------------------
The J-20 prototype designs displays a number of VLO design features, generally based on design rules developed for and employed in the construction of United States VLO combat aircraft. These display a good theoretical and practical understanding of the VLO design rules developed by US researchers in industry and US government research laboratories, between 1975 and 2000.
歼20原型机的设计显示了一些VLO的设计特点，在常规设计规则的基础上进行开发，同时借鉴了美国VLO战斗机的制造工艺。这些表明了对VLO设计规则有着良好的理论和实践中的理解，VLO设计规则是在1975年至2000年，由美国行业研究和美国政府研究实验室开发而成的。
Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States' F-35 Joint Strike Fighter.
总的来说，歼20原型机的隐身造型设计无疑大大优于俄罗斯的T-50五代机，甚至是美国计划投产的F35联合攻击战斗机。
The J-20 design appears to be mostly constructed around the stealth shaping design rules employed in the US Air Force F-22A Raptor:
歼20的设计似乎大多都是围绕美国空军的F22的隐形造型设计规则：
1.The chined J-20 nose section and canopy are close in appearance to the F-22, yielding similar specular RCS performance in a mature design.
1、歼20的机头部分和座舱罩和F22的外观接近，设计十分成熟，所以二者的隐身性能十分接近。
注释：飞机各个部位的主要散射源和散射机理。头向——座舱、雷达舱和进气道的凹腔效应；正侧向——机身与垂尾的镜面反射、机翼与机身以及平尾与垂尾的角反射；后向——喷口的凹腔效应；斜侧向——机翼和平尾前后缘的边缘绕射；其它——外挂物散射、缝隙绕射、尖点绕射、表面波绕射等。
歼20机头部分的RCS减缩。其中，座舱罩采取了金属镀膜处理技术（光电设计），既遮挡住了雷达波，同时又不会影响可见光的照射，为飞行员提供了良好的视野。而进气道的入口斜切并设计成S型进气道，不会使雷达波直接照射到发动机叶片而产生强烈的散射源；同时内壁敷设吸波材料，雷达波在进气道来回反弹吸波，损耗功率。
2.The J-20 trapezoidal edge aligned engine inlets are closest to the F-22, though they appear to be larger and employ an F-35 style DSI (Diverterless Supersonic Inlet) design, obviously intended to improve on F-22 inlet leading edge signature.
2、歼20梯形进气口的对齐方式与F22十分接近，但他们似乎更多地采用了F35的DSI（无附面层隔道超音速进气道 ）设计风格，显然他们打算改进F22的进气口边缘的信号特征。
3.The J-20 wing fuselage join, critical for beam and all aspect stealth, is in shaping and angle very similar to the F-22, and clearly superior to both the T-50 PAK-FA prototypes and the F-35 Joint Strike Fighter.
3、歼20的翼身融合在造型和角度上都与F22十分类似，对侧向和全向的隐身起到了重要作用，明显优于T50五代机和F35联合攻击战斗机。
注释：翼身融合，机翼和机身结合处的外形，无论取纵向截面或横向截面，其轮廓线都是连续曲线。消除了垂直侧面机身与机翼的角反射器效应。
4.The J-20 flat lower fuselage is optimal for all aspect wideband stealth, and emulates the F-22 design closely. It can produce a significant ground bounce return in some geometries, especially at lower altitudes, or angles approaching the normal.
4、歼20平滑的机身底部很好地模仿了F22的设计，是全频隐身的最佳选择。在一些地方，尤其是低空和靠近法线的角度，可以产生明显的地面反弹。
5.Planform alignment of the J-20 shows exact angular alignment between canard and delta leading edges, and exact crossed (starboard to port, port to starboard) angular edge alignment between canard and delta trailing edges. Leading edge sweep is ~43°, clearly intended for efficient supersonic flight.
5、歼20的平面对齐方式显示，鸭翼和三角翼的前缘对齐，鸭翼和三角翼对侧（右舷对左舷，左舷对右舷）后缘对齐。前缘后掠角约43度，显然倾向于超音速飞行。
注释：鸭式布局，是一种非常适于超音速空战的气动布局，座舱两侧有两个较小的三角翼（鸭翼），后边是一个较大的三角翼（主翼）。鸭式布局的优点是通过较小的鸭翼达到与水平尾翼同样的操纵效能，增强了低空的机动性。缺点是鸭翼一旦转动，角度就会变化，从而影响隐身效果。歼20的鸭翼采用隐身涂料和吸波/透波复合材料，估计对RCS的影响不会很大。
6.The J-20 nose and main undercarriage, and cheek weapon bay doors employ C-band through Ku-band optimised edge serration technology, based on F-117A and F-22 design rules.
6、歼20的机头、主起落架和两侧武器舱门采取了C波段到Ku波段的边缘锯齿优化技术，设计规则来自F117和F22。
7.The aft fuselage, tailbooms, fins/strakes and axi-symmetric nozzles are not compatible with high stealth performance, but may only be stop-gap measures to expedite flight testing of a prototype. Performance is notably poorer in the H polarisation.
7、后机身、尾段、安定翼/边条和轴对称喷口的设计不利于隐身，但也可能是为了加快原型机飞行试验的权宜之计。特别是在电磁波的H方向的隐身性能较差。
8.The airframe configuration and aft fuselage shape would be compatible with an F-22A style 2D TVC nozzle design, or a non-TVC rectangular nozzle designed for controlled infrared emission patterns and radio-frequency stealth. Infrared signature will be influenced by other considerations, especially engine bypass ratio.
8、如果使用二维推力矢量喷口设计或非推力矢量抑制红外和无线电隐身的喷口设计，机身结构和后机身外形将会与F22风格一致。红外特征还取决于其它因素，尤其是发动机涵道比。
注释：涵道比（bypass ratio），即涡轮发动机外涵道与内涵道空气流量的比值。内涵道的空气流入燃烧室与燃料混合，燃烧做功，外涵道的空气不进入燃烧室，而是与内涵道流出的燃气相混合后排出。外涵道的空气只通过风扇，流速较慢，且是低温，内涵道排出的是高温燃气，两种气体混合后降低了流速与温度，能够降低噪声，增加推力。
9.The choice of all moving slab stabilators and canards will impact RCS at deflection angles away from the neutral position. If large control deflections are produced in flight regimes other than close combat manoeuvring, the specular RCS of the all moving slab controls would need to be considered.
9、全动平尾和前翼在偏转角远离中间时会对RCS造成影响。与近距离作战不同，一般飞行状态下的大幅度偏转对RCS造成的影响必须考虑在内。
A qualitative assessment of the J-20 prototype clearly shows that the design has the potential for VLO capability, certainly in the very important forward hemisphere.
歼20原型机的质量评定清晰地表明设计拥有潜在的VLO性能，特别是在非常重要的前方半球。
Available imagery from similar or identical aspects permits direct comparisons between the J-20 and the United States F-22A and F-35 designs.
下面用图片从相似或相同的角度对歼20和美国的F22、F35加以直观的比较。
传不了附件 可以去原帖看支持原创翻译 可以访问 [大翻吐血]澳洲军事专家库珀：成都歼20原型机隐身性能初步评估（上）
http://www.ltaaa.com/bbs/forum.php?mod=viewthread&tid=7857&fromuid=844
本文是由澳大利亚军事专家卡罗·库珀和迈克尔·佩洛西联合撰写的一篇关于歼20隐身性能的初步评估的军事技术论文。由于篇幅过大，译者分上下两篇发表。上篇主要介绍了歼20的外形特点和隐形飞机的一些基本知识，包括隐身材料，并提出了估算RCS的方法。下篇将会进行具体的实验过程和图表分析，以及对歼20隐身性能的数值结果，并做以总结。附录部分没有进行翻译，其中的一些专业术语、理论、概念等均在译文中夹杂介绍。
鉴于译者在此之前对于航空航天及相关学科基本一窍不通，花费两周时间一边查资料一边完成翻译。文中对于一些常识的解释，一方面对外行们进行科普，另一方面也算自己的理解，希望懂行的大牛们勿嫌繁琐。另外还有一些艰深难懂的理论，译者也做了尝试性地解读，为了不影响篇幅，省略了大量的演算公式，只说结论，目的在于把原文所提到的每个参数的意义告诉读者。囿于译者能力所限，对于翻译错误或不准确的地方，欢迎提出批评，定会在第一时间予以修正，还望大家不吝赐教。
原文：http://www.ausairpower.net/APA-2011-03.html
译者：病中乃知
A Preliminary Assessment of Specular Radar Cross Section Performance in the Chengdu J-20 Prototype
成都歼20原型机隐身性能初步评估
Air Power Australia Analysis 2011-03
4th July 2011
A Monograph by
Dr Michael J Pelosi, MBA, MPA,
Dr Carlo Kopp, SMAIAA, SMIEEE, PEng
Text, computer graphics © 2011 Michael Pelosi, © 2011 Carlo Kopp
澳大利亚空中力量分析 2011-3
2011年7月4日
论文由
迈克尔·J·佩洛西 博士/MBA/MPA
卡罗·库珀 博士/MSAIAA/SMIEEE/PEng
文字，电脑绘图©2011 迈克尔·佩洛西，© 2011 卡罗·库珀
半小时前 上传下载附件 (824.05 KB)
First public flight of the Chengdu J-20 prototype, 11th January, 2011 . The shaping design of the J-20 presents no fundamental obstacles to its development into a genuine Very Low Observable design (Chinese Internet).
2011年1月11日，成都歼20原型机首次公开试飞。歼20的造型设计表明，不会对其改进型的超低可探测性（简称VLO，也就是隐身技术Stealth Technology）。设计造成实质影响。
--------------------------------------------------------------------------------------------------------------------------------------------------
Abstract
摘要
--------------------------------------------------------------------------------------------------------------------------------------------------
This study has explored the specular Radar Cross Section of the Chengdu J-20 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe. In addition, the performance of a range of Chinese developed radar absorbers was modelled, based on a reasonable survey of unclassified Chinese research publications in the area. None of the surveyed materials were found to be suitable for use as impedance matched specular radar absorbers. Modelling has determined, that if the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector. Conversely, if the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector. This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.
本课题探讨了成都歼20原型机隐身性能的造型设计，运用物理光学仿真算法在没有隐形涂层情况下分别进行了频率为150兆赫兹、600兆赫兹、1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹、16.0千兆赫兹和28千兆赫兹的模拟，以及在敷设了隐身涂层的情况下，进行了频率为1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹和16.0千兆赫兹的模拟，覆盖了整个机身的角度位面。此外，中国研制的雷达吸波材料的一系列性能已经建模，基于一份非机密的中国该领域研究发行的调查报告。调查表明，材料不适合作为匹配镜面雷达吸收剂的阻抗。在模型已经确定的情况下，如果歼20的生产保留轴对称喷口和符合面积律的平滑截面，飞机最多只能为机头部分提供强劲的超低可探测性能。反之，如果歼20的生产引进矩面喷口设计，改进侧面机身造型，强劲的超低可探测性能将会在S波段及以上范围展现出巨大的潜力，机头部分和机尾以及侧向也会有良好的性能。本课题是通过物理光学模拟穿越九个无线电波段，在歼20原型机的外形设计不存在根本缺陷的情况下，确保改进型达到真正的超低可探测设计。
注释：Radar Cross Section（RCS），雷达散射截面是目标的一种折算面积，用来度量在雷达波照射下所产生的回波强度大小。RCS越小，说明反射越小，越不容易被发现，从而达到“隐身”的效果。RCS减缩有两种途径：一种是外形隐身，通过改变机身造型，把雷达波反射到雷达无法接收的方向上；一种是材料隐身，通过对机身敷设吸波涂层，把雷达波的能量损耗掉。通常外形隐身占到整个RCS减缩的90%左右，也就是说，衡量一架飞机隐身性能的优劣，主要看造型设计是否合理。同时，造型设计关乎到飞机的气动布局，所以如何兼顾隐身和气动的性能，成为了隐身设计的一大课题。
阻抗匹配：当飞行器受到雷达波的照射时，飞行器本身将产生一个散射场，如果雷达吸波材料的阻抗负载合适，则可以使阻抗产生的电磁场与飞行器产生的散射场的场强矢量振幅相当，相位相反，从而相互干涉，使两个场的合成场强减弱，降低飞机的RCS。
·Introduction
·J-20 Prototype Very Low Observable Airframe Shaping Design Features
Chinese Absorbent Materials Technology
·Radar Cross Section Simulation Method / Simulator Design and Capabilities
Aircraft Model Features and Limitations
What the Simulation Does Not Demonstrate
What the Simulation Does Demonstrate
·Specular Radar Cross Section Simulation Results
Analysis of Shape Related Specular Radar Cross Section
Analysis of Specular RCS with a Representative RAM Coating
·Conclusions
·Endnotes, References and Bibliography:
·Annex A Scales, Bands, Geometries, and Representative Threats
·Annex B Basic Concepts in Absorbent Coatings Technology
·Annex C Axisymmetric Nozzle RCS Performance
·Annex D Viewing RCS Plots
·Annex E Glossary of Terms
·介绍
·歼20原型机超低可探测机身外形设计特点
中国的吸波材料技术
·RCS的模拟方法/模拟设计和功能
飞机模型的特点和局限性
什么是非论证模拟
什么是论证模拟
·镜面RCS的模拟结果
外形RCS的相关分析
涂抹典型雷达吸波材料的隐身性能分析
·结论
·附注、参考文献和参考书目：
·附录一 减缩、波段、几何和典型威胁
·附录二 吸收材料技术的基本概念
·附录三 轴对称喷口的隐身性能
·附录四 查看RCS图解
·附录五 术语
--------------------------------------------------------------------------------------------------------------------------------------------------
Introduction
介绍
--------------------------------------------------------------------------------------------------------------------------------------------------
There has been extensive media speculation about the Radar Cross Section [RCS] of the J-20 stealth fighter, since the PLA-AF first exposed the prototype to the public in late December, 2010. Sadly much of this speculation has no valid scientific basis, yet appears to be regarded seriously enough to have influenced public statements by numerous senior officials in Western defence departments.
自从2010年12月份中国空军首次公开透露了原型机以来，很多媒体都在猜测歼20隐形战斗机的RCS。这种猜测虽然没有科学依据，却似乎被认为是一份足以影响到许多西方国防部门高级官员的公开声明。
Performing a full assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft is not a trivial task, as due consideration needs to be given to all major and minor RCS contributors in the design.
进行任何低可探测（LO / -10到-30 dBSM，参见 表格A.1） 或者超低可探测（VLO / -30到-40 dBSM，参见 表格A.1）飞机的全面评估不是一项简单的任务，需要考虑到设计之中所有主要和次要的RCS贡献。
注释：RCS用σ（Sigma）表示，常用单位为㎡（平方米）或dBSM（分贝平方米），公式为σ=4π *（目标处单位立体角内的散射功率/目标处单位面积上的入射功率），两个单位之间的转换关系是：1000㎡=30dbsm，100㎡=20dbsm，10㎡=10dbsm，1㎡=0dbsm，0.1㎡=-10dbsm，0.01㎡=-20dbsm，也就是说，如果RCS的值是0分贝，那么目标的有效照射面积便是1平方米。（显然，目标的真实面积肯定比1平方米大的多）RCS的“贡献”越大，其值越高。
Moreover, such an assessment, if it is to be useful, must consider the RCS from a range of different angular aspects, this encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].
另外，要使评估有效，必须考虑一系列不同角度位面的隐身效果，包括旨在挫败LO/VLO设计的地面和空中威胁系统在各个方位面以及俯仰角的典型特征。（参见 图表A.3和A.4）（威胁系统指能够搜索、捕获、攻击飞机的雷达、导弹等军事设施）
The assessment of RCS must also be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].
对RCS的评估也必须建立在旨在挫败LO/VLO设计的地面和空中威胁系统的工作波长典型特征之下。（参见 表格A.2）
注释：RCS的大小取决于：目标的物理特性（电特性）、目标的几何特性、目标被雷达波照射的方位、入射波的波长、入射场极化方式和接受天线的极化方式。这里先谈谈几何形状对RCS的影响。1、角反射器：雷达波会在两三个平面相交构成的尖锐折角上折射放大，产生很强的回波信号，尤其是正交直角。2、凹腔效应：雷达波在凹腔内经过多次反射、叠加放大之后返回雷达。3、平行原则：对飞机上的边缘进行平行设计，从而将照射的雷达波集中反射到雷达接收不到的方向。（下文中提到的回波的主瓣和副瓣，就是指把电磁波集中反射的几个方向）4、隐藏强散射源：比如弹仓内挂武器或者S型进气道设计，防止雷达波直接照射发动机叶片。5、用一个部件遮挡住另一个强散射部件，比如背负式进气道（进气道在机身上方）或者用垂尾来遮挡尾喷口。6、结构细节处理：包括对铆钉、台阶等处理，防止次级散射；以及把舱门盖口的边缘和缝隙设计成锯齿形状，这样一来可以加剧散射，降低回波方向的强度。
Definitions of these and other terms employed in this document are summarised in Annex E. Reference data for RCS scales, radio-frequency bands, engagement geometries, and representative threat systems are summarised in Annex A.
这些定义和文章中引用的其它术语见附录E。参考资料来源于RCS减缩、无线电波段、接触几何和典型威胁系统见附录A。
If the RCS assessment does not consider angular and wavelength dependencies properly, it will be almost meaningless, in terms of providing a means of determining or estimating the survivability of the LO/VLO design. The common practice of providing a single RCS value for a single aspect at a single frequency yields little information about the actual effectiveness of the design. Such a single point figure permits at best a detection range estimate for a known radar operating at the specified wavelength and aspect.
如果RCS评估不考虑角度和波长的适当关联，只是按照某种方法来确定或估算LO/VLO设计的生存能力，这是毫无意义的。通常在单一频率下的单个面给定一个单一的RCS值，几乎不能印证真实的设计效果。这种单个点阵图所表示的最大范围只是一个已知雷达在规定波长和位面的探测距离。
The PLA's J-20 prototype is an important development in terms of grand strategy, as well as technological strategy, and basic technology. It shows that PLA thinking at the strategic level is focussed on defeating opposing IADS [Integrated Air Defence System] and fighter forces. In the domain of technological strategy, it shows a robust grasp of the limitations of Western technology deployed in Asia. In terms of basic technology, it shows that China's academic research and industrial base has mastered advanced LO/VLO shaping techniques.
解放军的歼20原型机是国家战略、科技战略和基础技术方面的重大进步。这表明了解放军在战略层面的考量已经对准了挫败IADS（综合防空系统）和空军力量。在科技战略领域，表明了PLA强有力地抓住了西方科技在亚洲部署的局限性。在基础技术方面，表明了中国的学术研究和工业基地已经掌握了先进的LO/VLO成形技术。
The intent of this study is to perform a preliminary assessment of the RCS of the J-20 prototype, to establish the potential of the aircraft to be fully developed as an LO/VLO combat asset.
本课题的目的是对歼20原型机的RCS进行初步评估，以确定飞机是否具有成为最先进的低可探测/超低可探测战斗王牌的潜能。
The assessment cannot be more than preliminary for a number of good reasons:
1. The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve
aerodynamic performance, operational characteristics, and LO/VLO performance;
2. The state of Chinese Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent
coatings technology is not well understood in the West;
3. The state of Chinese technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well
understood in the West;
4. The state of Chinese technologies for RCS flare spot reduction, in areas such as navigation/communications antennas,
seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
评估只能是最低级别的几个理由：
1、最终机身造型仍然未知，研发环节可能出现变数，进一步提高空气动力性能、操作特点和LO/VLO性能；
2、西方并不十分清楚中国的雷达吸波材料（RAM），雷达吸波结构（RAS）和雷达吸波涂层技术。
3、西方并不十分清楚中国的传感器（雷达、光电、被动射频）孔径的结构模式和RCS减缩技术。
4、西方并不十分清楚中国的RCS光斑减缩技术，还有导航/通信天线、封条、面板连接、排水孔、散热孔和紧固件等。
注释：雷达吸波材料（RAM）是照射到飞机上的电磁能量被吸收并转化为热能，使反射出去的电波能量越少越好。雷达吸波材料分为涂敷型吸波材料与结构型吸波材料两种。雷达吸波结构（RAS）是一种结合飞机外形的曲面和部位，由RAM、透波材料及其它材料构成独特的吸波-承载复合结构。也就是说，一部分复合材料既可以起到吸波的作用，又可以充当承载和减重的作用。
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these
categories.The relative importance of the respective categories should be discussed.
在所有类别中，使其具有RCS特性的设计，是为了达到可靠的LO/VLO性能。我们要讨论的是相对重要的分类。
Sound airframe shaping is a necessary prerequisite for good LO or VLO performance. If shaping is poor, no amount of credible materials application and detail flare spot reduction will overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be unattainable.
合理的机身造型是良好的LO/VLO性能的先决条件。如果造型很差，即便使用再可靠的材料和细微光斑减缩，也无法比拟机身外形对于减少RCS的贡献。
If airframe shaping is sound, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reductions techniques will yield a VLO design.
如果机身造型合理，只要谨慎地使用雷达吸波材料（RAM）、雷达吸波结构、雷达吸波涂层、孔径RCS减缩和较为次要的光斑减缩技术，就会凸显超低可探测设计。
As a result, modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect.
因此，与外形建模有关的任何VLO设计对于RCS贡献都具有非常高的价值，因为这不仅决定了飞机是否能达到可靠的隐身性能，同时也会使设计师致力于研究RAS、RAM和涂层的应用所产生的效果。
This paper will focus mostly on shape related RCS contributions, due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures. Some tentative modelling of published Chinese RAM coatings will be performed.
本文将重点关注与外形相关的RCS贡献，对RAS、RAM、涂料、孔径RCS减缩和次要的光斑减缩等未知技术性能进行估算时，其固有的不确定因素是无法避免的。在适当情形下，合理的假设可以推算出RCS减缩措施相关的吸波材料的性能。同时，对一些中国已公开的RAM涂料的实验性模拟也会展开。
--------------------------------------------------------------------------------------------------------------------------------------------------
J-20 Prototype Very Low Observable Airframe Shaping Design Features
歼20原型机超低可探测机身造型设计特点
--------------------------------------------------------------------------------------------------------------------------------------------------
The J-20 prototype designs displays a number of VLO design features, generally based on design rules developed for and employed in the construction of United States VLO combat aircraft. These display a good theoretical and practical understanding of the VLO design rules developed by US researchers in industry and US government research laboratories, between 1975 and 2000.
歼20原型机的设计显示了一些VLO的设计特点，在常规设计规则的基础上进行开发，同时借鉴了美国VLO战斗机的制造工艺。这些表明了对VLO设计规则有着良好的理论和实践中的理解，VLO设计规则是在1975年至2000年，由美国行业研究和美国政府研究实验室开发而成的。
Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States' F-35 Joint Strike Fighter.
总的来说，歼20原型机的隐身造型设计无疑大大优于俄罗斯的T-50五代机，甚至是美国计划投产的F35联合攻击战斗机。
The J-20 design appears to be mostly constructed around the stealth shaping design rules employed in the US Air Force F-22A Raptor:
歼20的设计似乎大多都是围绕美国空军的F22的隐形造型设计规则：
1.The chined J-20 nose section and canopy are close in appearance to the F-22, yielding similar specular RCS performance in a mature design.
1、歼20的机头部分和座舱罩和F22的外观接近，设计十分成熟，所以二者的隐身性能十分接近。
注释：飞机各个部位的主要散射源和散射机理。头向——座舱、雷达舱和进气道的凹腔效应；正侧向——机身与垂尾的镜面反射、机翼与机身以及平尾与垂尾的角反射；后向——喷口的凹腔效应；斜侧向——机翼和平尾前后缘的边缘绕射；其它——外挂物散射、缝隙绕射、尖点绕射、表面波绕射等。
歼20机头部分的RCS减缩。其中，座舱罩采取了金属镀膜处理技术（光电设计），既遮挡住了雷达波，同时又不会影响可见光的照射，为飞行员提供了良好的视野。而进气道的入口斜切并设计成S型进气道，不会使雷达波直接照射到发动机叶片而产生强烈的散射源；同时内壁敷设吸波材料，雷达波在进气道来回反弹吸波，损耗功率。
2.The J-20 trapezoidal edge aligned engine inlets are closest to the F-22, though they appear to be larger and employ an F-35 style DSI (Diverterless Supersonic Inlet) design, obviously intended to improve on F-22 inlet leading edge signature.
2、歼20梯形进气口的对齐方式与F22十分接近，但他们似乎更多地采用了F35的DSI（无附面层隔道超音速进气道 ）设计风格，显然他们打算改进F22的进气口边缘的信号特征。
3.The J-20 wing fuselage join, critical for beam and all aspect stealth, is in shaping and angle very similar to the F-22, and clearly superior to both the T-50 PAK-FA prototypes and the F-35 Joint Strike Fighter.
3、歼20的翼身融合在造型和角度上都与F22十分类似，对侧向和全向的隐身起到了重要作用，明显优于T50五代机和F35联合攻击战斗机。
注释：翼身融合，机翼和机身结合处的外形，无论取纵向截面或横向截面，其轮廓线都是连续曲线。消除了垂直侧面机身与机翼的角反射器效应。
4.The J-20 flat lower fuselage is optimal for all aspect wideband stealth, and emulates the F-22 design closely. It can produce a significant ground bounce return in some geometries, especially at lower altitudes, or angles approaching the normal.
4、歼20平滑的机身底部很好地模仿了F22的设计，是全频隐身的最佳选择。在一些地方，尤其是低空和靠近法线的角度，可以产生明显的地面反弹。
5.Planform alignment of the J-20 shows exact angular alignment between canard and delta leading edges, and exact crossed (starboard to port, port to starboard) angular edge alignment between canard and delta trailing edges. Leading edge sweep is ~43°, clearly intended for efficient supersonic flight.
5、歼20的平面对齐方式显示，鸭翼和三角翼的前缘对齐，鸭翼和三角翼对侧（右舷对左舷，左舷对右舷）后缘对齐。前缘后掠角约43度，显然倾向于超音速飞行。
注释：鸭式布局，是一种非常适于超音速空战的气动布局，座舱两侧有两个较小的三角翼（鸭翼），后边是一个较大的三角翼（主翼）。鸭式布局的优点是通过较小的鸭翼达到与水平尾翼同样的操纵效能，增强了低空的机动性。缺点是鸭翼一旦转动，角度就会变化，从而影响隐身效果。歼20的鸭翼采用隐身涂料和吸波/透波复合材料，估计对RCS的影响不会很大。
6.The J-20 nose and main undercarriage, and cheek weapon bay doors employ C-band through Ku-band optimised edge serration technology, based on F-117A and F-22 design rules.
6、歼20的机头、主起落架和两侧武器舱门采取了C波段到Ku波段的边缘锯齿优化技术，设计规则来自F117和F22。
7.The aft fuselage, tailbooms, fins/strakes and axi-symmetric nozzles are not compatible with high stealth performance, but may only be stop-gap measures to expedite flight testing of a prototype. Performance is notably poorer in the H polarisation.
7、后机身、尾段、安定翼/边条和轴对称喷口的设计不利于隐身，但也可能是为了加快原型机飞行试验的权宜之计。特别是在电磁波的H方向的隐身性能较差。
8.The airframe configuration and aft fuselage shape would be compatible with an F-22A style 2D TVC nozzle design, or a non-TVC rectangular nozzle designed for controlled infrared emission patterns and radio-frequency stealth. Infrared signature will be influenced by other considerations, especially engine bypass ratio.
8、如果使用二维推力矢量喷口设计或非推力矢量抑制红外和无线电隐身的喷口设计，机身结构和后机身外形将会与F22风格一致。红外特征还取决于其它因素，尤其是发动机涵道比。
注释：涵道比（bypass ratio），即涡轮发动机外涵道与内涵道空气流量的比值。内涵道的空气流入燃烧室与燃料混合，燃烧做功，外涵道的空气不进入燃烧室，而是与内涵道流出的燃气相混合后排出。外涵道的空气只通过风扇，流速较慢，且是低温，内涵道排出的是高温燃气，两种气体混合后降低了流速与温度，能够降低噪声，增加推力。
9.The choice of all moving slab stabilators and canards will impact RCS at deflection angles away from the neutral position. If large control deflections are produced in flight regimes other than close combat manoeuvring, the specular RCS of the all moving slab controls would need to be considered.
9、全动平尾和前翼在偏转角远离中间时会对RCS造成影响。与近距离作战不同，一般飞行状态下的大幅度偏转对RCS造成的影响必须考虑在内。
A qualitative assessment of the J-20 prototype clearly shows that the design has the potential for VLO capability, certainly in the very important forward hemisphere.
歼20原型机的质量评定清晰地表明设计拥有潜在的VLO性能，特别是在非常重要的前方半球。
Available imagery from similar or identical aspects permits direct comparisons between the J-20 and the United States F-22A and F-35 designs.
下面用图片从相似或相同的角度对歼20和美国的F22、F35加以直观的比较。
传不了附件 可以去原帖看
http://www.ltaaa.com/bbs/forum.php?mod=viewthread&tid=7857&fromuid=844
本文是由澳大利亚军事专家卡罗·库珀和迈克尔·佩洛西联合撰写的一篇关于歼20隐身性能的初步评估的军事技术论文。由于篇幅过大，译者分上下两篇发表。上篇主要介绍了歼20的外形特点和隐形飞机的一些基本知识，包括隐身材料，并提出了估算RCS的方法。下篇将会进行具体的实验过程和图表分析，以及对歼20隐身性能的数值结果，并做以总结。附录部分没有进行翻译，其中的一些专业术语、理论、概念等均在译文中夹杂介绍。
鉴于译者在此之前对于航空航天及相关学科基本一窍不通，花费两周时间一边查资料一边完成翻译。文中对于一些常识的解释，一方面对外行们进行科普，另一方面也算自己的理解，希望懂行的大牛们勿嫌繁琐。另外还有一些艰深难懂的理论，译者也做了尝试性地解读，为了不影响篇幅，省略了大量的演算公式，只说结论，目的在于把原文所提到的每个参数的意义告诉读者。囿于译者能力所限，对于翻译错误或不准确的地方，欢迎提出批评，定会在第一时间予以修正，还望大家不吝赐教。
原文：http://www.ausairpower.net/APA-2011-03.html
译者：病中乃知
A Preliminary Assessment of Specular Radar Cross Section Performance in the Chengdu J-20 Prototype
成都歼20原型机隐身性能初步评估
Air Power Australia Analysis 2011-03
4th July 2011
A Monograph by
Dr Michael J Pelosi, MBA, MPA,
Dr Carlo Kopp, SMAIAA, SMIEEE, PEng
Text, computer graphics © 2011 Michael Pelosi, © 2011 Carlo Kopp
澳大利亚空中力量分析 2011-3
2011年7月4日
论文由
迈克尔·J·佩洛西 博士/MBA/MPA
卡罗·库珀 博士/MSAIAA/SMIEEE/PEng
文字，电脑绘图©2011 迈克尔·佩洛西，© 2011 卡罗·库珀
半小时前 上传下载附件 (824.05 KB)
First public flight of the Chengdu J-20 prototype, 11th January, 2011 . The shaping design of the J-20 presents no fundamental obstacles to its development into a genuine Very Low Observable design (Chinese Internet).
2011年1月11日，成都歼20原型机首次公开试飞。歼20的造型设计表明，不会对其改进型的超低可探测性（简称VLO，也就是隐身技术Stealth Technology）。设计造成实质影响。
--------------------------------------------------------------------------------------------------------------------------------------------------
Abstract
摘要
--------------------------------------------------------------------------------------------------------------------------------------------------
This study has explored the specular Radar Cross Section of the Chengdu J-20 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe. In addition, the performance of a range of Chinese developed radar absorbers was modelled, based on a reasonable survey of unclassified Chinese research publications in the area. None of the surveyed materials were found to be suitable for use as impedance matched specular radar absorbers. Modelling has determined, that if the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector. Conversely, if the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector. This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.
本课题探讨了成都歼20原型机隐身性能的造型设计，运用物理光学仿真算法在没有隐形涂层情况下分别进行了频率为150兆赫兹、600兆赫兹、1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹、16.0千兆赫兹和28千兆赫兹的模拟，以及在敷设了隐身涂层的情况下，进行了频率为1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹和16.0千兆赫兹的模拟，覆盖了整个机身的角度位面。此外，中国研制的雷达吸波材料的一系列性能已经建模，基于一份非机密的中国该领域研究发行的调查报告。调查表明，材料不适合作为匹配镜面雷达吸收剂的阻抗。在模型已经确定的情况下，如果歼20的生产保留轴对称喷口和符合面积律的平滑截面，飞机最多只能为机头部分提供强劲的超低可探测性能。反之，如果歼20的生产引进矩面喷口设计，改进侧面机身造型，强劲的超低可探测性能将会在S波段及以上范围展现出巨大的潜力，机头部分和机尾以及侧向也会有良好的性能。本课题是通过物理光学模拟穿越九个无线电波段，在歼20原型机的外形设计不存在根本缺陷的情况下，确保改进型达到真正的超低可探测设计。
注释：Radar Cross Section（RCS），雷达散射截面是目标的一种折算面积，用来度量在雷达波照射下所产生的回波强度大小。RCS越小，说明反射越小，越不容易被发现，从而达到“隐身”的效果。RCS减缩有两种途径：一种是外形隐身，通过改变机身造型，把雷达波反射到雷达无法接收的方向上；一种是材料隐身，通过对机身敷设吸波涂层，把雷达波的能量损耗掉。通常外形隐身占到整个RCS减缩的90%左右，也就是说，衡量一架飞机隐身性能的优劣，主要看造型设计是否合理。同时，造型设计关乎到飞机的气动布局，所以如何兼顾隐身和气动的性能，成为了隐身设计的一大课题。
阻抗匹配：当飞行器受到雷达波的照射时，飞行器本身将产生一个散射场，如果雷达吸波材料的阻抗负载合适，则可以使阻抗产生的电磁场与飞行器产生的散射场的场强矢量振幅相当，相位相反，从而相互干涉，使两个场的合成场强减弱，降低飞机的RCS。
·Introduction
·J-20 Prototype Very Low Observable Airframe Shaping Design Features
Chinese Absorbent Materials Technology
·Radar Cross Section Simulation Method / Simulator Design and Capabilities
Aircraft Model Features and Limitations
What the Simulation Does Not Demonstrate
What the Simulation Does Demonstrate
·Specular Radar Cross Section Simulation Results
Analysis of Shape Related Specular Radar Cross Section
Analysis of Specular RCS with a Representative RAM Coating
·Conclusions
·Endnotes, References and Bibliography:
·Annex A Scales, Bands, Geometries, and Representative Threats
·Annex B Basic Concepts in Absorbent Coatings Technology
·Annex C Axisymmetric Nozzle RCS Performance
·Annex D Viewing RCS Plots
·Annex E Glossary of Terms
·介绍
·歼20原型机超低可探测机身外形设计特点
中国的吸波材料技术
·RCS的模拟方法/模拟设计和功能
飞机模型的特点和局限性
什么是非论证模拟
什么是论证模拟
·镜面RCS的模拟结果
外形RCS的相关分析
涂抹典型雷达吸波材料的隐身性能分析
·结论
·附注、参考文献和参考书目：
·附录一 减缩、波段、几何和典型威胁
·附录二 吸收材料技术的基本概念
·附录三 轴对称喷口的隐身性能
·附录四 查看RCS图解
·附录五 术语
--------------------------------------------------------------------------------------------------------------------------------------------------
Introduction
介绍
--------------------------------------------------------------------------------------------------------------------------------------------------
There has been extensive media speculation about the Radar Cross Section [RCS] of the J-20 stealth fighter, since the PLA-AF first exposed the prototype to the public in late December, 2010. Sadly much of this speculation has no valid scientific basis, yet appears to be regarded seriously enough to have influenced public statements by numerous senior officials in Western defence departments.
自从2010年12月份中国空军首次公开透露了原型机以来，很多媒体都在猜测歼20隐形战斗机的RCS。这种猜测虽然没有科学依据，却似乎被认为是一份足以影响到许多西方国防部门高级官员的公开声明。
Performing a full assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft is not a trivial task, as due consideration needs to be given to all major and minor RCS contributors in the design.
进行任何低可探测（LO / -10到-30 dBSM，参见 表格A.1） 或者超低可探测（VLO / -30到-40 dBSM，参见 表格A.1）飞机的全面评估不是一项简单的任务，需要考虑到设计之中所有主要和次要的RCS贡献。
注释：RCS用σ（Sigma）表示，常用单位为㎡（平方米）或dBSM（分贝平方米），公式为σ=4π *（目标处单位立体角内的散射功率/目标处单位面积上的入射功率），两个单位之间的转换关系是：1000㎡=30dbsm，100㎡=20dbsm，10㎡=10dbsm，1㎡=0dbsm，0.1㎡=-10dbsm，0.01㎡=-20dbsm，也就是说，如果RCS的值是0分贝，那么目标的有效照射面积便是1平方米。（显然，目标的真实面积肯定比1平方米大的多）RCS的“贡献”越大，其值越高。
Moreover, such an assessment, if it is to be useful, must consider the RCS from a range of different angular aspects, this encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].
另外，要使评估有效，必须考虑一系列不同角度位面的隐身效果，包括旨在挫败LO/VLO设计的地面和空中威胁系统在各个方位面以及俯仰角的典型特征。（参见 图表A.3和A.4）（威胁系统指能够搜索、捕获、攻击飞机的雷达、导弹等军事设施）
The assessment of RCS must also be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].
对RCS的评估也必须建立在旨在挫败LO/VLO设计的地面和空中威胁系统的工作波长典型特征之下。（参见 表格A.2）
注释：RCS的大小取决于：目标的物理特性（电特性）、目标的几何特性、目标被雷达波照射的方位、入射波的波长、入射场极化方式和接受天线的极化方式。这里先谈谈几何形状对RCS的影响。1、角反射器：雷达波会在两三个平面相交构成的尖锐折角上折射放大，产生很强的回波信号，尤其是正交直角。2、凹腔效应：雷达波在凹腔内经过多次反射、叠加放大之后返回雷达。3、平行原则：对飞机上的边缘进行平行设计，从而将照射的雷达波集中反射到雷达接收不到的方向。（下文中提到的回波的主瓣和副瓣，就是指把电磁波集中反射的几个方向）4、隐藏强散射源：比如弹仓内挂武器或者S型进气道设计，防止雷达波直接照射发动机叶片。5、用一个部件遮挡住另一个强散射部件，比如背负式进气道（进气道在机身上方）或者用垂尾来遮挡尾喷口。6、结构细节处理：包括对铆钉、台阶等处理，防止次级散射；以及把舱门盖口的边缘和缝隙设计成锯齿形状，这样一来可以加剧散射，降低回波方向的强度。
Definitions of these and other terms employed in this document are summarised in Annex E. Reference data for RCS scales, radio-frequency bands, engagement geometries, and representative threat systems are summarised in Annex A.
这些定义和文章中引用的其它术语见附录E。参考资料来源于RCS减缩、无线电波段、接触几何和典型威胁系统见附录A。
If the RCS assessment does not consider angular and wavelength dependencies properly, it will be almost meaningless, in terms of providing a means of determining or estimating the survivability of the LO/VLO design. The common practice of providing a single RCS value for a single aspect at a single frequency yields little information about the actual effectiveness of the design. Such a single point figure permits at best a detection range estimate for a known radar operating at the specified wavelength and aspect.
如果RCS评估不考虑角度和波长的适当关联，只是按照某种方法来确定或估算LO/VLO设计的生存能力，这是毫无意义的。通常在单一频率下的单个面给定一个单一的RCS值，几乎不能印证真实的设计效果。这种单个点阵图所表示的最大范围只是一个已知雷达在规定波长和位面的探测距离。
The PLA's J-20 prototype is an important development in terms of grand strategy, as well as technological strategy, and basic technology. It shows that PLA thinking at the strategic level is focussed on defeating opposing IADS [Integrated Air Defence System] and fighter forces. In the domain of technological strategy, it shows a robust grasp of the limitations of Western technology deployed in Asia. In terms of basic technology, it shows that China's academic research and industrial base has mastered advanced LO/VLO shaping techniques.
解放军的歼20原型机是国家战略、科技战略和基础技术方面的重大进步。这表明了解放军在战略层面的考量已经对准了挫败IADS（综合防空系统）和空军力量。在科技战略领域，表明了PLA强有力地抓住了西方科技在亚洲部署的局限性。在基础技术方面，表明了中国的学术研究和工业基地已经掌握了先进的LO/VLO成形技术。
The intent of this study is to perform a preliminary assessment of the RCS of the J-20 prototype, to establish the potential of the aircraft to be fully developed as an LO/VLO combat asset.
本课题的目的是对歼20原型机的RCS进行初步评估，以确定飞机是否具有成为最先进的低可探测/超低可探测战斗王牌的潜能。
The assessment cannot be more than preliminary for a number of good reasons:
1. The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve
aerodynamic performance, operational characteristics, and LO/VLO performance;
2. The state of Chinese Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent
coatings technology is not well understood in the West;
3. The state of Chinese technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well
understood in the West;
4. The state of Chinese technologies for RCS flare spot reduction, in areas such as navigation/communications antennas,
seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
评估只能是最低级别的几个理由：
1、最终机身造型仍然未知，研发环节可能出现变数，进一步提高空气动力性能、操作特点和LO/VLO性能；
2、西方并不十分清楚中国的雷达吸波材料（RAM），雷达吸波结构（RAS）和雷达吸波涂层技术。
3、西方并不十分清楚中国的传感器（雷达、光电、被动射频）孔径的结构模式和RCS减缩技术。
4、西方并不十分清楚中国的RCS光斑减缩技术，还有导航/通信天线、封条、面板连接、排水孔、散热孔和紧固件等。
注释：雷达吸波材料（RAM）是照射到飞机上的电磁能量被吸收并转化为热能，使反射出去的电波能量越少越好。雷达吸波材料分为涂敷型吸波材料与结构型吸波材料两种。雷达吸波结构（RAS）是一种结合飞机外形的曲面和部位，由RAM、透波材料及其它材料构成独特的吸波-承载复合结构。也就是说，一部分复合材料既可以起到吸波的作用，又可以充当承载和减重的作用。
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these
categories.The relative importance of the respective categories should be discussed.
在所有类别中，使其具有RCS特性的设计，是为了达到可靠的LO/VLO性能。我们要讨论的是相对重要的分类。
Sound airframe shaping is a necessary prerequisite for good LO or VLO performance. If shaping is poor, no amount of credible materials application and detail flare spot reduction will overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be unattainable.
合理的机身造型是良好的LO/VLO性能的先决条件。如果造型很差，即便使用再可靠的材料和细微光斑减缩，也无法比拟机身外形对于减少RCS的贡献。
If airframe shaping is sound, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reductions techniques will yield a VLO design.
如果机身造型合理，只要谨慎地使用雷达吸波材料（RAM）、雷达吸波结构、雷达吸波涂层、孔径RCS减缩和较为次要的光斑减缩技术，就会凸显超低可探测设计。
As a result, modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect.
因此，与外形建模有关的任何VLO设计对于RCS贡献都具有非常高的价值，因为这不仅决定了飞机是否能达到可靠的隐身性能，同时也会使设计师致力于研究RAS、RAM和涂层的应用所产生的效果。
This paper will focus mostly on shape related RCS contributions, due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures. Some tentative modelling of published Chinese RAM coatings will be performed.
本文将重点关注与外形相关的RCS贡献，对RAS、RAM、涂料、孔径RCS减缩和次要的光斑减缩等未知技术性能进行估算时，其固有的不确定因素是无法避免的。在适当情形下，合理的假设可以推算出RCS减缩措施相关的吸波材料的性能。同时，对一些中国已公开的RAM涂料的实验性模拟也会展开。
--------------------------------------------------------------------------------------------------------------------------------------------------
J-20 Prototype Very Low Observable Airframe Shaping Design Features
歼20原型机超低可探测机身造型设计特点
--------------------------------------------------------------------------------------------------------------------------------------------------
The J-20 prototype designs displays a number of VLO design features, generally based on design rules developed for and employed in the construction of United States VLO combat aircraft. These display a good theoretical and practical understanding of the VLO design rules developed by US researchers in industry and US government research laboratories, between 1975 and 2000.
歼20原型机的设计显示了一些VLO的设计特点，在常规设计规则的基础上进行开发，同时借鉴了美国VLO战斗机的制造工艺。这些表明了对VLO设计规则有着良好的理论和实践中的理解，VLO设计规则是在1975年至2000年，由美国行业研究和美国政府研究实验室开发而成的。
Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States' F-35 Joint Strike Fighter.
总的来说，歼20原型机的隐身造型设计无疑大大优于俄罗斯的T-50五代机，甚至是美国计划投产的F35联合攻击战斗机。
The J-20 design appears to be mostly constructed around the stealth shaping design rules employed in the US Air Force F-22A Raptor:
歼20的设计似乎大多都是围绕美国空军的F22的隐形造型设计规则：
1.The chined J-20 nose section and canopy are close in appearance to the F-22, yielding similar specular RCS performance in a mature design.
1、歼20的机头部分和座舱罩和F22的外观接近，设计十分成熟，所以二者的隐身性能十分接近。
注释：飞机各个部位的主要散射源和散射机理。头向——座舱、雷达舱和进气道的凹腔效应；正侧向——机身与垂尾的镜面反射、机翼与机身以及平尾与垂尾的角反射；后向——喷口的凹腔效应；斜侧向——机翼和平尾前后缘的边缘绕射；其它——外挂物散射、缝隙绕射、尖点绕射、表面波绕射等。
歼20机头部分的RCS减缩。其中，座舱罩采取了金属镀膜处理技术（光电设计），既遮挡住了雷达波，同时又不会影响可见光的照射，为飞行员提供了良好的视野。而进气道的入口斜切并设计成S型进气道，不会使雷达波直接照射到发动机叶片而产生强烈的散射源；同时内壁敷设吸波材料，雷达波在进气道来回反弹吸波，损耗功率。
2.The J-20 trapezoidal edge aligned engine inlets are closest to the F-22, though they appear to be larger and employ an F-35 style DSI (Diverterless Supersonic Inlet) design, obviously intended to improve on F-22 inlet leading edge signature.
2、歼20梯形进气口的对齐方式与F22十分接近，但他们似乎更多地采用了F35的DSI（无附面层隔道超音速进气道 ）设计风格，显然他们打算改进F22的进气口边缘的信号特征。
3.The J-20 wing fuselage join, critical for beam and all aspect stealth, is in shaping and angle very similar to the F-22, and clearly superior to both the T-50 PAK-FA prototypes and the F-35 Joint Strike Fighter.
3、歼20的翼身融合在造型和角度上都与F22十分类似，对侧向和全向的隐身起到了重要作用，明显优于T50五代机和F35联合攻击战斗机。
注释：翼身融合，机翼和机身结合处的外形，无论取纵向截面或横向截面，其轮廓线都是连续曲线。消除了垂直侧面机身与机翼的角反射器效应。
4.The J-20 flat lower fuselage is optimal for all aspect wideband stealth, and emulates the F-22 design closely. It can produce a significant ground bounce return in some geometries, especially at lower altitudes, or angles approaching the normal.
4、歼20平滑的机身底部很好地模仿了F22的设计，是全频隐身的最佳选择。在一些地方，尤其是低空和靠近法线的角度，可以产生明显的地面反弹。
5.Planform alignment of the J-20 shows exact angular alignment between canard and delta leading edges, and exact crossed (starboard to port, port to starboard) angular edge alignment between canard and delta trailing edges. Leading edge sweep is ~43°, clearly intended for efficient supersonic flight.
5、歼20的平面对齐方式显示，鸭翼和三角翼的前缘对齐，鸭翼和三角翼对侧（右舷对左舷，左舷对右舷）后缘对齐。前缘后掠角约43度，显然倾向于超音速飞行。
注释：鸭式布局，是一种非常适于超音速空战的气动布局，座舱两侧有两个较小的三角翼（鸭翼），后边是一个较大的三角翼（主翼）。鸭式布局的优点是通过较小的鸭翼达到与水平尾翼同样的操纵效能，增强了低空的机动性。缺点是鸭翼一旦转动，角度就会变化，从而影响隐身效果。歼20的鸭翼采用隐身涂料和吸波/透波复合材料，估计对RCS的影响不会很大。
6.The J-20 nose and main undercarriage, and cheek weapon bay doors employ C-band through Ku-band optimised edge serration technology, based on F-117A and F-22 design rules.
6、歼20的机头、主起落架和两侧武器舱门采取了C波段到Ku波段的边缘锯齿优化技术，设计规则来自F117和F22。
7.The aft fuselage, tailbooms, fins/strakes and axi-symmetric nozzles are not compatible with high stealth performance, but may only be stop-gap measures to expedite flight testing of a prototype. Performance is notably poorer in the H polarisation.
7、后机身、尾段、安定翼/边条和轴对称喷口的设计不利于隐身，但也可能是为了加快原型机飞行试验的权宜之计。特别是在电磁波的H方向的隐身性能较差。
8.The airframe configuration and aft fuselage shape would be compatible with an F-22A style 2D TVC nozzle design, or a non-TVC rectangular nozzle designed for controlled infrared emission patterns and radio-frequency stealth. Infrared signature will be influenced by other considerations, especially engine bypass ratio.
8、如果使用二维推力矢量喷口设计或非推力矢量抑制红外和无线电隐身的喷口设计，机身结构和后机身外形将会与F22风格一致。红外特征还取决于其它因素，尤其是发动机涵道比。
注释：涵道比（bypass ratio），即涡轮发动机外涵道与内涵道空气流量的比值。内涵道的空气流入燃烧室与燃料混合，燃烧做功，外涵道的空气不进入燃烧室，而是与内涵道流出的燃气相混合后排出。外涵道的空气只通过风扇，流速较慢，且是低温，内涵道排出的是高温燃气，两种气体混合后降低了流速与温度，能够降低噪声，增加推力。
9.The choice of all moving slab stabilators and canards will impact RCS at deflection angles away from the neutral position. If large control deflections are produced in flight regimes other than close combat manoeuvring, the specular RCS of the all moving slab controls would need to be considered.
9、全动平尾和前翼在偏转角远离中间时会对RCS造成影响。与近距离作战不同，一般飞行状态下的大幅度偏转对RCS造成的影响必须考虑在内。
A qualitative assessment of the J-20 prototype clearly shows that the design has the potential for VLO capability, certainly in the very important forward hemisphere.
歼20原型机的质量评定清晰地表明设计拥有潜在的VLO性能，特别是在非常重要的前方半球。
Available imagery from similar or identical aspects permits direct comparisons between the J-20 and the United States F-22A and F-35 designs.
下面用图片从相似或相同的角度对歼20和美国的F22、F35加以直观的比较。
传不了附件 可以去原帖看支持原创翻译 可以访问 [大翻吐血]澳洲军事专家库珀：成都歼20原型机隐身性能初步评估（上）
http://www.ltaaa.com/bbs/forum.php?mod=viewthread&tid=7857&fromuid=844
本文是由澳大利亚军事专家卡罗·库珀和迈克尔·佩洛西联合撰写的一篇关于歼20隐身性能的初步评估的军事技术论文。由于篇幅过大，译者分上下两篇发表。上篇主要介绍了歼20的外形特点和隐形飞机的一些基本知识，包括隐身材料，并提出了估算RCS的方法。下篇将会进行具体的实验过程和图表分析，以及对歼20隐身性能的数值结果，并做以总结。附录部分没有进行翻译，其中的一些专业术语、理论、概念等均在译文中夹杂介绍。
鉴于译者在此之前对于航空航天及相关学科基本一窍不通，花费两周时间一边查资料一边完成翻译。文中对于一些常识的解释，一方面对外行们进行科普，另一方面也算自己的理解，希望懂行的大牛们勿嫌繁琐。另外还有一些艰深难懂的理论，译者也做了尝试性地解读，为了不影响篇幅，省略了大量的演算公式，只说结论，目的在于把原文所提到的每个参数的意义告诉读者。囿于译者能力所限，对于翻译错误或不准确的地方，欢迎提出批评，定会在第一时间予以修正，还望大家不吝赐教。
原文：http://www.ausairpower.net/APA-2011-03.html
译者：病中乃知
A Preliminary Assessment of Specular Radar Cross Section Performance in the Chengdu J-20 Prototype
成都歼20原型机隐身性能初步评估
Air Power Australia Analysis 2011-03
4th July 2011
A Monograph by
Dr Michael J Pelosi, MBA, MPA,
Dr Carlo Kopp, SMAIAA, SMIEEE, PEng
Text, computer graphics © 2011 Michael Pelosi, © 2011 Carlo Kopp
澳大利亚空中力量分析 2011-3
2011年7月4日
论文由
迈克尔·J·佩洛西 博士/MBA/MPA
卡罗·库珀 博士/MSAIAA/SMIEEE/PEng
文字，电脑绘图©2011 迈克尔·佩洛西，© 2011 卡罗·库珀
半小时前 上传下载附件 (824.05 KB)
First public flight of the Chengdu J-20 prototype, 11th January, 2011 . The shaping design of the J-20 presents no fundamental obstacles to its development into a genuine Very Low Observable design (Chinese Internet).
2011年1月11日，成都歼20原型机首次公开试飞。歼20的造型设计表明，不会对其改进型的超低可探测性（简称VLO，也就是隐身技术Stealth Technology）。设计造成实质影响。
--------------------------------------------------------------------------------------------------------------------------------------------------
Abstract
摘要
--------------------------------------------------------------------------------------------------------------------------------------------------
This study has explored the specular Radar Cross Section of the Chengdu J-20 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe. In addition, the performance of a range of Chinese developed radar absorbers was modelled, based on a reasonable survey of unclassified Chinese research publications in the area. None of the surveyed materials were found to be suitable for use as impedance matched specular radar absorbers. Modelling has determined, that if the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector. Conversely, if the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector. This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.
本课题探讨了成都歼20原型机隐身性能的造型设计，运用物理光学仿真算法在没有隐形涂层情况下分别进行了频率为150兆赫兹、600兆赫兹、1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹、16.0千兆赫兹和28千兆赫兹的模拟，以及在敷设了隐身涂层的情况下，进行了频率为1.2千兆赫兹、3.0千兆赫兹、6.0千兆赫兹、8.0千兆赫兹、12.0千兆赫兹和16.0千兆赫兹的模拟，覆盖了整个机身的角度位面。此外，中国研制的雷达吸波材料的一系列性能已经建模，基于一份非机密的中国该领域研究发行的调查报告。调查表明，材料不适合作为匹配镜面雷达吸收剂的阻抗。在模型已经确定的情况下，如果歼20的生产保留轴对称喷口和符合面积律的平滑截面，飞机最多只能为机头部分提供强劲的超低可探测性能。反之，如果歼20的生产引进矩面喷口设计，改进侧面机身造型，强劲的超低可探测性能将会在S波段及以上范围展现出巨大的潜力，机头部分和机尾以及侧向也会有良好的性能。本课题是通过物理光学模拟穿越九个无线电波段，在歼20原型机的外形设计不存在根本缺陷的情况下，确保改进型达到真正的超低可探测设计。
注释：Radar Cross Section（RCS），雷达散射截面是目标的一种折算面积，用来度量在雷达波照射下所产生的回波强度大小。RCS越小，说明反射越小，越不容易被发现，从而达到“隐身”的效果。RCS减缩有两种途径：一种是外形隐身，通过改变机身造型，把雷达波反射到雷达无法接收的方向上；一种是材料隐身，通过对机身敷设吸波涂层，把雷达波的能量损耗掉。通常外形隐身占到整个RCS减缩的90%左右，也就是说，衡量一架飞机隐身性能的优劣，主要看造型设计是否合理。同时，造型设计关乎到飞机的气动布局，所以如何兼顾隐身和气动的性能，成为了隐身设计的一大课题。
阻抗匹配：当飞行器受到雷达波的照射时，飞行器本身将产生一个散射场，如果雷达吸波材料的阻抗负载合适，则可以使阻抗产生的电磁场与飞行器产生的散射场的场强矢量振幅相当，相位相反，从而相互干涉，使两个场的合成场强减弱，降低飞机的RCS。
·Introduction
·J-20 Prototype Very Low Observable Airframe Shaping Design Features
Chinese Absorbent Materials Technology
·Radar Cross Section Simulation Method / Simulator Design and Capabilities
Aircraft Model Features and Limitations
What the Simulation Does Not Demonstrate
What the Simulation Does Demonstrate
·Specular Radar Cross Section Simulation Results
Analysis of Shape Related Specular Radar Cross Section
Analysis of Specular RCS with a Representative RAM Coating
·Conclusions
·Endnotes, References and Bibliography:
·Annex A Scales, Bands, Geometries, and Representative Threats
·Annex B Basic Concepts in Absorbent Coatings Technology
·Annex C Axisymmetric Nozzle RCS Performance
·Annex D Viewing RCS Plots
·Annex E Glossary of Terms
·介绍
·歼20原型机超低可探测机身外形设计特点
中国的吸波材料技术
·RCS的模拟方法/模拟设计和功能
飞机模型的特点和局限性
什么是非论证模拟
什么是论证模拟
·镜面RCS的模拟结果
外形RCS的相关分析
涂抹典型雷达吸波材料的隐身性能分析
·结论
·附注、参考文献和参考书目：
·附录一 减缩、波段、几何和典型威胁
·附录二 吸收材料技术的基本概念
·附录三 轴对称喷口的隐身性能
·附录四 查看RCS图解
·附录五 术语
--------------------------------------------------------------------------------------------------------------------------------------------------
Introduction
介绍
--------------------------------------------------------------------------------------------------------------------------------------------------
There has been extensive media speculation about the Radar Cross Section [RCS] of the J-20 stealth fighter, since the PLA-AF first exposed the prototype to the public in late December, 2010. Sadly much of this speculation has no valid scientific basis, yet appears to be regarded seriously enough to have influenced public statements by numerous senior officials in Western defence departments.
自从2010年12月份中国空军首次公开透露了原型机以来，很多媒体都在猜测歼20隐形战斗机的RCS。这种猜测虽然没有科学依据，却似乎被认为是一份足以影响到许多西方国防部门高级官员的公开声明。
Performing a full assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft is not a trivial task, as due consideration needs to be given to all major and minor RCS contributors in the design.
进行任何低可探测（LO / -10到-30 dBSM，参见 表格A.1） 或者超低可探测（VLO / -30到-40 dBSM，参见 表格A.1）飞机的全面评估不是一项简单的任务，需要考虑到设计之中所有主要和次要的RCS贡献。
注释：RCS用σ（Sigma）表示，常用单位为㎡（平方米）或dBSM（分贝平方米），公式为σ=4π *（目标处单位立体角内的散射功率/目标处单位面积上的入射功率），两个单位之间的转换关系是：1000㎡=30dbsm，100㎡=20dbsm，10㎡=10dbsm，1㎡=0dbsm，0.1㎡=-10dbsm，0.01㎡=-20dbsm，也就是说，如果RCS的值是0分贝，那么目标的有效照射面积便是1平方米。（显然，目标的真实面积肯定比1平方米大的多）RCS的“贡献”越大，其值越高。
Moreover, such an assessment, if it is to be useful, must consider the RCS from a range of different angular aspects, this encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].
另外，要使评估有效，必须考虑一系列不同角度位面的隐身效果，包括旨在挫败LO/VLO设计的地面和空中威胁系统在各个方位面以及俯仰角的典型特征。（参见 图表A.3和A.4）（威胁系统指能够搜索、捕获、攻击飞机的雷达、导弹等军事设施）
The assessment of RCS must also be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].
对RCS的评估也必须建立在旨在挫败LO/VLO设计的地面和空中威胁系统的工作波长典型特征之下。（参见 表格A.2）
注释：RCS的大小取决于：目标的物理特性（电特性）、目标的几何特性、目标被雷达波照射的方位、入射波的波长、入射场极化方式和接受天线的极化方式。这里先谈谈几何形状对RCS的影响。1、角反射器：雷达波会在两三个平面相交构成的尖锐折角上折射放大，产生很强的回波信号，尤其是正交直角。2、凹腔效应：雷达波在凹腔内经过多次反射、叠加放大之后返回雷达。3、平行原则：对飞机上的边缘进行平行设计，从而将照射的雷达波集中反射到雷达接收不到的方向。（下文中提到的回波的主瓣和副瓣，就是指把电磁波集中反射的几个方向）4、隐藏强散射源：比如弹仓内挂武器或者S型进气道设计，防止雷达波直接照射发动机叶片。5、用一个部件遮挡住另一个强散射部件，比如背负式进气道（进气道在机身上方）或者用垂尾来遮挡尾喷口。6、结构细节处理：包括对铆钉、台阶等处理，防止次级散射；以及把舱门盖口的边缘和缝隙设计成锯齿形状，这样一来可以加剧散射，降低回波方向的强度。
Definitions of these and other terms employed in this document are summarised in Annex E. Reference data for RCS scales, radio-frequency bands, engagement geometries, and representative threat systems are summarised in Annex A.
这些定义和文章中引用的其它术语见附录E。参考资料来源于RCS减缩、无线电波段、接触几何和典型威胁系统见附录A。
If the RCS assessment does not consider angular and wavelength dependencies properly, it will be almost meaningless, in terms of providing a means of determining or estimating the survivability of the LO/VLO design. The common practice of providing a single RCS value for a single aspect at a single frequency yields little information about the actual effectiveness of the design. Such a single point figure permits at best a detection range estimate for a known radar operating at the specified wavelength and aspect.
如果RCS评估不考虑角度和波长的适当关联，只是按照某种方法来确定或估算LO/VLO设计的生存能力，这是毫无意义的。通常在单一频率下的单个面给定一个单一的RCS值，几乎不能印证真实的设计效果。这种单个点阵图所表示的最大范围只是一个已知雷达在规定波长和位面的探测距离。
The PLA's J-20 prototype is an important development in terms of grand strategy, as well as technological strategy, and basic technology. It shows that PLA thinking at the strategic level is focussed on defeating opposing IADS [Integrated Air Defence System] and fighter forces. In the domain of technological strategy, it shows a robust grasp of the limitations of Western technology deployed in Asia. In terms of basic technology, it shows that China's academic research and industrial base has mastered advanced LO/VLO shaping techniques.
解放军的歼20原型机是国家战略、科技战略和基础技术方面的重大进步。这表明了解放军在战略层面的考量已经对准了挫败IADS（综合防空系统）和空军力量。在科技战略领域，表明了PLA强有力地抓住了西方科技在亚洲部署的局限性。在基础技术方面，表明了中国的学术研究和工业基地已经掌握了先进的LO/VLO成形技术。
The intent of this study is to perform a preliminary assessment of the RCS of the J-20 prototype, to establish the potential of the aircraft to be fully developed as an LO/VLO combat asset.
本课题的目的是对歼20原型机的RCS进行初步评估，以确定飞机是否具有成为最先进的低可探测/超低可探测战斗王牌的潜能。
The assessment cannot be more than preliminary for a number of good reasons:
1. The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve
aerodynamic performance, operational characteristics, and LO/VLO performance;
2. The state of Chinese Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent
coatings technology is not well understood in the West;
3. The state of Chinese technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well
understood in the West;
4. The state of Chinese technologies for RCS flare spot reduction, in areas such as navigation/communications antennas,
seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
评估只能是最低级别的几个理由：
1、最终机身造型仍然未知，研发环节可能出现变数，进一步提高空气动力性能、操作特点和LO/VLO性能；
2、西方并不十分清楚中国的雷达吸波材料（RAM），雷达吸波结构（RAS）和雷达吸波涂层技术。
3、西方并不十分清楚中国的传感器（雷达、光电、被动射频）孔径的结构模式和RCS减缩技术。
4、西方并不十分清楚中国的RCS光斑减缩技术，还有导航/通信天线、封条、面板连接、排水孔、散热孔和紧固件等。
注释：雷达吸波材料（RAM）是照射到飞机上的电磁能量被吸收并转化为热能，使反射出去的电波能量越少越好。雷达吸波材料分为涂敷型吸波材料与结构型吸波材料两种。雷达吸波结构（RAS）是一种结合飞机外形的曲面和部位，由RAM、透波材料及其它材料构成独特的吸波-承载复合结构。也就是说，一部分复合材料既可以起到吸波的作用，又可以充当承载和减重的作用。
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these
categories.The relative importance of the respective categories should be discussed.
在所有类别中，使其具有RCS特性的设计，是为了达到可靠的LO/VLO性能。我们要讨论的是相对重要的分类。
Sound airframe shaping is a necessary prerequisite for good LO or VLO performance. If shaping is poor, no amount of credible materials application and detail flare spot reduction will overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be unattainable.
合理的机身造型是良好的LO/VLO性能的先决条件。如果造型很差，即便使用再可靠的材料和细微光斑减缩，也无法比拟机身外形对于减少RCS的贡献。
If airframe shaping is sound, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reductions techniques will yield a VLO design.
如果机身造型合理，只要谨慎地使用雷达吸波材料（RAM）、雷达吸波结构、雷达吸波涂层、孔径RCS减缩和较为次要的光斑减缩技术，就会凸显超低可探测设计。
As a result, modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect.
因此，与外形建模有关的任何VLO设计对于RCS贡献都具有非常高的价值，因为这不仅决定了飞机是否能达到可靠的隐身性能，同时也会使设计师致力于研究RAS、RAM和涂层的应用所产生的效果。
This paper will focus mostly on shape related RCS contributions, due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures. Some tentative modelling of published Chinese RAM coatings will be performed.
本文将重点关注与外形相关的RCS贡献，对RAS、RAM、涂料、孔径RCS减缩和次要的光斑减缩等未知技术性能进行估算时，其固有的不确定因素是无法避免的。在适当情形下，合理的假设可以推算出RCS减缩措施相关的吸波材料的性能。同时，对一些中国已公开的RAM涂料的实验性模拟也会展开。
--------------------------------------------------------------------------------------------------------------------------------------------------
J-20 Prototype Very Low Observable Airframe Shaping Design Features
歼20原型机超低可探测机身造型设计特点
--------------------------------------------------------------------------------------------------------------------------------------------------
The J-20 prototype designs displays a number of VLO design features, generally based on design rules developed for and employed in the construction of United States VLO combat aircraft. These display a good theoretical and practical understanding of the VLO design rules developed by US researchers in industry and US government research laboratories, between 1975 and 2000.
歼20原型机的设计显示了一些VLO的设计特点，在常规设计规则的基础上进行开发，同时借鉴了美国VLO战斗机的制造工艺。这些表明了对VLO设计规则有着良好的理论和实践中的理解，VLO设计规则是在1975年至2000年，由美国行业研究和美国政府研究实验室开发而成的。
Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States' F-35 Joint Strike Fighter.
总的来说，歼20原型机的隐身造型设计无疑大大优于俄罗斯的T-50五代机，甚至是美国计划投产的F35联合攻击战斗机。
The J-20 design appears to be mostly constructed around the stealth shaping design rules employed in the US Air Force F-22A Raptor:
歼20的设计似乎大多都是围绕美国空军的F22的隐形造型设计规则：
1.The chined J-20 nose section and canopy are close in appearance to the F-22, yielding similar specular RCS performance in a mature design.
1、歼20的机头部分和座舱罩和F22的外观接近，设计十分成熟，所以二者的隐身性能十分接近。
注释：飞机各个部位的主要散射源和散射机理。头向——座舱、雷达舱和进气道的凹腔效应；正侧向——机身与垂尾的镜面反射、机翼与机身以及平尾与垂尾的角反射；后向——喷口的凹腔效应；斜侧向——机翼和平尾前后缘的边缘绕射；其它——外挂物散射、缝隙绕射、尖点绕射、表面波绕射等。
歼20机头部分的RCS减缩。其中，座舱罩采取了金属镀膜处理技术（光电设计），既遮挡住了雷达波，同时又不会影响可见光的照射，为飞行员提供了良好的视野。而进气道的入口斜切并设计成S型进气道，不会使雷达波直接照射到发动机叶片而产生强烈的散射源；同时内壁敷设吸波材料，雷达波在进气道来回反弹吸波，损耗功率。
2.The J-20 trapezoidal edge aligned engine inlets are closest to the F-22, though they appear to be larger and employ an F-35 style DSI (Diverterless Supersonic Inlet) design, obviously intended to improve on F-22 inlet leading edge signature.
2、歼20梯形进气口的对齐方式与F22十分接近，但他们似乎更多地采用了F35的DSI（无附面层隔道超音速进气道 ）设计风格，显然他们打算改进F22的进气口边缘的信号特征。
3.The J-20 wing fuselage join, critical for beam and all aspect stealth, is in shaping and angle very similar to the F-22, and clearly superior to both the T-50 PAK-FA prototypes and the F-35 Joint Strike Fighter.
3、歼20的翼身融合在造型和角度上都与F22十分类似，对侧向和全向的隐身起到了重要作用，明显优于T50五代机和F35联合攻击战斗机。
注释：翼身融合，机翼和机身结合处的外形，无论取纵向截面或横向截面，其轮廓线都是连续曲线。消除了垂直侧面机身与机翼的角反射器效应。
4.The J-20 flat lower fuselage is optimal for all aspect wideband stealth, and emulates the F-22 design closely. It can produce a significant ground bounce return in some geometries, especially at lower altitudes, or angles approaching the normal.
4、歼20平滑的机身底部很好地模仿了F22的设计，是全频隐身的最佳选择。在一些地方，尤其是低空和靠近法线的角度，可以产生明显的地面反弹。
5.Planform alignment of the J-20 shows exact angular alignment between canard and delta leading edges, and exact crossed (starboard to port, port to starboard) angular edge alignment between canard and delta trailing edges. Leading edge sweep is ~43°, clearly intended for efficient supersonic flight.
5、歼20的平面对齐方式显示，鸭翼和三角翼的前缘对齐，鸭翼和三角翼对侧（右舷对左舷，左舷对右舷）后缘对齐。前缘后掠角约43度，显然倾向于超音速飞行。
注释：鸭式布局，是一种非常适于超音速空战的气动布局，座舱两侧有两个较小的三角翼（鸭翼），后边是一个较大的三角翼（主翼）。鸭式布局的优点是通过较小的鸭翼达到与水平尾翼同样的操纵效能，增强了低空的机动性。缺点是鸭翼一旦转动，角度就会变化，从而影响隐身效果。歼20的鸭翼采用隐身涂料和吸波/透波复合材料，估计对RCS的影响不会很大。
6.The J-20 nose and main undercarriage, and cheek weapon bay doors employ C-band through Ku-band optimised edge serration technology, based on F-117A and F-22 design rules.
6、歼20的机头、主起落架和两侧武器舱门采取了C波段到Ku波段的边缘锯齿优化技术，设计规则来自F117和F22。
7.The aft fuselage, tailbooms, fins/strakes and axi-symmetric nozzles are not compatible with high stealth performance, but may only be stop-gap measures to expedite flight testing of a prototype. Performance is notably poorer in the H polarisation.
7、后机身、尾段、安定翼/边条和轴对称喷口的设计不利于隐身，但也可能是为了加快原型机飞行试验的权宜之计。特别是在电磁波的H方向的隐身性能较差。
8.The airframe configuration and aft fuselage shape would be compatible with an F-22A style 2D TVC nozzle design, or a non-TVC rectangular nozzle designed for controlled infrared emission patterns and radio-frequency stealth. Infrared signature will be influenced by other considerations, especially engine bypass ratio.
8、如果使用二维推力矢量喷口设计或非推力矢量抑制红外和无线电隐身的喷口设计，机身结构和后机身外形将会与F22风格一致。红外特征还取决于其它因素，尤其是发动机涵道比。
注释：涵道比（bypass ratio），即涡轮发动机外涵道与内涵道空气流量的比值。内涵道的空气流入燃烧室与燃料混合，燃烧做功，外涵道的空气不进入燃烧室，而是与内涵道流出的燃气相混合后排出。外涵道的空气只通过风扇，流速较慢，且是低温，内涵道排出的是高温燃气，两种气体混合后降低了流速与温度，能够降低噪声，增加推力。
9.The choice of all moving slab stabilators and canards will impact RCS at deflection angles away from the neutral position. If large control deflections are produced in flight regimes other than close combat manoeuvring, the specular RCS of the all moving slab controls would need to be considered.
9、全动平尾和前翼在偏转角远离中间时会对RCS造成影响。与近距离作战不同，一般飞行状态下的大幅度偏转对RCS造成的影响必须考虑在内。
A qualitative assessment of the J-20 prototype clearly shows that the design has the potential for VLO capability, certainly in the very important forward hemisphere.
歼20原型机的质量评定清晰地表明设计拥有潜在的VLO性能，特别是在非常重要的前方半球。
Available imagery from similar or identical aspects permits direct comparisons between the J-20 and the United States F-22A and F-35 designs.
下面用图片从相似或相同的角度对歼20和美国的F22、F35加以直观的比较。
传不了附件 可以去原帖看
Chinese Absorbent Materials Technology
中国的吸波材料技术
--------------------------------------------------------------------------------------------------------------------------------------------------
The state of Chinese research in low observables absorbent materials technology is not well understood in Western nations, as there have been no substantial official disclosures to date. The absence of disclosures, physical samples, or even viable imagery presents numerous challenges in determining what materials are intended for use in the J-20 design, or even what options are available to the Chengdu designers.
中国在低可探测吸波材料技术上的研究，西方国家仍然一知半解，迄今为止仍然没有翔实的官方披露。由于缺少披露、材料样本和图片，这对判断歼20使用何种材料以及成都的设计者可能的选择都带来了极大的困难。
While official disclosures on production technologies are absent, these is a surprising number of recent unclassified basic research publications available, produced by Chinese researchers, dealing with the materials science of absorbers, especially Carbon Nano-Tube (CNT) absorbers, including absorbers loaded with conductive or magnetic materials. The number of papers and abstracts identified in this and related areas was of the order of thirty, mostly authored over the last several years, and published in English language journals and conferences. No attempt was made to survey Mandarin language publications.
虽然官方没有披露生产技术，但最近发表的非机密的基础研究数量惊人，中国科学家在研究吸波材料技术，特别是碳纳米管（CNT）吸波材料，包括电磁吸波材料。相关领域论文和文摘的数量多达三成，多半在近些年被收录，并在英语期刊和学术会议上发表，从而不必去查阅汉语出版物。
注释：雷达吸波材料通常由两种或两种以上物质组成，按功能不同分为基体和填充剂。其中，填充剂决定了材料的吸波功能，基体则主要负载填充剂，并使材料具备一定的机械性能。填充剂会影响基体的机械性能，基体也会影响填充剂固有的电磁特性。
基体的电磁常数越小，对填充剂性能影响越少，所以通常用作基体的物质是有机高聚物和无机粘结剂。文中提到的基体主要是碳纳米管和环氧树脂。碳纳米管是一维纳米材料，具有高强度、高韧性、耐高温（已知材料中熔点最高的，3600℃以上）和良好的导电性。环氧树脂是分子结构中含有环氧基团的高分子化合物。由于分子结构中含有活泼的环氧基团，使它们可与多种类型的固化剂发生交联反应而形成不溶、不熔的具有三向网状结构的高聚物。
而填充剂主要分为两类，磁损性填充剂和电损性填充剂。常用的磁损性填充剂主要有铁氧体和金属粉末，其中，铁氧体是一种具有铁磁性的金属氧化物（比如四氧化三铁，俗称磁铁），具有高电阻、高介电性能和在高频时有着较高的磁导率等特点。常用的电损性填充料主要有炭黑和石墨。一旦雷达波进入吸波材料内， 由于材料的导电率而引起能量损耗。
通常，电损性材料高频吸收效果好，磁损性材料低频吸收效果好。在实际应用中，把两者结合起来， 可以制得一种在较宽频率范围内吸收效果好的复合吸波材料。
Chinese research in RCS reduction is not confined to materials alone. A recent paper by Zhenghong and Mingliong details a derived Method of Moments algorithm for RCS computations. Work by Jiang et al details the use of genetic algorithms for the optimal design of complex multilayer absorber structures. Earlier research in conventional RCS modelling for design was produced by Cao et al.
中国在RCS减缩方面的研究并不仅仅局限于材料。最近一份由郑宏和明龙（音译）发表的论文详细叙述了如何用矩量法来计算RCS。江等人利用遗传算法来进行多层复合吸波结构的优化设计工作。在此之前，曹等人就开始了传统的RCS建模设计的研究。
注释：矩量法（Moments Algorithm）是求解电磁场边界值问题的一种数值方法。主要是将积分方程化为差分方程，或将积分方程中积分化为有限求和，从而建立代数方程组 。遗传算法（Genetic Algorithm）是一种通过模拟自然进化过程搜索最优解的方法，由于遗传算法不依赖于梯度信息或其它辅助知识，只需要影响搜索方向的目标函数和相应的适应度函数，所以对于解决复杂的组合优化问题有着明显的效果。
Most of the materials research papers and abstracts surveyed were experimental, involving the fabrication and subsequent performance parameter testing of the fabricated material. The deeper theoretical analysis of loss mechanisms, and theoretical study of material behaviour in production applications, are uncommon in openly published work from China. This in many respects emulates the pattern observed in many Soviet unclassified basic research publications during the Cold War period.
大多数材料研究论文和文摘，涉及制造和随后材料半成品性能参数的测试，都是试验性质的。中国公开发表了损耗机制的深层理论分析和应用产品材料特性的理论研究，这是十分罕见的，在很大层面上借鉴了冷战时期苏联非涉密基础研究的出版模式。
Annex B outlines the basic theoretical and practical concepts underpinning the design of absorbent materials.
附录B列出了基础理论和吸波材料设计的实践思想。
Of specific interest in the context of Chinese stealth design is the respectable volume of high quality academic research performed on CNT, ferrite loaded epoxy, or other materials for use as the absorbent or lossy component in epoxy or other polymer matrix absorbent or lossy coatings, laminates, panels or radar absorbent structures.
倍受关注的中国隐形设计是建立在数量惊人的高质量学术研究之上的，包括碳纳米管、填充铁氧体的环氧树脂和其它吸波材料；环氧树脂损耗成分；其它高分子基质吸收剂；损耗涂层、层板、面板；雷达吸波结构。
注释：吸波材料按其成型工艺和承载能力，可分为涂敷型吸波材料和结构型吸波材料。一、涂敷型吸波材料又称吸波涂料，主要有铁氧体和金属超细粉末两种类型。铁氧体的优点是吸波性能好，便宜易得，缺点是比重太大；金属超细粉末的优点是重量轻，缺点是难以制造，价格昂贵。二、结构型吸波材料至少包括三层，其中最外层是透波层，如玻璃钢或芳纶纤维为基体的复合材料；中间层为电磁损耗层，由具有良好吸波特性的蜂窝结构或泡沫组成；最底层是反射层，必须具有反射雷达波的特性，一般采用强度刚度性能好的碳纤维复合材料制成。由于涂敷型吸波材料不参与结构承力，要付出额外的重量代价，而且还存在易脱落、侵蚀、工作不稳定的缺点，结构型吸波材料不存在上述问题，除此之外还有一定的透波性和吸波性，以及电磁特性的可设计性。
In CNT/epoxy materials a powder filler comprising CNT is loaded into an epoxy matrix, in a manner similar to traditional inclusion methods for powdered materials intended to alter the dielectric and magnetic properties of the resin. Epoxy resins in the microwave bands exhibit εr ~ 3.0 - 4.6 and δ ~ 0.01, making them a viable matrix for many applications, due to the toughness and durability of the material, and its relative ease of application.
CNT/环氧树脂材料的填充粉末是由加载在环氧基上的CNT所组成，在某种意义上，这和利用粉状材料来改变树脂的电磁特性的传统内嵌工艺十分类似。在微波波段，环氧树脂的 εr（相对介电常数）大约是3.0到4.6，δ （介质损耗角）大约是0.01，这些可用基质能否应用于实际，取决于材料的韧性和强度，还有易用性。
注释：吸波材料的基本特性。一、匹配特性，电磁波入射到材料表面时，它能最大限度地进入材料的内部，而不是简单地被材料表面反射掉。二、损耗特性，进入材料内部的电磁波能迅速地几乎全部地衰减掉。调整吸波材料的介电常数和磁导率，可使材料的电磁特性既满足匹配特性，又满足衰减特性。
按吸波材料的吸收电磁波的方式，可分为谐振型吸波材料和吸收型吸波材料。一、谐振型吸波材料，从原理上讲，是靠回波之间的相互干涉作用来减弱回波强度。比如，在金属平板表面上涂上一层这种材料，除了一部分入射波直接反射外，其余部分透过涂层从平板反射，再穿过涂层形成另一部分回波。如果这两部分回波的振幅大致相等，相位相反，则发生相互干涉而被减弱。（也就是相消干涉）二、吸收型吸波材料，从原理上讲，是将入射波的电磁能量经在吸波材料中所产生的各种弱电和磁滞的损耗，转化为热量散失掉，从而减弱回波强度。第一种吸波材料与文中提到的相对介电常数εr和介质损耗角δ 有关。
Chinese research in CNT/epoxy absorbers seems to be mostly focussed on lossy dielectrics, rather than magnetically loaded materials intended as impedance matched coatings. Such materials are more useful as components in multilayered absorbent coatings or structures, rather than for applications such as control of specular skin reflections in aircraft, where exactly controlled impedance matching of the single layer coating strongly influences the performance of the coating.
中国对CNT/环氧树脂吸波材料的研究似乎集中在损耗性电介质上，而不是把磁性材料作为匹配涂层的阻抗。这些材料应用在多层吸波涂料或结构上可以起到更显著的作用，而不是应用在诸如飞机表面镜面反射控制上，精确地控制单层涂层的阻抗匹配，可以影响涂层的性能。
There is no evidence in the open literature of a coordinated or focussed effort to develop thin lightweight impedance matched absorbent coatings for specular backscatter control in aircraft applications.
在已公开的文献中，没有证据表明中国正在协调或集中研究既轻且薄的阻抗，使之可以应用在飞机镜面反射的吸波涂层上。
No effort was made to assess the performance of the surveyed materials as surface travelling wave absorbers. While numerical modelling of surface travelling wave absorption performance was feasible, without experimental data, calibration of any such simulation model was not possible.
评估表明，把被研究材料作为表面行波吸收剂是不可行的。即便没有试验数据，表面行波吸收性能的数值也是可以模拟的，但是不能校准这些模拟数值。
As a result, most of the English language published Chinese materials research would yield products possibly suitable for other applications, but mostly not suitable for high performance coatings useful in aircraft microwave band specular RCS reduction.
总而言之，大部分英文出版的中国材料研究出来的产品适用于其它应用，而不能用于飞机在微波波段的镜面RCS减缩的高性能涂料上。（也就是说，中国公开的隐形材料研究都不涉及军用，丫的白忙活了）
--------------------------------------------------------------------------------------------------------------------------------------------------
Radar Cross Section Simulation Method / Simulator Design and Capabilities
RCS的模拟方法/模拟设计和功能
--------------------------------------------------------------------------------------------------------------------------------------------------
The Physical Optics (PO) method is used to predict the RCS of complex targets, in this instance the Chengdu J-20 prototype. The three dimensional model for any such target comprises a collection of triangular facets, with shared edges.
物理光学（PO）方法被用来预测复杂目标，也就是成都歼20原型机的RCS。这种目标的三维模型都是由很多共享棱边的三角切面组成的。
注释：物理光学（PO）法是采用stratton-chu（斯特拉顿-朱兰成）散射场的积分公式对复杂目标进行RCS的近似进算，但必须先满足三个条件。第一、高频条件，这样一来就保证了入射波波长远小于目标尺寸，那么就可以把入射波近似看作光线，认为目标上射线照不到的地方，其表面各点的场强为零。（也就是说在某一方向被遮挡住的机身其它部分的RCS贡献不参与计算）第二、远场近似，如果测量点到目标的距离要远大于目标尺寸，那么入射波可以看成是平面波。第三、切平面近似，假设目标表面上的任一点及其附近表面曲率半径比波长大得多，可以推导出一般目标散射场的物理光学法的计算公式。（下文会提到这三个条件，但语焉不详，看不懂没关系，复杂的公式就不罗列了，知道结论就行了）
The scattered field from each and every visible facet, for a given angle pair {θ, Φ} in elevation and azimuth, is computed using the far field radiation integrals. It is assumed that the wavefront is planar and no parallax errors arise. The contributions from each of the facets are then summed to produce a total RCS for the angle pair {θ, Φ} in question. This method is a high frequency approximation that provides the best results for electrically large targets, and performs well in the specular direction
假定波阵面是二维的，并且没有出现视差，对于一个给定的角度{θ, Φ} ，每个可见面的散射场都可以计算出它的远场辐射积分。每个面的贡献加起来就是{θ, Φ} 角度的总RCS。这种方法是高频的近似值，大型电子目标的最佳结果，并很好地演示了反射的方向。
注释：俯角是以铅垂线为基准，观察者的视线与铅垂线之间的夹角，用θ表示，范围是0°到180°。（当观察者在水平面以下的时候，也就是仰视，仍可以用大于90°的俯角来表示）方位角是二维平面中，从某点的指北方向线起，顺时针方向到目标方向线之间的水平夹角，用Φ表示，范围是0°到360°。俯角和方位角合起来构成一对视界角{θ, Φ}，决定了独一无二的三维视角。这个视角就是雷达波照射飞机的方向，上文提到过，入射波的方向也会影响RCS，下面的模拟会从不同的方向来测量飞机的RCS。
The simulation uses geometric self-shadowing of facet calculations, such that RCS contributions hidden by shadowing airframe features are removed. This mechanism does not implement diffraction effects at larger wavelengths.
模拟器用来进行几何面的自投影计算，以致被屏蔽机身特性的RCS贡献被隐藏。这种机制不能实现更大波长的绕射效应。
The PO RCS simulation program implementation has manageable run–times because it requires minimum computer resources. It is implemented in C++ language to provide shorter computation times than earlier Physical Optics simulators, such as the NPS POFacets code, which is implemented in the interpreted Matlab language.
出于对计算机资源占用最小化的考虑，物理光学RCS模拟程序的运行必须有可控的运行时间。C++语言比之前的物理光学模拟器运行更短的估算时间，例如 NPS POFacets（基于物理光学近似的面元法程序）代码，就是在Matlab语言下运行的。
At this time the simulator does not implement surface travelling wave modelling and associated edge or gap backscatter modelling, or edge diffraction scattering effect modelling. As the backscatter from these, in real aircraft, depends upon leading and trailing edge absorbent treatments, it is a reasonable assumption that in a production design these RCS contributions would be strongly suppressed as a result of effective treatments, and thus the magnitude of these RCS contributions would be smaller than specular returns, from angles other than the peak mainlobes.
这次模拟器没有对表面行波、相邻边界和缝隙的反向散射，或者边缘绕射散射效应进行建模。由于这些反向散射取决于前后缘的吸收剂处理，因此在生产这些RCS贡献中采取合理的假设，将会强有力地抑制有效处理的结果，这些RCS的贡献将会比来自各个角度的量级要少的多，除了频域主瓣峰值的镜面回波。
注释：谈谈几种基本散射源。1、镜面反射，当电磁波照射到飞机的光滑表面时，反射光是平行的。镜面反射的回波的大部分能量集中在很窄的方向上，是一种很强的散射源，比如座舱罩、机翼和垂尾。2、边缘绕射，当电磁波入射到目标的边缘棱线时，镜面反射不复存在，散射波主要来自于目标边缘对入射波的绕射。边缘绕射是一种较强的散射源，比如平板或楔的边缘。3、爬行波绕射，电磁波照射到物体上，有一些入射线正好与物体表面相切，把物体分为照明区和阴影区。切于表面的入射线将沿阴影区表面一边“爬行”，一边向外辐射电磁波。比如电磁波侧向照射飞机，便会产生爬行波绕射现象。4、行波绕射，当电磁波沿细长物体头端方向附近入射时，在细长物体的表面不连续处（其数学模型二次不可导点）、不同介质交界处（如金属棒与塑料棒的连接处）以及细长体的端头处将产生绕射现象。（整个机身可以看做一个“细长体”，如果飞机的细长比越大，行波回波也就越大）5、尖顶绕射，当入射波入射到尖顶上，也会产生绕射现象。尖顶绕射是一种弱散射源，比如锥体的锥顶和飞机机头顶端。
The PO RCS simulator generates a raw data output as RCS magnitude values for a specified operating frequency, polarisation, and aspect angle pair {θ, Φ}, in ASCII text format.
在指定了工作频率、极化方向和视界角 {θ, Φ}的情况下， 物理光学RCS模拟器生成RCS幅度值作为原始数据以ASCII文本格式输出。
The integrity of the PO RCS simulation program was validated by modelling a range of basic shapes and materials coated panels, and comparing against published experimental third party results. The simulator generally displayed very low errors compared to published measurements, typically of the order of the error produced by digitising printed hard copy plots of experimental measurement results.
物理光学RCS模拟程序要经过一系列的基本形状和涂层材料面板的建模，并且与第三方已发表的实验结果进行比对，才能验证其完整性。与已发布的测量值相比，模拟器拥有非常低的误差，特别是数字化印刷实验测量结果划分的硬拷贝时产生的误差。
Postprocessing tools were developed and employed to generate two different representations of the RCS data.
后处理工具的开发和应用形成了两种不同的RCS数据表示法。
The first representation devised was labelled as the PolyChromatic Spherical Representation (PCSR), in which a translucent sphere is rendered around a two-dimensional rendering of the aircraft, where the surface of the sphere is divided into tiles by aspect angle pair {θ, Φ}. The colour of each tile represents the RCS from the angular direction determined by the path between the tile and the centroid of the aircraft. The colour encoding of RCS employs the same ordered colour sequence as is employed by US Government and other agencies for weather radar rainfall density representation, as this is a well understood and intuitive encoding scheme.
第一种表示法是用多色球面表示法来标记，让一个透明球体围绕飞机，然后把飞机的二维透视图投影到球面上，同时球面被视界角 {θ, Φ}划分成若干区块。每个区块的颜色都代表了由区块和飞机重心之间的路径所决定的角方向上的RCS。RCS的颜色编码采取的色序排序，与美国政府和其它气象雷达降雨强度发布部门使用的一样。
半小时前 上传下载附件 (883.68 KB)
Example PolyChromatic Spherical Representation (PCSR) of J-20 specular RCS at 150 MHz. The dBSM value is represented by the colour scale at the bottom of the plot [Click to enlarge].
150MHz下，歼20的镜面RCS多色球面表示法示例图。图片底部的色标就是dBSM值。
The second representation devised was labelled as the PolyChromatic Planar Representation (PCPR), in which a rectangular area is divided into tiles by aspect angle pair {θ, Φ}. The colour of each tile represents the RCS from the angular direction determined by the path between the tile and the centroid of the aircraft. The colour encoding of RCS employs the same ordered colour sequence as is employed in the PCSR scheme. All PCPR charts are further enhanced by the addition of rulers which separate the most critical azimuthal sectors, and elevation/depression angles
第二种表示法是用多色平面表示法来标记，矩形平面被视界角 {θ, Φ}划分成若干区块。每个区块的颜色都代表了被区块和飞机重心之间的路径所决定的角方向上的RCS。RCS的颜色编码采取了与多色球面表示法相同的色序排序。所有PCPR图表都可以被添加的直尺所加强，区分最重要的方位面、仰角和俯角。
半小时前 上传下载附件 (315.98 KB)
中国的吸波材料技术
--------------------------------------------------------------------------------------------------------------------------------------------------
The state of Chinese research in low observables absorbent materials technology is not well understood in Western nations, as there have been no substantial official disclosures to date. The absence of disclosures, physical samples, or even viable imagery presents numerous challenges in determining what materials are intended for use in the J-20 design, or even what options are available to the Chengdu designers.
中国在低可探测吸波材料技术上的研究，西方国家仍然一知半解，迄今为止仍然没有翔实的官方披露。由于缺少披露、材料样本和图片，这对判断歼20使用何种材料以及成都的设计者可能的选择都带来了极大的困难。
While official disclosures on production technologies are absent, these is a surprising number of recent unclassified basic research publications available, produced by Chinese researchers, dealing with the materials science of absorbers, especially Carbon Nano-Tube (CNT) absorbers, including absorbers loaded with conductive or magnetic materials. The number of papers and abstracts identified in this and related areas was of the order of thirty, mostly authored over the last several years, and published in English language journals and conferences. No attempt was made to survey Mandarin language publications.
虽然官方没有披露生产技术，但最近发表的非机密的基础研究数量惊人，中国科学家在研究吸波材料技术，特别是碳纳米管（CNT）吸波材料，包括电磁吸波材料。相关领域论文和文摘的数量多达三成，多半在近些年被收录，并在英语期刊和学术会议上发表，从而不必去查阅汉语出版物。
注释：雷达吸波材料通常由两种或两种以上物质组成，按功能不同分为基体和填充剂。其中，填充剂决定了材料的吸波功能，基体则主要负载填充剂，并使材料具备一定的机械性能。填充剂会影响基体的机械性能，基体也会影响填充剂固有的电磁特性。
基体的电磁常数越小，对填充剂性能影响越少，所以通常用作基体的物质是有机高聚物和无机粘结剂。文中提到的基体主要是碳纳米管和环氧树脂。碳纳米管是一维纳米材料，具有高强度、高韧性、耐高温（已知材料中熔点最高的，3600℃以上）和良好的导电性。环氧树脂是分子结构中含有环氧基团的高分子化合物。由于分子结构中含有活泼的环氧基团，使它们可与多种类型的固化剂发生交联反应而形成不溶、不熔的具有三向网状结构的高聚物。
而填充剂主要分为两类，磁损性填充剂和电损性填充剂。常用的磁损性填充剂主要有铁氧体和金属粉末，其中，铁氧体是一种具有铁磁性的金属氧化物（比如四氧化三铁，俗称磁铁），具有高电阻、高介电性能和在高频时有着较高的磁导率等特点。常用的电损性填充料主要有炭黑和石墨。一旦雷达波进入吸波材料内， 由于材料的导电率而引起能量损耗。
通常，电损性材料高频吸收效果好，磁损性材料低频吸收效果好。在实际应用中，把两者结合起来， 可以制得一种在较宽频率范围内吸收效果好的复合吸波材料。
Chinese research in RCS reduction is not confined to materials alone. A recent paper by Zhenghong and Mingliong details a derived Method of Moments algorithm for RCS computations. Work by Jiang et al details the use of genetic algorithms for the optimal design of complex multilayer absorber structures. Earlier research in conventional RCS modelling for design was produced by Cao et al.
中国在RCS减缩方面的研究并不仅仅局限于材料。最近一份由郑宏和明龙（音译）发表的论文详细叙述了如何用矩量法来计算RCS。江等人利用遗传算法来进行多层复合吸波结构的优化设计工作。在此之前，曹等人就开始了传统的RCS建模设计的研究。
注释：矩量法（Moments Algorithm）是求解电磁场边界值问题的一种数值方法。主要是将积分方程化为差分方程，或将积分方程中积分化为有限求和，从而建立代数方程组 。遗传算法（Genetic Algorithm）是一种通过模拟自然进化过程搜索最优解的方法，由于遗传算法不依赖于梯度信息或其它辅助知识，只需要影响搜索方向的目标函数和相应的适应度函数，所以对于解决复杂的组合优化问题有着明显的效果。
Most of the materials research papers and abstracts surveyed were experimental, involving the fabrication and subsequent performance parameter testing of the fabricated material. The deeper theoretical analysis of loss mechanisms, and theoretical study of material behaviour in production applications, are uncommon in openly published work from China. This in many respects emulates the pattern observed in many Soviet unclassified basic research publications during the Cold War period.
大多数材料研究论文和文摘，涉及制造和随后材料半成品性能参数的测试，都是试验性质的。中国公开发表了损耗机制的深层理论分析和应用产品材料特性的理论研究，这是十分罕见的，在很大层面上借鉴了冷战时期苏联非涉密基础研究的出版模式。
Annex B outlines the basic theoretical and practical concepts underpinning the design of absorbent materials.
附录B列出了基础理论和吸波材料设计的实践思想。
Of specific interest in the context of Chinese stealth design is the respectable volume of high quality academic research performed on CNT, ferrite loaded epoxy, or other materials for use as the absorbent or lossy component in epoxy or other polymer matrix absorbent or lossy coatings, laminates, panels or radar absorbent structures.
倍受关注的中国隐形设计是建立在数量惊人的高质量学术研究之上的，包括碳纳米管、填充铁氧体的环氧树脂和其它吸波材料；环氧树脂损耗成分；其它高分子基质吸收剂；损耗涂层、层板、面板；雷达吸波结构。
注释：吸波材料按其成型工艺和承载能力，可分为涂敷型吸波材料和结构型吸波材料。一、涂敷型吸波材料又称吸波涂料，主要有铁氧体和金属超细粉末两种类型。铁氧体的优点是吸波性能好，便宜易得，缺点是比重太大；金属超细粉末的优点是重量轻，缺点是难以制造，价格昂贵。二、结构型吸波材料至少包括三层，其中最外层是透波层，如玻璃钢或芳纶纤维为基体的复合材料；中间层为电磁损耗层，由具有良好吸波特性的蜂窝结构或泡沫组成；最底层是反射层，必须具有反射雷达波的特性，一般采用强度刚度性能好的碳纤维复合材料制成。由于涂敷型吸波材料不参与结构承力，要付出额外的重量代价，而且还存在易脱落、侵蚀、工作不稳定的缺点，结构型吸波材料不存在上述问题，除此之外还有一定的透波性和吸波性，以及电磁特性的可设计性。
In CNT/epoxy materials a powder filler comprising CNT is loaded into an epoxy matrix, in a manner similar to traditional inclusion methods for powdered materials intended to alter the dielectric and magnetic properties of the resin. Epoxy resins in the microwave bands exhibit εr ~ 3.0 - 4.6 and δ ~ 0.01, making them a viable matrix for many applications, due to the toughness and durability of the material, and its relative ease of application.
CNT/环氧树脂材料的填充粉末是由加载在环氧基上的CNT所组成，在某种意义上，这和利用粉状材料来改变树脂的电磁特性的传统内嵌工艺十分类似。在微波波段，环氧树脂的 εr（相对介电常数）大约是3.0到4.6，δ （介质损耗角）大约是0.01，这些可用基质能否应用于实际，取决于材料的韧性和强度，还有易用性。
注释：吸波材料的基本特性。一、匹配特性，电磁波入射到材料表面时，它能最大限度地进入材料的内部，而不是简单地被材料表面反射掉。二、损耗特性，进入材料内部的电磁波能迅速地几乎全部地衰减掉。调整吸波材料的介电常数和磁导率，可使材料的电磁特性既满足匹配特性，又满足衰减特性。
按吸波材料的吸收电磁波的方式，可分为谐振型吸波材料和吸收型吸波材料。一、谐振型吸波材料，从原理上讲，是靠回波之间的相互干涉作用来减弱回波强度。比如，在金属平板表面上涂上一层这种材料，除了一部分入射波直接反射外，其余部分透过涂层从平板反射，再穿过涂层形成另一部分回波。如果这两部分回波的振幅大致相等，相位相反，则发生相互干涉而被减弱。（也就是相消干涉）二、吸收型吸波材料，从原理上讲，是将入射波的电磁能量经在吸波材料中所产生的各种弱电和磁滞的损耗，转化为热量散失掉，从而减弱回波强度。第一种吸波材料与文中提到的相对介电常数εr和介质损耗角δ 有关。
Chinese research in CNT/epoxy absorbers seems to be mostly focussed on lossy dielectrics, rather than magnetically loaded materials intended as impedance matched coatings. Such materials are more useful as components in multilayered absorbent coatings or structures, rather than for applications such as control of specular skin reflections in aircraft, where exactly controlled impedance matching of the single layer coating strongly influences the performance of the coating.
中国对CNT/环氧树脂吸波材料的研究似乎集中在损耗性电介质上，而不是把磁性材料作为匹配涂层的阻抗。这些材料应用在多层吸波涂料或结构上可以起到更显著的作用，而不是应用在诸如飞机表面镜面反射控制上，精确地控制单层涂层的阻抗匹配，可以影响涂层的性能。
There is no evidence in the open literature of a coordinated or focussed effort to develop thin lightweight impedance matched absorbent coatings for specular backscatter control in aircraft applications.
在已公开的文献中，没有证据表明中国正在协调或集中研究既轻且薄的阻抗，使之可以应用在飞机镜面反射的吸波涂层上。
No effort was made to assess the performance of the surveyed materials as surface travelling wave absorbers. While numerical modelling of surface travelling wave absorption performance was feasible, without experimental data, calibration of any such simulation model was not possible.
评估表明，把被研究材料作为表面行波吸收剂是不可行的。即便没有试验数据，表面行波吸收性能的数值也是可以模拟的，但是不能校准这些模拟数值。
As a result, most of the English language published Chinese materials research would yield products possibly suitable for other applications, but mostly not suitable for high performance coatings useful in aircraft microwave band specular RCS reduction.
总而言之，大部分英文出版的中国材料研究出来的产品适用于其它应用，而不能用于飞机在微波波段的镜面RCS减缩的高性能涂料上。（也就是说，中国公开的隐形材料研究都不涉及军用，丫的白忙活了）
--------------------------------------------------------------------------------------------------------------------------------------------------
Radar Cross Section Simulation Method / Simulator Design and Capabilities
RCS的模拟方法/模拟设计和功能
--------------------------------------------------------------------------------------------------------------------------------------------------
The Physical Optics (PO) method is used to predict the RCS of complex targets, in this instance the Chengdu J-20 prototype. The three dimensional model for any such target comprises a collection of triangular facets, with shared edges.
物理光学（PO）方法被用来预测复杂目标，也就是成都歼20原型机的RCS。这种目标的三维模型都是由很多共享棱边的三角切面组成的。
注释：物理光学（PO）法是采用stratton-chu（斯特拉顿-朱兰成）散射场的积分公式对复杂目标进行RCS的近似进算，但必须先满足三个条件。第一、高频条件，这样一来就保证了入射波波长远小于目标尺寸，那么就可以把入射波近似看作光线，认为目标上射线照不到的地方，其表面各点的场强为零。（也就是说在某一方向被遮挡住的机身其它部分的RCS贡献不参与计算）第二、远场近似，如果测量点到目标的距离要远大于目标尺寸，那么入射波可以看成是平面波。第三、切平面近似，假设目标表面上的任一点及其附近表面曲率半径比波长大得多，可以推导出一般目标散射场的物理光学法的计算公式。（下文会提到这三个条件，但语焉不详，看不懂没关系，复杂的公式就不罗列了，知道结论就行了）
The scattered field from each and every visible facet, for a given angle pair {θ, Φ} in elevation and azimuth, is computed using the far field radiation integrals. It is assumed that the wavefront is planar and no parallax errors arise. The contributions from each of the facets are then summed to produce a total RCS for the angle pair {θ, Φ} in question. This method is a high frequency approximation that provides the best results for electrically large targets, and performs well in the specular direction
假定波阵面是二维的，并且没有出现视差，对于一个给定的角度{θ, Φ} ，每个可见面的散射场都可以计算出它的远场辐射积分。每个面的贡献加起来就是{θ, Φ} 角度的总RCS。这种方法是高频的近似值，大型电子目标的最佳结果，并很好地演示了反射的方向。
注释：俯角是以铅垂线为基准，观察者的视线与铅垂线之间的夹角，用θ表示，范围是0°到180°。（当观察者在水平面以下的时候，也就是仰视，仍可以用大于90°的俯角来表示）方位角是二维平面中，从某点的指北方向线起，顺时针方向到目标方向线之间的水平夹角，用Φ表示，范围是0°到360°。俯角和方位角合起来构成一对视界角{θ, Φ}，决定了独一无二的三维视角。这个视角就是雷达波照射飞机的方向，上文提到过，入射波的方向也会影响RCS，下面的模拟会从不同的方向来测量飞机的RCS。
The simulation uses geometric self-shadowing of facet calculations, such that RCS contributions hidden by shadowing airframe features are removed. This mechanism does not implement diffraction effects at larger wavelengths.
模拟器用来进行几何面的自投影计算，以致被屏蔽机身特性的RCS贡献被隐藏。这种机制不能实现更大波长的绕射效应。
The PO RCS simulation program implementation has manageable run–times because it requires minimum computer resources. It is implemented in C++ language to provide shorter computation times than earlier Physical Optics simulators, such as the NPS POFacets code, which is implemented in the interpreted Matlab language.
出于对计算机资源占用最小化的考虑，物理光学RCS模拟程序的运行必须有可控的运行时间。C++语言比之前的物理光学模拟器运行更短的估算时间，例如 NPS POFacets（基于物理光学近似的面元法程序）代码，就是在Matlab语言下运行的。
At this time the simulator does not implement surface travelling wave modelling and associated edge or gap backscatter modelling, or edge diffraction scattering effect modelling. As the backscatter from these, in real aircraft, depends upon leading and trailing edge absorbent treatments, it is a reasonable assumption that in a production design these RCS contributions would be strongly suppressed as a result of effective treatments, and thus the magnitude of these RCS contributions would be smaller than specular returns, from angles other than the peak mainlobes.
这次模拟器没有对表面行波、相邻边界和缝隙的反向散射，或者边缘绕射散射效应进行建模。由于这些反向散射取决于前后缘的吸收剂处理，因此在生产这些RCS贡献中采取合理的假设，将会强有力地抑制有效处理的结果，这些RCS的贡献将会比来自各个角度的量级要少的多，除了频域主瓣峰值的镜面回波。
注释：谈谈几种基本散射源。1、镜面反射，当电磁波照射到飞机的光滑表面时，反射光是平行的。镜面反射的回波的大部分能量集中在很窄的方向上，是一种很强的散射源，比如座舱罩、机翼和垂尾。2、边缘绕射，当电磁波入射到目标的边缘棱线时，镜面反射不复存在，散射波主要来自于目标边缘对入射波的绕射。边缘绕射是一种较强的散射源，比如平板或楔的边缘。3、爬行波绕射，电磁波照射到物体上，有一些入射线正好与物体表面相切，把物体分为照明区和阴影区。切于表面的入射线将沿阴影区表面一边“爬行”，一边向外辐射电磁波。比如电磁波侧向照射飞机，便会产生爬行波绕射现象。4、行波绕射，当电磁波沿细长物体头端方向附近入射时，在细长物体的表面不连续处（其数学模型二次不可导点）、不同介质交界处（如金属棒与塑料棒的连接处）以及细长体的端头处将产生绕射现象。（整个机身可以看做一个“细长体”，如果飞机的细长比越大，行波回波也就越大）5、尖顶绕射，当入射波入射到尖顶上，也会产生绕射现象。尖顶绕射是一种弱散射源，比如锥体的锥顶和飞机机头顶端。
The PO RCS simulator generates a raw data output as RCS magnitude values for a specified operating frequency, polarisation, and aspect angle pair {θ, Φ}, in ASCII text format.
在指定了工作频率、极化方向和视界角 {θ, Φ}的情况下， 物理光学RCS模拟器生成RCS幅度值作为原始数据以ASCII文本格式输出。
The integrity of the PO RCS simulation program was validated by modelling a range of basic shapes and materials coated panels, and comparing against published experimental third party results. The simulator generally displayed very low errors compared to published measurements, typically of the order of the error produced by digitising printed hard copy plots of experimental measurement results.
物理光学RCS模拟程序要经过一系列的基本形状和涂层材料面板的建模，并且与第三方已发表的实验结果进行比对，才能验证其完整性。与已发布的测量值相比，模拟器拥有非常低的误差，特别是数字化印刷实验测量结果划分的硬拷贝时产生的误差。
Postprocessing tools were developed and employed to generate two different representations of the RCS data.
后处理工具的开发和应用形成了两种不同的RCS数据表示法。
The first representation devised was labelled as the PolyChromatic Spherical Representation (PCSR), in which a translucent sphere is rendered around a two-dimensional rendering of the aircraft, where the surface of the sphere is divided into tiles by aspect angle pair {θ, Φ}. The colour of each tile represents the RCS from the angular direction determined by the path between the tile and the centroid of the aircraft. The colour encoding of RCS employs the same ordered colour sequence as is employed by US Government and other agencies for weather radar rainfall density representation, as this is a well understood and intuitive encoding scheme.
第一种表示法是用多色球面表示法来标记，让一个透明球体围绕飞机，然后把飞机的二维透视图投影到球面上，同时球面被视界角 {θ, Φ}划分成若干区块。每个区块的颜色都代表了由区块和飞机重心之间的路径所决定的角方向上的RCS。RCS的颜色编码采取的色序排序，与美国政府和其它气象雷达降雨强度发布部门使用的一样。
半小时前 上传下载附件 (883.68 KB)
Example PolyChromatic Spherical Representation (PCSR) of J-20 specular RCS at 150 MHz. The dBSM value is represented by the colour scale at the bottom of the plot [Click to enlarge].
150MHz下，歼20的镜面RCS多色球面表示法示例图。图片底部的色标就是dBSM值。
The second representation devised was labelled as the PolyChromatic Planar Representation (PCPR), in which a rectangular area is divided into tiles by aspect angle pair {θ, Φ}. The colour of each tile represents the RCS from the angular direction determined by the path between the tile and the centroid of the aircraft. The colour encoding of RCS employs the same ordered colour sequence as is employed in the PCSR scheme. All PCPR charts are further enhanced by the addition of rulers which separate the most critical azimuthal sectors, and elevation/depression angles
第二种表示法是用多色平面表示法来标记，矩形平面被视界角 {θ, Φ}划分成若干区块。每个区块的颜色都代表了被区块和飞机重心之间的路径所决定的角方向上的RCS。RCS的颜色编码采取了与多色球面表示法相同的色序排序。所有PCPR图表都可以被添加的直尺所加强，区分最重要的方位面、仰角和俯角。
半小时前 上传下载附件 (315.98 KB)
lz强啊！！好人一个，请继续
楼主太强了！！！
支持lz！这个人看样子是澳洲的红裤衩啊，很客观，了解那么多知识，赶快找人去干掉。
强贴留名。
这个库伯以前不是早就发过类似的文章咩？ 难道我记错了…
翻译的人辛苦了，等高手出来解读。
小弟在此由衷的感谢
LZ为了广大的英语盲而付出的努力
LZ为了广大的英语盲而付出的努力
楼主辛苦了！！
这老外KC很红啊...
LV威武算是客观的评价了，好像前几天在中华图库上看到过这个文章的截图
袋鼠国的专家又有吃饭的话题了，就象《红楼梦》一样，养了很多人。
这算是专业的科技情报分析了吧
看样子库珀很了解情况啊。
mod4 发表于 2011-7-18 04:43 ![]()
这个库伯以前不是早就发过类似的文章咩？ 难道我记错了…
可能根据最新资料更新了
这个库伯以前不是早就发过类似的文章咩？ 难道我记错了…
可能根据最新资料更新了没觉得什么新鲜货啊
嗯，龙腾网的这篇翻译很不错。
兰州辛苦了
怎么会了解的这么清楚！
翻译的人 很专业了，辛苦了！！{:soso__6588600266607373974_3:}
可以做内参的范本
LZ注明转载啊，这是龙腾网友病中乃知两个星期的辛苦翻译
楼主辛苦，强人啊
rsrzrcj 发表于 2011-7-18 10:19 ![]()
LZ注明转载啊，这是龙腾网友病中乃知两个星期的辛苦翻译
我没注明转载么？
LZ注明转载啊，这是龙腾网友病中乃知两个星期的辛苦翻译
我没注明转载么？