澳大利亚人如何看待歼20(翻译帖--转自龙腾)

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导读:本帖最后由 病中乃知 于 2011-7-23 00:13 编辑 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

本帖最后由 病中乃知 于 2011-7-23 00:13 编辑



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




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。





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