http://tinyurl.com/4k9gfma Stealthy Chinese J-20 Vulnerable （脆弱的中国匿踪J-20） Jan 18, 2011 By David A. Fulghum, Bill Sweetman, Bradley Perrett, Robert Wall Washington, Washington, Beijing, London China’s newest combat aircraft prototype, the J-20, will require an intense development program if it is going to catch up with fast-moving anti-stealth advances. （中国最新的J20原型机将需要密集的发展计画以赶上快速发展 反匿踪科技） In fact, anti-stealth will bring into question all stealth designs: How much invulnerability will current low-observability techniques offer as air defense systems adopt larger and more powerful active, electronically scanned array (AESA) radars? From the early days of AESA development, a key goal was to build a radar that could detect very small objects—such as a cruise missile at a distance great enough to target and shoot it down—or a larger object like a fighter with a very low-observable treatment. （早期AESA发展的目标之一是在够远之处侦测小型目标或如匿 踪机之类的低可视度目标） Airborne detection of stealth aircraft may already be an operational capability. In a series of tests at Edwards AFB, Calif., in 2009, Lockheed Martin’s CATbird avionics testbed—a Boeing 737 that carries the F-35 Joint Strike Fighter’s entire avionics system—engaged a mixed force of F-22s and Boeing F-15s and was able to locate and jam F-22 radars, according to researchers. Raytheon’s family of X-band airborne AESA radar—in particular, those on upgraded F-15Cs stationed in Okinawa—can detect small, low-signature cruise missiles. （空载对匿踪机的侦测科技可能已实用化了。2009年於加州爱德 华空军机地的一系列测试中，根据研究人员的说法，LM的CATbird 测试平台（一架搭载所有F35空载电子的波音737）於对抗F22 和F15混合编组中定位并干扰了F22的雷达。雷神的x波段AESA 雷达，特别是搭载於驻紮於冲绳的昇级版F15C上的，能侦测小型 低可视度的巡航飞弹。） Moreover, Northrop Grumman’s lower-frequency, L-band AESA radar on Australia’s Wedgetail airborne early warning and control aircraft is larger and potentially more capable of detecting stealth aircraft at longer ranges. （更进一步地，搭载於澳大利亚的楔尾鹰AWACS的NG的低频、 L波段AESA雷达是更大且更有潜力侦测匿踪目标的雷达） Lockheed Martin also hinted at a JSF anti-stealth capability in 2009 in a reference to combat with sophisticated, foreign aircraft. “The F-35’s avionics include onboard sensors that will enable pilots to strike fixed or moving ground targets in high-threat environments, day or night, in any weather, while simultaneously targeting and eliminating advanced airborne threats,” said Dan Crowley, then-executive vice president and F-35 program general manager. （LM也在2009年的一场会议上暗示了F35对抗外国先进战机的 反匿踪能力。Dan Crowley，当时的执行副总和F-35计划的总负 责人说：「F35的航电包括能让飞行员全天候於高危险战场攻击固 定或移动目标，并同时标定且消灭先进空中威胁的能力。」 Better images emerging from China point clearly to the J-20’s use of stealth technology, but major uncertainties and questions remain unresolved. （传自中国的较清晰照片显示J20采用了匿踪科技，但若干疑点仍 未解除。） The overall shape resembles that of the F-35 and F-22, which have a single “chine line” uniting the forebody, upper inlet lips, and wing and canard edges with a curved surface above that line and flat, canted body surfaces below it. The wing and canard edges are aligned: The wing and canard leading edges are parallel and the trailing edge of each canard is aligned with the opposite wing’s trailing edge. The same basic philosophy also has been adopted in British, Swedish and Japanese studies for stealth fighters. （J20的整体外型类似F22/35的，也就是一融合了前机身、上机 气道唇、主翼和前翼的V型设计（注：上视角度），V型线之上采 弧线设计，V型线之下则为平直的斜面。主翼和前翼边缘对齐；主 翼和前翼前缘平行，前翼後缘和相反侧的主翼後缘对齐。同样的设 计原理也被用在英国、瑞典和日本的匿踪机设计上） The aim in all cases is to endow a practical, agile fighter configuration with a “bow-tie” radar signature, with the smallest signature around the nose and the greatest (still much lower than that of a conventional aircraft with curved or vertical-slab sides) to the side. The fighter’s mission planning system, using a database of known radar locations, then derives a “blue line” track that weaves between radars and avoids exposing the side-on signature to those radars more than transiently. （所有这一类的设计目的都是为了让雷达反射讯号呈一个「蝴蝶 结」式的图谱：也就是正前方有最小的而侧面有最大但仍不怎麽大 的讯号。战机的任务规划系统能利用已知雷达位置的资料来规划 「蓝线」路径以穿过雷达间并避免侧面暴露在对方雷达之前过久。 The “diverterless” supersonic inlet avoids a signature problem caused by a conventional boundary layer diverter plate. For example, the F-22 has a conventional inlet, which is likely to require extensive radar absorbent material (RAM) treatment. （J20的DSI进气道能避免传统边界层隔板造成对匿踪的问题。 例如，F22的传统进气道就需要用上大量的雷达波吸收材料。） The biggest uncertainty about the Chinese design concerns the engine exhausts, which as seen on the prototype are likely to cause a radar cross-section (RCS) peak from the rear aspect. One possibility is that a stealthier two-dimensional nozzle will be integrated later in the program; however, the nozzles on the current aircraft show some signs of RCS-reducing sawtooth treatment, suggesting that the People’s Liberation Army has accepted a rear-aspect RCS penalty rather than the much greater weight and complexity of 2D nozzles. （J20设计的最大问题在发动机喷口可能造成J20後向的RCS大 增。一个可能性是日後中国将换用2D喷嘴，但目前所使用的喷嘴 已有减少RCS的锯齿状处理，这暗示了PLA可能接受了後向RCS 的缺点而不采用较重且复杂的2D喷嘴） Other features are less clear. Stealth development has been dogged by detail-design challenges. All the antennas on the aircraft have to be flush with the skin and covered with surfaces that retain stealth properties while being transparent in a specific frequency. Maintainability becomes a complex tradeoff: Some systems requiring frequent attention will be accessed via landing gear and weapon bays, and others by latched and actuated doors that can open and close without affecting RCS—but the latter involves a weight penalty. （其他设计较不清楚。匿踪的发展一直受到细部设计能力的影响。 J20各部的天线都藏於透波的表皮之下。可维护性是一个复杂的取 舍：比较常要维护的得要能自起落架舱和武器舱进行维修，其他的 得要透过能开阖而不影响RCS的动力门─这样的门会制造额外的 重量。） Perhaps the toughest hurdle is managing radio-frequency surface currents over the skin. Early stealth designs used heavy, maintenance-intensive RAM. The F-22 introduced a much lighter surface treatment, but it has proven unexpectedly difficult to maintain, causing corrosion issues. Lockheed Martin now asserts that the F-35 will be robust and affordable to maintain in service, with a combination of a high-toughness, sprayed-on topcoat and a conductive layer cured into composite skin panels. The Chengdu J-20 design has struck many analysts and observers as familiar and somewhat different from the F-22, F-35 or Sukhoi T-50. （最大的挑战可能是管理蒙皮上雷达波造成的电流。早期的匿踪设 计用上的是重而难以维护的吸波材料。F22用的是较轻的材料，但 其遭遇出乎意料的腐蚀性问题而难以维护。F35采用较强靭而便宜 的材料，包括高强度的涂布表层和嵌入复合蒙皮的导电层。J20的 设计让设多分析师看到了和F22, F35, T50相似但不同的设计。） “The J-20 is reminiscent of the Russian MiG-1.42 both in terms of planform and also with regard to the rear fuselage configuration,” says Douglas Barrie, senior fellow for military aerospace at London’s International Institute for Strategic Studies. “The most obvious difference is the greater forward fuselage shaping as the basis for low-observable characteristics, along with the different engine intake configuration. The MiG program was canceled by the Russian government around 1997,” he notes. However, the similarity to the MiG concept may suggest some collusion with the Russian aviation industry. （有分析师认为J20和Mig I42的相似之类暗示了中国和俄国航 空业在这方面的接触。） The J-20 made its first flight shortly before 1 p.m. Beijing time on Jan. 11. The flight ended three weeks of anticipation that began in late December when the new design started taxi tests. （J20的试飞） The discussion about the program will now shift to the aircraft’s mission (fighter or, more likely, long-range strike), sensors (strike missions would require a high-resolution, long-range radar) and communications (which would demand high-speed data links and sophisticated integration). （现在一般多在讨论J20的用途（空优，或更可能的，长程打击）， 它的感测器（长程打击要有高解晰度的长程雷达），和它的通讯系 统（其需要高速资料链和精密的资料融合） Conventional radars have only one-half to one-third of the range of an AESA radar. Moreover, the movement of a conventional, mechanically scanned radar antenna provides a tell-tale glint of radio-frequency reflections to enemy aircraft with advanced radars. Such reflections undercut the effectiveness of a stealth airframe. China is known to be pursuing newer radar technology. （传统雷达的侦测距离只有AESA雷达的一半到三分之一。而且传统 雷达会造成一个不断晃动的反射面影响匿踪。中国一直在追求最 新的雷达科技。） “It’s too early to tell the true status of the Chinese AESA program,” says a Washington-based intelligence official. “We’ve seen lots of press and air show information on the program, but that doesn’t automatically translate into a robust development or give us an accurate look at where [China] is as far as fielding one anytime soon. （一名在华盛顿的情报官员说，现在还太难说中国AESA科技的情 况。我们看见了很多航展的资料，但这并不能代表稳固的发展或提 供精确的评估。） “Like the [high-performance] engine, it’ll be a challenge to take the step from older radars to one designed for a fifth-generation fighter,” he says. “Again, though, the J-20 is just the first or second—depending on whom you believe—prototype in a very long development program.” If the Chinese conduct a few months of flight tests and there are no more aircraft involved in the program, this might indicate that the J-20 is a proof-of-concept or technical demonstrator. If there are several aircraft eventually, a prototype program would be a more likely conclusion. （中国还有很长的路要走。J20只是第一或第二步。如果中国进行 了数个月的测试而没有新机出现，那它可能只是技术展示机，但如 果有数架新机出现，则它很有可能是原型机。） The flight occurred during a visit to China by U.S. Defense Secretary Robert Gates, who says Chinese President Hu Jintao confirmed the event to him in talks. However, Gates still believes the U.S. will retain a preponderance of stealth fighters through 2025. （胡锦涛向盖茨证实了J20的试飞，但盖茨相信美国仍将在2025 年之前保有匿踪机的优势。） --

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