Re: [閒聊] 老共的新戰機

[ryannieh (new)]

http://tinyurl.com/4k9gfma
Stealthy Chinese J-20 Vulnerable
（脆弱的中國匿蹤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.
（中國最新的J20原型機將需要密集的發展計畫以趕上快速發展
反匿蹤科技）

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發展的目標之一是在夠遠之處偵測小型目標或如匿
蹤機之類的低可視度目標）

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.
（空載對匿蹤機的偵測科技可能已實用化了。2009年於加州愛德
華空軍機地的一系列測試中，根據研究人員的說法，LM的CATbird
測試平台（一架搭載所有F35空載電子的波音737）於對抗F22
和F15混合編組中定位並干擾了F22的雷達。雷神的x波段AESA
雷達，特別是搭載於駐紮於沖繩的昇級版F15C上的，能偵測小型
低可視度的巡航飛彈。）

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.
（更進一步地，搭載於澳大利亞的楔尾鷹AWACS的NG的低頻、
L波段AESA雷達是更大且更有潛力偵測匿蹤目標的雷達）

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年的一場會議上暗示了F35對抗外國先進戰機的
反匿蹤能力。Dan Crowley，當時的執行副總和F-35計劃的總負
責人說：「F35的航電包括能讓飛行員全天候於高危險戰場攻擊固
定或移動目標，並同時標定且消滅先進空中威脅的能力。」

Better images emerging from China point clearly to the
J-20’s use of stealth technology, but major uncertainties
and questions remain unresolved.
（傳自中國的較清晰照片顯示J20採用了匿蹤科技，但若干疑點仍
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的整體外型類似F22/35的，也就是一融合了前機身、上機
氣道唇、主翼和前翼的V型設計（註：上視角度），V型線之上採
弧線設計，V型線之下則為平直的斜面。主翼和前翼邊緣對齊；主
翼和前翼前緣平行，前翼後緣和相反側的主翼後緣對齊。同樣的設
計原理也被用在英國、瑞典和日本的匿蹤機設計上）

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.
（所有這一類的設計目的都是為了讓雷達反射訊號呈一個「蝴蝶
結」式的圖譜：也就是正前方有最小的而側面有最大但仍不怎麼大
的訊號。戰機的任務規劃系統能利用已知雷達位置的資料來規劃
「藍線」路徑以穿過雷達間並避免側面暴露在對方雷達之前過久。

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進氣道能避免傳統邊界層隔板造成對匿蹤的問題。
例如，F22的傳統進氣道就需要用上大量的雷達波吸收材料。）

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設計的最大問題在發動機噴口可能造成J20後向的RCS大
增。一個可能性是日後中國將換用2D噴嘴，但目前所使用的噴嘴
已有減少RCS的鋸齒狀處理，這暗示了PLA可能接受了後向RCS
的缺點而不採用較重且複雜的2D噴嘴）

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.
（其他設計較不清楚。匿蹤的發展一直受到細部設計能力的影響。
J20各部的天線都藏於透波的表皮之下。可維護性是一個複雜的取
捨：比較常要維護的得要能自起落架艙和武器艙進行維修，其他的
得要透過能開闔而不影響RCS的動力門─這樣的門會製造額外的
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.
（最大的挑戰可能是管理蒙皮上雷達波造成的電流。早期的匿蹤設
計用上的是重而難以維護的吸波材料。F22用的是較輕的材料，但
其遭遇出乎意料的腐蝕性問題而難以維護。F35採用較強靭而便宜
的材料，包括高強度的塗佈表層和嵌入複合蒙皮的導電層。J20的
設計讓設多分析師看到了和F22, F35, T50相似但不同的設計。）

“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.
（有分析師認為J20和Mig I42的相似之類暗示了中國和俄國航
空業在這方面的接觸。）

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的試飛）

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).
（現在一般多在討論J20的用途（空優，或更可能的，長程打擊），
它的感測器（長程打擊要有高解晰度的長程雷達），和它的通訊系
統（其需要高速資料鏈和精密的資料融合）

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.
（傳統雷達的偵測距離只有AESA雷達的一半到三分之一。而且傳統
雷達會造成一個不斷晃動的反射面影響匿蹤。中國一直在追求最
新的雷達科技。）


“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.
（一名在華盛頓的情報官員說，現在還太難說中國AESA科技的情
況。我們看見了很多航展的資料，但這並不能代表穩固的發展或提
供精確的評估。）

“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.
（中國還有很長的路要走。J20只是第一或第二步。如果中國進行
了數個月的測試而沒有新機出現，那它可能只是技術展示機，但如
果有數架新機出現，則它很有可能是原型機。）


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.
（胡錦濤向蓋茨証實了J20的試飛，但蓋茨相信美國仍將在2025
年之前保有匿蹤機的優勢。）


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