Chinese J-20 5th Generation Fighter Jet

Discussion in 'China' started by Martian, Dec 23, 2010.

  1. MiG-23MLD
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    [​IMG]
     
    Last edited: Apr 26, 2014
  2. MiG-23MLD
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  4. MiG-23MLD
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    adar Cross Section
    [​IMG]
    [​IMG]
    Figure 1: the experimental radar cross section of the B-26aircraft at 3 GHz frequency as a function of azimuth angle (after Skolnik)

    The size and ability of a target to reflect radar energy can be summarized into a single term, σ, known as the radar cross-section, which has units of m². This unit shows, that the radar cross section is an area. If absolutely all of the incident radar energy on the target were reflected equally in all directions, then the radar cross section would be equal to the target's cross-sectional area as seen by the transmitter. In practice, some energy is absorbed and the reflected energy is not distributed equally in all directions. Therefore, the radar cross-section is quite difficult to estimate and is normally determined by measurement.

    The target radar cross sectional area depends of:

    • the airplane’s physical geometry and exterior features,
    • the direction of the illuminating radar,
    • the radar transmitters frequency,
    • the used material types.
    The use of stealth technology to reduce radar cross section increases the survivability and decreases the target detection of military aircraft. But the stealth technology depends of the used radar transmitters frequency and has none effect against VHF- radars like P-12 or P-18, both used by serbian air defense units during the Kosovo war.

    Calculation of the radar cross section
    Radar cross section (RCS) is the measure of a target's ability to reflect radar signals in the direction of the radar receiver, i.e. it is a measure of the ratio of backscatter density in the direction of the radar (from the target) to the power density that is intercepted by the target. Since the power is distributed on the shape of a sphere, a small part of this ((4·π·r2)) can be received by the radar.
    Radar cross section σ is as defined as:

    σ =4·π·r2·Sr

    mitσ: measure of the target's ability to reflect radar signals in direction of the radar receiver, in [m²]
    St: power density that is intercepted by the target, in [W/m²]
    Sr: scattered power density in the range r, in [W/m²](1)
    St
    The RCS of a target can be viewed as a comparison of the strength of the reflected signal from a target to the reflected signal from a perfectly smooth sphere of cross sectional area of 1 m².

    The following backscattering formulas from shapes occurs in an optical independent of frequency region.

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    reflected signal from a spherical shape
    σmax = π ·R2(2)
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    reflected signal from a cylinder
    σmax =2·π·r·h2(3)
    λ
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    reflected signal from a flat plate
    σmax =4·π·b2·h2(4)
    λ2
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    reflected signal from a tilted plate
    ...Real as the previous example. Unusual feature: the reflected energy is reflected in another direction. Well, the transmitting radar cannot receive this energy. Therefore there are bistatic radars at which the transmitter and the receivers are separated from each other spatially.

    Table 1: RCS for geometrically bodies

    RCS for Point-Like Targets
    TargetsRCS
    [m2]RCS[dB]
    bird0.01-20
    man10
    cabin cruiser1010
    automobile10020
    truck20023
    corner reflector2037943.1
    Table 2: RCS for Point-Like Targets

    Some targets have large values of RCS owing to their size and orientation and consequently, reflect a large portion of the incident power. The beside table shows the values of RCS for some targets atX-Band

    (Table from: M. Skolnik, “Introduction to radar systems”, 2nd Edition, McGraw-Hill, Inc 1980, page 44.
    The RCS of the corner reflector is given for a triangular reflector with a length of 1.5 m.)

    Radar Basics - Radar Cross Section
     
  5. MiG-23MLD
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    At lower frequencies, we encounter the opposite problem—the shaping we rely on to
    cut RCS in the microwave region becomes more and more indistinct as the wavelength
    starts to approach the dimensions of the target. (For reference, the length of an F/A-18C
    is about 17 meters.) It’s like the case of light and dust particles—the complexities of the
    particle’s shape make no difference because its size is close to a wavelength of light. Like
    dust particles dancing in a shaft of sunlight, when viewed at low frequencies targets tend
    to scatter radar energy in all directions regardless of shape.

    Low frequencies are a problem also for RAM and RAS. The effect of radar absorbers is
    affected by their thickness relative to the wavelength—one quarter of the wavelength is
    best. As the wavelength reaches a foot or more, radar absorbers become impractical for
    most targets.
    The net effect is that at very low frequencies, the RCS of normal stealthy targets tends
    to approach that of non-stealthy targets of similar physical size—close to the physical
    area of the target. This is called resonant scattering because the wave is in resonance
    with the target, leading to scattering of radiation in a broad fan

    http://www.analysis.williamdoneil.com/Stealth.pdf
     
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  6. MiG-23MLD
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  8. tusharm
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    Anees Mod Staff Member MODERATOR

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    Looks cheap just like any other Chinese made product.
     
  11. Gessler
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    The J-31 is a pretend-5th gen fighter for very low-budget air forces like Pakistan, some African & South American countries.

    I really do not think China intends to use it themselves. They will stick with the J-20 for air superiority (a bad choice against F-22/FGFA)
    and there's another next-gen plane upcoming for strike roles (like the roles F-35 performs).
     
  12. AKIIN
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    J-31 5th generation fighters can defeat US fourth-generation fighters in combat
    Staff Reporter 2014-11-09 11:44 (GMT+8)

    The J-31, China's second fifth-generation stealth fighter designed by Shenyang Aircraft Corporation, is capable of outfighting all US fourth-generation fighters in aerial combat, according to an US fighter pilot cited in our sister newspaper Want Daily.
    Looking similar to the F-22 and F-35, the J-31 was developed based on US technology stolen by Chinese spies, said the pilot. He added that all US fourth-generation fighters including the AV-8, F-15 and F/A-18 are unable to compete against the J-31 in aerial combat. It will become the perfect fighter for the People's Liberation Army to carry out its anti-access and area-denial strategies in the Western Pacific.
    The Chinese fighter will become a big challenge to the F-35 in the overseas market, said the pilot. It may not be as advanced as the F-35, but it is much cheaper than its US counterpart. By displaying the J-31 during the Zhuhai Air Show, the pilot suspects that China is trying to attract attention from potential buyers. It will certainly be more popular among developing nations, he added.
    The only weakness the J-31 and J-20 have is that China is still unable to design proper engines for them. Until now, China had depended on purchasing engines from Russia. New designs of Chinese aircraft are now replacing this dependency, though they are still kept secret. said the pilot. What the United States should worry about is the J-31's quantity instead of its quality, he added. Despite having better trained pilots, the US will still find it difficult to face a swarm of J-31s
     
  13. BoQ77
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    The problem is that J-31 need not only 1 but 2 imported engines to produce the same thrust as 1xF135 P&W on F-35.
    And J-31 has both low max and supercruise speed.

    Nothing to say about superiority of J-31 but its price would be low.

    Don't you dare to buy Chinese aircrafts with old-era Russian engines, which supply could be halted anytime.
    If J-31 has single-engine from Russia or USA, your risk reduce a half, but that engine never been supplied to China.
    If J-31 has single-engine from China, your risk may double or triple.
    So that J-31 has 2 engines.
     
  14. MiG-23MLD
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  15. AKIIN
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    PLAAF DACT with JASDF F-2 in mind
    PLAAF fighters from the southern part of China recently conducted a dissimilar air combat training exercise and the enemy being simulated was the Mitsubishi F-2.

    [​IMG]
     

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