The stealth ace: F -20 fighter of top-secret performance shock analysis
accurate RCS of complex objects such as aircraft there is still a lot of problems, on the one hand, only through different scenarios, different theories and equations to approximate the accurate calculation and simulation estimates, on the one hand to be corrected by a large number of actual measurement parameters and make up theoretical defects, or for a statement, stealth rules we are more familiar appearance designed aircraft of any one single on the shape of the RCS can be said now are can not be accurately calculated accumulation of experience in modeling, but by a large number of measured you can get some of the projections and the optimization model can estimate pretty close, not too far at least an order of magnitude.
This should also consider the metal structure of the aircraft, such as the fuselage load-bearing frame and wing structural components, after several anti-N times scattered wave backscatter diffraction like , the situation is even more complex, but this part of the scattering value after application laying or entrained absorbing materials composite structures can be effectively suppressed. There are also some active active stealth measures and so the ions means we are unable to visually see that, for example, the paper will not be discussed, stealth effect mainly in the traditional appearance passive stealth, electronic warfare antenna Han also can barely see, simple analysis under.
Now that can not be accurately calculated, then the best YY way is the similar appearance characterization to compare the F-22, F-35, so estimates of the different orientations of the point of view of J-20 stealth effect, RCS magnitude should be comparable. Before analysis and then briefly mention several premises, there are number of clear assessment criteria:
The first is the J-20 in the F-2235 after nearly 20 years, there is a clear reference object and research direction on the basis of a lot of technical means to study and verify more mature, obviously the basic requirements of the bait to be able to confront the air superiority F-22, suppression of the F-35 stealth effect on nature can not be more than 22 Cross-magnitude difference;
2, followed by the stealth effect evaluation Remember a few commonly used reference values: RCS is reduced to 1/10, 1/100, 1/1000, 1/10000, respectively, corresponding to the echo the signal strength is reduced to 10dB, 20dB, 30dB, 40dB, corresponding to the same incident source radar detection range is reduced to 56%, 32%, 18% and 10% (assume that the radar completely distinguished);
3 air superiority fighter horizontal orientation + +20 to -40 degrees -30 degrees and vertical orientation is a strong threat to regional effect stealth optimized forward this part of the echo. Of course, before the enemy found before the enemy attack and fast from the ideal pick-up mode, large motor to adjust the posture and the exposed tail probability is not small, it must take into account the aircraft side, the bottom and the tail of the incident field RCS effect.
4, finally, from the contribution of the RCS focused look at four types of scattering: the forefront of specular reflection trailing edge scattering, line wave and crawling wave reflection cavity effect, as to such cutting-edge diffraction absorbing materials like laying by the state-of-the-art parts can better backscatter sidelobe suppression is not that big, and on the RCS the impact is basically negligible.
talk about some form of J-20 stealth speculated analysis.
one, J-20 head-on RCS analysis
fighters head-RCS affect the largest source of general effects of inlet cavity the plane radar array in the nose, cockpit cavity effects, including the hatch the front and rear edge of the slit, the wing and the inlet lip such frontier reflection surfaces, on the other hand wing straight trailing edge also has a strong reflection of the relative angle of incidence greater than 0 degrees of the vertically polarized wave backscatter, the straightness of the fuselage and wing trailing edge machine table row wave form.
J-20 front look a little smaller than the F-22 projection, positive direct mirror reflective surface; wing and canard front swept large angle, all kinds of back and forth along including Cutaway and jagged edges flap angle of reflection are consistent with the cutting-edge angle of the main wing, to ensure that this part of the level of polarization of the reflected echo scattered to the major threat to areas outside the limited direction, the trailing edge of the main wing wingtip Cutaway and former anti-angle 22 situation angle and cutting is not reflected by the reflection and surface traveling wave of the vertically polarized wave treatment effect and made a balanced rudder effectiveness and pneumatic stealth effect than the YF-23, but the mobility is more favorable. Hatch back and forth along a similar 22 as jagged transfer scattering angle processing machine table are basically continuous surface variation before and after, and the edge of a continuous ridge, up and down relatively flat bottom, basically no sharp protrusions opening cover much surface rivets from several big picture processing and opening edge processing well (of course, that layer of blue-black paint to cover up a lot of details), crevice treatment from exposure to some of the places look like with 22, including some places with conductive tape hide this means almost engine end of the fuselage skin in accordance with the two sawtooth design (fuselage skin and guayule Last vents gap, will not pass the surface traveling wave, but the current the guayule tail mouth design Some issues, discussed later).
J-20 fuselage longer, we all know the incident field length is much larger than the wavelength of the irradiated object, physical resonance is not close to the optical backscatter law tends to be constant, so the fuselage no significant effect on the length of the RCS, but rather machine table material conductivity induction and the end of the traveling wave backscatter contrast models conductivity of the surface material is consistent stealth effect will not differ much. Total scattering, see J-20 shape designer of the machine table creeping wave diffraction and reflection of traveling wave is still relatively good control. Some of the more common means of stealth, careful design point multi-test to verify that we are almost the same.
metal coating overall hatch stealth effect of the cockpit of the cavity should be the same with 22, J-20 inlet cavity effect forward scattering source suppression significantly better than the 22, and 35 are similar, can face completely obscured a direct reflection of the engine fan blades and through the long S-shaped inlet (absorbing paint, the basic means) in the incident wave multiple reflections to achieve a significant attenuation purposes, most seem to 18E tract as to engage in a shielded gate, but no matter how laying absorbing paint DSI + lip Cutaway the galette stealth effect the isolation chamber boundary layer should be more than 22 + the internal radar absorbing oblique board + casual air intake, supersonic intake The effect is stronger than the 35 inlet design (J-20DSI shape more sharp adjustment plate to improve the low intake) while stealth effect because the inlet is longer signal attenuation, conical the DSI surface after backscatter slightly better at a 35 oval DSI surface, integrated stealth effect will be slightly better than 35, T50 Needless to say, with the boundary layer isolation gap is short and shallow S-shaped inlet, even with Absorbing Materials shielding gate will be at the head generated within the large range of angles not weak backscattering, and most did not optimize promising one (Otherwise after play the DSI?); Finally, galette inlet sectional The aspect ratio The RCS also influential, this value theoretically about 0.6 to 1.4 will be relatively low inlet aspect ratio of the J-20 photos slightly less than 22 diamond-shaped camber slightly smaller, it is estimated that the difference in the RCS impact small. Overall, inlet J-20 the relative 22 accounted RCS cheap estimates may have about 5dB relative T-50 advantage is greater than 10 dB.
nose radar stealth deal with the invisible bad speculation, the view from before coming out of the 10B active phased array radar should have been solved, as 22 as Yang array frame , increasing FSS impedance secondary face and other measures, and achieved forward above the inhibitory effect of the X-band horizontally polarized incident-20dB, thereby substantially eliminate a large echo highlights these years due to this aspect of the technology and the scene is relatively simple, basic have been studied thoroughly, J-20 should also adopt similar means, both antenna area close to, J-20 may also be slightly larger in order to detect the distance However the integrated RCS abatement effect should or in a middleweight on.
canard before the main wing is more a place for everyone controversial criticized, but through the use of wave-transparent materials in the structure, surface laying absorbing coating, swept back and forth along the other measures, the impact on the RCS far did not imagine then, actual positive direction for small and medium-angle deflection, deflection axial sweepback, coupled with limited deflection angle backward inclined plate changes in the overall RCS will be much affected, according to J-20 canard the area of ??the forward RCS estimated to be no more than 2dB consider stealth coatings and sucked through the wave structure material will be lower, and then consider the J-20 V-type full-motion small vertical tail height and area of ??far less than 22 two banner, two-phase comprehensive fact aerodynamic airfoil overall backscatter can basically evened slightly worse than the conventional layout of the V-shaped full-motion vertical tail T-50, but not with the overall RCS to the order of magnitude of difference when it comes to which also had the top design J-20′s designers, courage necessary bigger.
existing appearance stealth technology to obtain general about-20dB stealth effect is relatively easy to achieve, when fighters part of the RCS tends to average the rest to -30 or-40dB the effects need to be upgraded and a large number of calculated and measured accumulated optimized, considerable difficulty, doing the best will B2, because they do not emphasize mobility, stealth strategy to implement the most thorough, the best results. Contrast 22, head-direction of pure physical radar cross-section of the stealth effect of -25 ~-27dB, the J-20 stealth effect will reach about -28 ~ -30 dB, plus absorbing coatings and structural parts optimization, if 22 along The orientation RCS less than 0.0065dBsm, J-20 ought to better than this value. To put it another way, a the 100KM radar detection range of standard reflector section, the maximum detection range of 22 23 ~ 25KM like J-20 detection range should be in 20KM. Of course, these are not considering additional initiatives such as plasma stealth like, as well as absorbing coatings and structural components of the technology level differences, the estimated error of this wind irresponsible.
two, side RCS
wing trailing edges of the big dip and fuselage gap, edge aliasing fixed angle of reflection azimuth reasons, 22 and J-20 in the side of some angles horizontally polarized waves are relatively strong reflection effect, but the angle is very limited, aircraft attitude angle slightly change may not be detected, another the fuselage curvature continuous surface of the wing-body fusion of body and lifting body design, outside poured the design of the V-shaped tail, which substantially eliminate the angle of reflection effect, but with the camber angle of about 30 degrees of the V-tail in the horizontal plane of the incident wave signal abatement can reach about-15dB, but because the 22 vertical tail area indeed too big, this part of the scattering contribution has not yet reduced to the point of completely ignored, which is considering the directional stability of the high angle of attack, and motor control of last resort compromise, or who do not want to carry a big two flags. Although a portion of the wing and tail block obliquely downward from the side surface of about 30 degrees incident, but still strong specular reflection is formed relatively small, but can be measured angle. J-20 fuselage projected lateral area slightly larger than 22, mainly long, but all-moving vertical tail area much smaller, the same side oblique angle measured before. In addition to the application of absorbing coatings and transparent wave of structural materials, few other measures, addition of anti-interference or cancellation, J-20, on the tail that three antennas and the top of the block can be installed induction antenna to receive threat detection shaped antenna surface estimation is used to dry the nose direction can also see similar means. The
J.-20 fin and pelvic fins inclination on the main wing carefully to avoid the the main sidelobe angle reflection effect, but the positive side is also not completely blocked end vents Fortunately leaked cylindrical nozzle not many, the reflection also not too obvious. IR stealth effect, the orifice of the guayule obvious reinforcing rib-like protrusions and quadrilateral recess Obviously, is a member having a hollow structure, one can reduce the weight, on the other hand conducive to the introduction of the cold air circulating cooling, reducing the nozzle external infrared signature.
this surface structure is easy to increase the rear side of a larger range of angles within the RCS, do not know Eupolyphaga not think the impact is acceptable or simply whether measured through anyway vents up only consider the surface Infrared Stealth.
similar 35 vents can not be completely blocked, but the vents peltate leaves were fine tip along the cylinder tangent increased fluctuations knuckle, so you can maximize measured as the wave reflection to the other direction, reducing RCS influence, and said trailing sharp corners can pull out the turbulence conducive to cold air mixed with the high-temperature air plume to reduce the infrared signature, and this regard we never learned aerodynamic design is not to pull, anyway, the current silver Ju bad taste in addition to surface cooling and to meet some of the leading, may other aspects Ma Ma Tei. Of course, the vector control is another to say, the government must, elevation and unconventional motorized tie that all-moving vertical tail must.
side of the RCS, J-20 and 22 each has its advantages, the level of less.
three tail RCS
In fact, the front analysis testing also said, end vents have problems, maybe there’ll optimization, but relatively speaking, when the trailing edge of the aircraft becomes frontier, relatively flat and small front anti-angle rear view RCS adverse the main wing perishable actuator cover cover large, larger than 22 and 50, possibly with a canard layout, the main wing flaps, ailerons action surface but also the relative participation related to the longitudinal trim required torque bigger, perhaps it have a say in this regard Fang Fang, Shashi Hou reveal a face analysis to explain?
tail RCS biggest contribution the same effect of the cavity of the tailpipe, basically no way, B2 and YF23 as extending the vents at the bottom of the shelter can guard certain the backsight angle of depression under the RCS, but behind the above and after there is no way to shade a 117 kind of measurable angle can only be reduced, J-20 and 35, 50, so that would not have said, chrysanthemums are open, you have no ability convex got.
So after the RCS, either one can eliminate to the desired effect, the only difference in the size of the angle measurement range attack finished for tactical targets to get rid of, it is best not to immediately make a U-turn at the large motor run, to people find and track opportunities around the large circle Paoyuan point and then bugger better, of course, if the threat airspace too big direction too, might can only tighten the engine. Stealth air superiority fighter
combat mode, or as much as possible to fight off opponents attacks and the ability to detect first knocked the otherwise off a down that money, but losses at full blast.
tail RCS, J-20 and 50 bad, 35 is slightly better, 22 re-gifted.
J-20 is already Eupolyphaga currently available technology, the strongest embodies the basic is what good pile up the progress of a hurry so it is inevitable that some defects engine piece most obvious, the material aspects of the naked eye can not see, only to see the J-20 surface craft and coatings visual effect is very good, very smooth, good accuracy of skinning process, and can withstand the discerning eye of the different angles, even a little gap estimates are affixed to the conductive tape buttoned up from 10 FC 10B since the verification of the various pneumatic means doing the very continuity of the spirit of innovation is needless to say the spirit of the requirements that conforms to 386,486, and 586 after the main slogan I do not know.
canard + larger side bar + delta wing is indeed very powerful, well-coupled canard trim lift, eddy currents can pull out the smaller angle of elevation to the main wing appropriate lift bring canard dihedral elevation angle increased downwash little effect due to the longer distance of slightly under the surface of the main wing anti airflow when the edge of the vortex began to play a stronger role of lift, the aerodynamic design really cool ~ In addition, V-type full-motion small vertical tail all accounts are the finishing touch, do not know the Fang Fang’s view on this. Long physique of J-20 is still a lot of benefits, associated side of the magazine and the magazine space belly big fuel load is guaranteed, pneumatic on to favor ultra patrol, and the rest depends on the engine to not give force.
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