How the heck did the guys on Feiyang get this graph? How???
J-20 5th Gen Fighter Thread IV (Closed to posting)
- Thread starter siegecrossbow
- Start date
- Status
How the heck did the guys on Feiyang get this graph? How???
Either an academic paper or the leaked parts of an academic paper.
I am not sure but I think they may have shaved the edges here circled in red also:
They also seems to be of a lighter grey colour - placement positions for back looking sensor/PAR?
Second look seems like it is just different colour.
Also the centre part in between the nozzles changed too?
OH NO! Heads are going to roll, somebody forgot to lower the cover on the Rotary-Discumbobulator, or is that the Molecular-Nebulizer, the KGB is gonna find out that somebody else is messing with time travel, the ultimate missle defense! Somebody else has been to Roswell?????? darn it!
With their secret agent de-coder ring out of cracker-jacks! man somebody needs to take you under their wing, er I mean share their ring! Ah, that's nuthin, BHO and Hagel are training the Monkeys at the Cinncinati Zoo to Fly the U-2s, Air Force Pilots are too mouthy, and the local walmart raised price on UAVs so they're gonna let the Monkeys do the flying, and they work for peanuts, no worry about promotions, retirement, and pay raises, its all good over here in Central Obamastan! You know Ohio is the birthplace of aviation..........oh and them monkeys, they don't need no ladder to get in the plane, they's some smart little buggers, gonna let em work on the budget next????
I would guess that the clipped edge threatment is mainly to deal with waves travelling along the edge
Below is a really crude pic and explanation of what I think may be happening.
Red arrow signified incomming energy direction, and purple after interacting with surface.
1 Would be a direct reflection. Which is what we don't want.
2 Would be an angled reflection, won't be picked up by the illuminating radar but may be picked up by off-boresignt passive receivers.
3 Would be diffraction when hitting corners. The energy will spread out in all directions but because it is not as focused thir magnitudes tends to be smaller. The sharper the angle, the more energy is diffracted and less is transmitted along the object's edge as creeping surface wave.
4 Would be a rounded corner, there will be some direct reflection, because at some point along the curve the surface would be normal to the incomming wave. Because the surface transition is gentle compare to an sharp corner, a large component will flow along the surface until it encounters another sharp transition such as another corner and diffraction would occur. How much energy flows along the surface and how much is shed along the way would be determined by object material's physical and electric properties as well as the size of the curve to the wavelength of the signal.
5 Would be the shaved edge example. The less sharp corner (rough rule greater than right angle) encourages more energy to flow along the edge until it reaches the second corner and more energy would bleed off as diffraction and what remains flows along still and it gets progressively smaller. The diffracted signal spreads in all directions to discourage a strong return in one particular orientation. And because there are many corners the signals will add irregularly to cancel out somewhat amongst themselves. At far enough distance from the plane, the return from all the corners would seem almost parallel which means their magnitudes are more or less the same which helps with cancellation.
So we shape for stealth by angled surface to deflect wave away from it's incomming direction. The RAM coatings will hopefully attenuate signals so that not much is reflected anyway. corners and sharp discontinuities are a problem so we shave them to make them more oblique, and we encourage the singal to bleed as it goes around different corners and 'spread the signature out' so that you don't get strong returns in one particular direction. We would also encourage controlled surface waves as they would be flowing on the RAM coatings which would attenuate them fast.
what about when canard is rotated to close to 90 degrees against the incoming signal (which is not likely, but possible if you are facing an environment with AWACs, fighter jets, naval ships), then you are basically only getting case 1, where everything is getting reflected back. Seems like this is more likely to happen against a rotated canard then against the wing surfaces or the belly of the aircraft.
RAM might help for that, but my guess is that like any other control surfaces, while at BVR the FCS will try to optimize flight so as to limit deflections as much as possible, and if there is such a moment where control surfaces must be deflected severely enough to spike RCS, then that spike is only temporary until the plane no longer has to deflect, has moved out of the beam area of the radar, or is facing the beam at an angle/face that has a more favourable return, which may still prevent or kill a track and lock. If they're in an EM saturated environment at all azimuths, then stealth is probably pointless anyways.
material scientists and enginners will deal with this issue. If this is fiber enhanced polymer materials instead of metal based, it is possible.
then, you will be a very bright primary return, this will likely only occur if you have been drawn into a "furball" so there will be lots of action to get lost in, and its possible that once you have been engaged, that the element of stealth has been compromised, but when its over, you may go "quiet" once again and proceed out of the hot area, and on to the next target?
That made my day... and now just let this dragon fly !!
Deino
Upppss
... just noticed that the image was added only as a smaller version ... here at least '2011' ! Attachments
-
J-20 2011 - best so far.jpg
when facing enviroment with awacs, ground/ship based radar etc radiating from various directions it doesn't matter if youre in j20 or f22, both planes would suffer the same problems. that's why vlo design is made in accordance with planned operational use patterns.
vlo design is concentrated on ingress, and somewhat on egress. it can't also provide small rcs from most angles most of the time when f22/j20 actually get in combat and start manouvering left and right. which is why, as any fighter in history did really, vlo planes pick their fights, pick their ingress routes, do their job quikcly and then get the hell out of there. in real world its hard to have a bunch of opposition everywhere, all the time.
also, it'd be nice to know the author of the alleged academic paper. is it a random student from a random university? or an engineer with known experience working for avic?
vlo design is concentrated on ingress, and somewhat on egress. it can't also provide small rcs from most angles most of the time when f22/j20 actually get in combat and start manouvering left and right. which is why, as any fighter in history did really, vlo planes pick their fights, pick their ingress routes, do their job quikcly and then get the hell out of there. in real world its hard to have a bunch of opposition everywhere, all the time.
also, it'd be nice to know the author of the alleged academic paper. is it a random student from a random university? or an engineer with known experience working for avic?
- Status