Shame that the mods removed all Jo’s personal comments in his initial post leaving just the referenced docs. Did wonders for the accuracy of his post though.

For example:

The Shape Materials Materials Materials Justification for Poor Shape
As we all know, RCS units of measurement are based off relative return ratio from a target compared to a metallic sphere with a projected area of 1m2 at any frequency within the optical scattering regime for the target.

Given this, the omni-directional RCS formula for a metallic sphere is πr2 as shown in the list of RCS equations for basic shapes shown below, thus for a 1m2 (or 0 dBsm) RCS, the radius of a metallic, 1m2 sphere is roughly 56cm.

A quick confirmation of the equations can be done using POFacets to simulate the RCS of a 56cm radius sphere. As can be seen, it fairly accurately shows the RCS as 0dBsm except for some minor anomalies (almost all within 0.5dBsm) due to the way the basic 3D modelling tool packaged with POFacets creates its spheres. If I could be bothered converting blender meshes, it would be more consistent.

The list above also shows the basic formulas for the peak RCS for a cylinder and a flat, rectangular/square plate. Comparing the RCS of a 1m2 sphere (radius approx. 56cm) to a cylinder with the same radius and with a length the same as the sphere’s diameter, with the equation we can calculate the peak RCS of the PEC cylinder with 0.56418958354m radius and 1.12837916709m length to be 150.4506m2 or 21.77394 dBsm.
A quick check with POFacets reveals a very close result of 21.425dBsm (approx. 0.35 dBsm difference to the calculated value, pretty accurate based on the reasonably low res model I used to speed up computational performance)

So with confirmation that POFacets is very accurate on these simple shapes we can make an approximation of the (best case scenario) RCS of the T-50’s rear engine cowling made of PEC and using some fairly old ram technology spotted by JoJo on a manufacturer site.
Assuming the length of the engine problem area of 2m, and engine radius of 0.64m (based on the older AL-31F) and adding another 0.15m to the radius for surrounding structure and surface panelling (no point arguing this value as it makes little difference, don’t be that simpleton guy by responding), we can predict the RCS of the cylindrical engines which are exposed from 5 degrees below horizontal to be 210.7m2 (23.23dBsm) at 9GHz if made from PEC.

Even Jo’s non-existent aircraft RAM (revision 2) with a -30dB reflection coefficient (-30dB relative to a PEC normal to the surface) brings the RCS of these PAK FA engine-sized cylinders down to -6.8dBsm or roughly 0.21m2 at -5 degrees below horizontal (4.23dBsm or 2.65m2 in science reality), not taking into account double reflection off the underside of the wings and tail – forming a dihedral corner reflector – from a low depression angle (the worst angle).

Most modern field radars can track a 0.1m2 target from numerous hundreds of kilometres away, so a 10 degree wide, .21m2 RCS lobe projected out to around 230km (assuming 65kft altitude) presents a very serious problem for anything trying to operate like a real stealth aircraft.

For some perspective an AN/TPY-2 that can detect a 0.01m2 MIRV from 900km would potentially see a 0.21m2 target from 1926km away if it had line of sight. Even a low flying, airborne radar like the Irbis-E (tiny compared to ground based arrays) with a known 90km range for a 0.01m2 target could pick up 0.21m2 target from 192km away.

Comparing the relative RCS of the above 56cm radius cylinder to a 1.12m by 1.12m flat plate at angles representative of those on some stealth aircraft, the following is observed about the numbered points on the polar chart below:

1) The red circle represents the 56cm radius, PEC cylinder’s RCS

2) Represents the reflected main lobe angle off an F-35 or J-20, PEC, flat side panel of 1.12m x 1.12m illuminated from 5 degrees below horizontal. Effectively 84 times lower RCS in m2 and detected by radar at 1/3rd the range of the cylinder.

3) Represents the reflected main lobe angle off an F-22, PEC, flat side panel of 1.12m x 1.12m illuminated from 5 degrees below horizontal. Effectively 234 times lower RCS in m2 and detected at 1/4th the range of the cylinder.

4) Represents the reflected main lobe angle off an X-47B, PEC, flat side panel of 1.12m x 1.12m illuminated from 5 degrees below horizontal. Effectively 1500 times lower RCS in m2 and detected at 1/6th the range of the cylinder.

POFacets chart showing comparisons of .56m radius Cylinder and 1.12m * 1.12m flat plate illuminated from various angles, indicative of the panel cant angle on real stealth aircraft. Note the peak RCS at 0 degree angle of incidence to the flat plate is also consistent with the formulas above.

“L-Band is the new black for fighter radars, didn’t you know?”

Jo commented that L-band radars (in reference to the Nebo ZSU?) were built large because miniaturization technology wasn’t available for L-band transmitters before but has come far enough now to make it viable for fighters to sport S and L band radars exclusively in their main array?

The half power beam width (and subsequently angular resolution and minimum detectable velocity) of a given phased array is calculated with wavelength/array diameter as the main contributing factor. Wide array + long wavelength = good, thin array + long wavelength = bad.

Array detection range changes relative to the 4th root of Gt (transmit Gain) and range also changes with the 4th root of receive Gain. Both maximum transmit and receive Gain are products of array area/wavelength^2. High gain = good, low gain = bad.

Jo simply didn’t know they make em big so they have at least a reasonable level of angular resolution and so radiated power isn’t completely lost to the side-lobes.

“HPA’s Analogous to Cree products!!”
I was amused with Jo’s foray into the Russian GaN developments and trying to claim that certain Russian high power amps for radar front ends are on par with western equivalents, basically “Russia have caught up and exceeded the west overnight”.
The 2 examples he gave were the М421315-1 and the М421315-2 that he claimed were extremely compact and capable, “analogous to the Cree product” he linked. He later claimed directly that they had a 400W output.

Starting with the М421315-1: L-Band, 0.1-1.4GHz, 25% efficiency, 22x10mm area and a PPO of 34dBm (2.5Watts) in the lower frequency region. It has a minimum power of 30dBm (1 watt).

The Cree product has 500Watts max output, with a minimum output of 422Watts and a radiated to prime power efficiency of 67% compared to 2.5watts and 25% efficiency of the OKBPlanet production.

He later claimed he “knows a guy” who confirmed that this 2.5W wonder-amplifier is going into the S-500’s L-Band array, riiiight.

Ironically, dBm is the same unit of measure Jo humiliated himself with when he said cylinders were a stealthy shape ages back (case well and truly closed on stealthy cylinders above). He merely looked at a graph in his source which showed reflected power (in dBm) and thought -70dBm was a really low RCS value for the test target.

The S-band М421315-1 has a low end output of sub – 1watt and 19dB Gain. A quick look at Triquint’s S-band offerings and they have products at 80Watts, 22dB Gain, 1/8th the size and immensely higher power densities.

“If the average power output is THIS high, imagine what the peak must be!!”
Jo’s frequent quotes regarding unit power outputs not only proved him to be completely ignorant on the subject, he also proved to be, well… completely full of sh** too.

Yet from the manufacturer web site he discussed….

Judging by his quote I almost forgave him for not knowing the relationship between peak and average output as he so clearly doesn’t. APO is a function or duty cycle * PPO, or in this case 6% *200 = 12W

I couldn’t forgive him for being flat-out full of it when the manufacturer site clearly states the following though…

There’s uneducated ignorance, then there’s plain bulls**tting

“look at these NATO test results of fan blade tests?”
When Jo was dictating to everyone that the T-50 was to only use stealthy fan blades and partial duct shaping he provided a link to a documented RCS test of a test stand containing a fan with 45 degree angled blades (significantly more canted than his own images of T-50 blades). Unfortunately it only showed how badly fan blades scatter.

So on the target aircraft, combine this (from Jo’s source)…

With the CNT absorption he quoted…

Then factor in this on the enemy radar…

Pretty sure 2 x -13dBsm engines wouldn’t have cut it, but in the end Jo ended up having to suck up defeat to smarter people and had to concede a blocker was used anyway.

http://www.findpatent.ru/patent/237/2375395.html

“OMG 50dB/cm!!!!!”
Why would a radar component manufacturer want to produce a form of RAM. If your name is Jo it’s because “OMG I just found the biggest dB absorption number EVER! It most certainly is going on the T-50, guaranteed, what other use would RAM have?”

Others would know that RAM covered components are frequently used around radar installations, especially when they are mounted near comms gear and other radars to prevent interference from side lobes (and main lobes) from other emitters and the radar itself. A fine example would be on a ship with numerous arrays.

The patent for his wunder-ram shows a temperature tolerance of 300 to -60 degrees Celsius. Just hope the T-50 doesn’t have to cruise within the tropopause anywhere in the tropics where the AVERAGE ambient temperature is -75 degrees.

Alternatively, perhaps the temperature of the engines it’s hiding inside might be an issue as seen on a similar engine config…

But anyhow, the patent never mentioned application on an aircraft and certainly didn’t mention the substance’s tolerances for solvents, jet fuel, oil, grease …etc like other, specific aircraft RAM patents do.

Still confused as to where a radar manufacturer might want to use a soft rubbery RAM though, perhaps..

“Avionics & sensor fusion architecture of the PAK-FA (prepare to be blown away). Confirms AN/ALR-94 equivalent system, thermal channel for OLS, EA for radar(s), which can only mean GaN”
ALR-94 equivalent? Really. The posted article provided no listing of the supported frequencies, waveforms and SIGINT libraries used by both highly classified systems? No receiver counts, widths and effective area, just Jo’s word for it.

What he should have said is that um, it has a RWR like every fighter from the last 30 years.

Why are we suggesting weapons bays for F-14’s now? I really hope this is not an effort to say the F-14’s hulking and stealth incompatible airframe can be made usefully LO?

So you want to do a rich man’s RCS reduction upgrade to make a poor man’s version of the PAK FA, which is the poor man’s version of an actual stealth airframe.

What’s the tag for double face palm?

Even if I only had an 80% strike rate, that’s still 79% more than him.

But when you do, you do it in such spectacular fashion. I remember this one time at band-camp, you said a cylinder was a stealthily shaped object …. screaming it to the heavens, hurling your usual insults and providing sources of real-life RCS tests.

Unfortunately you completely botched the unit of measure in your source and failed to even comprehend the supporting text proving that a cylinder has one of the worst RCS profiles of all simple objects.

Damn, I’ll be talked about in the third person again 😎

To save more ignorant forum hijacking made a new thread on this concept.

There’s a little bit more science to designing an actual VLO stealth fighter than merely drawing up a model with a few facets and applying the word “stealth”.

Think angle and role.

With those side fuselage angles (main fuselage surface at 82.5 degrees cant angle) it’s side faceting is entirely pointless.

The very large 83 degree side surface will allow it to be tracked in a networked environment for extended periods of time (TIP: the longer the range at which it can be detected, the longer it can be tracked as it passes a radar) allowing engagement from missiles from quite a long range.

The missile doesn’t have to come from the the vehicle that spots you on radar any more. Being seen from the side makes you just as dead as being seen from the front.

There’s a reason why stealth fighters tend to be wide, its not just a matter of preference or whimsy. It’s because to create shallow side angles to increase the angle of incidence of RADAR beams illuminating the surface from relevant depression angles ( 0 to 30 degrees below horizontal for medium altitude aircraft and 0 to 40 degrees for high altitude aircraft), you need to increase the width (subsequently the cross section) of the aircraft.

Contrary to some grossly uneducated and uninformed opinions, materials will not compensate for bad shaping and with the enormous (and mobile) X-Band radars now being put into operation by the US (and maybe China in the next few decades), every little compromise is a killer.

Oh yeah, wing and fuselage intersection on this design is a MASSIVE dihedral corner reflector.

Speed of light IN A VACUUM is a constant.

Speed of light changes depending on the medium it is travelling through. If it did not then lenses would not work.

Speed of light in a medium is constant, so the claim that it is slower on the return trip remains incorrect.

Given the fact that using Kopp (and APA in general) as a backing source whenever the F-35 is discussed equals to outright herecy on this and other forums I wonder why suddenly his claims and methods should be considered when they are used to evaluate the T-50.

One way or another… the door swings both ways.

The “facts” and data on APA’s site is fine, its a great source of information. Its the nutty conclusions they draw that contradicts their data that lowers their credibility.

Its only people without enough knowledge on various subject matters that either dismiss or believe them entirely.

A lot of real science goes into Kopp’s data generation and modelling, it’s just a shame the supporting text is frequently tarnished with nonsense.