This is what the F-22 can do

[GGTharos]

You need to detect this aircraft to begin with. Secondly, you need to somehow power your death ray with enough power to fry your own EWR without even trying ... are we starting to understand the impracticality of this stuff yet? :D

[Guest IguanaKing]

Ahhh - I thought you'd misunderstood me & meant deliberately turning it into IR - with a receiver turning it into lectrickery & then powering an emitter -that took a lot of power - not just indirectly heating by causing eddy currents in the skin & struture - & I didn't mean that so I repeated myself.

 

Re the capilary thing - You could always get the pilot to wear one of those tin foil hats so popular in the psych wards - put brail on the controls ...

 

So - does 1.2KW/m^2 count as a lethal beam - my stomach turns & says yes ? -leaving aside the damage it might do to the pilot, & even assuming 40% is absorbed (because stealth planes have that nice radar absorbing coating) that's 480W/m^2 that's being absorbed by the plane & having to be dissipated - that's a fair amount of radiating somewhere in the spectrum - or is it?? Compared to heating through friction etc - don't know..

 

Heh...you thought I had misunderstood? I'm a radar tech, dude...and not the average monkey, I knew precisely that you were speaking of indirect airframe heating. As for the 480W/m^2, does it necessarily have to be absorbed and dissipated...or could it simply be reflected/refracted/otherwise re-directed? Microwave freqs are much more difficult to misdirect, as they are not nearly as directional as light freqs...IR is the closest to microwaves...but light freqs are also much easier to filter out...hence...DEFEAT.

[Weta43]

I'm just playing with the idea, but I guess if you're worried about frying your own EWR or personel, the sensible thing to do would be to not put the EWR between the microwave plane warmer/deathray & the target then wouldn't it :-)

maybe - now here's a thought - you could mount the mirowave transmitter on a mast 50m directly ABOVE the EWR receiver then the EWR would only have to deal with the returned signal, which from a 'radar stealth' plane (because that's the point of them) would be quite small & easily filterable.

 

Speaking of which (radar returns)..

 

GG or IK either of you might know this -

 

'Stealthy' planes still have a radar return, the return is just too weak to detect because they just have a very small effective radar cross section.

However the strength of the return is also proportional to the strength of the beam landing on the target, which is a function of power output, beam shape & distance between transmitter & target..

Beam shape is affected by transmitter area & is constrained in planes, which means their beams spread more than they might with an optimal shaped transmitter.

Beam output power is also constrained on a plane - you've got to generate power for it, carry the equipment around, & you've got to sheild the pilot from it (?).

How powerful would a ground based radar - working at the frequencies that search & track radars operate at & using an optimally shaped transmitter (no constraints on weight or size (radar dish the size of bunch of billboards stuck together if you like) have to be to detect an F-22 at 120km or 160km assuming no constraints on the receiver side either - assuming no jamming is going on & accepting the (as yet not physically tested by the manufacturers) calculated RCS of 0.001m2

[Weta43]

IK - I said absorbed because the skins on stealth planes are designed to absorb radar. 480W/m^2 was 20% of the power falling on the plane, the rest was reflected.

If it's reflected - cool - just look for the return on radar.

[GGTharos]

I just wanna know how you're gonna make an antenna to transmit all this and avoid frying it, and everything near it ... unless you make it a static installation, in which case it's eh, dead meat :D

[Guest IguanaKing]

Yes...what GG said...along with how one would easily carry and erect an antenna who's mast height is 50 meters. That's where the simplicity ends. A radar's receiver doesn't simply look for its transmitter frequency...it looks for its own pulses (through an RF signature). Otherwise...how in the hell would it know any other X-band pulse train from its own? These pulse trains bounce all over the gd place, and the RF signature is very important in signal rejection. For this rejection to occur in the first place, the incoming signal to the receiver antenna has to be beyond a set dB (this dB level is often set to reject noise)...so if the return from this "easily detectable" aircraft falls below the rejection floor...why would the emitting radar even care that its there? And...this is assuming the return even resembled the transmission of the threat radar...which it, most-likely, will not.

[Weta43]

Maybe deploy it with/on mobile EWR units. They appear to have fairly big collapsable antenna. I'd guess a 10m diameter dish would do it & that's not too large to be transportable & easily erectable + with a receiver that size at 10MW you might even get enough return from a stealthy plane to use it as a 'conventional' S&T radar.

 

However - & I think you forgot this IK - I didn't suggest this as a radar, I suggested it as away of heating anything in a target area designated by an EWR to the point where you could track it from its IR signature - because the plane wouldn't be providing a return to shorter wavelengths. GG suggested the return from the target would fry the EWR receiver & I said if you're getting that strong a return, either filter it out or just use the thing as an ordinary radar, but that I didn't think you would -because you're only doing this because it's a stealthy target - which is where the second question came from

 

The idea is that it's a tight focused coherent beam so not too much radiation irradiating the area unless you're on a ladder in front of the dish - & you could borrow an idea from the WW1 fighters & fit an interuptor that turns it off when you point it at the truck you have it mounted on - or the ground - or anything in the air with a transponder that makes you think you don't want to cook it.

 

(I wasn't suggesting a billboard sized dish for this -though those Russian mobile EWR's are getting on to this size - that was a side question about how powerful a radar you'd need to pick up a 1cm RCS object at 120 or 160 km if you weren't constrained in the size of the emitter & receiver by having to fit them in a plane)

[Guest IguanaKing]

Yes...10MW...and you can detect just about anything. How about the poor, enlisted troops caught in the side-lobes of that radar? They might live a couple of weeks, maybe even a month or two. I guarantee those last weeks wouldn't be happy memories for their family members. Victory means nothing if you kill your own people before achieving that.

[Weta43]

You don't need doppler filtering so you wouldn't intentionally create side lobes & would shield the transmitter to the maximum you could.

You're not tracking the target, just heating everything in the area the EWR says the target is in.

 

(if you can track , that's a bonus)

 

How much energy is there (proportionally) 30 degrees off center of a well focused microwave transmitter 100m away from the transmitter?

[Guest IguanaKing]

Side-lobes are just a necessary side-effect of any microwave transmitter antenna, they are not simply "selectable" by the people who emit them. If you emit a wave of that length and power, quite simply, your own people will die. No amount of hokus pokus...or "wish it won't" will change that.

 

Your question about off-center power from a transmitter at 100m is a loaded question. You left out frequency and power in your question. I could emit an 80Hz signal at 120dB, from an antenna 100 meters from my target, at 45 degrees, and the best I could hope for is making my target suddenly have an urge to relieve his bowels. Seriously though, only urban legend might suggest to my target that this was the proper thing to do in that situation...and its not an actual, physiological response.

[Weta43]

100GHz transmits pretty well doesn't it? From a 10m dish

This was the assumption I was working on -(after we left my first suggestion of a coherent wave microwave 'laser' - raser?) Tell me where i"m wrong & I'll leave it at that.

I can put a microwave transmitter of any strength on the ground & then with properly designed sheilding kill everything that comes off it.

waves leaving an apperture tend to diffract & spread. The larger the apperture is in comparison to the wavelengths, the less they do this.

A big dish, some properly designed housings & sheilding - a big effective apperture & I figured you can create a very tight beam (by sheilding, reflecting & absorbing all the radiation not going in the direction I want it to). If I stick a big electromagnet around the beam I can even focus it to a particular point.

 

Those microwave dishes they stick on comms towers. Their beams are only a couple of degrees wide aren't they ??

[Guest IguanaKing]

100Ghz? Is this the magical "lower" frequency that the stealth bashers are banking on? Stealth aircraft are detectable, but not trackable by long-wave radars. Long wave-length, equals low frequency, does it not...or did I miss a day in school somewhere? At what point did we learn that 100Ghz was lower than microwave frequencies?

[Weta43]

No - 100GHz is a microwave frequency that has good transmission through the atmosphere (one of the frequencies used by astronomers that is considered to have a good transmission 'window') & was my suggested 'warming' frequency.

10m is what I considered a large enough apperture to not cause a lot of beam spread through diffraction of a coherent wave beam at that frequency.

[Guest IguanaKing]

No...100GHz is not a microwave frequency, it is a millimeter wave frequency...and as I stated earlier, it is a shorter wavelength than that of standard radar freqs, thus it is even less useful in long-range detection of LO aircraft. The size of the radiator is really quite irrelevant when the transmitter frequency is not up to the task in the first place.

[Weta43]

Colorado state university considers it microwave...

 

http://amsu.cira.colostate.edu/spectrum.html

 

and I'll repeat again that my suggestion was not to use this frequency for detection, but for dumping energy into a plane.

 

edit: See also -

Microwaves are electromagnetic waves with wavelengths longer than those of Terahertz (THz) wavelengths, but relatively short for radio waves. Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz). However, the boundaries between far infrared light, Terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. The term microwave generally refers to "alternating current signals with frequencies between 300 MHz (3 x 108 Hz) and 300 GHz (3 x 1011 Hz)."[1]

 

 

http://en.wikipedia.org/wiki/Microwave

[Guest IguanaKing]

You are mis-reading the chart in that link, NASA and the FCC call 100GHz the "millimeter wave/telemetry" band. I understood what your suggestion was before, sir, and I'll repeat that this frequency of yours, at a sufficient power to indirectly generate IR significantly above background, will likely kill every lifeform in its path and out to as many as 120 degrees on either side of the radiator, at any point in its sweep, whatever that may be, within a certain distance. Also, to generate IR in a given substance, in the most efficient manner, one must match wavelength to the resonant frequency of the molecules in that substance. So...tell me...what is the exact size of a single molecule in the skin of the F-22? Or maybe its the paint that'll heat up. OK, then, what is the exact size of a paint molecule on the F-22? Don't know? Neither do I, its all academic, and my ultimate point is that people much smarter than you or I could ever aspire to be, have run through every imaginable scenario since the mid-70's, and the F-22 is the latest example of what they came up with. I think that trying to outsmart these gents is an exercise in futility...well...for us public forum-goers anyway. ;) Sure...Russia will provide all kinds of info that proves stealth doesn't work...of course they will. It was the studies of a Soviet, Pyotr Ufemtsev, that fueled the US stealth program after poor Pyotr was basically dismissed as a loon and his works were never classified. I think that still stings a little bit.

[tflash]

Hello Iguana,

 

We are neither in the business of F-22 bashing nor trying to outsmart anyone. We are just educating ourselves with imaginary scenario's how to defeat stealth. Like in all academics, these kind of exercises sharpen the mind and are the best way to learn the basics involved.

 

I found your discussion very instructive, since it clearly shows the issues at stake. For the moment, it seems we already have "Hiroshima revisited" and "The Big Frie". Seems we still have some work ahead.

 

I am not more optimistic than you that we will end up with a realistic solution :)

[nscode]

From what I understand, it doesn't mean a freq is worse if it's even higher than what is now commonly used in radars. This is because stealth aircraft, or to be more specific, their dimensions, need to be "tooned" to be stealth against some frequency range, much like you make an antenna for some freq range. The reason long wavelenght radars are capable of detecting them is that they fall out of this pre-tuned range. That means that wavelenghts shorter than that range can also be used for detection.

[Guest IguanaKing]

Long waves are also far less directional than shorter waves, thus they propagate better in air. That's one of the main reasons long wave devices can detect stealth aircraft better. ;)

[GGTharos]

If you look at RCS charts, it seems that *higher frequency* causea reduction in RCS.

[nscode]

Long waves are also far less directional than shorter waves, thus they propagate better in air. That's one of the main reasons long wave devices can detect stealth aircraft better. ;)

 

don't think that has anything to do with it.

[Guest IguanaKing]

If you look at RCS charts, it seems that *higher frequency* causea reduction in RCS.

 

Yup...exactly. :D

[Guest IguanaKing]

don't think that has anything to do with it.

 

Alright, fair enough...but it does, actually, have a lot to do with it. ;) The pulses have a much better chance of getting back to the antenna that emitted them in the first place. One major problem with this type of radar, however, is that the antenna...well...its a HUGE friggin' antenna.

[nscode]

higher freq = shorter wavelenght = smaller antenna

 

the reason you need a big antenna with these is to have a higher antenna "gain" because you do loose more in air, but that is also limited by various factors (one of them being that antenna size gets much larger than wavelenght and different antena prats get different phases). what you then do is increse emmiter power and reciver sencitivity.

 

but, all this is to know if the signal will be able to bounce from any object at distance and get back. let's presume it is. then there is no difference if that object is "stealth" or not, since it's not stealth at that freq.

 

 

OT: and since we're talking antennas, here's somethnig my buddies and I did a few moths ago:

 

NSWireless-BGWireless community networks link

 

5.6 GHz, 45+27 km 3 MB/s :punk:

no signal boosters used

all feeds are home made :chef:

[GGTharos]

It's 'stealth' at all frequencies. RCS is larger at long wavelength, but stealth STILL reduces this RCS. ;)