Microwaves, Stealth Aircraft and the Cold War

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Microwaves, Stealth Aircraft and the Cold War

Postby mercutio_stencil » Thu Jan 13, 2011 10:51 pm UTC

An old professor of mine told a very charming story that I have been completely unable to verify.

Apparently, the Hot Pocket wrapper utilizes the same technology as the coating on many stealth aircraft (a metal foil dissipating radiation as heat). This lead to a strange sort of espionage, wherein spies were caught trying to ship large amounts of microwavable goods to the Soviet Union in an attempt to reverse engineer the material.

I'm fairly certain the science works out roughly, and the dates sort of line up, but I was wondering if anyone had any additional information on this amusing anecdote?

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby BlackSails » Thu Jan 13, 2011 11:26 pm UTC

Isnt the main reason stealth aircraft are stealthed because of aircraft geometry? For sure, they are painted/made of some secret material, but I thought its mostly the shape.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby thoughtfully » Thu Jan 13, 2011 11:48 pm UTC

I don't think there's anything special about the hot pocket wrapper other than that it's a metal foil bonded to the cardboard.
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby The EGE » Fri Jan 14, 2011 12:56 am UTC

Radar Absorbent Material (RAM) tends to be made of a semiconductor inside an insulator. Carbon in plywood, graphite in rubber, carbon-loaded foam. The military (we think) uses mostly iron ball paint - mini particles of iron, in specially formulated paint.

I don't see how metal foil would be an effective RAM.
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Sir_Elderberry » Fri Jan 14, 2011 1:50 am UTC

If the military invented such a material to the point that those carrying large amounts were arrested because they were worried about the Soviets getting their hands on it, I really don't think that material would be available to private companies in general or whoever makes Hot Pockets in particular.
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby p1t1o » Fri Jan 14, 2011 12:00 pm UTC

The "stealth" of a "stealth" aircraft has alot to do with its geometry, yes, but they also take advantage of these absorbent coatings to minimise the return of any signal reflected towards the searching radar.

Sidebar: a common misconception is that "stealth" aircraft are, or can become, *invisible* to radar. This is not the case. They are engineered, by shape or material (also by controlling their own emissions, IR, radio, radar etc) to minimise the return of any radar directed at them towards the transmitting device - every radrar will have a range at which any return signal is too weak to use for detection purposes, "stealth" technology works to make that range smaller and smaller, which can open up holes in radar detection grids, reduce the effective range of missiles and increase the effectiveness of active countermeasures.
There are various techniques that an air-defence network can use to overcome "stealth" technology, but as in most similar things, it is a case of minimising and maximising and careful planning, eg: during desert storm the flight plans of the F-117 "stealth fighters" were planned with large, flat turns to avoid the aircraft pointing its large flat belly towards an enemy radar (which would give a strong return, RAM or no.).

Back to the point:
Materials that absorb various kinds of radiation are not a mystery or secret, if you want to absorb microwaves, water works very well (hence how a microwave oven works). The secrecy surrounding the radar-absorbent materials on "stealth" aircraft surrounds exactly what frequency ranges of radar they are best at dissipating, and I suppose there may be some difficulty in engineering a coating for certain frequencies that they might want to keep hush-hush too.

Bottom line, radar absorbent materials are not all that exotic, but if you want to build a "stealth" plane, you better keep your materials secret or the soviets will work out its weaknesses...those tricksy soviets...

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Moose Hole » Fri Jan 14, 2011 3:12 pm UTC

In Soviet Russia, Hot Pockets study you!

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby gorcee » Fri Jan 14, 2011 3:28 pm UTC

BlackSails wrote:Isnt the main reason stealth aircraft are stealthed because of aircraft geometry? For sure, they are painted/made of some secret material, but I thought its mostly the shape.


Geometry, nowadays, has very little to do with the overall RCS of a vehicle. The materials and coating are far more important. Early stealth designs utilized exotic geometries because the materials did not exist (or, more aptly, mostly existed only in laboratory environments). However, more recent designs have more conventional shapes, which allow for more traditional mission capabilities. Geometry still plays an important role, but it's really the materials that matter the most.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby p1t1o » Fri Jan 14, 2011 5:34 pm UTC

@gorcee
Really? I was under the impression that newer "stealth" aircraft had more conventional shapes due to better computational techniques - the F-117 had very unusual geometry because designing the aircraft to be "stealthy" from more than a few angles was prohibitively difficult at the time. If you look at aircraft such as the F22 or F35, their geometry can be seen to be fairly complex in certain places. Also these days designing for absolute "stealth" is not as desirable as sacrificing "stealth" for other capabilities such as speed and cost effectiveness.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Technical Ben » Fri Jan 14, 2011 5:55 pm UTC

p1t1o wrote:
Spoiler:
The "stealth" of a "stealth" aircraft has alot to do with its geometry, yes, but they also take advantage of these absorbent coatings to minimise the return of any signal reflected towards the searching radar.

Sidebar: a common misconception is that "stealth" aircraft are, or can become, *invisible* to radar. This is not the case. They are engineered, by shape or material (also by controlling their own emissions, IR, radio, radar etc) to minimise the return of any radar directed at them towards the transmitting device - every radrar will have a range at which any return signal is too weak to use for detection purposes, "stealth" technology works to make that range smaller and smaller, which can open up holes in radar detection grids, reduce the effective range of missiles and increase the effectiveness of active countermeasures.
There are various techniques that an air-defence network can use to overcome "stealth" technology, but as in most similar things, it is a case of minimising and maximising and careful planning, eg: during desert storm the flight plans of the F-117 "stealth fighters" were planned with large, flat turns to avoid the aircraft pointing its large flat belly towards an enemy radar (which would give a strong return, RAM or no.).

Back to the point:
Materials that absorb various kinds of radiation are not a mystery or secret, if you want to absorb microwaves, water works very well (hence how a microwave oven works). The secrecy surrounding the radar-absorbent materials on "stealth" aircraft surrounds exactly what frequency ranges of radar they are best at dissipating, and I suppose there may be some difficulty in engineering a coating for certain frequencies that they might want to keep hush-hush too.

Bottom line, radar absorbent materials are not all that exotic, but if you want to build a "stealth" plane, you better keep your materials secret or the soviets will work out its weaknesses...those tricksy soviets...


Would a Stealth plane flying outside of detectable range of a radar, but inside normal range of the radar, not be invisible to detection then?
Like a "silent" sub is not "silent". It is still untrackable at range. So at range it is "invisible" to detection. Yes, if you swam up to the side, you might be able to hear it moving, but in the context, it is "invisible" to detection.
So, with the Stealth, at "x miles away" or "at twice the distance" when compared to a normal plane, it is invisible to (that particular) radar?
[Edit]
We have many tricks and ways to make images invisible. Some are only so from certain angles. However, the word "invisible" still stands for the angles you cannot see it from. For example, invisible watermarks or UV paint. It is not invisible in all instances, just in normal ones.
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby p1t1o » Fri Jan 14, 2011 6:04 pm UTC

Yup, you're right of course - I make the distinction because the vast majority not acquainted with the concept assume that "stealth" aircraft are invisible-as-in-harry-potter-invisible to radar.

However, as signal processing techniques improve and processing power increases, then more sense can be made from the kind of distorted and weak signals that you might receive that might otherwise be rejected by an older system - thus an aircraft that was "invisible" yesterday, may not be today.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby gorcee » Fri Jan 14, 2011 7:15 pm UTC

p1t1o wrote:@gorcee
Really? I was under the impression that newer "stealth" aircraft had more conventional shapes due to better computational techniques - the F-117 had very unusual geometry because designing the aircraft to be "stealthy" from more than a few angles was prohibitively difficult at the time. If you look at aircraft such as the F22 or F35, their geometry can be seen to be fairly complex in certain places. Also these days designing for absolute "stealth" is not as desirable as sacrificing "stealth" for other capabilities such as speed and cost effectiveness.


The geometry of the aircraft is exotic in places where radar absorbent materials are less reliable or less effective, such as on the inlet ducts, near hardpoint/internal storage areas, etc. However, both the F-22 and F-35 have exotic geometries for aerodynamic and structural considerations as well. Some of these considerations include masking the IR signature of the engine(s).

In the end, however, radar absorbent materials are a far more effective way to "stealthify" an aircraft. Could you make a B-52 stealth by creating it out of composites and RAM? No, but you probably could substantially lower its RCS.

Technical Ben wrote:
Would a Stealth plane flying outside of detectable range of a radar, but inside normal range of the radar, not be invisible to detection then?
Like a "silent" sub is not "silent". It is still untrackable at range. So at range it is "invisible" to detection. Yes, if you swam up to the side, you might be able to hear it moving, but in the context, it is "invisible" to detection.
So, with the Stealth, at "x miles away" or "at twice the distance" when compared to a normal plane, it is invisible to (that particular) radar?
[Edit]
We have many tricks and ways to make images invisible. Some are only so from certain angles. However, the word "invisible" still stands for the angles you cannot see it from. For example, invisible watermarks or UV paint. It is not invisible in all instances, just in normal ones.


Stealth technology doesn't make an aircraft invisible to radar or undetectable/untrackable. However, it does substantially reduce the range at which it can be detected.

The Soviet air defense perimeter, during the cold war, was designed around stopping massive fleets of B-52 bombers from flying over. Early warning detection radars were set up around the nation's perimeter. Anything flying within about 200 miles would be detected, and then angry things would happen.

With the B-2 bomber, that range effectively got reduced to about 20 miles. Since the radar network was designed to overlap assuming about a 200 mile range, the B-2 effectively created a bunch of "holes" in the perimeter through which the aircraft could penetrate.

During the Gulf War, the F-117 was used in the opening week in a similar capacity. The first steps were to eliminate Iraq's ability to defend itself from aerial attack. Baghdad was heavily defended; however, the F-117 was able to vastly reduce the effective range of the air defense batteries. The first step was to attack the air defense system: command centers, radar stations and actual missile/AA units themselves. As these units were systematically destroyed, stealth fighters were able to rapidly reduce the enemy's ability to stage any sort of defense. It's worth noting that the initial F-117 assault on Baghdad was supported by EF-111 eletronic warfare aircraft, which are used to jam radar targeting and guidance systems.

So yeah, stealth doesn't make you invisible, it just makes you much harder to see at a distance.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby p1t1o » Sat Jan 15, 2011 12:43 pm UTC

@gorcee

Agreed.

One interesting note: there are "bulges" just ahead of the intakes on the F35, these have the same function as large "splitter plates", obvious on aircraft such as the F4 Phantom. The bulges were designed as a clever way of reducing the "dirty" RCS of a splitter plate whilst still performing the required function.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Technical Ben » Sat Jan 15, 2011 1:10 pm UTC

gorcee wrote:...
With the B-2 bomber, that range effectively got reduced to about 20 miles. Since the radar network was designed to overlap assuming about a 200 mile range, the B-2 effectively created a bunch of "holes" in the perimeter through which the aircraft could penetrate...


Which is what I am saying. Just that, people are not wrong to think "the plane is invisible to radar [at over 20 miles range]." No one expects these things to be invisible up close.
Just as they are described as "fast" within relation to other things, we can describe them as "invisible" too.

If I cannot see you walking about at 20 meters away because you have a Stealth CloakTM but can see you when you get to 2 meters, am I wrong to describe you as "invisible"?
Anything disappearing from a radar screen, would make most people say "Gosh, it's gone! It just vanished. It's invisible to me". ;)
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby p1t1o » Sat Jan 15, 2011 1:20 pm UTC

Thing is, even a "stealth" aircraft at some "safe" range will return a signal to the detector, but it will be ignored by the equipment as "noise" or some other anomalous signal. One could think it is closer to camouflage than invisibility, ie: you are looking right at a visible object but it blends in and you just don't notice it.

Sure, semantically it is correct to say it is "invisible" when under such conditions as are favorable - but generally, it can cause confusion by referring to the technology as rendering aircraft "invisible to radar".

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Carnildo » Sun Jan 16, 2011 12:05 am UTC

gorcee wrote:
p1t1o wrote:@gorcee
Really? I was under the impression that newer "stealth" aircraft had more conventional shapes due to better computational techniques - the F-117 had very unusual geometry because designing the aircraft to be "stealthy" from more than a few angles was prohibitively difficult at the time. If you look at aircraft such as the F22 or F35, their geometry can be seen to be fairly complex in certain places. Also these days designing for absolute "stealth" is not as desirable as sacrificing "stealth" for other capabilities such as speed and cost effectiveness.


The geometry of the aircraft is exotic in places where radar absorbent materials are less reliable or less effective, such as on the inlet ducts, near hardpoint/internal storage areas, etc. However, both the F-22 and F-35 have exotic geometries for aerodynamic and structural considerations as well. Some of these considerations include masking the IR signature of the engine(s).


The signature of the engines is important to keep track of when designing a stealthy aircraft. For example, an SR-71 sitting on the ground had a decent level of stealth for its time (the chines, tilted fins, and the like tended to reflect radar away from the source), but in the air, the exhaust plume stuck out like a sore thumb on radar.

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Technical Ben » Sun Jan 16, 2011 8:22 pm UTC

The SR-71 had no need for stealth. It needed nothing. It had one thing. One thing only, and by George, it had it in awesome amounts. Speed!
Think of it like thins. By the time you see it, it's probably gone already. :lol:
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby thoughtfully » Sun Jan 16, 2011 10:55 pm UTC

It also had oh-my quantities of altitude, which helped too.
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby letterX » Sun Jan 16, 2011 11:33 pm UTC

thoughtfully wrote:It also had oh-my quantities of altitude, which helped too.

Yes, but it gets beat in altitude by that silly plane named after some band, so we'll focus on the speed (at which it is still the fastest).

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Re: Microwaves, Stealth Aircraft and the Cold War

Postby jmorgan3 » Mon Jan 17, 2011 6:02 am UTC

letterX wrote:
thoughtfully wrote:It also had oh-my quantities of altitude, which helped too.

Yes, but it gets beat in altitude by that silly plane named after some band, so we'll focus on the speed (at which it is still the fastest).


Is there a band called MiG-25? Or perhaps X-15?
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Re: Microwaves, Stealth Aircraft and the Cold War

Postby Zamfir » Mon Jan 17, 2011 10:29 am UTC

jmorgan3 wrote:
letterX wrote:
thoughtfully wrote:It also had oh-my quantities of altitude, which helped too.

Yes, but it gets beat in altitude by that silly plane named after some band, so we'll focus on the speed (at which it is still the fastest).


Is there a band called MiG-25? Or perhaps X-15?

Almost, and yes. It's like rule 34

EDIT: Oh


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