It's interesting that inquiries to both Northrop Grumman and DARPA yield zero additional information - it doesn't matter if it's a journalist, USAF personnel or industry insiders. All inquiries regarding the nature of this project are met with blank stares, a shrug of the shoulder or a "You know I can't discuss that..."

Certainly at some point either NG or DARPA's PR division is going to have to say something concerning this project. But to date it's been nothing but silence.

Flagged. I think that this is verrrry interesting. Isn't this the way that many "black" projects start? A concept rendering that a small outlay of captal is given for?

I'm not up-to-date on the latest budget outlays for new government projects....

The next generation bomber is supposed to have all aspect stealth too. What I find more interesting is the IR and visual LO aspects of this project.

[edit on 7-10-2008 by WestPoint23]

For all intents and purposes,

You know I can't discuss that...

= positive confirmation.

It's the admission of a visual stealth requirement that REALLY stands out to me.

Originally posted by HatTrick
It's the admission of a visual stealth requirement that REALLY stands out to me.

Visual 'stealth' in some shape or form has been around for absolute ages*. This will be another iteration on it.


*the first widespread use of visual stealth was in world war 1.



Think of it less as a sci-fi cloak, and more as another iteration on camouflage, and you'll be nearer the mark.

Originally posted by kilcoo316

Originally posted by intelgurl
Well, it will be the most advanced stealth aircraft designed to date, incorporating all-aspect, wideband (high and low freq radar), aural, visual and infrared stealth.

Low freq?
At 10 GHz, the radar wavelength is approximately 0.3 metres.
Typical features are of the order of 0.3 metres. How do you hide features? (without resorting to active measures)

Low Frequency is not a magic bullet against stealth technologies. This is a common and erroneous assumption in much the same fashion as saying stealth makes an aircraft invisible to radar.

Judging from previous posts, you seem to be knowledgeable in this area, so I submit to you the following generalization;

High frequency reflection elimination trends toward a geometric solution while Low frequency reflection elimination trends toward an absorption solution.

All current stealth initiatives are in one way or another taking low freq into consideration, not making the craft invisible but lowering the observability.



[edit on 10-7-2008 by intelgurl]

Originally posted by intelgurl
High frequency reflection elimination trends toward a geometric solution while Low frequency reflection elimination trends toward an absorption solution.

It was my understanding that:


Short wavelength (with respect to the feature/surface/edge/whatever) meant that a high degree of control can be maintained over the wavelength as 1 full wave will always occur over a length-scale that is highly controllable by the designer (i.e. the facets on an F-117).

Longer wavelengths however, particularly wavelengths with size the same order as a feature/surface/edge/whatever can not be controlled in the same fashion.

For instance, wavelength = 30 centimetres, aileron = 15cm. No matter what you do, at best half the wave will be over the wing, half the wave over the aileron - and there is a discontinuity leading to scatter. Indeed, at half radar wavelength = feature length, constructive interference is set up, resulting in increased radar return.



I thought that was why designing low observables for long wavelength is so hard - because both RAM and directivity characteristics are working against you. Obviously the basic approach is to have large features that move very little (a la B-2).


I'm sure there are some tricks that are not published by the IEEE, but physics is physics. Without going active, options available to the designer to combat long wavelengths are limited.

Originally posted by kilcoo316
It was my understanding that:

Short wavelength (with respect to the feature/surface/edge/whatever) meant that a high degree of control can be maintained over the wavelength as 1 full wave will always occur over a length-scale that is highly controllable by the designer (i.e. the facets on an F-117).

Longer wavelengths however, particularly wavelengths with size the same order as a feature/surface/edge/whatever can not be controlled in the same fashion.
...

I'm sure there are some tricks that are not published by the IEEE, but physics is physics. Without going active, options available to the designer to combat long wavelengths are limited.

Kilcoo,

What you present is all valid science, and you are right, "physics is physics".
That said, I still stand by the former statement as it is "generally" the methodologies involved.

If there is a manner in which something can go active and absorb RF then perhaps there is something there to be considered.
Vague enough?

Originally posted by intelgurl
That said, I still stand by the former statement as it is "generally" the methodologies involved.

Absolutely - to achieve destructive interference through use of RAM (which would be the same as an acoustic liner), you need a cell depth of 1/4 the radar wavelength... as before, if wavelength is 30 cm, that means a skin "depth" of over 7 cm - utterly impractical.

Obviously there are more techniques to radar absorbent material than destructive interference, but the fundamentals are similar - more RAM depth = better attenuation for longer wavelengths.


I was kinda just pointing out that even shaping isn't particularly useful for the very long wavelength radars, when the wavelength is of similar size to an actual surface feature on the aircraft (like a rudder or aileron chord length)

Originally posted by intelgurl
If there is a manner in which something can go active and absorb RF then perhaps there is something there to be considered.
Vague enough?

Dassault have previously indicated that the Rafale is equipped with some means of active cancellation. I would see no reason why the US would be lagging in such approaches.

(Of course, that opens up a whole can of worms on directivity of the destructive signal)


Using copper mesh to absorbing the wave energy - like passing any circuit through a magnetic field - then dissipating as heat has been used on the B-2. But the trick is then getting the wavelength into the skin, and not bouncing off it - back to that RAM depth problem.

That was what... 25 years ago? No doubt improvements to the concept exist.

There have been pretty good strides in CNT (carbon nanotube) tech lately. No doubt this tech finds its way into our latest aircraft.

Sorry my bad.

1/4 wavelength for constructive interference (bad from point of view of stealth aircraft) and 1/2 wavelength for destructive interference (good from POV of stealth aircraft).

Why the differences between constructive and destructive?

Can we get a little RADAR Stealth 201 over here? (Yes I said 201, this is a little bit more advanced than the basics discussed in some other places).

Shattered OUT...

Originally posted by satcom
Just curious when you answered the question "So what is an Advanced Technology Survivability Demonstrator?" was that a guess? or something more?

It's something more. Every so often DARPA will contract a working scale model and throw all the goodies they've got into it to see how it turns out.

Wow, I haven't been on here for a long time...

In case you missed it, Aviation Leak had a tiny statement buried in an article, that said one recent war gaming simulation showed 35% losses of conventional aircraft when trying to penetrate an area of modern air defense in depth. Same game showed four F-22s and two B-2s capable of entering and exiting without being seen at all.

And this is old tech, anything currently being built for the most part, was developed about 20 years ago.

And for anyone that thinks that things like 7cm of RAM absorbent material is impractical, I say nonsense. It's been done long ago, you just don't know about it.

Laterz

Originally posted by ZPE StarPilot
And for anyone that thinks that things like 7cm of RAM absorbent material is impractical, I say nonsense. It's been done long ago, you just don't know about it.

Aircraft skin that is 7 cm thick?


Are you for real?!?!