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Tacit Blue's Airfoil

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plncraze

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According to Peter Westwick's book "Stealth" Tacit Blue had a Clark Y airfoil and the tail copied from a Beech Bonanza.
 

Victor Bravo

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Doesn't pass the smell test to me. The early stealth airplanes couldn't use any curved surface, IIRC they didn't have the computing power to figure out all the reflective factors. If Tacit Blue could use a curved airfoil then the 117 could have used one.
 

Kyle Boatright

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Tacit Blue was developed 5 years later than Have Blue (the F-117 predecessor). Tacit Blue benefited from more computational power to create its stealthy shape and had curved surfaces. The specific claims about the Clark Y or the Bonanza's V-tail are dubious, but Tacit blue definitely had a traditional curved airfoil and a V tail.
 

Victor Bravo

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If anyone puts this on the "most beautiful airplane" thread, there will be hell to pay...

I'm guessing that blade shaped extension on the nose is there to create a strong vortex at high AoA, to swirl energized air over the fuselage and into the engine intake? Anybody here know... anybody here able to tell me without being taken to Guantanamo?
 

poormansairforce

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If anyone puts this on the "most beautiful airplane" thread, there will be hell to pay...

I'm guessing that blade shaped extension on the nose is there to create a strong vortex at high AoA, to swirl energized air over the fuselage and into the engine intake? Anybody here know... anybody here able to tell me without being taken to Guantanamo?
It made me think about starting an "Ugliest airplane" thread!

My guess is it had to do with radar signature as in the plane would have to be pointed directly at the radar in order to have a signature which at that point the rest of the airplane behind it would be much smaller as opposed to being at an angle.
 

plncraze

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Yes, the edges of the flying surfaces are "louder" to radar than further inboard. Tacit Blue was supposed to be a stealthy flying box with a radar dish inside the shape was dictated by that. Apparently it did not have pleasant handing characteristics.
 

mcrae0104

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Anybody here know... anybody here able to tell me without being taken to Guantanamo?
The full-perimeter chine reduces the vertical portion of the aircraft's surface to a slim razor edge all the way around. It's not unlike the SR-71's RCS-reducing cross section profile.

Plus it looks goofy so the Russians wouldn't take it seriously.
 

Doggzilla

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The curvature of the airfoil has nothing to do with computational power. It’s a material issue.

Curved surfaces on stealth aircraft are possible by using a graphite mixture in composite skin, or is accomplished by placing an aerodynamic composite cap over a faceted surface.

In fact, the Japanese F-2 and F-16C have 1/5th the radar cross section of the original F-16 because of the composites they use. It is nearly the same aircraft but with different materials.
 

Wanttaja

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The curvature of the airfoil has nothing to do with computational power. It’s a material issue.

Curved surfaces on stealth aircraft are possible by using a graphite mixture in composite skin, or is accomplished by placing an aerodynamic composite cap over a faceted surface.
Actually, I believe the computational issue is related to issues regarding the Radar Cross Section (RCS) of the aircraft. A flat surface reflects light or radar waves in a single direction (depending on angle the radiation comes in from), while a curved surface tends to have a prism effect and splays the reflected radiation over a broader arc.

Years, YEARS ago, I developed a Mac-based mission simulation tool for development work on a new stealth aircraft. The aircraft had specific angles where the surfaces would tend to reflect more energy back at the emitter (hence producing a stronger signature). These were called "spikes," and the goal was to design the aircraft flight path and attitude profile to avoid pointing those spikes at known radar sites.

I'm guessing increased computational power allows better simulation of the spikes created by curved surfaces, and allows optimizing the surfaces to minimize RCS.

Ron Wanttaja
 

Doggzilla

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That is very fascinating. I heard about such a program back when that F-117 was shot down. Some mission analysts hadn’t been checking the flight plans and allowed several aircraft to fly identical routes instead of the random routes the program was designed to create, which is why the Serbs knew the flight path to target.
 

Doggzilla

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And since we are on the topic, the Iranians copied that stealth drone they captured years back, and the Israelis shot one down over Syria.

That is very impressive for both sides. Iran has a much more advanced aerospace industry than expected. And the Israelis as well if they can detect it.
 

Wanttaja

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That is very fascinating. I heard about such a program back when that F-117 was shot down. Some mission analysts hadn’t been checking the flight plans and allowed several aircraft to fly identical routes instead of the random routes the program was designed to create, which is why the Serbs knew the flight path to target.
Shades of Vietnam, when the Air Force sent B-52s to bomb following the same flight path. Shades of WWI, for that matter, when Beatty had his ships at Jutland changing course in succession, which meant all the Germans had to do was to aim at the single spot where each ship would start to turn.

The tool I wrote wasn't a full-blown mission planning program; it just simulated the flight path well enough so we could determine if spike-steering was possible.

And since we are on the topic, the Iranians copied that stealth drone they captured years back, and the Israelis shot one down over Syria.

That is very impressive for both sides. Iran has a much more advanced aerospace industry than expected. And the Israelis as well if they can detect it.
I suspect there's very little in the material arena that's truly secret in the stealth world anymore. I remember ~40 years ago you could buy a car "bra" that included RAM (Radar Absorptive Material). IIRC, it didn't work. :) Heck, Robert Heinlein included a basic stealth concept in "Between Planets" in 1951:

"The upper-works of the boat were covered by a low, polished cone of sheet metal intended to reflect horizontal radar waves skyward, or vice-versa."

The crown jewels of US stealth technology are probably the computer codes used to optimize the signature of aircraft shapes and the facilities that permit testing of full-sized aircraft.

By the way, the novel "Chooser of the Slain" by James H. Cobb is a great layman's introduction to stealth...and a cracking good naval/air combat yarn, as well. The author made an unfortunate choice in the name of the ship, but how was he to know....

Ron Wanttaja
 

Doggzilla

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The real challenge is the engines and thermal stealth.

We captured a Chinese spy who gave them the engine designs for the B-2 and they still haven’t been able to reproduce them yet.

In fact, they have a fighter with the nose of an F-35 but has to use a pair of old Soviet engines because they cannot reproduce the engines correctly.

Even if they can reproduce the radar stealth features, their thermal stealth is so bad that they will be detected at 3-4 times the distance of an F-35.

This gives the F-35 a distinct advantage in mid range combat, which is where most real world engagements occur.
 

plncraze

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That Chinese fighter was "reviewed" by someone in Flight Journal magazine who said the front of the airplane looked stealthy but the back was regular old jet. Sir Stanley Hooker said the same thing about Chinese engineering that you did back when the Chinese had just quit talking to the Russians.
 

Kyle Boatright

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That Chinese fighter was "reviewed" by someone in Flight Journal magazine who said the front of the airplane looked stealthy but the back was regular old jet. Sir Stanley Hooker said the same thing about Chinese engineering that you did back when the Chinese had just quit talking to the Russians.
You make your choices. Depending on your mission, you may not need rear aspect stealth. Best anyone can tell, the Chinese canard is optimized for front aspect stealth. It is a large, long range platform, intended to take out tankers, AWAC's, and the like in rear areas. So, it sneaks in close enough to launch long range missiles, turns away and is moving out of range by the time it shows up on radar screens.

The F-35 also leans much more heavily on front aspect stealth than rear aspect stealth.
 
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