Aerodynamics Question: Aerion AS2 Supersonic Biz Jet

AggieMike88

AggieMike88

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The original "I don't know it all" of aviation.
Referencing this photo for the Aerion AS2

aerionas2ext_1.jpg


How do these small wings set so far back "work" from a lateral stability standpoint?

My experience with the various wing placement for GA aircraft has me understanding how wing placement within the CG envelope works since the center of lift isn't too far from the CG. And the Wing is pretty close to the center of the "nose to tail" dimension.

But for the Aerion airplane, to me, the wing is so far back, and no canard near the nose. So how is this a stable aircraft?
 
AggieMike88 said:
Referencing this photo for the Aerion AS2

aerionas2ext_1.jpg


How do these small wings set so far back "work" from a lateral stability standpoint?

My experience with the various wing placement for GA aircraft has me understanding how wing placement within the CG envelope works since the center of lift isn't too far from the CG. And the Wing is pretty close to the center of the "nose to tail" dimension.

But for the Aerion airplane, to me, the wing is so far back, and no canard near the nose. So how is this a stable aircraft?
Click to expand...

Looks reasonably balanced to me. Look at all that engine aft... the elevator provides downforce...


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gsengle said:
Looks reasonably balanced to me. Look at all that engine aft... the elevator provides downforce...


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Click to expand...
Yep, and the fuel should be somewhere around the wings. People are relatively lightweight! But that plane is just supersonic, in the "low boom" regime.
 
Given enough thrust-anything can fly. Exhibit A the F-4 Phantom. The CG and the center of lift appear to be at the forward part of the wing and the tail has a very long arm to control the AOA.
 
Low boom usually refers to the noise signature of pressure wave passage, not the Mach no. All the low boom configurations I worked on were targeting 1.4M and above.
All of that weird shaping is to get the noise signature down. A wing's center of pressure (or airplane's aerodynamic center) moves aft in supersonic flight - further from the CG, making an airplane more stable. Moving the wing aft can move the CG aft more than it moves the aero center aft and a wide nose can bring the AC forward a bit, both destabilizing somewhat. Low boom configurations like low trim drag (relaxed stability [edit] and low untrimmed pitching moment), and big pointy protuberances out front (i.e. long bulbous noses) to make the forward and aft primary shocks diffuse and get the noise down.

Nauga,
and days gone by
 
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If I was buying a plane that is designed to fly at 1.6, well I want my pilots to fly it at 1.6.
 
Stability will play a lesser role as computer control can make up for some of it. That is why designs like this have been tried in the past and have not worked out. With the computers assisting it makes control of the craft more possible. Damn skynet!


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nauga said:
Low boom usually refers to the noise signature of pressure wave passage, not the Mach no. All the low boom configurations I worked on were targeting 1.4M and above.
All of that weird shaping is to get the noise signature down. A wing's center of pressure (or airplane's aerodynamic center) moves aft in supersonic flight - further from the CG, making an airplane more stable. Moving the wing aft can move the CG aft more than it moves the aero center aft and a wide nose can bring the AC forward a bit, both destabilizing somewhat. Low boom configurations like low trim drag (relaxed stability), and big pointy protuberances out front (i.e. long bulbous noses) to make the forward and aft primary shocks diffuse and get the noise down.

Nauga,
and days gone by
Click to expand...
See also:
800px-Douglas_X-3_NASA_E-1546.jpg

https://en.m.wikipedia.org/wiki/Douglas_X-3_Stiletto
 
overdrive148 said:
See also:
https://en.m.wikipedia.org/wiki/Douglas_X-3_Stiletto
Click to expand...
While I love that airplane, it was intended to go fast, but not quietly like Aerion and others. It was also a rude introduction to inertial coupling, roll into pitch.
There's more details an the whole low boom concept and NASA's prototype in the works here: https://www.nasa.gov/mission_pages/lowboom/index.html . This program used to occupy a good bit of my time. No more.

Nauga,
the dot on the horizon
 
nauga said:
Low boom usually refers to the noise signature of pressure wave passage, not the Mach no. All the low boom configurations I worked on were targeting 1.4M and above.
All of that weird shaping is to get the noise signature down. A wing's center of pressure (or airplane's aerodynamic center) moves aft in supersonic flight - further from the CG, making an airplane more stable. Moving the wing aft can move the CG aft more than it moves the aero center aft and a wide nose can bring the AC forward a bit, both destabilizing somewhat. Low boom configurations like low trim drag (relaxed stability [edit] and low untrimmed pitching moment), and big pointy protuberances out front (i.e. long bulbous noses) to make the forward and aft primary shocks diffuse and get the noise down.

Nauga,
and days gone by
Click to expand...
The "low boom" specs for this particular one are low supersonic, ~ 1.2 mach. Heck, the US version of the SST was 3.0 mach, and the Concorde was 2.0. Going 0.9 in a Citation X will surely be much cheaper than going 1.2 in this dart.
 
This is the jet that always looked like it couldn’t possibly be balanced to me.

59aa2e9631405415fa7cbf8814f49d58.jpg



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The concept you used and the concept on the Aerion site differ quite a bit.
 
Velocity173 said:
https://en.wikipedia.org/wiki/Shaped_Sonic_Boom_Demonstration
Click to expand...
Stay with me here :D. If you look at the pics of the SSBD you'll see the long bulbous nose mentioned earlier, but a normal F-5E wing and aft fuselage. Supersonic airplanes usually have a strong shock wave formed by the nose, and another formed by the tail (or aftmost part of the fuselage). These shocks are what cause the boom you hear, and the separation of leading and trailing shocks are why you sometimes hear a double boom as each one passes over you.

The goal of the low-boom program is (among other things) to develop flyable configurations that 'shape' the leading and trailing shocks to either diffuse them or direct them so that they somewhat cancel each other (or deflect them in some direction other than directly below the flight path), making the waves that pass over you weaker or less abrupt, both of which are perceived as quieter.

The SSBD in the link @Velocity173 posted was a successful experiment to show that the leading shock could be shaped and that tools could predict the effects - but it didn't address the trailing shock, a much more difficult problem, at all. Newer configurations and the NASA/LM demonstrator address both shocks. Once a demonstrator is available it can be used to show that these configurations are significantly quieter than traditional supersonic airplanes, and use that to drive a rule change to allow supersonic flight over CONUS.

Nauga,
with not so much a boom as a whisper
 
nauga said:
Stay with me here :D. If you look at the pics of the SSBD you'll see the long bulbous nose mentioned earlier, but a normal F-5E wing and aft fuselage. Supersonic airplanes usually have a strong shock wave formed by the nose, and another formed by the tail (or aftmost part of the fuselage). These shocks are what cause the boom you hear, and the separation of leading and trailing shocks are why you sometimes hear a double boom as each one passes over you.

The goal of the low-boom program is (among other things) to develop flyable configurations that 'shape' the leading and trailing shocks to either diffuse them or direct them so that they somewhat cancel each other (or deflect them in some direction other than directly below the flight path), making the waves that pass over you weaker or less abrupt, both of which are perceived as quieter.

The SSBD in the link @Velocity173 posted was a successful experiment to show that the leading shock could be shaped and that tools could predict the effects - but it didn't address the trailing shock, a much more difficult problem, at all. Newer configurations and the NASA/LM demonstrator address both shocks. Once a demonstrator is available it can be used to show that these configurations are significantly quieter than traditional supersonic airplanes, and use that to drive a rule change to allow supersonic flight over CONUS.

Nauga,
with not so much a boom as a whisper
Click to expand...

Air show shot I took years ago. Even though I couldn’t keep him full frame, to see visible waves aft of the vapor cone is kinda cool.

1B4A1A3C-CC9B-4075-8348-3B0D5EDAB81D.jpeg
 
The SSBD in the link @Velocity173 posted was a successful experiment to show that the leading shock could be shaped and that tools could predict the effects - but it didn't address the trailing shock, a much more difficult problem, at all. Newer configurations and the NASA/LM demonstrator address both shocks. Once a demonstrator is available it can be used to show that these configurations are significantly quieter than traditional supersonic airplanes, and use that to drive a rule change to allow supersonic flight over CONUS.
Click to expand...

One thing I stressed while testing at the missile defense agency is that the purpose of flight testing is to verify the computer models. One flight test can be extrapolated into multiple simulations to determine the optimum solution or to find holes in your theory.
 
Low boom technology is fascinating to me. I talked the ear off one of the NASA guy’s about it at Oshkosh this year. More evidence I’m still a child when it comes to airplanes.
 
I did a report on the SSBD for my ASE degree. That was 12 years ago, glad they are trying to make some progress on the technology.
 
I wonder how loud the boom was when the 707 went through Mach 1.0? If the size of the airplane and its sorta "dirty" shape made it worse?

I remeber fighters booming when I was a kid in Virginia - it was fun. Fir a kid, anyway.
 
Sundancer said:
I wonder how loud the boom was when the 707 went through Mach 1.0? If the size of the airplane and its sorta "dirty" shape made it worse?
Click to expand...

I know NASA pushed a DC-8 past M1. Are you sure someone did that with a 707?
 
How do these newer designs address the other large problem they had with supersonic planes for commercial use, high costs due to very poor fuel efficiency? From what I have read about older designs is that between about mach 0.9 and about mach 1.2 the planes are very inefficient and burn tons of fuel. So how are these low supersonic designs dealing with that issue?

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drotto said:
How do these newer designs address the other large problem they had with supersonic planes for commercial use, high costs due to very poor fuel efficiency? From what I have read about older designs is that between about mach 0.9 and about mach 1.2 the planes are very inefficient and burn tons of fuel. So how are these low supersonic designs dealing with that issue?
Click to expand...
Engines have gotten more efficient and drag prediction and mitigation has gotten better but in the end going fast is still going to be much more expensive than going slow. But hey, we're worth it.

Nauga,
and all the fuel he can carry
 
kyleb said:
I know NASA pushed a DC-8 past M1. Are you sure someone did that with a 707?
Click to expand...
Heh. There's probably a 'fleet lore' "I busted Mach" for every swept-wing jet out there. At least NASA documented it.

Nauga,
who was inverted
 
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