Finalized Rockwell ATF Design?

[Kryptid]

Not so much a theoretical project as a theoretical visualization of a project.

The pre-final ATF design by Rockwell is pretty well-known (the one with highly-blended strakes and widely-spaced engines): http://www.secretprojects.co.uk/forum/index.php/topic,331.15.html

To my knowledge, the final "stealthy" design was never shown to the public.

The idea behind this thread is...would anyone be interested in helping me develop a speculative image on this design? I will post some sketches, and you give me critique on what looks good and what to change. Or you can do drawings of your own if you wish.

In Dr. Daniel P. Raymer's biography, he gives a few details on how it may have looked. These tidbits could prove useful. Here are a few of the quotes he gives about it:

Eventually, we reasoned that if we kept the overall design planform (shadow) about the same, and kept the area distribution from nose to tail about the same, and didn't do anything hugely stupid, then the aerodynamics would be about the same.

We have a 3-view of the original design, so that helps.

The engines got pulled in alongside the fuselage, and the inlet ducts were tucked into "armpits" in a reshaped forward fuselage.

Engines are apparently closely-spaced now (perhaps like the F-22?).

We ran a sharp strake down the side of the aft fuselage to keep the shadow of the airplane the same. Made the back end of the strake a movable pitch control flap, replacing the movable flap we'd had between the nozzles.

Seems that it had aft-strakes/a backporch configuration. I presume that the vertical tails are placed at the edges of these strakes.

We kept our V-tails for stealth and drag.

They were all-moving in the original design, so for performance's sake, I imagine the final design had all-moving tails also.

So, we stuck with the efficient conical inlet we'd been using, but sliced it at an angle for better stealth.

This is a bit harder for me to visualize. Would these be "armpit" semi-conical inlets similar to those on the F-111, but perhaps integrated with a canted fuselage side?

By now, though, the engine companies were favoring a double-ramp square nozzle that was eventually used on the F-22, so we switched. This was rolled sideways in our design so that we didn't have to build big wedge-shaped fairings to cover the flat sides.

Rolled sideways? So the nozzles would be horizontally opened and closed? The opposite of the F-22?

I do remember that when the Dem/Val winners were unveiled, I thought it was amusing that our design had looked somewhat like the F-22 fuselage but with F-23 wings and tails.

F-23 wings suggest to me that it had diamond wings with leading edges and trailing edges being equal and opposite in sweep. Same sweep as in the original proposal?

 

[Merv_P]

Raymer proposed an F-16 /F-35 class fighter called NGAF in a RAND monograph. Some of the features you mention seem to have made it into this later design.

 

[Kryptid]

Thanks for that.

First attempt: http://i198.photobucket.com/albums/aa176/Kryptid/RockwellSpeculation1.jpg

I'm noticing that using diamond wings makes it diverge quite a bit from the "shadow" of the original design. I do have a theory in regards to that. Perhaps it was the original intention to make the stealth ATF look like the shadow of the original ATF, but it proved unworkable. For example, adding the internal weapon bay would have added weight, which would have necessitated larger wings in order to keep the wing loading the same. Perhaps the normal swept wings proved to be too heavy when they were enlarged, so they went for a lower aspect ratio diamond wing to keep the weight down. Just my theory.

 

[BAROBA]

I noticed it too, that he seem to contradict himself, or he is using another lingo then we understand...

Shadow could mean other things.... Some expert can shed some light on it?

But this is my interpretation ( so far)


Cheers,

Rob

 

[Grey Havoc]

Nice.

 

[overscan (PaulMM)]

Intake is wrong. He specifically says they kept the half-cone inlets but the rim would be swept back at an appropriate angle for stealth. I think something like this - but with the intake lip swept back in alignment with another edge.


Also the engines were moved inboard, with strakes outside to maintain the same overall planform.

 

[Kryptid]

A new conception, this time based more directly on the original ATF schematic.

 

[BAROBA]

Another update, thanks Paul for the feedback on the inlet-design.
The 3rd image is a topview.

Cheers,

Rob

 

[Kryptid]

That's better, but I'm thinking that there needs to be room for a boundary layer diverter for the inlets. Also, the engines need to be placed more closely together.

I've had a new thought in regards to the inlets. I know I originally interpretted that they might have been near-quarter cone armpit inlets like on the F-111, but I'm thinking that perhaps the arrangement may have been more similar to Raymer's Lightweight Supercruise Fighter concept. In that design, the inlet retains the complete half-cone inlet design, but they are simply canted sideways so that they are mated neatly with the canted fuselage side. Their curved design does make me wonder about side-aspect RCS concerns. Might they have been angled slightly?

I've also thought of a new interpretation of the engine nozzle comment from Raymer, but I'll save that for when I've gotten a drawing depicting it.

 

[Kryptid]

Forgive me for the double post. I wanted to illustrate the nozzle idea. I forgot the aft-strakes, but the idea is still relevant.

After thinking about it, I don't think Raymer was saying that the nozzles were rotated a full 90 degrees. Instead, I think he meant that they were rotated on their axis enough so that their flat sides would line up with the fuselage sides.

The "big wedge-shaped fairings" refer to, I think, the extra material that would have been needed to be added to the sides of the fuselage to make the otherwise flat-sided engines conform with the tail angle/fuselage side angle. In the original drawing, the tails seem to be canted right at 20 degrees (compared with 15 degrees for the F/A-18 and 30 degrees for the F-22).

The main problem I have with this is that now the upper side and underside of the fuselage looks weird...

 

[overscan (PaulMM)]

I came to the same conclusion about the nozzles, 20 - 25 degrees cant angle so radar returns go in a better direction. Beneficial side effect would be pseudo 3D thrust vectoring a la Su-37.

Regarding the intakes, I think your idea is definitely possible, but I think the "angle" he mentions introduced for stealth reasons is on the intake lip, which would be swept backwards at an angle aligned to the wing leading edge.

"Armpit" location specifically references the junction between wing and fuselage.

I think the Lightweight Supercruise Fighter design is illuminating for several reasons, I will post a drawing later.

 

[overscan (PaulMM)]

Another update, thanks Paul for the feedback on the inlet-design.
The 3rd image is a topview.

Cheers,

Rob

The two engines have to be together not widely spaced.

 

[overscan (PaulMM)]

The engines got pulled in alongside the fuselage, and the inlet ducts were tucked into "armpits" in a reshaped forward fuselage.

If you take the old ATF design and compare it to the Lightweight Supercruise Fighter, the intakes on the latter fit exactly the description of the advanced ATF design.

Basically, push engines inboard, push intakes forward to not far behind canopy, and move to lower side of now diamond section front fuselage below chine/strake.

Note Raymer also talks of rotary weapons bay, so the fuselage must get fatter in the centre section to accommodate - the original design used conformal AAM carriage.

 

[BAROBA]

Hi guys,

The Lightweight Supercruise Fighter looks like it is a smaller fighter the ATF design.... Has anyone any numbers on both designs?
I changed a few things, the wingarea is now smaller. Splitterplates are added.
Engines and intakes are closer together. The design looks smaller now and a bit faster.
I hope you like it

Oh and added ( the beginning of )camo.

Cheers,

Rob

 

[Kryptid]

Very attractive job, BAROBA!

The Lightweight Supercruise Fighter looks like it is a smaller fighter the ATF design.... Has anyone any numbers on both designs?

If by "numbers" you mean data like wingspan, weight, etc., then I can supply some of them. The Lightweight Supercruise Fighter has quite a few pieces of information about it in Raymer's design book:

Length: 45 feet, 2 inches
Take-off Gross Weight: 16,480 pounds
Military Thrust: 13,776 pounds*
Full Afterburner Thrust: 16,150 pounds
Maximum Speed: over Mach 1.8
Supercruise Speed: over Mach 1.4
Nozzle Type: 2D Pitch-vectoring
Tail Type: Variable-dihedral V-tail

*I derived the dry/military thrust from a place in the book where its cruise was descrbed. The speed listed was Mach 1.4 (around supercruise speed) and it stated the thrust used was 85.3%. I inferred this to be the percent of full thrust that dry thrust represented.

Some dimensional numbers for the Pre-stealth ATF can often be found on 3-views of the design:

Length: 60 feet, 2 inches
Wingspan: 47 feet, 5 inches

You can probably calculate the height from the schematic.

If you take the old ATF design and compare it to the Lightweight Supercruise Fighter, the intakes on the latter fit exactly the description of the advanced ATF design.

Basically, push engines inboard, push intakes forward to not far behind canopy, and move to lower side of now diamond section front fuselage below chine/strake.

Note Raymer also talks of rotary weapons bay, so the fuselage must get fatter in the centre section to accommodate - the original design used conformal AAM carriage.

Nice observation. Will probably help when developing a side-view of the design.

I'm thinking about trying to size a diamond wing based on weight growth from the Pre-stealth ATF to the Stealth ATF. There are equations in Raymer's book that will also help determine where to put the center of lift. I think I'll go with a 40 degree sweep (that used in the YF-23 and also the Lightweight Supercruise Fighter).

EDIT: Here are what the respective reference wings may have looked like. The original is in black and the diamond wings are in red. They are about the same area (I know I may need to beef up the size of the diamond wings to represent the growth in weight of the stealth design. Does anyone know how much an internal weapon bay increases weight? A rough percentage?). The sweep isn't exactly 40 degrees (I did use a YF-23 schematic to design the wings, so it may have been an error by the artist. Not a big deal, I don't think). I tried to put them both on the same center of lift, since it's likely that they would want the center of lift and center of gravity to be as close to the original plane as possible in order to keep performance and handling similar.

 

[BAROBA]

Changed a bit on the design, the tail is a bit more F-23 like. So that the tail has more range in movement and can't hit the wings.
My final design I think

Cheers,

Rob

 

[Kryptid]

Excellent work once again.

 

[Anderman]

Indeed great work looks even better then the YF-23

 

[Grey Havoc]

Indeed great work looks even better then the YF-23

Heresy! ;D

 

[Anderman]

Indeed great work looks even better then the YF-23

Heresy! ;D

Jehova, Jeho.......eh ..... Rockwell ATF, Rockwell ATF B)


And now to something completely different any ideas how this beauty would be named ?

 

[BAROBA]

We could ask Dan Raymer for a name....
I don't think anyone at Rockwell will answer the phone ...

 

[Kryptid]

Raymer seems to be pretty busy right now (check his blog). I'd certainly like to get his opinion on our depictions of the ATF, but I'll wait until he gets caught up with comments and such.

Maybe a blade/cutting-type name would fit? Several of their other aircraft fit that: the XF-108 Rapier, F-86 Sabre, F-100 Super Sabre, F-107 Ultra Sabre, and B-1 Lancer.

Perhaps "Machete"?

 

[flateric]

something says me that Dan will say that it was quite different

 

[overscan (PaulMM)]

Rob's design is nice but doesn't fit the description at all.

 

[BAROBA]

After receiving some feedback from Paul, I altered the design to match the description even better.
The strakes are now a part of the design, and the engines are moved into a single block.


Cheers,

Rob

 

[Kryptid]

It keeps looking better all the time!

 

[Stargazer]

Indeed great work looks even better then the YF-23

Heresy! ;D

Ditto!!

 

[Kryptid]

something says me that Dan will say that it was quite different

You were right about that.

I have some news.

I e-mailed Dr. Raymer enquiring about this design, whilst also showing him BAROBA's renders and my own top profile view. He said they weren't accurate. He also gave a few more tidbits of information about the design.

The top view sihlouette was almost identical between the pre-stealth and post-stealth designs. The wings indeed were not YF-23-shaped as we had thought. The strake was also smoothly curved as in the original design. The vertical tails were angled at 45 degrees and mounted on the engine nacelles (not at the edge of the aft-strakes). He said the nacelles weree angled as well (I'm thinking that the engines were rotated 45 degrees, giving the nozzles a diamond shape from the rear view).

Here is the best news: Dr. Raymer says that he is willing to work with me to produce a decent interpretation of the design. I plan on making a 5-view of the design, and hoping that one of the 3D artists here (I'm eyeing you BAROBA ) will be willing to make some renders of it. Dr. Raymer is interested in using resulting artwork in future books, classes, advertisements, etc.

I haven't heard back from him in a couple of days, so I imagine he is busy. I'll just be patient and wait until he can get his sketch drawn up.

 

[BAROBA]

Keep me informed

 

[flateric]

cool news, thanks!

 

[sferrin]

something says me that Dan will say that it was quite different

You were right about that.

I have some news.

I e-mailed Dr. Raymer enquiring about this design, whilst also showing him BAROBA's renders and my own top profile view. He said they weren't accurate. He also gave a few more tidbits of information about the design.

The top view sihlouette was almost identical between the pre-stealth and post-stealth designs. The wings indeed were not YF-23-shaped as we had thought. The strake was also smoothly curved as in the original design. The vertical tails were angled at 45 degrees and mounted on the engine nacelles (not at the edge of the aft-strakes). He said the nacelles weree angled as well (I'm thinking that the engines were rotated 45 degrees, giving the nozzles a diamond shape from the rear view).

Here is the best news: Dr. Raymer says that he is willing to work with me to produce a decent interpretation of the design. I plan on making a 5-view of the design, and hoping that one of the 3D artists here (I'm eyeing you BAROBA ) will be willing to make some renders of it. Dr. Raymer is interested in using resulting artwork in future books, classes, advertisements, etc.

I haven't heard back from him in a couple of days, so I imagine he is busy. I'll just be patient and wait until he can get his sketch drawn up.

Will he let you post the 5-view here? There are several 3D modellers that post on this board.

 

[Triton]

Raymer seems to be pretty busy right now (check his blog). I'd certainly like to get his opinion on our depictions of the ATF, but I'll wait until he gets caught up with comments and such.

Maybe a blade/cutting-type name would fit? Several of their other aircraft fit that: the XF-108 Rapier, F-86 Sabre, F-100 Super Sabre, F-107 Ultra Sabre, and B-1 Lancer.

Perhaps "Machete"?

The United States Air Force originally named the Lockheed Martin F-22 the Rapier. As a North American Rockwell design, I would vote for the name Rapier II. There is also Mustang II from the P-51 Mustang and Fury II from the FJ-series Fury. Both names were considered for the Lockheed Martin F-35 Lightning II. The name Machete reminds me of a COIN aircraft concept from a company that should not be named.

 

[Stargazer]

Perhaps "Machete"?

I seem to remember that "Machete" was initially considered for the F-102 but replaced by Delta Dagger.

The name Machete reminds me of a COIN aircraft concept from a company that should not be named.

??? Can you develop? I don't get the hint (in PM if not on this page). Thanks!

 

[SOC]

I can give you a hint, referring to the "organization" as a "company" is a really bad joke ;D

 

[Kryptid]

@sferrin: Yes, he said that he will allow us to use the resulting artwork in anyway we want (as part of the deal).

I'll definitely be throwing it on here when it gets finished.

 

[sferrin]

@sferrin: Yes, he said that he will allow us to use the resulting artwork in anyway we want (as part of the deal).

I'll definitely be throwing it on here when it gets finished.

Sweet!

 

[Kryptid]

I haven't heard back from Dr. Raymer in a long while, so I did a sketch based on what I know. From that, bagera3005 has agreed to produce a clean profile view. Hopefully, if I E-mail that to Dr. Raymer I can get a response. Might be even better if we could get a 3-D model made of it too...

EDIT: Added a perspective view.

 

[BAROBA]

Hi all,

I made a new model based on the new information that has come to light.
Not yet finished, will take a while...

My design is a bit different then the drawing,because the drawing isn't internally consistent..
I still can tweak the design

Comments and crits are welcome

Cheers,

Rob

 

[Stargazer]

Very nice, BAROBA!

 

[AAAdrone]

Cool! Thanks for sharing!