Northrop Grumman B-21A Raider (LRS-B)

[The Artist]

Foxtrot Alpha posted this logo with their story. Agree with the planform sweep?

It sure doesn't look right. But at this stage, it's impossible to. Remember the introduction to the F-117? Depending on how you present an image, you can really mess with peoples assessment of angles.

And of course, this being an artists impression, it could be intentionally wrong.

I spent some studying that F-117 image and I've concluded that it was printed from a frame of 16mm film footage that had been shot from a distance with a long lens.

 

[overscan (PaulMM)]

Wher do you find this design in 2011 ?

I've found it in one of NASA ERA powerpoints

Environmentally Responsible Aviation N plus 2 Advanced Vehicle Concepts NRA Status - NASA Technical Reports Server (NTRS)

The NASA Environmentally Responsible Aviation Project (ERA) has a NASA Research Announcement (NRA) that is performing a systems study and conceptual design. The purpose of the systems study is to determine possible configurations that are capable of simultaneously meeting NASA's Subsonic N+2...

ntrs.nasa.gov

 

[Ian33]

.

 

[overscan (PaulMM)]

Thats a Photoshop effort by Stephane, nothing real. Pretty similar though

 

[overscan (PaulMM)]

Here's the well-known Northrop Grumman NGB design artwork alongside the one Grigori found in the NASA document. Intakes are hard to discern.

 

[Avimimus]

I just wanted to thank you guys (as usual) for the intelligent discussion of RCS reduction - it is always a pleasure to learn more from you guys.

 

[overscan (PaulMM)]

NGB design to B-21 comparison. Note the slightly cranked leading edge versus the absolute straight leading edge. Exhausts and intake comparisons are interesting. B-21 design appears to be somewhat larger. I can't help feeling that the B-21 image could be a wide angle shot of something with the same basic geometry of the NGB design.

 

[quellish]

NGB design to B-21 comparison. Note the slightly cranked leading edge versus the absolute straight leading edge. Exhausts and intake comparisons are interesting. B-21 design appears to be somewhat larger. I can't help feeling that the B-21 image could be a wide angle shot of something with the same basic geometry of the NGB design.

Scott has a wonderful drawing that shows most of the known Northrop flying wing configurations.
From the released artist rendering and what we know of the program requirements a number of things can be inferred. We know that the LRS-B is *likely* to be smaller than the B-2 for several reasons. We also know that propulsion is a primary driver for the length of a flying wing configuration - engines, inlets, and exhaust. The length of the aircraft will drive many of the other dimensions and affect the speed, range, payload mass and RCS.

Given those things it would be worthwhile to look at the Northrop ATA and original ATB. Inlet and exhaust design has certainly advanced significantly since the period when those were designed and is likely to be a smaller % of the engine or vehicle length. There may be enough information in the LRS-B rendering to estimate how much of the length is engine and how much is duct.

 

[Flyaway]

Is it likely to have fluidic thrust vectoring, does a bomber require this?

 

[seruriermarshal]

:

polecat

 

[dark sidius]

The Polecat was realy UGLY

 

[NeilChapman]

Why did low altitude penetration require the additional trailing edge serration?

http://www.northropgrumman.com/Capabilities/B2SpiritBomber/Documents/pageDocuments/B-2-Spirit-of-Innovation.pdf
page 55 ->

This is a fantastic read. Fascinating. You get great stuff flateric.

So the original B2 design looks like a ringer for B21. B2 low altitude requirements lead to larger flight controls and the change to the planform. I wonder what they've learned about flight controls that has reverted the planform?

Anyone seen any hints on where production will take place? I know they have the final production location from B2 by Edwards. The old Ford plant they used for B2 is gone.

Any likely hood that engine efficiencies would allow two engines for B21 vs four for B2 - considering the mission is probably not changed other than payload?

 

[quellish]

I wonder what they've learned about flight controls that has reverted the planform?

Since the B-2 was designed there have been many developments in flight controls - some of them in the last few years.
Tailless aircraft have been the focus of a lot of attention since the late 1980s. Removing the tail has benefits from a signature standpoint but removing that tail introduces yaw problems.

In the 90s there was a lot of work done on thrust vector control (including fluidic yaw vectoring). The state of the art in that area has advanced considerably since the B-2, which has a limited degree of thrust-based yaw control using differential engine thrust. That differential engine thrust is used on the B-2 to limit required control surface deflections - because those big control surfaces are not so good for the RF signature.

Also during the 90s DoD funded work to develop new kinds of control surfaces for both subsonic and supersonic aircraft. Some of that work is documented in "FATE" and "ICE" threads on the forum. The product of that work can be seen on the X-47A.

View: https://www.youtube.com/watch?v=Jt-Yp5WMW7s


More recently there has been work on "morphing" aircraft structures. This ranges from gapless control surfaces to changing the shape of the whole aircraft. Back in the 1980s the AFTI F-111 tested what we would now call a "morphing" wing. A morphing wing could offer many things to a flying wing aircraft. This could be dynamic twist to control yaw, "seamless" control surfaces, a changing airfoil, or an outer wing that changes shape and size for performance reasons.

View: https://www.youtube.com/watch?v=9ZpAHxMj5lU


And in the last few years NASA has experimented with altering the distribution of lift on a wing to control adverse yaw. The Prandtl-D test aircraft demonstrated a new way of implementing some old ideas using modern tools which could have significant advantages for an aircraft like the LRS-B.

View: https://www.youtube.com/watch?v=Hr0I6wBFGpY

 

[NeilChapman]

Is it likely to have fluidic thrust vectoring, does a bomber require this?

The mission of these "fly-alone" bombers is surprising. They evidently need to maneuver extremely well at very high sub-sonic speeds. Also need to fly out of pretty much any 737-capable landing strip (B2).

 

[marauder2048]

NGB design to B-21 comparison. Note the slightly cranked leading edge versus the absolute straight leading edge. Exhausts and intake comparisons are interesting. B-21 design appears to be somewhat larger. I can't help feeling that the B-21 image could be a wide angle shot of something with the same basic geometry of the NGB design.

Scott has a wonderful drawing that shows most of the known Northrop flying wing configurations.
From the released artist rendering and what we know of the program requirements a number of things can be inferred. We know that the LRS-B is *likely* to be smaller than the B-2 for several reasons. We also know that propulsion is a primary driver for the length of a flying wing configuration - engines, inlets, and exhaust. The length of the aircraft will drive many of the other dimensions and affect the speed, range, payload mass and RCS.

Given those things it would be worthwhile to look at the Northrop ATA and original ATB. Inlet and exhaust design has certainly advanced significantly since the period when those were designed and is likely to be a smaller % of the engine or vehicle length. There may be enough information in the LRS-B rendering to estimate how much of the length is engine and how much is duct.

They've also gotten really good at building low-aspect ratio Boundary layer ingestion inlets so a good chunk of that apparent propulsion system length could be engine and exhaust cooling.

 

[Black Dog]

Wher do you find this design in 2011 ?

I've found it in one of NASA ERA powerpoints

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015351.pdf

Bottom left - RQ 180?

 

[quellish]

Bottom left - RQ 180?

NG SensorCraft design.

 

[marauder2048]

Bottom left - RQ 180?

NG SensorCraft design.

Quellish may have more information but I thought I had read that Northrop had examined deformable control surfaces early in B-2's design.

 

[XP67_Moonbat]

My two cents

 

[Sundog]

Why did low altitude penetration require the additional trailing edge serration?

http://www.northropgrumman.com/Capabilities/B2SpiritBomber/Documents/pageDocuments/B-2-Spirit-of-Innovation.pdf
page 55 ->

This is a fantastic read. Fascinating. You get great stuff flateric.

So the original B2 design looks like a ringer for B21. B2 low altitude requirements lead to larger flight controls and the change to the planform. I wonder what they've learned about flight controls that has reverted the planform?

Anyone seen any hints on where production will take place? I know they have the final production location from B2 by Edwards. The old Ford plant they used for B2 is gone.

Any likely hood that engine efficiencies would allow two engines for B21 vs four for B2 - considering the mission is probably not changed other than payload?

Final production will be in Palmdale as it was for the B-2. One of the "rumored" major sub contractors is Spirit Aero Systems out of Wichita. Also, it's most likely a twin engined aircraft, as that would also greatly reduce cost. It's also smaller than the B-2.

 

[quellish]

Final production will be in Palmdale as it was for the B-2. One of the "rumored" major sub contractors is Spirit Aero Systems out of Wichita. Also, it's most likely a twin engined aircraft, as that would also greatly reduce cost. It's also smaller than the B-2.

A lot of the manufacturing will not be in CA, or at least isn't planned to be right now. This is one of the things affecting the EMD and unit costs. There is obviously a huge political dimension to where jobs and dollars will be going.

 

[overscan (PaulMM)]

So.

B-2 = 4 x F118 @ 17,300 lb st = 69,200lb st
Loaded Weight: 336,500 lb
Maximum Weight: 376,000 lb

B-21 = 2 x F135 @ 28,000lb st = 56,000lb st

Ratio of thrust : 0.8:1

Assuming same thrust/weight ratio, same basic performance:

Loaded Weight: 336,500 lb = 269,200lb
Maximum Weight: 376,000 lb = 300,800lb

The engine choice determines maximum speed, altitude and range. A low bypass ratio is better for top speed and high ceiling, a higher bypass ratio better for long range cruise.

F118 bypass ratio is I believe 0.87:1. F135 bypass ratio is 0.57:1. That could translate to potentially higher speed/altitude capability.

If the engine type is correct, these weight figures should be upper boundaries. If the emphasis for B-21 is high subsonic speed, it might have a higher thrust/weight ratio taking the maximum weights down from the above.

What are other candidate engines?

F414
F110-GE-129/132
F118
New design (e.g. Advent studies)

 

[marauder2048]

Final production will be in Palmdale as it was for the B-2. One of the "rumored" major sub contractors is Spirit Aero Systems out of Wichita. Also, it's most likely a twin engined aircraft, as that would also greatly reduce cost. It's also smaller than the B-2.

A lot of the manufacturing will not be in CA, or at least isn't planned to be right now. This is one of the things affecting the EMD and unit costs. There is obviously a huge political dimension to where jobs and dollars will be going.

A good chunk of their recent Special Access Program hiring has been for the Melbourne, Florida site.

 

[marauder2048]

What are other candidate engines?

F414
F110-GE-129/132
F118
New design (e.g. Advent studies)

The notional PW9000 @ 30,000 lbs s.t.

 

[overscan (PaulMM)]

Yep, thats a definite possibility - using the F135 low speed spool, similar thrust levels but lower fuel burn, and its based on new but already existing technology.

 

[dark sidius]

I think two F-135 don't have the capacity to push something like the B-21 not enough trust for a heavy bomber.

 

[flateric]

I think two F-135 don't have the capacity to push something like the B-21 not enough trust for a heavy bomber.

I think you need read some entry-level aerospace courses to discuss the subject.

 

[Airplane]

The story about the B-2 and the Lacrosse satellite is well known; it was public knowledge at the time. What will be the off-board target location platform for the -21? Will it be manned or unmanned, or a combination? Is there evidence of a platform being developed? Most likely there are a handful of RQ180s, and I wonder about the reliability of unmanned systems that theoretically can be jammed and rendered useless. Will there be a system fielded specifically for the B-21?

 

[sferrin]

I think two F-135 don't have the capacity to push something like the B-21 not enough trust for a heavy bomber.

The F118 in the B-2 produces 19,000lbs thrust. A modified F135 could easily produce mid-30s dry. (The variant in the X-32 produced 34+ dry.) The B-21 is smaller than the B-2. There is nothing in the picture (and I don't recall any official announcement) to indicate either that it only has two engines or that it uses the F135.

 

[Flyaway]

The story about the B-2 and the Lacrosse satellite is well known; it was public knowledge at the time. What will be the off-board target location platform for the -21? Will it be manned or unmanned, or a combination? Is there evidence of a platform being developed? Most likely there are a handful of RQ180s, and I wonder about the reliability of unmanned systems that theoretically can be jammed and rendered useless. Will there be a system fielded specifically for the B-21?

The RQ-180 will do the job is my speculation.

 

[Airplane]

So you think they would trust an unmanned drone to do the job over China or Russia if that time ever came? I don't. For scenarios like Syria with the F-22s that makes sense. I have to speculate the one of missions of the B-21 is the same one the B-2 was famously fielded for, and that is destroying mobile ICBMs. Of course nothing is known of the RQ-180, but that is a lot to gamble on an unmanned system being "flown" out of CONUS, or some other place in the world. Communications to a drone can't be knocked out by disabling the comm satellites or by jamming when dealing with a modernized adversary as opposed to the low level stuff we've dealt with for 15 years?

 

[flateric]

 

[seruriermarshal]

what's this ?

 

[TomS]

it's a Philosoraptor.

 

[sferrin]

I'm guessing he knows what it is and is just wondering why it's there.

 

[overscan (PaulMM)]

flateric is wondering if his posted images are relevant to topic. Hence the philosoraptor

 

[Flyaway]

Has the state of the art advanced sufficiently that you could build a plane like the B-21 without any control surfaces?

 

[overscan (PaulMM)]

Sure, so long as you want to fly in a straight line. ;D

Using wing deformation instead? Thrust vectoring?

Possible I guess. Likely? Probably not.

 

[Flyaway]

Sure, so long as you want to fly in a straight line. ;D

Using wing deformation instead? Thrust vectoring?

Possible I guess. Likely? Probably not.

I suppose the problem is some stuff related to this may have been matured behind the curtain so to speak.

 

[TomS]

I think two F-135 don't have the capacity to push something like the B-21 not enough trust for a heavy bomber.

I think you need read some entry-level aerospace courses to discuss the subject.

That typo might be illuminating. I'm sure they could get enough thrust to power a bomber like this on two engines. But do they have enough trust? I'm not sure they'd be happy with the military equivalent of an ETOPS rating for a bomber carrying nuclear weapons over long distances.