Northrop Grumman B-21 Raider (LRS-B)

[Arjen]

I do not / did not claim development of B-21's FCS will use agile methods. Mess up agile, and you simply do not get the return on investments you would like. We are straying off-topic.

 

[marauder2048]

Mess up agile, and you simply do not get the return on investments you would like. We are straying off-topic.

vs.

FUBAR if you get it wrong.

Hence my confusion.

 

[Arjen]

Messing up beyond recognition happens in the office too. Organisational hell ensues.

 

[Sundog]

B-21 Main Base 1 Beddown. It has some interesting information about noise and flight levels.

 

[Sundog]

My analysis of the B-21 is based off of the first two images shown below; the third is what I generated.

Northrop is known for releasing the silhouettes of their designs before we even know the aircraft's size, so I assumed the one shown in the logo is accurate, in much the same way they made that star image from B-2 planforms before the B-2 rolled out. Also, the image of the shadow in what I assume to be the production plant is what I used to scale the wingspan of 108 feet. I then used the reference wing area from my drawing, 2011 square feet compared to the B-2's 5140 square feet, to scale the fuel fraction with regard to the B-2. I also used the same scale factor to scale the empty weight. I assumed the crew weight and gear, etc., to be the same for the B-21 as with the B-2, which came out to be approximately 1000lbs. I assumed the payload was half that of a B-2, which is 40,000 lbs. normal and 50,000 lbs. overload for the B-2. So for the B-21, I used 20,000 lbs. for the standard payload and 25,000 lbs. for the overload condition. Which works out well, as another Aero Engineer who attended school with me and reviewed my work said he figured it should be able to carry one MOAB which weighs around 21,000 lbs.

I then used the aspect ratio and the wetted area aspect ratio from Raymer's book in the first chapter to estimate the max L/D. I also assumed the T/W ratio would be similar to that of the B-2. As a result, I determined the engine the B-2 would use would most likely be a version of the passport engine, the same one P&W is proposing to re-engine the B-52. That would greatly help the supply chain/maintenance depots to have that much commonality across the bomber fleet. Also, given the thrust needed for the B-21 and the thrust range available for the passport range, these engines can generate plenty of excess energy to power the onboard systems. The P&W data card also notes that the passport engine has ten percent better tsfc than comparable engines. So I just used the F-118's tsfc as reference, which is .67, which yields a tsfc for the B-21s engines of .603 . As a result, I get that B-21 will have approximately 1000 miles greater range than the B-2. The specifications are listed below. This is just my best guess based off of the currently available information. Take it with a grain of salt. I just thought it would be an interesting analysis.

	B-2		B-21
We (lbs):	158000		61817​
Wg (lbs):	376000		148155​
Wf(lbs):	167000		65338​
Wcrew (lbs):	1000		1000​
Wpayload (lbs):	50000		20000​
Engine Thrust (lbs/each):	17000		13397​
No. of Engines:	4		2​
Wingspan, b (ft.):	172		108​
Wing Area, S (sq. ft.)	5140		2011​
Wetted Area Ratio:	2.4		2.4​
Wetted Aspect Ratio:	2.4		2.4​
L/D (max):	22		22​
Wing Area Scale Factor:			0.39​
(used to scale fuel load)
Total Thrust (lbs):	68000		26794​
T/W Ratio (Take-off):	0.18		0.18​
Wing Loading (Take-off):	73.15		73.67​
Fuel Fraction:	0.44		0.44​
Payload Fraction:	0.13		0.13​
Aspect Ratio:	5.76​		5.80​
Loiter L/D:	22​		22​
Cruise L/D:	19.1​		19.1​
Cruise Speed (mph):	560​		560​
Max. Speed (mph):	630​		630​
Powerplant:	F118-GE-100		P&W PW800
Max Thrust (lbs):	19000​		18000​
sfc (lbf/(lbs*hr):	0.67​		0.603​
W1(lbs):			141621​
W2 (lbs):			89351​
Range (SM):	6900​		8149​
Range (NM):	6000​		7082​

 

[Bhurki]

50,000 lbs. overload for the B-2

B-2 carries 2xMOP in overload, thats 60,000 lbs
B21 shall carry 1 MOP, so 30k lbs.

I determined the engine the B-2 would use would most likely be a version of the passport engine, the same one P&W is proposing to re-engine the B-52.

Mr. Wittman said the B21 will have a variant of F135 engine(no reheat)

 

[Sundog]

50,000 lbs. overload for the B-2

B-2 carries 2xMOP in overload, thats 60,000 lbs
B21 shall carry 1 MOP, so 30k lbs.

I determined the engine the B-2 would use would most likely be a version of the passport engine, the same one P&W is proposing to re-engine the B-52.

Mr. Wittman said the B21 will have a variant of F135 engine(no reheat)

Who is Mr. Wittman? I would just like to see all of the info he has to offer. Also, thanks for the update on the MOP. I'll have to adjust the loadout accordingly. Although, there is talk of the next gen MOP being smaller with a rocket motor to achieve the same kinetic effect.

 

[Bhurki]

Who is Mr. Wittman?

HASC member. He stated back in 2018 that B21 would feature modified F135 engines.

Congressman Details Integration Issues With The B-21's Exotic Air Inlet Design

The representative provided more information than ever before on a number of "hiccups" the next generation stealth bomber project is facing.

www.thedrive.com

Lt.Gen Chris Bogdan, F35 program chief had hinted but not directly confirmed the same back in 2016.

 

[Bhurki]

Wingspan, b (ft.):172 108

Wingspan at 108 ft is too small.

If payload fraction is assumed to be the identical(due to largely similar shape) and total payload is reduced to 50% of B2, then every dimension of the jet will reduce about 20% (1/2^0.33, since mass∝volume and volume∝dimension³)
As such the wingspan should be about 130-140ft.

In terms of payload carriage, I think it'll feature a single bay the same size as the two on B-2 to make use of existing configurations (using the AF rotary launcher and so on).

 

[TomcatViP]

@apparition13 : if she has distributed propulsion (exhausts), the wings won't probably fold!

 

[Sundog]

Wingspan, b (ft.):172 108

Wingspan at 108 ft is too small.

If payload fraction is assumed to be the identical(due to largely similar shape) and total payload is reduced to 50% of B2, then every dimension of the jet will reduce about 20% (1/2^0.33, since mass∝volume and volume∝dimension³)
As such the wingspan should be about 130-140ft.

In terms of payload carriage, I think it'll feature a single bay the same size as the two on B-2 to make use of existing configurations (using the AF rotary launcher and so on).

OK, I read the article at the drive. The congressman didn't speculate about the engines, the Drive did. Two F-135s would generate too much thrust which would cut into range. I also assumed the design I have shown above would have the same size weapons bay as the B-2, hence half the load. Also, given that it has longer range than the standard B-2, I assume it wouldn't carry as much fuel to carry the MOP, so I'll stick with my original analysis.

 

[sublight is back]

My analysis of the B-21 is based off of the first two images shown below; the third is what I generated...... (snip)

Where are your altitude figures? Does the B-21 not have a ceiling significantly higher that B-2? Remember that flutter from much longer wings was part of the risk reduction program. It think that changes your proposed dimensions significantly.

 

[sferrin]

Which works out well, as another Aero Engineer who attended school with me and reviewed my work said he figured it should be able to carry one MOAB which weighs around 21,000 lbs.

MOAB is shoved out the back of a C-130, and is not carried by any bomber. MOP (GBU-57), which is carried by the B-52 and B-2, weighs 30,000lbs.

MOAB


MOP (GBU-57)

 

[rooster]

My analysis of the B-21 is based off of the first two images shown below; the third is what I generated.

Dude. Your 20,000 pound payload is not even 8 agm86.

 

[rooster]

Wingspan, b (ft.):172 108

Wingspan at 108 ft is too small.

If payload fraction is assumed to be the identical(due to largely similar shape) and total payload is reduced to 50% of B2, then every dimension of the jet will reduce about 20% (1/2^0.33, since mass∝volume and volume∝dimension³)
As such the wingspan should be about 130-140ft.

In terms of payload carriage, I think it'll feature a single bay the same size as the two on B-2 to make use of existing configurations (using the AF rotary launcher and so on).

OK, I read the article at the drive. The congressman didn't speculate about the engines, the Drive did. Two F-135s would generate too much thrust which would cut into range. I also assumed the design I have shown above would have the same size weapons bay as the B-2, hence half the load. Also, given that it has longer range than the standard B-2, I assume it wouldn't carry as much fuel to carry the MOP, so I'll stick with my original analysis.

Too much thrust????? Yeah ok, considering that we can safely assume the 21 will need EXCESS thrust for flight control as deflecting surfaces increases RCS. I guess we may as well build a half scale b2 and call it a night.

 

[Sundog]

Which works out well, as another Aero Engineer who attended school with me and reviewed my work said he figured it should be able to carry one MOAB which weighs around 21,000 lbs.

MOAB is shoved out the back of a C-130, and is not carried by any bomber. MOP (GBU-57), which is carried by the B-52 and B-2, weighs 30,000lbs.

MOAB
View attachment 642335

MOP (GBU-57)
View attachment 642336

Yeah, meant MOP. Such is life.

 

[Sundog]

My analysis of the B-21 is based off of the first two images shown below; the third is what I generated...... (snip)

Where are your altitude figures? Does the B-21 not have a ceiling significantly higher that B-2? Remember that flutter from much longer wings was part of the risk reduction program. It think that changes your proposed dimensions significantly.

My understanding is that was Lockheed-Martin, not Northrop-Grumman. But that has to do with structural efficiency by lowering the structural weight of the wing. Also, you don't need high aspect ratio wings for high altitude. You need a large wing area. See the Avro Vulcan. The design I showed above is based off the information released by N-G in the images above, so far. If you have other information actual from them, please provide it. BTW, I assumed it would operate at 50,000 to 55,000 ft.

 

[Josh_TN]

Most observers agree the B-21 would have a higher ceiling given its superior shape (diamondback Tail vs sawtooth). I would also assume composite structures have advanced greatly since the b-2 was designed. 50-55k feet seems reasonable. Pretty sure even B-2 can hit that ceiling depending on load.

 

[sferrin]

Which works out well, as another Aero Engineer who attended school with me and reviewed my work said he figured it should be able to carry one MOAB which weighs around 21,000 lbs.

MOAB is shoved out the back of a C-130, and is not carried by any bomber. MOP (GBU-57), which is carried by the B-52 and B-2, weighs 30,000lbs.

MOAB
View attachment 642335

MOP (GBU-57)
View attachment 642336

Yeah, meant MOP. Such is life.

But MOP doesn't weigh 21,000lbs. It weighs 30,000lbs.

 

[sublight is back]

I assumed it would operate at 50,000 to 55,000 ft.

I saw figures of 60,000 to 70,000 in one presentation.

 

[Josh_TN]

B-2's use a pressurized cabin, right? At some point just above 60K you run into the problem of water boiling.

 

[flateric]

My analysis of the B-21 is based off of the first two images shown below; the third is what I generated.

This is another official planform image. Needless to say it may be pure disinformation with altered proportions as it doesn't match original 2016 rendering.
Rounded tips though match newly released "in hangar' renderings

Striking similarity to original high-altitude Senior CJ

 

[quellish]

My understanding is that was Lockheed-Martin, not Northrop-Grumman. But that has to do with structural efficiency by lowering the structural weight of the wing. Also, you don't need high aspect ratio wings for high altitude. You need a large wing area. See the Avro Vulcan. The design I showed above is based off the information released by N-G in the images above, so far. If you have other information actual from them, please provide it. BTW, I assumed it would operate at 50,000 to 55,000 ft.

BFF and X-56 were both based on an (older) Lockheed platform (early QUARTZ) that had flutter issues at altitude (which killed that configuration in that program). The configuration was not representative of any LRS-B work and was not explictly risk reduction for LRS-B and findings from those test programs would have been too late for LRS-B.

 

[quellish]

But MOP doesn't weigh 21,000lbs. It weighs 30,000lbs.

From what I understand, having discussed it with people who should know, MOP was not driving requirements for LRS-B. It was not intended for LRS-B to carry it.

In general there has been a mentality in recent years that conventional weapons can be developed / modified for the platform, rather than the platform being designed around the weapon. Hypersonic and unconventional weapons are a different story. There were other penetrating weapons in development that were intended for LRS-B (and others) and would have fit within more conventional envelopes. I do not know the current status of those programs.

 

[bob225]

I assumed it would operate at 50,000 to 55,000 ft.

I saw figures of 60,000 to 70,000 in one presentation.

Couldn't the Avro Vulcan fly up at 50-55K??

 

[sferrin]

I assumed it would operate at 50,000 to 55,000 ft.

I saw figures of 60,000 to 70,000 in one presentation.

Couldn't the Avro Vulcan fly up at 50-55K??

I'd read 60k to 65k.

 

[rooster]

Doesn't flying too high have penalties in observability? My limited knowledge is that infrared signatures travel further at higher altitudes because there is less atmospheric absorbing occurring because of fewer molecules hence making something more visible in that spectrum. Also by flying higher the aircraft is illuminated sooner by radar as the target appears over the horizon sooner. Though there are no satellite constellations now that look down for stealth aircraft I understand that the early warning satellites are sensitive enough to in theory detect aircraft exhaust. Hence being too high has a penalty to satellites and other high flying sensor platforms in the ir spectrum

Don't flame me too badly. I work in automotive engineering.

 

[Dragon029]

Flying higher is advantageous for modern stealth aircraft simply because:
1. You're immune to AAA.
2. Your own sensors can detect threats earlier and allow you to route around them.
3. Your weapons have more range (especially if they're glide weapons), meaning you can stay further away from the target.

 

[TomcatViP]

Higher = colder also (lower emissivity).

 

[helmutkohl]

The Air Force Plans to Retrain Weapons System Officers to Be B-21 Bomber Pilots

The Air Force plans to slash the number of weapons system officers by half to make room for more pilots, a top general said.

www.military.com

 

[Josh_TN]

In the context of retiring the B-1, it makes sense. I'm just hoping that the transition makes good use of all the established talent...I hope any able bodied B-1 nav or ECM guy gets the opportunity to transition their experience to the new platform. If you split a B-1 crew in half, you're left with two pilot/commander positions and two offense/defense positions. Seems to me with a little retraining you could make a lot of two man crews and take advantage of operational experience.

 

[sferrin]

In the context of retiring the B-1, it makes sense. I'm just hoping that the transition makes good use of all the established talent...I hope any able bodied B-1 nav or ECM guy gets the opportunity to transition their experience to the new platform. If you split a B-1 crew in half, you're left with two pilot/commander positions and two offense/defense positions. Seems to me with a little retraining you could make a lot of two man crews and take advantage of operational experience.

You do know they're going to be around for probably another 20 years, at least, right?

 

[Flyaway]

The Air Force Plans to Retrain Weapons System Officers to Be B-21 Bomber Pilots

The Air Force plans to slash the number of weapons system officers by half to make room for more pilots, a top general said.

www.military.com

Still makes me laugh that USAF bomber force going forward is going to consist of two aircraft built some seventy years apart. Mind you it does give the idea that the B-52 is the best US bomber so far ever built.

 

[mkellytx]

The Air Force Plans to Retrain Weapons System Officers to Be B-21 Bomber Pilots

The Air Force plans to slash the number of weapons system officers by half to make room for more pilots, a top general said.

www.military.com

Wow, surprised they didn't elect to stick them in the back of the F-15EX's, that would only be a short course in an FTU instead of UPT and a long course in the FTU.