ZaphodHarkonnen
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Re: Northrop Grumman B-21 Raider Production And Delivery Thread

Wed Feb 05, 2020 1:09 am

texl1649 wrote:
Exactly, a mini B-2. Single truck MLG’s, this looks more akin to an FB-111 size delivery platform than a B-1, let alone a B-52. Presumably it is to be vastly more easily maintained than the B-2 parent design, or B-1’s shown in the background.


Oh, totally. Especially if they were able to make good reuse of the hardware and avionics built for the F-35. The biggest difference then becomes the basic airframe and other larger components.
 
DigitalSea
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Re: Northrop Grumman B-21 Raider Production And Delivery Thread

Wed Feb 05, 2020 5:27 pm

Maybe the USAF/USG did it right this time, field something not incredibly exotic that can utilize existing technology to achieve high production numbers without the high price tag.
 
744SPX
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Re: Northrop Grumman B-21 Raider Production And Delivery Thread

Wed Feb 05, 2020 6:08 pm

Sizing it around 2 F135's (if that is the final config) is a good call.
 
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Slug71
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Re: Northrop Grumman B-21 Raider Production And Delivery Thread

Thu Feb 06, 2020 1:32 am

texl1649 wrote:
Exactly, a mini B-2. Single truck MLG’s, this looks more akin to an FB-111 size delivery platform than a B-1, let alone a B-52. Presumably it is to be vastly more easily maintained than the B-2 parent design, or B-1’s shown in the background.


A larger frame is probably not needed in today's battlefield. I think the Bomber role has diminished over the years with advancements of missiles. Ships and Subs can now deliver a bulk of the payload.
 
MohawkWeekend
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Re: Northrop Grumman B-21 Raider Production And Delivery Thread

Thu Feb 06, 2020 1:55 am

Silly thought I guess but I read recently that the USN is working on fitting more air to surface weapons to the P-8. Might an even more adapted version of her be the bombtruck the Aussie's could use instead of a B-21. And the USAF could use her as a with a much cheaper replacement of the B-52? Imagine a rotary cruise missile launcher and a few extra wing pylons. Silly thought.
    300 319 320 321 707 717 720 727 72S 737 73S 734 735 73G 738 739 747 757 762 ARJ B11 C212 CRJ CR2 CR7 CR9 CV5 D8S DC9 D9S D94 D95 D10 DH8 DTO EMB EM2 E135 E145 E190 FH7 F28 F100 FTRIMTR HRN L10 L15 M80 M90 SF3 SWM YS11
     
    texl1649
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 06, 2020 2:36 am

    Slug71 wrote:
    texl1649 wrote:
    Exactly, a mini B-2. Single truck MLG’s, this looks more akin to an FB-111 size delivery platform than a B-1, let alone a B-52. Presumably it is to be vastly more easily maintained than the B-2 parent design, or B-1’s shown in the background.


    A larger frame is probably not needed in today's battlefield. I think the Bomber role has diminished over the years with advancements of missiles. Ships and Subs can now deliver a bulk of the payload.


    I agree it makes some sense. The FB-111 was, after all (in perhaps a bit of irony) a supplemental type developed due to USAF concerns about B-52’s wearing out (cracks/fatigue)...and was retired when the B-1B made it un-needed (again, the irony is palpable). A 120,000 lb MTOW and 35K lb ordinance payload is probably, if I am guessing right, in the range of what this aircraft could deliver based on the renderings (that’s what the FB-111A spec’d out at).

    I would also agree that it makes sense to size around something similar/based on two F135’s, and just pray it isn’t as obnoxiously underpowered as the T-30’s (not that this can go Mach 2 anyway). An F135, if modified without an afterburner and to fly subsonic, might be quite efficient, but I’d be curious if folks like Revelation here might opine as to modifications that might make that engine work better for this, and other possible future subsonic non-tactical operations. Using ‘standard’ fighter engines on long bomber missions isn’t really ideal; the B-2 has to refuel every 6 hours.
     
    DigitalSea
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 06, 2020 5:18 am

    texl1649 wrote:
    Using ‘standard’ fighter engines on long bomber missions isn’t really ideal; the B-2 has to refuel every 6 hours.


    No kidding? Wow.
     
    aumaverick
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 06, 2020 2:16 pm

    texl1649 wrote:
    Slug71 wrote:
    texl1649 wrote:
    Exactly, a mini B-2. Single truck MLG’s, this looks more akin to an FB-111 size delivery platform than a B-1, let alone a B-52. Presumably it is to be vastly more easily maintained than the B-2 parent design, or B-1’s shown in the background.


    A larger frame is probably not needed in today's battlefield. I think the Bomber role has diminished over the years with advancements of missiles. Ships and Subs can now deliver a bulk of the payload.


    I agree it makes some sense. The FB-111 was, after all (in perhaps a bit of irony) a supplemental type developed due to USAF concerns about B-52’s wearing out (cracks/fatigue)...and was retired when the B-1B made it un-needed (again, the irony is palpable). A 120,000 lb MTOW and 35K lb ordinance payload is probably, if I am guessing right, in the range of what this aircraft could deliver based on the renderings (that’s what the FB-111A spec’d out at).

    I would also agree that it makes sense to size around something similar/based on two F135’s, and just pray it isn’t as obnoxiously underpowered as the T-30’s (not that this can go Mach 2 anyway). An F135, if modified without an afterburner and to fly subsonic, might be quite efficient, but I’d be curious if folks like Revelation here might opine as to modifications that might make that engine work better for this, and other possible future subsonic non-tactical operations. Using ‘standard’ fighter engines on long bomber missions isn’t really ideal; the B-2 has to refuel every 6 hours.


    I think you hit the nail on the head. With the F-15E/F-35 payloads specked at 23,000 and 18,000 lbs respectively, and the B-2 at 40,000 lbs, there is a sweet spot gap. The B-21 can fill the payload gap of the F-35 and provide a contested environment penetration platform via stealth the F-15E lacks. The B-2 is overkill a lot of times, and was always meant to be a nuclear deterrent. The B-52 is overkill, and the B-1s are just plain worn out. Meanwhile, the F-15Es lack the legs or stealth for some missions, and the F-35 was never meant to be a medium sized bomber. This is where I hope the B-21 fills that sweet spot of capability.
    I'm just here so I won't get fined. - Marshawn Lynch
     
    LightningZ71
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 06, 2020 8:22 pm

    I would imagine that the only substantive changes that could be made to the F-135 for use in the B-21 would be the removal of the Afterburner section and the associated plumbing changes that go with that. It might not be too crazy to suggest that the could keep the majority of the HPT and LPT sections, as well as the "hot" section while using a larger fan with a larger bypass, keeping the more expensive portions of the engine the same, but making it more efficient in other areas where the cost is lower, but, I would suspect that that's too much of a change for them to keep development costs under control. I do suspect that, due to its smaller size, and generally more efficient engines, that it should get better range than the B-2 between required refills if it keeps the same fuel fraction.
     
    Ozair
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 06, 2020 9:17 pm

    LightningZ71 wrote:
    I would imagine that the only substantive changes that could be made to the F-135 for use in the B-21 would be the removal of the Afterburner section and the associated plumbing changes that go with that. It might not be too crazy to suggest that the could keep the majority of the HPT and LPT sections, as well as the "hot" section while using a larger fan with a larger bypass, keeping the more expensive portions of the engine the same, but making it more efficient in other areas where the cost is lower, but, I would suspect that that's too much of a change for them to keep development costs under control. I do suspect that, due to its smaller size, and generally more efficient engines, that it should get better range than the B-2 between required refills if it keeps the same fuel fraction.

    Given the B-21 has long range operations in the pacific theatre as its primary mission I expect it will surprise on the distances the jet will operate without refuelling. The advantage the B-21 has is that the F135 will continue to go through significant upgrade. P&W have already proposed the Growth Option One and Two packages which both bring increased thrust and reduced fuel burn.

    Depending on what happens with the AETP the B-21 could also be a candidate for conversion to that engine which would increase range again, potentially by as much as 25% beyond current projections. Noting as well the B-21 is considered an excellent candidate for DEW and therefore an efficient engine that can also rapidly recharge those weapons would be advantageous.
     
    744SPX
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Fri Feb 07, 2020 12:15 am

    Given that the B-21 is "2/3" size of B-2, putting a larger fan on the F-135 would probably be overkill as it already has enough thrust (unless they want a better thrust to weight ratio than the B-2) 2 F-135's dry is 56K lbs thrust and the 4 F-118's are 68k, so it would appear the B-21 will already have a superior thrust to weight ratio assuming it is 2/3 the weight...
     
    SuperiorPilotMe
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Fri Feb 07, 2020 1:09 am

    744SPX wrote:
    Given that the B-21 is "2/3" size of B-2, putting a larger fan on the F-135 would probably be overkill as it already has enough thrust (unless they want a better thrust to weight ratio than the B-2) 2 F-135's dry is 56K lbs thrust and the 4 F-118's are 68k, so it would appear the B-21 will already have a superior thrust to weight ratio assuming it is 2/3 the weight...


    LightningZ71’s post had me thinking. The F135 is not quite, but close enough to 2 engines in one as far as (afterburner) thrust is concerned. I wonder if you could use one for a strictly unmanned, “mini-me” version of the B-21.
    Stop the stupids!- Claus Kellerman
     
    Ozair
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Fri Feb 07, 2020 2:25 am

    SuperiorPilotMe wrote:
    LightningZ71’s post had me thinking. The F135 is not quite, but close enough to 2 engines in one as far as (afterburner) thrust is concerned. I wonder if you could use one for a strictly unmanned, “mini-me” version of the B-21.


    No reason they couldn’t and there are plenty of single engine UCAVs already, additionally the B-21 has been suggested all along as an optionally unmanned platform. The X-47b operated with an F100 off a carrier deck so you are in essence suggesting an upsize to that platform. Do you need the thrust of F135 though? Thrust would be dependent on what you perceive as the intent of the development, a loyal wingman to manned B-21s, additional unmanned assets to make up for not enough bombers, assume conventional weapons only? If you drop the payload to say 10k lbs in two bays (enough to take a 5k GBU-28 or similar sized weapon) and keep the same basic planform you should be able to maintain a decent range, would need to have pacific theater in mind, in a high stealth package.

    How about operating a fleet of “B-212s” associated with a mothership “KB-21” tanker and (USAF turn off now) use hose and drogue with the software developed for the X-47b and MQ-25?
     
    LightningZ71
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Fri Feb 07, 2020 1:18 pm

    In reference to using a larger fan section on the F-135 as it is installed in the B-21, I was suggesting it more as an efficiency measure and less as a thrust production issue. The F-135, for the B-21, is plenty powerful. However, it is optimized for its use in a multi-role supersonic fighter as it currently exists. Given that it is expected that the B-21 will be subsonic, it makes sense to use a higher bypass ratio for fuel efficiency gains. The caveat here is that it will be costly to have such a significant difference on the F-135 in the B-21 from a development, purchasing and maintenance perspective, and, it will consume more volume inside of the already restricted interior volume that the B-21 will have to work with.
     
    texl1649
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Fri Feb 07, 2020 5:57 pm

    It’s intriguing to consider and hopefully USAF has some of this in the ‘big picture’ development plans, Ozair. I do think the prospects of that stuff (remote refueling/drone versions) being part of the development programs though is pretty darn low. Procurement has been too costly/delayed on too many platforms for the USAF to actively encourage that, at this point.

    I do think hose/drogue refueling is the only thing that can make sense once a drone tanker is considered for actual development.

    Lightningz71 I agree it would be an issue it’s just that running two F135’s for 10-20 hour subsonic 30K foot missions seems a bit...inefficient. We don’t need this thing to compete with an A321NEO/779 in fuel efficiency by any means, per pound of cargo per mile, but it’s always good to see a rational amount of fuel burn (and operational cost when incorporating tankers) in real mission planning/training.
     
    RJMAZ
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    Re: Northrop Grumman B-21 Raider Production And Delivery Thread

    Thu Feb 20, 2020 1:36 am

    texl1649 wrote:
    Lightningz71 I agree it would be an issue it’s just that running two F135’s for 10-20 hour subsonic 30K foot missions seems a bit...inefficient.

    I think it will use a pair of GE passport engines. Most likely uprated slightly from the standard 84kn to about 90kn. That would be extremely efficient.

    The B-2 has four 77kn for a total of 308kn. Two 90kn passport engines would have 59% of the thrust. So the aircraft weights would be about 60% of the current B-2.

    OEW: 46t
    MTOW: 102t
    Fuel capacity: 45t
    Internal bomb capacity: 11t

    This seems perfect and it would not surprise me if it can still go close to the B-2 range of 6900nm.

    The GE passport engines are the same weight and slightly shorter than the F-135. The fan diameter is only 6inch larger.

    The bypass ratio is 5.6 vs 0.57 that would result in a 20-30% range boost right there.

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