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Author Topic: Air Force Could Pursue Stealthy Aerial-Refueling Tanker  (Read 26322 times)

Offline TomS

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #15 on: September 22, 2016, 06:14:12 am »
Sounds obvious to me - There is a very simple way of having a stealth tanker. Just put some fuel tanks in a Northrop B-2A bomb bays, and use the Navy probe-and-drogue system (no need for a fixed boom)

And retrofit every F-22 and USAF F-35 with a probe instead of (or in addition to) a receptacle.  Suddenly not so trivial a process.


Offline kagemusha

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #16 on: September 22, 2016, 09:19:57 am »
Why not a KB-21 with fuel tanks into the bomb bay and a retractable boom?

Offline FighterJock

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #17 on: September 22, 2016, 10:29:14 am »
Why not a KB-21 with fuel tanks into the bomb bay and a retractable boom?

That could work if the USAF puts up a future requirement, just look at what happened to the RAF V-Force bombers towards the end of their lives?  They were converted to tankers.

Offline marauder2048

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #18 on: September 22, 2016, 12:44:45 pm »
Sounds obvious to me - There is a very simple way of having a stealth tanker. Just put some fuel tanks in a Northrop B-2A bomb bays, and use the Navy probe-and-drogue system (no need for a fixed boom)
According to Wikipedia,
Quote
The B-2 is capable of carrying 40,000 lb (18,000 kg) of ordnance

Not a lot of fuel, but well enough for a F-35 or even a F-22.

Part of the question might be: what was the planned operating empty weight of the B-2C?

Offline _Del_

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #19 on: September 22, 2016, 03:08:45 pm »
I would think a true "stealth" tanker would be very low on the priority list for a service which desperately needs to recapitalize nearly every facet of its fleet.
A big flying wing might make some sense and incorporate some signature reduction methods, but a truly stealthy tanker seems like a giant waste of money and a guarantee for delays and cancelation.
Does a B-2 have a useful offload capacity? I wouldn't think so.

Offline NeilChapman

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #20 on: September 22, 2016, 03:11:04 pm »
Sounds obvious to me - There is a very simple way of having a stealth tanker. Just put some fuel tanks in a Northrop B-2A bomb bays, and use the Navy probe-and-drogue system (no need for a fixed boom)
According to Wikipedia,
Quote
The B-2 is capable of carrying 40,000 lb (18,000 kg) of ordnance

Not a lot of fuel, but well enough for a F-35 or even a F-22.

upside
B-2 carries ~170klbs of its own fuel.  As a tanker it wouldn't need a 6000 mi range.

downside
B-2 is a 35yo design.  All tech has come a long way since then (engines RAM etc)
B-2 carries MOP.  I wouldn't expect B-21 to have that capability.
B-2 is a pig for maintenance - also needs unique hangers.  Tankers need to operate from more widespread locations.
There is no existing production line.  Retrofitting a single-purpose built aircraft is extremely expensive.   
US has ~100 (97?) combat coded bombers.  Retrofitting a US$2billion aircraft that has life left as a bomber and constitutes ~15-20% of that figure won't happen

It may be that the B-21 maintenance will also be a pig.  But I doubt it.  It's one reason I like the T/A-21 variant idea.

The biggest reason I like the T/A-21 idea is that the US is already spending US$23.5Billion on EMD for B-21.  The subcontractors, assembly line and workers are being lined up.  Creating a T/A variant is going to be much cheaper than developing a new stealth airframe of about the same size.  B-21 will probably carry 150k lbs of it's own fuel.  Modifying it for a tanker/attack variant is not a herculean effort. 

I wouldn't expect a T/A-21 to carry it's own armament.  T/A-21 would defend itself by providing targeting information for munitions from other systems then vanish 'like a f*rt in the wind'.  Those systems would include any of the ~1,000 US F-35's (by 2030), AEGIS systems and perhaps even some type of future arsenal platform such as a variant of the AC-130.








Offline NeilChapman

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #21 on: September 22, 2016, 04:01:54 pm »
I would think a true "stealth" tanker would be very low on the priority list for a service which desperately needs to recapitalize nearly every facet of its fleet.
A big flying wing might make some sense and incorporate some signature reduction methods, but a truly stealthy tanker seems like a giant waste of money and a guarantee for delays and cancelation.
Does a B-2 have a useful offload capacity? I wouldn't think so.



Programs take a decade to complete.  In some cases two.

Building a stealthy tanker is already part of the AF tanker development plan.  Perhaps they're making a case to skip KC-Y to actually save the development costs and skip directly to KC-Z utilizing the B-21 platform.  We all know that Boeing has spent ~US7Billion on modifying an existing platform.  It's not even a new airframe.  I write it but I still can't believe it.  I'm guessing no-one wants to go back to Boeing for a KC-Y platform for precisely the reason you stated - too many pressing priorities.  As a result, KC-46 will be around for 50+ years.

Skipping KC-Y for KC-Z is just recognizing the reality of the expected A2/AD expansion and the need to fuel 4th and 5th gen fighters within that expanded A2/AD area.  If one wants US Air supremacy in that environment in the 2030 timeframe a B-21 variant is likely the only viable option for a large stealthy tanker.  The US method of war fighting doesn't work without air supremacy.











Offline Rhinocrates

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #22 on: September 22, 2016, 06:36:18 pm »
A B-21 tanker variant would be expensive and have relatively low capacity, but not all tanker missions would be flown in contested airspace, so I could imagine an unmanned B-21 variant specialised to loiter at high altitude on the edge of the battle space and offer top-ups while the majority of the tanker force is non-stealthy.

As for Boeing having little incentive to work with NG on developing a boom, it would be a shortly-to-be-unemployed CEO that would let spite get in the way of an opportunity to make money, I would think.
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Offline TomS

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #23 on: September 22, 2016, 06:40:40 pm »
... I like the T/A-21 variant idea.

Just to nitpick, the designation of such an aircraft would be KB-21.  The basic mission designation (B for bomber) doesn't change and the modified mission designation for tankers is K, not T (that's for trainers).


Offline NeilChapman

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #24 on: September 22, 2016, 06:58:56 pm »
... I like the T/A-21 variant idea.

Just to nitpick, the designation of such an aircraft would be KB-21.  The basic mission designation (B for bomber) doesn't change and the modified mission designation for tankers is K, not T (that's for trainers).

Thanks T -

If it were a variant with no bomber capacity would it still carry the B designation? 

Offline NeilChapman

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #25 on: September 22, 2016, 10:31:53 pm »
A B-21 tanker variant would be expensive and have relatively low capacity,


If the expanded A2/AD risk in 2030 is as portrayed then I don't think it is expensive relative to the risk.
It's not expensive compared to potentially losing pilots, an entire strike package of aircraft or multiple 46's.
It's certainly not expensive compared to the risk of no at-will air superiority.
KC-46 is ~US$250Million a copy.  B-21 is ~US$511Million a copy for 100 jets.  More jets would be lower per unit costs.

Low capacity compared to the KC-10 but not KC-135 or KC-46.  Recall that tankers don't typically separate their fuel from that which they pump.  There was a KC-135 version that did but that was because it carried JP-4 as well as JP-7 for the SR-71.  The B-21 is speculated to have a 5000nmi range.  That's not including the estimated 30k lbs of bomb load.  Don't know what the pumps and boom would weigh but I'm sure they're not light.  Might even use up that 'bomb' load capacity.

KC-135 -           ~200,000lbs of fuel
KC-10               ~350,000lbs
KC-46               ~200,000lbs
K-21 variant est ~150,000+lbs 

Granted it wouldn't serve a transport role as the 135, 10 and 46 but it would serve a niche that is needed in the not to distant future.


but not all tanker missions would be flown in contested airspace, so I could imagine an unmanned B-21 variant specialised to loiter at high altitude on the edge of the battle space and offer top-ups while the majority of the tanker force is non-stealthy.


That's what I was thinking.  USAF is still flying 415 KC-135's - model is ~55 years old.  USAF will have 25 more years of KC-10's.  USAF will have 50+ years of KC-46.  This variant would be an augmentation of the tanker fleet for those highly-contested environments.  The K-21 could run back out at will and gas up from 10's, or 46's. 

Risk is mitigated by showing your opponents that while they have expanded the A2/AD area, the US can still achieve air superiority at will.  You need enough K variants to ensure your opponent is not confident they can overwhelm your advantage - even for a short term gain.


As for Boeing having little incentive to work with NG on developing a boom, it would be a shortly-to-be-unemployed CEO that would let spite get in the way of an opportunity to make money, I would think.

Well, let me qualify.  If I were NG I'd work with Airbus on the boom.  One would be loath to work w/a company that requires US$7Billion for EMD on an existing airframe to be a tanker especially when the work was done 40 years ago for the KC-10. 

This boom would likely be somewhat different than that used in the past anyway.  May need to telescope more radically (bomb bay length limit) and you'd certainly want it to retract back into that space.  It may even drop down along the length of the bomb bay then extend back behind the airframe prior to a pivot down in a traditional way.  Who knows.  The fewer changes to the B-21 basic design equals less dev time, less EMD costs, less changes to production line.  You certainly don't want to change the cg.  Packaging matters.









Offline Rhinocrates

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #26 on: September 23, 2016, 02:00:18 am »
Thanks, very informative.
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Offline TomS

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #27 on: September 23, 2016, 02:52:17 am »
... I like the T/A-21 variant idea.

Just to nitpick, the designation of such an aircraft would be KB-21.  The basic mission designation (B for bomber) doesn't change and the modified mission designation for tankers is K, not T (that's for trainers).

Thanks T -

If it were a variant with no bomber capacity would it still carry the B designation?

Yep.  The basic designation stays with an aircraft design even when modified to the point that it can't perform the original mission.  To pick a relevant example, the old KB-50 tanker conversions of the B-50 bomber removed all of the plane's armament and bomb-aiming equipment but the B designation remained. 

Offline FighterJock

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #28 on: September 23, 2016, 08:04:59 am »
A couple more images of stealth tanker concepts:

Of the two designs above the one that I think that has the most going for it would be the Blended Winged Body tanker.  Also would it really be able to refuel two F-22As at the same time?

Offline NeilChapman

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Re: Air Force Could Pursue Stealthy Aerial-Refueling Tanker
« Reply #29 on: September 23, 2016, 11:52:35 am »
A couple more images of stealth tanker concepts:

Of the two designs above the one that I think that has the most going for it would be the Blended Winged Body tanker.  Also would it really be able to refuel two F-22As at the same time?



Seems like the two most limiting issues in fueling fighters is refueling rate, rate the receiver can take on fuel, and time waiting for your turn at the pump.  For fighters needing fuel every hour or so it's a logistical bottle-neck that takes them away from their cap mission.

Having two booms would be a game changer for refueling fighters.

The concern w/two booms is not refueling fighters but having three large aircraft in such close proximity.  If the solution is limited to fighters as receivers then it's much less of a problem.

Current tanker solutions are a combination of cargo and tanker requirements.  So the tanker has to be large enough to participate in the AMC requirement.  There just aren't enough C-17's and C-5's to meet the 1-4-2-1 needs.

At some point USAF will want a stealthy tanker w/C-17 capabilities and size.  With current stealth tech this is going to be extremely expensive.  This is why the KB-21 variant interests me as an interim solution. 

I'd be interested in a dual boom KB-21 based solution as perhaps a Block-20/30 target after autonomous boom refueling is perfected.  That aircraft would not need a boom operator and by then the lessons of initial, low risk Block 10 aircraft would be integrated into the tanker fleet.  That aircraft might have larger wings to accommodate the retracting dual boom design with perhaps wet tanks along the center of the airframe.  The unmanned capabilities of B-21 would also be further along should it make sense for KB-21.