Air Force Could Pursue Stealthy Aerial-Refueling Tanker

Flyaway

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They could skip the KC-Y competition and go straight to the KC-Z.

http://www.defensenews.com/articles/air-force-could-pursue-stealthy-penetrating-kc-z-tanker
 

sferrin

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Stealth tanker? Why not just save time and money and cancel that plan right now. This should be the KC-Y:
 

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sferrin

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Looks cool but too expensive. Sometimes I wonder if there's somebody who's sole function is to come up with ways that guarantee program cancellation.
 

FighterJock

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What would happen to the Flying Boom once it had refueled a fighter or bomber? Looks rather cool if I say so myself. B)
 

AeroFranz

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- the UARRSI receptacle is not stealthy, otherwise B-2s, F-117s, F-22 would not have that feature retractable.
- Flying booms are not stealthy
- two aircraft flying in formation more than double the individual RCS

so you can make a stealthy receiver and a stealthy tanker airframes, but how do you make a stealthy connection and transfer of fuel?
I dunno, i don't see penetrating assets refueling inside contested air space...i could see a reduction of the standoff distance required, that yes.
Not saying it can't be done, just that the physics and the penalties associated are against you.
 

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Dynoman said:
Stealthy Mobility and Support Aircraft

Let's face it. The idea isn't that you're flying a tanker into the middle of a high-threat environment. It's that the high-threat environment is extending to where tankers have typically flown. The expectation is that high-threat will be - or is - 600-1000nmi out from targets. The adversary will by-pass your fighters to eliminate the tankers leaving the fighters w/o fuel to return. This leaves several billion dollars of strike package that will take forever to replace likely floating in the ocean somewhere.

But let's look at some options.

Flying a KC-46 into a high threat environment. Designed for a low to medium threat environment.

KC-46 - US$250Million a pop - ~200k lbs of fuel - 200 planned inventory - Critical asset
Upside
1) Existing tanker

Downside
1) You can't bolt on enough stuff to ensure it's survivable in a high-threat environment. At most you'll 'augment' it's capabilities. It's a big, fat RCS target even when it's not fueling.
2) You'll assign an air patrol to protect these assets. That increases the value/costs of KC-46 by the value of the other airframes. (4-F-35's valued at ~US$400Million)
3) Integrate into naval defensive systems. Add weapons systems. Add a weapons officer. - Serious development costs. Still a big fat target.

Make the MQ-25 stealthy - Use it as a connector for the KC-46. KC-46 stays back, MQ-25's deploy forward coming back to KC-46 for fill ups.
1) Won't have a boom - AF is left stranded.
2) Navy seems to have little interest in this. Not likely to be successful.

Build tanker variant of B-21

KA-21 (Tanker/Attack B-21 variant) - ~US$500Million - ~150k+lbs of fuel - limited inventory - Critical asset
Upside
1) Designed for high threat environment. When it's not fueling it's not there. Will disappear quickly.
2) Designed for unmanned operations
3) Airframe in development w/2025-28 IoC
4) Additional airframes or variant of B-21 will lower acquisition, operations and upgrade costs of strategic bomber fleet.
5) Forward deployed sensor fusion - assists in it's own defense - no need for HVACAP
6) If it uses F-35 code - AEGIS & F-35 weapons integration.
7) Limit 1st version to boom only (dev costs) - Navy has MQ-25
8) Leverage NG's autonomous aerial refueling knowledge
9) Possibly replace co-pilot w/boom operator leveraging unmanned operations tech in lieu of co-pilot.

Downside
1) Seems expensive - tough sell
2) Have to work w/Boeing to develop new boom - telescoping to fit in area of bomb bay perhaps.
3) Add boom operator for initial version - dev program to work toward autonomous system

EDIT - Expect NG would work w/Airbus on the refueling boom. I'm guessing that Boeing would have absolutely zero motivation to work with 'NG' on this.
 

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marauder2048

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AeroFranz said:
- the UARRSI receptacle is not stealthy, otherwise B-2s, F-117s, F-22 would not have that feature retractable.
- Flying booms are not stealthy
- two aircraft flying in formation more than double the individual RCS

so you can make a stealthy receiver and a stealthy tanker airframes, but how do you make a stealthy connection and transfer of fuel?
I dunno, i don't see penetrating assets refueling inside contested air space...i could see a reduction of the standoff distance required, that yes.
Not saying it can't be done, just that the physics and the penalties associated are against you.

My understanding is that a hose-reel system for B-2 -> F-22 refueling was seriously examined more than a decade ago and was shown to meet the survivability requirements.
It only fell down on the retrofit costs for both aircraft.
 

AeroFranz

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Interesting - i had never heard of that.
Do you know if it was a probe and drogue setup just like the Navy's or somehow it plugged into the current receptacle?
 

marauder2048

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AeroFranz said:
Interesting - i had never heard of that.
Do you know if it was a probe and drogue setup just like the Navy's or somehow it plugged into the current receptacle?
It was to be a probe retrofit for the F-22. This was during the era of Northrop Grumman's unsolicited B-2C proposal.
 

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I'm slightly confused as to where the KC-Z fits in and concepts like the Arsenal Plane.

According to a recent quote from Flightglobal Brig Gen Alexus Grynkewich, team lead for the 2030 air superiority study, said he sees the Arsenal Plane as a large platform with a heavy payload that would not need to be manoeuvrable or stealthy because its long-range would ensure its survival; “An Arsenal Plane is something that’s large, long-range, not very manoeuvrable, [with] very long weapons.”

So is KC-Z designed to go ahead of the Arsenal Plane? At what point do your tanker assets need to be ahead of your strike package. Of course the F-35s and F-22s need to be ahead of the arsenal plane to provide it with the targeting data, but the concept of the Arsenal Plane gives them some stand-off capability. A stealthy KC-Z would give the fighters more loiter time perhaps but it seems an odd choice.
Though I must admit the Arsenal Plane seems the odd one out, there seems to be some overlap, F35 + AP and B21 + PCAP; in effect a fighter-led strike package and a fighter-supported strike package.
Just trying to make sense of the choices or is the DoD just chucking around ideas?
 

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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,
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.
 

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Archibald said:
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.
 

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Why not a KB-21 with fuel tanks into the bomb bay and a retractable boom?
 

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kagemusha said:
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.
 

marauder2048

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Archibald said:
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,
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?
 

_Del_

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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.
 

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Archibald said:
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,
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.
 

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_Del_ said:
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.
 

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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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NeilChapman said:
... 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).
 

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TomS said:
NeilChapman said:
... 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?
 

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Rhinocrates said:
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.

Rhinocrates said:
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.

Rhinocrates said:
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.
 

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NeilChapman said:
TomS said:
NeilChapman said:
... 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.
 

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Dynoman said:
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?
 

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FighterJock said:
Dynoman said:
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.
 

marauder2048

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I think most of the blended wing body proposals (that the AF has funded at least) have had notional tanker variants.
 

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sferrin

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The obvious solution is right here. Tanker, transport, and cruise missile carrier, all in one. And cheaper than a "stealth" tanker.
 

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sferrin said:
The obvious solution is right here. Tanker, transport, and cruise missile carrier, all in one. And cheaper than a "stealth" tanker.
I like the LM design - C-5 cargo capacity with 1/2 the C-17 fuel consumption. It's a 'technology leap' and the history of technology leaps is long development times, unexpected costs and under performance. Like to see more risk reduction to better ensure the tech maturity is there before a program is begun.

Ran some numbers and a C-17 would be >~US$300Million including EMD costs in 2016 dollars. Can't expect the LM design to be any less expensive in acquisition. Sounds like operational costs would be dramatically reduced though.

Don't see it going into a high contested area to bring back a receiver though. Still see a need for a stealthy tanker (with a boom) in the 2025-2035 - if - the A2/AD projections are correct.
 

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sferrin said:
The obvious solution is right here. Tanker, transport, and cruise missile carrier, all in one. And cheaper than a "stealth" tanker.
And a couple hundred AMRAAMs or longer range next generation AAM cause you have lots of space now.
 

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Realistically if we are talking about really survivable tanker assets to refuel in high-level contested airspace there will be the need for a multiple platform approach, while being realistic about what can be achieved.

The simplist and most obvious part of the solution would be to make greater use of buddy-refuelling; a F-35 refuelling a F-35, a B-21 refuelling a B-21, etc. This hasn't been part of US airforce culture/ thinking (luxury of large SAC sourced refuelling force) and has obvious limitations (some platforms having limited fuel loads they can give away, limiting the range extension for the receiver, etc). However has the advantage of being relatively cheap, potentialy providing many survivable platforms that are more "disposable" than a few very high cost but with higher refuelling capability platforms. Examples would include naval air arms and the French Mirage IV force (which also used KC-135 support for uncontested airspace refuelling). Not a perfect solution but part of a workable affordable solution.

A B-21 capable of refuelling a B-21 could also refuel smaller fighters but apart from relatively one-off specific missions not sure of the wider role/ utility as a more general tanker (B-21 not that big an aircraft, considerably smaller than a B-2 and with much smaller fuel load than an actual tanker aircraft - not much fuel to give away). Hence only likely to be a small niche player as a tanker.

As the range and capability of air defences improve there is an argument for making a whole range of aircraft filling a range of roles (transport, tanker, AWACS, CnC, ASW etc) more survivable so can enter future less-contested airspace. However the cost and technical challenges behind really pushing for high levels of survivability makes this a laudable but probably unrealisable goal - no one (not even China or the US) likely to prioritise this aspect, will just be another factor deterring peer powers from actually going to war with each other.
 

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kaiserd said:
The simplist and most obvious part of the solution would be to make greater use of buddy-refuelling; a F-35 refuelling a F-35, a B-21 refuelling a B-21, etc. This hasn't been part of US airforce culture/ thinking (luxury of large SAC sourced refuelling force) and has obvious limitations (some platforms having limited fuel loads they can give away, limiting the range extension for the receiver, etc). However has the advantage of being relatively cheap, potentialy providing many survivable platforms that are more "disposable" than a few very high cost but with higher refuelling capability platforms. Examples would include naval air arms and the French Mirage IV force (which also used KC-135 support for uncontested airspace refuelling).
Problem being that the USAF boom refuelling system is inherently incompatible with buddy fuelling. You can't just strap a boom onto an aircraft in the same way you can put a hose reel in a pod and hang it from a hard point. Even assuming the simple mechanics could be dealt with via, say, a pallet in the bomb bay, the crew skills are totally different. The boom operator actually flies the boom onto to receiver; it's a highly specialized skill that you can't just make a secondary job for a normal navigator/copilot.

The alternative is to switch to hose and drogue, which means a) refitting the entire Air Force and b) taking much longer to refuel large aircraft. The USAF didn't adopt the boom just to be contrary. It passes gas much faster than the hose and drogue approach. Using a hose and drogue would mean staying connected and detectable for much longer in hostile airspace.
 

kaiserd

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TomS said:
kaiserd said:
The simplist and most obvious part of the solution would be to make greater use of buddy-refuelling; a F-35 refuelling a F-35, a B-21 refuelling a B-21, etc. This hasn't been part of US airforce culture/ thinking (luxury of large SAC sourced refuelling force) and has obvious limitations (some platforms having limited fuel loads they can give away, limiting the range extension for the receiver, etc). However has the advantage of being relatively cheap, potentialy providing many survivable platforms that are more "disposable" than a few very high cost but with higher refuelling capability platforms. Examples would include naval air arms and the French Mirage IV force (which also used KC-135 support for uncontested airspace refuelling).
Problem being that the USAF boom refuelling system is inherently incompatible with buddy fuelling. You can't just strap a boom onto an aircraft in the same way you can put a hose reel in a pod and hang it from a hard point. Even assuming the simple mechanics could be dealt with via, say, a pallet in the bomb bay, the crew skills are totally different. The boom operator actually flies the boom onto to receiver; it's a highly specialized skill that you can't just make a secondary job for a normal navigator/copilot.

The alternative is to switch to hose and drogue, which means a) refitting the entire Air Force and b) taking much longer to refuel large aircraft. The USAF didn't adopt the boom just to be contrary. It passes gas much faster than the hose and drogue approach. Using a hose and drogue would mean staying connected and detectable for much longer in hostile airspace.
All reasonable points.
As stated above I appreciate it wouldn't be a perfect solution but considering the very low likelihood of any significant numbers of stealthy survivable tankers (with flying booms) ever being fielded then equipping at least part of your future deep strike force with both types of refuelling probes (and be able take fuel from Navy tankers too) has the advantages of at least being technically achievable and affordable.
And the buddy tanker would be more survivable than any likely new boom-equipped stealthy tanker/transporter.
All in all a solution scaled to the need (capability needed to help deter a major peer war but recognising the low likelihood it will be needed and if it is it won't be for long, given likely nuclear escalation if not ended rapidly).
 

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AeroFranz said:
- two aircraft flying in formation more than double the individual RCS
theoretically the total rcs from a collection of scatterers is the square of the phasor summation of the square-roots of the rcs of each scatterer...

so for two objects the maximum (ie. coherent sum) of the echo cross section would be (given: a=rcs of 1st object, b=rcs of 2nd object):

(a^1/2 + b^1/2)^2

if both objects had the same rcs value (ie. a=b) then the maximum coherent sum would be 4 times the rcs of the individual object...

if one object had a fractional rcs as compared to the other object's rcs, ie. b=k*a, where 0<k<1, then the coherent maximum would be:

a * (1 + k^1/2)^2

so if for example your "stealth" tanker had an rcs of 1 sqm and your fighter had an rcs of 0.001 sqm, the maximum coherent rcs of the two combined would be: ~1.06 sqm, or just a bit over 6% higher than that of the tanker alone...

if you got your tanker down to an rcs of 0.1 sqm together with the same 0.001 sqm fighter, then the coherent rcs of the two combined would be 0.121 sqm, or around 21% higher than your tanker alone...

one can also add in the rcs of the boom as a 3rd object in the system and work the math to figure out what ratios of rcs for each object in the system would be needed to get an acceptable rcs increase for the combined system over that of the tanker alone...
 

AeroFranz

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I appreciate the effort to put numbers to this - by the way, i had yet to see expressions like the ones you used in the discussion of RCS, this is very useful! The example doesn't make it sound too bad...
But just wondering if this (of necessity) simplification takes into account radar bouncing off one of the vehicles onto the second one. After all the majority of the signature reduction measures aim first and foremost at redirecting energy somewhere other than at the emitter. It seems like with multiple objects in close proximity you're going to have a hard time controlling unintended spikes. Granted, two bounces are going to decrease the amount of energy re-emitted, but I wonder if you don't unintentionally end up with an air vehicle formation which forms a corner reflector.
 

sferrin

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NeilChapman said:
I like the LM design - C-5 cargo capacity with 1/2 the C-17 fuel consumption. It's a 'technology leap' and the history of technology leaps is long development times, unexpected costs and under performance. Like to see more risk reduction to better ensure the tech maturity is there before a program is begun.
I'd think this design would be less risky, and far more useful, than a full BWB or stealth solution. Also, the only way "technology leaps" are accomplished are by doing them. They don't come for free.

"Like to see more risk reduction to better ensure the tech maturity is there before a program is begun."

Like what? They're already (supposedly) planning on flying a subscale X-plane. Aside from that what else is there to be proven? All the construction methods are already being used. All the required avionics could be based on existing hardware. Aside from the shape, there is no required new "tech" for this design.
 
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