At the 2023 AIAA SciTech Forum, both Boeing and Lockheed have scale models for what their BWB tanker/cargo transport concepts are, in response to the USAF RFI. Both include stealth features.

https://www.thedrive.com/the-war-zone/s ... -by-boeing

Very interesting. Pretty crude models, I doubt this is much beyond an early engineering scale-concept, but would be nice to see something like this advance.

seems very expensive for a tanker. Sure, you can operate them much nearer to contested airspace, but still.

Gonna speak my mind on this topic first and come back with more research and data later, but I severely dislike the Boeing concept's window configuration. It looks overbearing and way oversized. If they shrunk the windows down to something more realistic, I'd start leaning to them. With that said, Lockheed's proposal looks like a stingray had a kid with a C-17, in other words, ugly as all get up. Now I understand its a computer generated model, but it needs some serious work before the Air Force should take a look at either option. Besides, we are just now getting finished with the C-5M upgrades, and taking delivery of the KC-46, however much of a technological abomination and innovation it might be, so the Air Force really doesn't need yet another BMW (Big Money Waster) project *looks at the F-35 and KC-46 programs*.

As others have noted above, these are early concepts that may be put forward in the USAF RFI for a future tanker/transport, that would not be derived from the commercial sector. It's really just asking whether that's at all feasible, what would it cost, how would it work, etc.

The trade space for commercial derivatives is already fully fleshed out, USAF knows the answers to the above questions. This is really looking at a new alternative. But it has a very long way to go before it becomes eligible for a production program.

My suspicion is that the Boeing windows are nothing more than letting an intern print stickers to fit the model. Just as we saw some absurd window hints with the B-21 ‘leaks’ that were nothing else, the Boeing cockpit windows/tight shape for a manned aircraft make little real world sense. At least the original XB-52 design had a legacy rationale behind its layout (which was of course replaced/superseded).

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

That might work in peacetime, but commercial providers might not want to fly into conflict zones with unhardened and unprotected aircraft. You couldn't force them and you couldn't do without them. I think TRANSCOM understands that need, in maintaining military airlift capability.

Avatar2go wrote:

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

That might work in peacetime, but commercial providers might not want to fly into conflict zones with unhardened and unprotected aircraft. You couldn't force them and you couldn't do without them. I think TRANSCOM understands that need, in maintaining military airlift capability.

Then they activate CRAF.

jetwet1 wrote:

Then they activate CRAF.

CRAF supplements capacity, but does not provide combat zone capability. They are still unprotected civilian aircraft.

As we saw in Afghanistan, civilian aircraft were used as shuttles from airports outside the conflict zone, but TRANSCOM aircraft flew within it.

Mikenike wrote:

If they shrunk the windows down to something more realistic,

The size of the window is proportional to the size of the cockpit which is proportional to the size of the pilot. If their intention is for a smaller aircraft, then the oversize window may be appropriate. With the highly sloped nose crown, the windshield can look humongous from certain angles. Similar to how disporoportional the windshield of a Lamborgini can appear.

texl1649 wrote:

My suspicion is that the Boeing windows are nothing more than letting an intern print stickers to fit the model.

Possibly, but that sticker would have been generated from the 3D model which the intern probably was tasked to model as well.


bt

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

Except CRAF freighters don’t have roll-on, roll-off capability as the C-5 and C-17 do. Try driving a tank, a Mark V boat, or multiple helicopters on a 747. Try airdrop in the 747.

GalaxyFlyer wrote:

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

Except CRAF freighters don’t have roll-on, roll-off capability as the C-5 and C-17 do. Try driving a tank, a Mark V boat, or multiple helicopters on a 747. Try airdrop in the 747.

Better yet, try ordering civilian pilots to fly into hostile environs or known threat areas. At that point you're reduced to "pretty please's" and a LOT of money to coax them; even then the answer will often not only be no, but f**k no.

All of a sudden your "cheaper" option costs much more than the $3.50 per day of USAF in-theater per diem.

Looking at those pictures, those aircraft look to be purely tankers?
Unless on the Lockheed design a smallish cargo hold is somehow between the engines (depending on how big the final aircraft will be - but looking at the cockpit window not very big)

https://www.thedrive.com/uploads/2022/0 ... =380&dpr=2

I suppose the boom will be retracted into a "Boom bay" (TM) to maintain stealth?

KB-2 has a nice ring to it...

ReverseFlow wrote:

Looking at those pictures, those aircraft look to be purely tankers?

I thought I read somewhere that the Boeing design has the clam shell rear cargo door. So transport is also an objective.

The link in the thread starter has lots of details and specifically said transport as well.


bt

bikerthai wrote:

The size of the window is proportional to the size of the cockpit which is proportional to the size of the pilot. If their intention is for a smaller aircraft, then the oversize window may be appropriate. With the highly sloped nose crown, the windshield can look humongous from certain angles. Similar to how disporoportional the windshield of a Lamborgini can appear.

This is of course the case, but going purely based off of this, the Boeing cocept I saw wouldn't be able to transport much in terms of cargo, and isn't big enough to serve as a AAR platform. As always, these are educated guesses based off what info we know and what we know in general, so this could be completely wrong, its anyones guess for now.

LyleLanley wrote:

GalaxyFlyer wrote:

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

Except CRAF freighters don’t have roll-on, roll-off capability as the C-5 and C-17 do. Try driving a tank, a Mark V boat, or multiple helicopters on a 747. Try airdrop in the 747.

Better yet, try ordering civilian pilots to fly into hostile environs or known threat areas. At that point you're reduced to "pretty please's" and a LOT of money to coax them; even then the answer will often not only be no, but f**k no.

All of a sudden your "cheaper" option costs much more than the $3.50 per day of USAF in-theater per diem.

Except they did. I’m pretty sure after this incident, civies kept flying into Iraq during the height of the insurgency. I do agree to a point about transporting tanks by air being easier on roll-on aircraft, but 99% of the time tanks are transported by sea.

https://en.wikipedia.org/wiki/2003_Bagh ... n_incident

My understanding is the USAF interest in stealth was primarily in regard to tankers, with the possibility that the BWB design could be extended to unpressurized cargo. And that these could be a common platform.

Those are the concepts the USAF is exploring, recognizing that the commercial sector interest in BWB wouldn't produce a convertible airframe within the timeframe they needed.

Mikenike wrote:

This is of course the case, but going purely based off of this, the Boeing cocept I saw wouldn't be able to transport much in terms of cargo, and isn't big enough to serve as a AAR platform.

I agree that I does look small for a transport. As a small tanker however, I see it bigger than rhe MQ-25. So enough to tank some NGADs or a couple of B-21?

The tech demonstrator would probably need to be small to keep the cost down. Boeing did say the tech would be scaleable to some degree.

bt

Buckeyetech wrote:

LyleLanley wrote:

GalaxyFlyer wrote:

Except CRAF freighters don’t have roll-on, roll-off capability as the C-5 and C-17 do. Try driving a tank, a Mark V boat, or multiple helicopters on a 747. Try airdrop in the 747.

Better yet, try ordering civilian pilots to fly into hostile environs or known threat areas. At that point you're reduced to "pretty please's" and a LOT of money to coax them; even then the answer will often not only be no, but f**k no.

All of a sudden your "cheaper" option costs much more than the $3.50 per day of USAF in-theater per diem.

Except they did. I’m pretty sure after this incident, civies kept flying into Iraq during the height of the insurgency. I do agree to a point about transporting tanks by air being easier on roll-on aircraft, but 99% of the time tanks are transported by sea.

https://en.wikipedia.org/wiki/2003_Bagh ... n_incident

The Baghdad A300 incident was after combat theoretically ceased. And, wasn’t US civil, either. It’s not just about tanks, nice shorthand answer, but I’ve carried dozens of military loads that’d never possibly be loaded on a civil plane, except the AN-124. Land at a a ANG fighter base, kneel, drop the ramps, load a hangar full of maintenance and arming equipment and gone in 4 hours. Take a whole rescue helo squadron from US to Europe the same way. USMIL is a logistics monster. Deep diving sub, destroyer transmission, sub components, helicopters for starters. 17’x17’x141’ box has qualities all its own.

Buckeyetech wrote:

Except they did. I’m pretty sure after this incident, civies kept flying into Iraq during the height of the insurgency. I do agree to a point about transporting tanks by air being easier on roll-on aircraft, but 99% of the time tanks are transported by sea.

https://en.wikipedia.org/wiki/2003_Bagh ... n_incident

Some did. Most didn't. So long as pilots have alimonies, you'll always have some portion who will fly into anything for a paycheck. Most won't, however, and the more dangerous the conditions the fewer still. Of those left, you can't rely on the Russians in their AN-124s to help deliver equipment to their own backyard.

In the end, Transcom, like any other military organization, can't function if their available pool of flight crew is so fluid.

You need to get past cost being your only indicator.

Plus with the nature of the world today, TRANSCOM has to deliver around the world with a few hours notice. Can't do that as a contracting agency. It's a huge ask.

TRANSCOM is a relatively quiet branch of the service, but what they do is incredible, and definitely not optional.

Avatar2go wrote:

Plus with the nature of the world today, TRANSCOM has to deliver around the world with a few hours notice. Can't do that as a contracting agency. It's a huge ask.

TRANSCOM is a relatively quiet branch of the service, but what they do is incredible, and definitely not optional.

Exactly. Try doing a contractor-run airlift during wartime when nations along the way won't grant overfly/gas-n-go rights... Too bad those refueling tankers don't work with FedEx 767s...

And, it’s not like TRANSCOM doesn’t charter for the USG. There’s a huge amount of charter everyday.

bikerthai wrote:

I agree that I does look small for a transport. As a small tanker however, I see it bigger than rhe MQ-25. So enough to tank some NGADs or a couple of B-21?

The tech demonstrator would probably need to be small to keep the cost down. Boeing did say the tech would be scaleable to some degree

Maybe a single B-21, if it has a lot of bag space and doesn't need much fuel to stay aloft. But I see it being akin to the old TOAD (Take Off And Die, an old joke from CW era Tanker crews about their mission if nuclear war were to start) moniker if it fully refuels a B-21 or B-52. But I could see it definitly being able to refuel a few NGADs, Raptors, or the Panthers (unofficial USAF nickname for the F-35A Lightning II or JSF).

As far as the demo bird goes, I hope that Boeing scales it. Because if it's not scalable I don't see a reason for us to invest so heavily on it. This isn't to say that I hate on anything that isn't scalable, its just to say I don't see it worth it to build yet another aircraft tech demonstator that is a waste of money and doesn't show off the technological benefits. I could understand it in the old days, with all the XB (50/70/to an extent the 35/49) programs, because we didn't have the tech we do now and it wasn't that easy back then. Nowadays we do have the required tech and the fancy stuff, so see if it works small scale before we have to scale it to size. We can work out the kinks of the large demo bird after we prove that it works on a small aircraft. Kind of like Boeing's smaller(but still large) scale Blended Wing Body project with NASA.

Avatar2go wrote:

My understanding is the USAF interest in stealth was primarily in regard to tankers, with the possibility that the BWB design could be extended to unpressurized cargo. And that these could be a common platform.

Those are the concepts the USAF is exploring, recognizing that the commercial sector interest in BWB wouldn't produce a convertible airframe within the timeframe they needed.

1. I don't understand the USAF's inherent interest in the Tanker topic all of a sudden. I fully understand and recognise the fact that the poor KC-135 fleet has been on it's last legs and around since the like 1957, but they still serve reliably and there are plenty of them left to keep the others flying for another 10 years. The KC-10 fleet is dwindling rapidly due to the increased number of KC-46's on the roster, which I still don't quite understand the choice for KC-135s and KC-46s over the larger, newer, more fuel capacity KC-10 (but with less numbers) with the new KC-46's. The KC-46's problems don't even need to be addressed here, and there are too many to list.

2. Blended Wing Body designed airliners are still very much in their infancy, and may not be around for at least another decade plus. Neither Boeing nor Airbus have any interest in the BWB concept anyway. Boeing did their little NASA mockup and that's it, but they ar focused on that new wing design that NASA is pushing because it could be profitable due to the efficiency of the wing, couple that with the new UDF and or high bypass turbofans and you have a perfect new airliner that airlines will want when they get finished with their B737 and A320 series. Airbus on the other hand is said to be focused on sustainable zero-carbon emissions, both by improved economy and hydrogen powered aircraft. Neither has the market, time, or inclination to shake up the market with BWB's on a gamble that would be bigger and harder to sell than that of the original B747. At least cargo airlines showed interest in the 747 if the passenger aspect went belly up(as was proved by the -8i/f sales).

Mikenike wrote:

1. I don't understand the USAF's inherent interest in the Tanker topic all of a sudden. I fully understand and recognise the fact that the poor KC-135 fleet has been on it's last legs and around since the like 1957, but they still serve reliably and there are plenty of them left to keep the others flying for another 10 years. The KC-10 fleet is dwindling rapidly due to the increased number of KC-46's on the roster, which I still don't quite understand the choice for KC-135s and KC-46s over the larger, newer, more fuel capacity KC-10 (but with less numbers) with the new KC-46's. The KC-46's problems don't even need to be addressed here, and there are too many to list.

The USAF is interested in the BWB due to the pivot to the Pacific and the potential for conflict with China.

The distances are far larger and the BWB has efficiency advantages for those kinds of missions. It can travel longer and farther with less support and greater payload. If you couple that with the new AETP engine technology, it allows for even greater efficiency.

The KC-46 has already demonstrated it can conduct missions in the Western Pacific from bases on the US East Coast, but it requires a lot of intermediate support along the way.

Plus it's limited to standoff operations due to a combination of large RCS, and Chinese missile ranges. It has ways of mitigating that, but having an inherently stealthy airframe helps to close the gap in mission distances, to be more favorable to allied operations with other stealth aircraft.

Even with a BWB tanker, there is still a need for the KC-46 to handle the majority of refueling missions, which it could do more cost-effectively than the BWB or a larger tanker.

2. Blended Wing Body designed airliners are still very much in their infancy, and may not be around for at least another decade plus. Neither Boeing nor Airbus have any interest in the BWB concept anyway. Boeing did their little NASA mockup and that's it, but they ar focused on that new wing design that NASA is pushing because it could be profitable due to the efficiency of the wing, couple that with the new UDF and or high bypass turbofans and you have a perfect new airliner that airlines will want when they get finished with their B737 and A320 series. Airbus on the other hand is said to be focused on sustainable zero-carbon emissions, both by improved economy and hydrogen powered aircraft. Neither has the market, time, or inclination to shake up the market with BWB's on a gamble that would be bigger and harder to sell than that of the original B747. At least cargo airlines showed interest in the 747 if the passenger aspect went belly up(as was proved by the -8i/f sales).

The problem in the commercial market for BWB is the lack of suitability to passenger transport. Given that, it's far more cost-efficient for the manufacturers to design passenger aircraft and then adapt them to cargo use. As it has been for tanker use, as well.

One reason is that it's hard to beat the structural efficiency of tube and wing for the pressurized spaces required for passengers and some cargo. If your pressure vessel is also the structural element of your design, you can't improve on that with BWB, which will inevitably be heavier for the same pressurized volume.

If you remove the pressure constraint, that opens up the design to BWB, which is what the USAF is doing here. But independent commercial development is unlikely for an unpressurized aircraft. And unless other efficiency gains can be made to justify the added weight of BWB pressurization, that too would remain unlikely.

I don't think blended wing is a great idea for air transport. All the cargo is going to be in the center of the aircraft, it can't be placed right or left. At least not for air drops. It might work in a combined tanker/transport if the fuel is stored in the blended wing area and the cargo in center.

Since we're on the topic of future transport aircraft projects, is the USAF ever planning to replace the C-5 with a similarly sized transport that can accommodate oversize cargo, or will they go for a smaller more versatile solution ?

Buckeyetech wrote:

The USAF doesn’t need transport aircraft at all really. It’s much cheaper for Transcom to contract out cargo to civilian airliners.

Contractors cannot deliver military freight to a contested area. as this is what that airplane would primarily be used for. had that been the case? Flying Tiger would have been delivering freight while I was in Viet Nam. Couldn't you see a K loader up to a Freighter in Iraq? you have got to be kidding!

I think these BWB designs are for the future stealth tanker. The cargo bay is only to hold the retractable boom that is why it appears small. Only Boeing and Lockheed have showed their designs as Northrop will clearly use the B-21 design.

JetBuddy wrote:

I don't think blended wing is a great idea for air transport.

Agreed. Once you add a decent cargo bay it would have little fuel efficiency advantages over a tube with a low swept wing.

The Radar Cross Section (RCS) doesn't have to go from 50m2 down below 0.01m2 like the F-22 or F-35. A RCS of 1m2 could easily be achieved with a conventional high wing transport design such as the following:



Such a design keeps the the cargo bay as a circular tube to allow it to be easily pressurised. The exterior chine and canted tails reduces the side RCS. The wings, tails and landing gear doors have planform alignment. The engines mounted above the wingbox helps hide the fan blades and reduce the IR heat signature from below.

The Super Hornet had a big RCS reduction over the classic Hornet. There are lots of easy and cheap ways to reduce radar cross section. Reducing the radar detection range from 200km to 50km for a transport would be a substantial improvement and it doesn't need to come down to 20km. The IR heat signature reduction would be important to combat the MANPAD threat.

The engines would have to be low bypass ratio ratio but so would a stealthy BWB design. Lets assume designs scaled to use non afterburning F135 engines.
Two F135 engines would give C-130 size.
Three F135 engines would give A400M size.
Four F135 engines would be half way between the A400M and C-17.

In terms of a future very large transport. The C-5M and C-17 fleet could have a very long life if they only do simple long haul strategic work. Beyond 2050 would be no problem. The C-17 retirement dates assume it continues to do some hard tactical missions. If a smaller stealthy transport is purchased to do the hard work then that also solves the very large transport problem.

RJMAZ wrote:

The engines mounted above the wingbox helps hide the fan blades and reduce the IR heat signature from below.

But it doesn’t seem like it would help avoid detection from airborne radars, i.e. an AWACS or Mig-31.

HowardDGA wrote:

RJMAZ wrote:

The engines mounted above the wingbox helps hide the fan blades and reduce the IR heat signature from below.

But it doesn’t seem like it would help avoid detection from airborne radars, i.e. an AWACS or Mig-31.

The F-117 had the engines directly behind the intakes. Intake mesh angled correctly like on the F-117 could easily solve that problem. The engines wouldn't need to be fully buried in the fuselage to eliminate any line of sight with the fan blade. The goal isn't to have a radar cross section below 0.1m2.

The design wouldn't even need special skin materials. Planform alignment of all the gaps and surfaces will provide most of the RCS reduction. Add some durable radar absorbing paint and gold tinted windows to reduce cockpit reflections.

A C-17 landing in Taiwan would be detectable by Chinese mainland ground radar. A radar cross section of 1m2 or below would allow a transport to fly from Guam to Taiwan undetected. This level of stealth wouldn't add that much to the development cost of a cleansheet transport. The lower bypass engines probably reduces the range by like 20% compared to high bypass engines under the wings. That's really the only sacrifice. Guam to Taiwan is 1,500nm so a return flight is 3,000nm. That sort of distance should be ok with low bypass engines.

RJMAZ wrote:

HowardDGA wrote:

RJMAZ wrote:

The engines mounted above the wingbox helps hide the fan blades and reduce the IR heat signature from below.

But it doesn’t seem like it would help avoid detection from airborne radars, i.e. an AWACS or Mig-31.

The F-117 had the engines directly behind the intakes. Intake mesh angled correctly like on the F-117 could easily solve that problem. The engines wouldn't need to be fully buried in the fuselage to eliminate any line of sight with the fan blade. The goal isn't to have a radar cross section below 0.1m2.

The design wouldn't even need special skin materials. Planform alignment of all the gaps and surfaces will provide most of the RCS reduction. Add some durable radar absorbing paint and gold tinted windows to reduce cockpit reflections.

A C-17 landing in Taiwan would be detectable by Chinese mainland ground radar. A radar cross section of 1m2 or below would allow a transport to fly from Guam to Taiwan undetected. This level of stealth wouldn't add that much to the development cost of a cleansheet transport. The lower bypass engines probably reduces the range by like 20% compared to high bypass engines under the wings. That's really the only sacrifice. Guam to Taiwan is 1,500nm so a return flight is 3,000nm. That sort of distance should be ok with low bypass engines.

Coming from Guam, a C-5 or C-17 could descend to 500’ above the water 40 miles east of the island, terrain mask behind the Taiwanese mountains, undetected by mainland radar. We practiced low level arrivals 20 years ago.

Mikenike wrote:

I don't understand the USAF's inherent interest in the Tanker topic all of a sudden.

Because Mini has done a fantastic job sounding the alarm over the state of the tanker fleet and the indisputable fact that China doesn't need to take a Raptor or NGAD on to gain air superiority: China simply has the far easier task of denying the USAF the ability to have tankers wherever and whenever they want. Fighters (and even bombers) can't kick a$$ without tanker gas, and the USAF has taken tankers for granted since the days of the fail-safe orbits.

Times have changed, and AMC is changing with them. Finally. Against all odds.