It's time once again for our regular Open Thread. Talk about whatever you want, so long as it isn't culture war.
Overhauls are Information, Communication and Naval Warfare Part 1, Falklands Part 5, The Battleship of the Future?, Wedding Decorations, A Brief Overview of the United States Fleet, Naval Radar - More Advanced Stuff, Speed and Range in Battleships, and for 2025, SCUBA Parts one and two, The Tanker War Part 2 and Exotic Hulls Part 1.
Comments
Are we looking at the return of the Catalina PBY-5A?
"Pan American Airways System (PAAS) has submitted a funded Letter Of Intent (LOI) to Catalina Aircraft Trust, LLC (Catalina Aircraft) for the purchase of up to forty-six (46) new production amphibious flying boats. Equipped with spacious Art Déco passenger cabins, each Next Generation Amphibious Aircraft (NGAA) Catalina II will be powered by modern turboprop engines and certified as commercial airliners to the FAA’s rigorous Transport Category standards."
In addition to civilian versions there are also military & water tanker versions.
Chantry:
The market for 46 passenger flying boats probably doesn't exist.
For anyone in the Puget Sound Area, I would recommend going to visit the Coast Artillery Museum at Fort Worden (Port Townsend) before it closes on September 7th. It's a nice museum, and worth the trip if you live in the area.
Will the Air Force procure a straight cargo version of the KC-46? If not, should it be renamed the K-46 as the base variant? (Also raising the possibility of a future CK-46, RK-46 Rivet Joint II, and other innovations in tri-service nomenclature)
It is worth noting that the base KC-46 can and does carry cargo fairly often. The whole fuselage isn't a fuel tank. That would be far too heavy to take off. So I don't see them designating it as K-46.
Beyond that, it does seem like the obvious platform to do a lot of the special missions that the C-135 airframe currently does, although some of those may end up on the 737 airframe instead, depending on details. Personally, I'm very much in favor of a BKC-46 to replace the B-52, but I appear to be mostly alone in that crusade.
redRover:
Yes, it's called the Civil Reserve Air Fleet.
bean:
The 737 is cheaper to buy and run and unlikely to be too small for any of them.
The obvious platform to replace most of the RC-135 ELINT/SIGINT, WC-135 and E-8 JSTARS missions is a stealthy variant of the RQ-4 Global Hawk. I'm aware that the USAF is retiring the Global Hawk next year so this might already exist as a black project (perhaps the RQ-180). Quite honestly the B-21 (should be B-3) Raider is about the right size and endurance for what you want, and the RQ-180 is supposedly in the same size class. With modern technology for autonomous control, electronics miniaturization and SATCOM there is no longer any need to haul a huge cylinder of pressurized air up in the sky to bring along the flight engineers, navigators and radio operators to perform those roles.
The KC-46 would be the right airframe for replacing: -The handful of RC-135S Cobra Ball aircraft, only because I assume they use the large diameter of the fuselage to hold a camera that would not fit in a stealthy flying wing. -The VC-32, the aircraft normally used as Air Force Two by the Vice President, or by the Secretaries of State and Defense. The widebody 767 fuselage would be a huge upgrade over the width provided by the 757 based VC-32. -The E-4 National Airborne Operations Center and the E-6 Mercury TACAMO aircraft for control of SSGNs and ICBMs. I know that surplus 747-8Is have been purchased to rebuild as replacements for the E-4, but again, with modern electronics I'm not sure a 767 doesn't have the space to do what a 747 used to (for instance, the E-4 originally had a projection room to display slides into the conference room, totally unnecessary square footage in an age of flat screens). The EC-130J is a huge step down in capability from the E-6, both in range and endurance and also in not having the "Looking Glass" capabilities to support the USAF bomber and ICBM missions. Having a common aerial command post platform would allow a great deal of flexibility in assignments, and ideally a large enough fleet would allow the restoration of aerial CPs for high level commanders in the Europe and the Pacific, as the EC-135s used to do in addition to the strategic role. As with the VC-32, the wide body platform of the KC-46 would be a huge upgrade over the 707 sized EC-135s and E-6s for command and control.
As Bean notes, for some of these roles you could go with a 737 based aircraft for commonality with the P-8 and C-40. Larger 737s are basically the size of the 707ish C-135 variants. So an "RC-40" could probably take a large enough camera for the Cobra Ball mission. In fact, for some roles, particularly VIP transport below the highest echelons, a Gulfstream G700/G800 is probably the answer. The wingspan of the G7/G8 is larger than the original 737, which together with the smaller fuselage/weight gives the G7/G8 truly global range (from the continental US the only places you can't reach non-stop are Western Australia, Malaysia, Sri Lanka, and points in between). Capacity is obviously less, but for electronic/VIP roles the cargo is limited, while range/endurance is a key operational factor. It also helps that the G7/G8 can use smaller runways than 737s/767s. The USAF has already started going this route with the G550 based C-37/EC-37 aircraft, while the E-11 is based on the similar Bombardier Global Express 6000.
The most important thing in all of this is to make sure that the replacement for the WC-135 is derived from the B-21 bomber (should be B-3). The WC-135 is a specialist aircraft designed to test air samples for radioactive isotopes and thus detect or monitor nuclear weapons development or testing. Why is it important to have the replacement based on the B-21? Because with an aircraft designated "WB-21", the Air Force would once again officially have a "Weather Reconnaissance Bomber" in service....
@Onux
How many of the current xC-135 missions actually require or meaningfully benefit from stealth? I would be concerned that using an RQ-180 base platform ends up paying a lot of stealth tax for minimal use. This is doubly so for the variants that have large protuberances. I do agree though that modern electronics make a 737 based successor more likely.
@bean
Concur that the BKC-46 is an excellent idea, both for standoff B-52 missions and also as a loitering bomb platform over low intensity conflicts.
The E-130J does seem like a colossal misstep.
@redRover
I would say that the RC-135V/W Rivet Joint missions would absolutely benefit from stealth, for two reasons. First, in a non-conflict situation, or a hostile but permissive one, not knowing that the aircraft is there might give an advantage where the enemy emits signals from devices they would turn off if they thought they would be intercepted. This is a tactic as old as electronic warfare. In 1939 the German airship Graf Zeppelin II made a flight along the British coast with electronic technicians on board to try and analyze the under-construction British Chain Home radar system that was going to become so famous during the Battle of Britain a year later. According to some accounts the British realized why the zeppelin was there and kept their radar turned off to deny electronic intelligence to the Germans; according to others the German's detected the signals but disregarded them as radar because the long 12m wavelength was considered too crude to be useful - German radar under development used much more advanced 0.5m wavelength.
The second reason is that in a hostile environment stealth would allow a Sigint/Elint aircraft to operate closer to the battlefield or with less risk of detection or engagement. The airliner based RC-135s are not really capable of operating in anything resembling contested airspace, let alone penetrating any air defenses. A stealth design would be more survivable and offer the option of going over enemy territory to collect signals that might not be detected when orbiting in friendly airspace.
I assume that a modern Rivet Joint of whatever design would not have the large domes and fairings of prior generations. Phased array and conformal antennas have been a thing for quite a while now, with the B-2/F-22/F-35 not having any projections despite many types of radars, receivers and EW/ECM. For detecting things coming from the ground a flying wing design provides a nice flat surface underneath the plane for flush mounting of flat antennas. Again, modern electronics and transmitters means you no longer need "this antenna sends UHF signals to SATCOM, this one UHF signals to other planes, this one detects enemy UHF signals..." or antennas that physically rotate to do their job.
For the RC-135U Combat Sent these considerations are similar but lesser. Combat Sent is designed to collect information on enemy radars for later analysis to understand threat profiles and develop countermeasures. It is not used operationally during a conflict, but beforehand to prepare. The first consideration of a stealth aircraft not letting your opponent know today is the day their air defense system is under the microscope could provide some advantage. With modern technology it might be that a separate variant for the Combat Sent mission is not needed, and a Rivet Joint replacement could do both functions.
As noted before there is no reason for a stealthy RC-135S Cobra Ball. It's job is to track and photograph missile launches. Not only is there not need to be stealthy when tracking a space launch or ICBM test from possibly thousands of miles away from its launch (as it flies overhead, not that the cameras see that far), but the need for fitting the cameras and pointing them basically rules out a flying wing design, which is too thin.
I disagree that a BKC-46 is a good idea for the loiter-at-a-distance stand-off bomber role. That role should be filled by transport aircraft such as the C-17 or C-130. The USAF has just 391 jet tankers, and they are a critical force multiplier for global deployments or keeping planes on station. There are however 608 ramped cargo aircraft (including C-130 variants that can also act as hose and drogue tankers and some inactive C-17s) plus C-130s operated by the USN and USMC.
Deploying munitions from inside of a KC-46 is a difficult to impossible situation - there is a cargo door but at ~11 ft wide it is not large enough to directly eject a cruise missile like the AGM-158 (~14 ft) and there is an obvious concern about putting out a missile at the front of the aircraft in front of and above the wing. New doors for missile release would effectively be a redesign/rebuild of the aircraft, and any sort of "bomb bay" below the aircraft (safest for airborne release) would take space from the lower deck fuel tanks and compromise the critical tanker mission other planes cannot perform. External hardpoints are a possibility, but this greatly limits capacity due to weight on a wing not designed to carry it, range/endurance due to increased drag, or both.
With ramped cargo aircraft the solution already exists - Rapid Dragon / Dragon Cart is in use with the AGM-158 and being tested with the JDAM-ER and ADM-160 decoy. Compared to the problems of launching from an airliner, using Dragon Cart requires no modifications to the cargo plane, is no different than any other airdrop when used, and when not in use does not affect cargo handling at all. I can't see any reason or advantage for a BKC-46.
@Onux
All fair points. However, I think the BK-46 would (nominally) fill two roles, with somewhat contradictory requirements.
The first is as a persistent bomb delivery platform for low intensity conflicts - being able to drop 500lb bombs in support of troops in contact while already airborne. In that role, the high dispatch rate and ability to consistently fly one or two hundred hours a month gives commercially derived platforms an advantage over military specific platforms, which tend to spend their marginal R&D dollar on mission enhancement rather than maintainability and reliability. (Though they have made great strides there)
The other role is to replace the B-52 as a standoff missile launcher, in which role the C-17 with Rapid Dragon is more competitive, though the B-52 and BK-46 have a better EW suite and additional mission systems. However, whether it’s worth preserving this capacity, rather than spending the money on more B-21s, seems a bit of an open question.
From a payload perspective the K-46 is between the C-17 and C-130, and fairly close to the B-52, at least from a weight perspective.
I agree that the BK-46 would require substantial engineering to be able to launch most munitions via a rail/trapeze or wing hard points, but I think that would also mitigate your concerns about fleet utilization /mission capability reduction. The BK-46s would be additional airframes, rather than cannibalizing the existing KC-46 fleets flight hours.
To be clear, I'm calling this the BKC-46 to make it clear what I'm proposing, not because I expect the final result to still have tanker capability, in which case, yes, it would be a BC-46. You'd have to do some mods to get a bomb bay, probably in the aft section, but that's hardly something unique here. (Yes, it would be bigger than the one in the P-8, and you'd probably need some moderately fancy rail system internally to move weapons around.) And the idea is that it would be a B-52 replacement, so criticizing it for cannibalizing other systems is a bit weird.
Rapid Dragon is a cool thing, and critical on day one of the war when we have a big, complicated plan to execute and need all the missiles we can get in the air. But in that case, we can pre-load all the missions and send the transport crews up with instructions to kick the pallets out the back at a certain time. The problem with it comes on day 2, when you start to need more complicated things. The transport crews are not trained or set up to deal with things like changing targets in real time, which is more complicated than it sounds. Also, you're limited to throwing the whole pallet out at once, and can't just fire off a missile or two if that's what you need.
I don't think a stealthy Rivet Joint would work well. Stealth tends to impose a lot of packaging constraints, and for that kind of plane, you want to be able to do mods easily. The case for the KC-46 is that it's an airframe already going into wide service (which isn't really true for the USAF and the 737) and it's nice and easy to modify, with lots of room for whatever they may dream up down the road.
@redRover
If the objective is persistent bomb delivery for low intensity conflicts then a BK-46 is still the wrong choice, because once again the correct choice already exists: the MQ-9 Reaper. A flight of four MQ-9s including ground stations and equipment costs about $150M (upper end estimates) while a single KC-46 costs about $150M (lower end estimate). A flight of 4 MQ-9s can easily maintain long term 24 hour coverage (720 flight hours per month with one drone in repair, 3 in flight/maintenance rotation) while civilian widebodies average 240-360 flight hours per month. A MQ-9 uses 150 lbs of fuel per flight hour with a total cost per flight hour of ~$3,500; the KC-46 uses 11,000 lbs per hour at a total cost of ~$13,500. So keeping one KC-46 on station means 2-3x the capital cost and 3.5-4x the operational cost while using 70+x the fuel.
A BK-46 would of course carry more ordinance, but this isn't of much benefit in a low intensity conflict where the battle against a small group of insurgents can be decided by a single smart bomb or guided missile. Conversely for the same procurement cost you could keep a drone on station over 2-3 locations instead of one, which is of vastly more benefit in a low intensity environment, and still do it at lower operating cost and fuel use. With a 4 drone flight you have the option, depending on maintenance availability, of surging 2-3 units for a major operation or immediately launching another drone if the one in the air malfunctions, while the single BK-46 you get for the same cost will never be in more than one place at once, and while it is in its maintenance cycle or if it suffers an sudden breakdown there is nothing to replace it.
But of course you won't get a BK-46 for the same cost, because the current KC-46 doesn't have any provisions for weapons, or more important for low intensity conflict, the EO sensor of the MQ-9. Adding that will drive up cost, meaning an even worse cost ratio compared to the MQ-9 for the same amount of availability.
If the suggestion is to just hanging a few weapons from the KC-46 because it is already up there and can respond immediately, it still doesn't work out. A tanker with it's boom attached to another plane cannot drop or launch ordinance so your actual availability is less than your nominal time on station. Also, just being in the sky doesn't mean you are in the right location. A plane orbiting over Kandahar is not going to be able to respond to a request for ordinance in the Korengal Valley. It could try flying there, but by the time it arrives the situation could have changed and the need for the strike gone. And while it is doing so it can't be performing its actual job of fueling other planes, so not only do you not get the strike in the Korengal Valley when you need it, but the jet that had to return to base because it was low on fuel also cannot provide a strike somewhere else.
And again, the key thing in low intensity conflict is not the persistence of ordinance on station, but the persistence of observation to find small groups of insurgents hiding in various ways (in plain sight pretending to be civilians, in camouflaged bunkers, splitting up into small groups before coming together right before the attack, etc.) Knowing when and where to drop by observing these patterns is much more valuable than just having a bomb overhead you can drop, and a tanker doing fuel things doesn't provide that observation even if you've spent the extra money to make it a BK-46 and given it sensors.
Once again, the way to leverage existing aircraft in the sky for responsive fire support is with tactical airlifters because the system already exists: the USMC Harvest HAWK for the C-130J. There are always tactical airlifters flying around a given theater which means that there is a higher likely hood of one being nearby when you need it, and diverting a transport mission doesn't ultimately effect that mission (cargo arrives a little late) or interrupt other air sorties like taking away a tanker does. Similarly the final version of Harvest HAWK with pylon mounted Hellfires and door launched Griffins didn't occupy the ramp and prevent loading other cargo. Nine systems was said to cost $22M, so for a single KC-46 without BK modifications you could equip 54 C-130s. The USMC just retired Harvest HAWK because no one is expecting a low intensity conflict over Taiwan, but if you needed the capability again that is the route to go.
@redRover
If the intent is to supplement or replace the B-52 as a standoff missile launcher . . . a hypothetical BK-46 is still the wrong choice. A KC-46 can carry a max payload of 65,000 lbs, which works out to 25-28 AGM-158s, but that is before accounting for the weight of the storage/launch system. A BK-46 would probably be carrying no more than 20 or so missiles by weight, which is the same as a B-52, or only 12 if it used the underwing pylons of the B-52 to avoid fuselage modifications.
A C-17 by contrast can launch 45 AGM-158s with Dragon Cart, limited only by space not weight. Just activating the 26 C-17s the USAF owns but doesn't have in service as a "BC-17" would provide 80% of the standoff missile capacity of the entire 75 aircraft B-52 fleet with no additional procurement. Even the C-130 can carry 12 missiles with Dragon Cart, the same as a BK-46 could with wing pylons, for about half the cost of just a KC-46.
But of course your BK-46 is going to cost much more after the structural modifications (even if you only go wing mounted that wing will need redesign) and adding an EW suite to match at B-52. If you have a budget for procuring additional airframes, buying one C-17 and two KC-46s will probably cost less than three BK-46s for the same missile capacity (or four C-17 / five KC-46 versus nine BK-46 if assuming 20 internal not 12 external).
But if going internal you still have the problem of how to launch the missiles. There was a proposal to use the 747 as a standoff cruise missile launcher back in the 1970s: https://www.reddit.com/r/WeirdWings/comments/e61vqx/theboeing747cmcaorcruisemissile_carrier/
There was an even more wild plan to vertically launch missiles from a 747: https://www.popularmechanics.com/military/research/a22197/icbms-on-747s-plan/
But the problem with either of these is that they turn your BK-46 into a BC-46 because they are both incompatible with the tanking role. In the tail drop version you are of course taking the space that is used by the boom; in the vertical launch version you will intrude into the lower deck fuel tanks that give the KC-46 a lot of the fuel it gives to other planes. So now you have spent valuable procurement funds on a single purpose bomber than doesn't have the flexibility of the B-52 to take on tasks like dropping JDAMs, or the stealth of the B-2/B-21 for penetration missions. At this point we are back to it's better to restart C-17 production because in addition to more missiles per aircraft you at least have a strategic airlifter when you don't need a standoff missile launcher.
@bean,
I did not see your comment before I posted my last two.
My understanding of the Tri-Service designation system is that calling it the BC-46 would make clear what you are proposing, because BKC-46 implies it still has tanking capability. (Although between the F-117, F/A-18, B-21, F-35, F-47, MV-22/CV-22/CMV-22 Tri-Service is now basically useless).
To add some thoughts now that your proposal is clear. If you are looking for a non-stealthy bomber to replace the B-52 then you should just propose developing a B-4 (because it should be the B-3 not B-21, I can't let it go). Using airliners as bombers hasn't been successful since the Ju-52/He-111, and it wasn't that successful then. If anything the technology goes the other way, Boeing's work on the B-47 and B-52 directly led to the wing design of what would become the 707. As I noted a standoff missile launcher derived from the KC-46 is useless for basically any sort of other bomber mission, of which the B-52 undertakes several.
For what it's worth, I expect that a low tech bomber to supplement the hi-tech B-21 would still probably be a stealth looking flying wing, B-2 sized not B-21 sized, just without any of the expensive materials and precision required to get true stealth. The knowledge how to use design a flying wing to minimize radar cross section exists, with no good reason not to use it for a combat aircraft, similar to how the B-1 has 1% the RCS of the B-52 even though it wasn't 'stealth'. It's true the B-2 carries 16 missiles internally versus 24-32 for a BC-46 built from scratch with some kind of rail system. But you could fit a third rotary bay inside a new design flying wing with a higher max take off weight if you didn't require perfect stealth, or design for 12 missiles externally from the start as augment for simple stand-off launcher missions. But for other missions you have much lower observability which translates to better survivability even if you aren't stealthy enough for penetration missions.
You have a good point about single round shots and flexible retargeting with Dragon Cart, but there a few simple answers. One is that you could put wing hard points for 4-6 external missiles when conducting the standoff launcher role for those 1-2 shot missions; I'm fairly confident C-17 and C-130 wings would not require redesign given their original cargo and short field design requirements.
Second, as I mentioned the USAF has 26 C-17s mothballed; you could take 25 B-52's out of service, equip a bomber wing with 25 C-17s, increase your national standoff missile capacity by 40%, and have crews that train full time for the missile drop mission along with the equipment and skills to target/retarget in flight. These 25 aircraft would be obvious candidates to get wing mounted missiles, of course, maximizing their usefulness in the "BC-17" role. As mentioned Dragon cart is being tested to add weapons like JDAM and drones, which means your "BC-17" can train and specialize in other missions like minelaying. There is precedence for this, back during the Cold War the USAF wired a few B-52 squadrons to fire the Harpoon missile and trained their crews in maritime attack operations when it seemed like repelling the Soviet Fleet from US shores might be a thing (ok, it was never really a thing, the USN was too dominant, but the concept of "most of these planes/crews train for strategic deterrence but these few will train to sink ships" could equally apply to cargo carrying / standoff missile deployment in the C-17 community).
Third, you can get what you want just by buying more B-21s with the budget you would spend on the hypothetical BC-46. Yes, you get fewer of them, but you also get a platform you can use for the most demanding missions, instead of one that does standoff loiter only. As before, when you need a bunch of standoff munitions you use Dragon Cart, for everything else you have more of the most advanced bomber on the planet.
It's also worth noting that for the standoff loiter role could be fulfilled by a drone. Predators/Reapers have been dealing with complicated things like real time target changes for a decade and a half or longer. If that is the goal there is no need to haul a crew up there to do it, let alone a pressurized cylinder sized for hundreds of passengers. Design an high altitude long endurance drone large enough to carry tens of thousands of pounds of ordinance instead.
But wait, the B-21 has been described as "optionally manned." Maybe the 'low tech' bomber you want is a B-21B that is "never manned" so you can lose the cost and weight of the cockpit, life support, display screens, etc. Data links that support drones like the Reaper have a concern with jamming (how did Iran down that RQ-170?!?!), and fully autonomous AI flight systems are not agile enough to handle the fluid situations found in a deep penetration mission (yet, that we know of) but either could handle the standoff missile role. More importantly, they could also handle medium threat tasks (mine the approaches to this harbor, drop bombs in support of frontline units on call, launch ASMs against these ships) that a BC-46 with the signature and flight profile of today's Newark-LAX never could.
The need for a lot of space to do mods on planes like Rivet Joint is a legacy of the days when equipment had vacuum tubes, your radio encryption device was a separate piece of rack mounted equipment from your decryption device, and cockpits had a window in the ceiling so the navigator could take sextant readings while sitting next to the guy who wasn't the pilot but controlled all the switches for the engines. Modern electronics have basically eliminated packaging constraints. A few years back the as a test USAF turned the F-22s radar into a 1 Gbit/s data link, and they didn't need space to make any mods, they just reprogrammed. As long as you have an AESA for each relevant band pointed in most directions, you will be able to do whatever reconnaissance missions you like, synthetic aperture radar, analysis of radar signatures, signals intelligence collection, etc. Whatever you can program into the bunch of CPUs/GPUs inside the plane that weigh basically nothing and take up almost no space.
That said, if we did adopt the C-46 airframe for missions where space provided value (the VIP transport, C2 and TACAMO missions I identified) I'm sure there would be a few extra airframes that could find their way into various special functions like a flying camera/Cobra Ball, etc. when needed.
Yes, technically it should be the BC-46 instead of the BKC-46, but the latter is funnier and you are the first person in years of me pushing this that got confused.
I am fairly certain I have spent more time thinking about the B-52's mission than you have, and I don't agree. The only things it couldn't do effectively are the nuclear mission (not a problem, we should be buying enough B-21s to take that fully) and low-level mining, which is on its way out once Quickstrike ER fields.
I'm really doubtful on this. Airframe development isn't everything, but it's also not free. More importantly, pushing this as a commercial derivative is a way to make it clear that this is the low-end option and mission creep shouldn't turn it into a gold-plated boondoggle.
No, it really isn't. "Optionally manned" is what we were saying 10 years ago to get the "drones uber alles" crowd to shut up. I can't think of much in the way of practical reasons to actually fly that way, and taking out the cockpit is likely to add cost in the short and medium term.
"The only things it couldn’t do effectively are the nuclear mission (not a problem, we should be buying enough B-21s to take that fully) and low-level mining, which is on its way out once Quickstrike ER fields."
There are a couple of ways to look at this. One is that if your BC/BKC-46 is configured as a standoff missile launcher with a rail system customized for the AGM-158 or similar, then it absolutely cannot do all B-52 roles because it will not have the ability to drop JDAMs, etc. If you give it a P-8 style bomb bay that fits underneath the main deck and doesn't interfere with exiting landing gear, etc. then you get really small capacity for your non-missile load and you are not able to effectively replace B-52s on a one for one basis.
You could try to add external hard points on the wings, or totally reconfigure the fuselage for larger internal bomb bays, but this would require a total redesign of of the structural system of the aircraft because no airliner is designed to carry external stores on its wing and the entire fuselage is built around the transverse support provided by the main deck. As you said, airframe development is not free, and at that point why not just design a clean sheet bomber for the non-stealth bombering missions if that is what you think you need.
The second way is to say that for non-standoff missions in a modern AAW environment nothing short of a stealth or at least low observable aircraft would survive, in which case the B-52 is obsolete and so there is no need to replace it with anything resembling it. Instead you need a stealth or stealthier replacement, either more B-21s or a dumbed down B-2 (for the larger payload).
Case in point, Quickstrike ER has a range of about 75km. The HQ-9B is thought to have a range of 250km. So no, your airliner-derived bomber is not cruising over to conduct a "stand off" mining mission from cruising altitude. You either need a stealthy/low observable aircraft can get close enough to drop the Quickstrike-ER before it generates enough of a return to be detected, or you need something that can come in low underneath the radar horizon or taking advantage of radar clutter (but with modern pulse doppler radars, computer processing, and look down AEW even that flight profile is probably no longer reliably safe and you are back to needing some level of stealth).
Re: a less expensive B-2. Airframe development isn't free, but airframe development is also done and paid for for the B-2. Just build more aircraft of the same size and shape, but do it in El Segundo with conventional aluminum skin instead of at Plant 42 with whatever exotic materials the B-2/B-21 are coated with. I guarantee you the RCS will be lower than the B-1,B-52,BKC-46 which would give that aircraft vastly more ability to maneuver in airspace even if it cannot go straight into the teeth of major air defense network as if it were invisible.
"taking out the cockpit is likely to add cost in the short and medium term."
Is this a joke? There is no unmanned aircraft in the world that is more expensive than a manned aircraft with same role and capabilities. Just unbolting and removing the seats, screens, oxygen and pressurization systems, toilet etc. would result in an immediate drop in short term cost by reducing fuel use after thousands of pounds are unloaded, to say nothing of the ongoing maintenance costs to keep those items working. Designing without pilots from the start would see even greater benefits. The USAF operates drones on missions that resemble a bomber's flight profile now (RQ-4, RQ-170, RQ-180 maybe if that's what those flying wing pictures were of) so we know the technology exists.
See, this is the sort of thing that makes it hard to take you seriously, because you speak with confidence on something you pretty obviously don't actually know about. Pretty much all US military air-to-surface weapons use the same MAU-12 adapter. If I'm building a system set up that gives me access to a reasonable amount of the fuselage volume on a 767 for JASSM, adding "can also do JDAM" to the requirements for that same system is pretty trivial. The big JDAMs weigh about the same, are no less durable and are physically slightly smaller. I didn't bother saying this, because I assumed it was obvious.
P-8 does it, and I'm not aware of any really significant structural mods there. (Also, the same applies to your beloved airlifters.)
This is nonsense. Yes, there would be structural mods. But to say that the cost of doing the structural mods to be able to take out the main deck (assuming that was necessary, and you couldn't just cut a hole in it for the bomb bay and use the volume above the deck, which is significant on a widebody) is equivalent to developing a new airframe bespeaks a lack of familiarity with aircraft engineering that boggles the mind. One requires a team of structures engineers to make some moderately difficult modifications to one part of an existing design. The other requires more structures people because there's more structure to figure out, to say nothing of the teams in aerodynamics, engines, systems, and so on.
What? There are so many problems with that I don't know where to start. The B-2 has been out of production for decades, which means none of the supply chain is still there, and for designs like that, the stealth materials are pretty integral.
Not even slightly. You're assuming that "optionally manned" means "has full capability to fly unmanned all missions we would give the crew". I do not think that is a good assumption, because that would be really expensive to develop, and I haven't heard the phrase in years. If it even makes it to fielding, it's probably going to be used for three demos and then forgotten about because it's basically a fancy autopilot. Beyond that, drones are cheaper because they are built to a lower standard. You're either doing systems development (which I know that you think is free, but my bank balance begs to differ) or you're not really getting any savings versus the normal version except in maintenance. And I don't think that's a good tradeoff for the loss of versatility, which is very real.
@Onux Re: stripping out the human-interface parts of an "optionally manned" airframe: given (as far as I know) the mass of those parts is almost entirely concentrated towards the front, wouldn't we be worried about the center-of-gravity shift? Given the photos of F35s with exercise weights in place of a radar, you either don't get any actual savings, or you're having to redo all your balancing math, adjust weights elsewhere.
@ShasUi
That is a good point, however, while all "human interface" parts (i.e. screens, controls) are up front, you should not assume that all "manned support" parts are there as well. Carrying people 50,000 feet up in the sky means pressurization equipment, oxygen equipment, etc. I don't know where that all is, so this is something one would have to look at, but it is also not an enormous deal. If you take 2,000 lbs from the front and 1,000 from the back then you need a 1,000 lbs weight in front to balance while saving a ton. Or you move 1,000 lbs of equipment from rear to front and save all 1.5 tons. Or you add an extra fuel tank for better range/endurance.
@bean "See, this is the sort of thing that makes it hard to take you seriously, because you speak with confidence on something you pretty obviously don’t actually know about. Pretty much all US military air-to-surface weapons use the same MAU-12 adapter."
Actually, this makes you look like you don't know what you are talking about. Yes, the MAU-12 can carry most forms of air to ground ordinance, but that does not mean it is the only device for doing so. The B-2 uses a rotary launcher and the smart bomb rack assembly inside of its bomb bays, for instance. More importantly, the MAU-12 is designed to hang things in a static position and drop them, usually (not exclusively) externally. There is no way to make use of the MAU-12 from inside of a 767 fuselage without massive redesign to include bomb bay doors. So no, it should not be assumed that the nebulous rail system you mentioned would be able handle different types of ordinance, since it most certainly won't be using a MAU-12.
But that's only part of it, because you really don't know what you are talking about if you assume that just because a weapon fits in the form factor of a mounting that it can be used from that aircraft. Certifying an aircraft to use a particular piece of ordinance is a time consuming process that goes through extensive testing. This is why you are always seeing articles in the various mil blogs and publications like "weapon x finally integrated into plane y" even though plane z has been using that same weapon for years - and even though they both might be dropping it from a MAU-12. So once again, no, just because you design some rail system designed to move around drop an AGM-158 out of the back of at 767 derivative does not mean you can assume it will be able to do the same with other weapons.
"P-8 does it, and I’m not aware of any really significant structural mods there. (Also, the same applies to your beloved airlifters.)"
The P-8: 1) Uses the wing of the 737-900 on a 737-800 body because the -900 wing is structurally stronger 2) Reinforces the wings on top of that for the hardpoints 3) Also adds a reinforced keel and extra bulkheads 4) Despite all of that only has four wing hard points rated to 2,500 lbs each, which means that it cannot carry the AGM-158B JASSM-LR . . . which is the principle standoff missile that you want your standoff missile bomber to carry.
So good luck carrying 12 AGM-158Bs, like the B-52 does, on the wings of a C-46 derivative.
I don't know all of the specifics of C-130 and C-17 design, but I will comfortably stay near the trunk and state that wings of airflifters designed for low altitude operations and flights from shorter runways will be naturally stronger than airliner wings designed for gentle climbs and cruising at altitude. Maneuvers in thicker air and steeper climbs/decent simply puts greater stress on a wing.
"the cost of doing the structural mods to be able to take out the main deck (assuming that was necessary, and you couldn’t just cut a hole in it for the bomb bay and use the volume above the deck, which is significant on a widebody)"
As I said before, the main deck is an integral structural element of the fuselage. Failure of the main deck due to otherwise insignificant decompression of the cargo hold has led to aircraft losses and near losses. Differential decompression is no longer a concern because modern jets have blowout panels in the floor, but the point remains that the floor is not something you can just take out or cut holes in without other changes. Is there some way to structurally do it, of course, but you also then have to consider how you are supporting all of those munitions inside your new large bomb bay, since passenger aircraft fuselages are also not designed to hang dense heavy weights inside them.
"The B-2 has been out of production for decades, which means none of the supply chain is still there, and for designs like that, the stealth materials are pretty integral."
The stealth materials have nothing to do with the shape of the aircraft. The stealth materials are integral to making something the size of a barn have the RCS of a bird, not to how the aircraft is held together or flies. I am not advocating making a clone of the B-2 (which as you note would be next to impossible due to supply chain changes over the past 35 years) but using the existing aerodynamics to build an aircraft of the same size and shape but with different materials, or at least none of the expensive custom coatings and extreme manufacturing tolerances. This is entirely plausible.
"You’re assuming that “optionally manned” means “has full capability to fly unmanned all missions we would give the crew”. I do not think that is a good assumption, because that would be really expensive to develop,"
I think its a great assumption, since the MQ-9 Reaper has been conducting combat operations for almost two decades, and flies all the same missions that manned observation and ground attack aircraft do. The MQ-20 exists. "Optionally manned" does not have to mean "fully AI autonomous" it can be a ground controlled drone. For any mission you would want the BC-46 to do (i.e. any mission currently undertaken by the B-52, and perhaps only in lower threat environments than the B-52 would) a ground controlled drone could absolutely do it, and you would spend nothing to develop it because the technology has existed for decades! This would be true if you put it in a crewless B-21, a new less stealthy flying wing aircraft, or just a really large long-wing drone optimized to carry a large payload up high and loiter around waiting to release munitions when needed. FWIW, I think that for any BC-46 mission the technology also already exists to do it fully autonomously - you're just talking about a cruise missile that flies a specific path and releases warheads along the way instead of being a warhead, and Tomahawk had that down four decades ago not two.
"volume above the deck, which is significant on a widebody"
Here we have identified the key point. The fundamental issue is one of density. The average human weighs say 150lbs, and on an airliner has about 50 cubic feet of space between room at their seat, and their share of aisles, bathrooms, etc. So 3 lbs/cuft. An AGM-158 weighs 2,600 lbs and has a bounding box of some 40 cubic feet, or 65 lbs/cuft. This is 22 times more dense. If you want to move a bunch of people somewhere, you want a wide fuselage with room for them to sit, move and breath. If you want to move a bunch of bombs somewhere, you want a thin or narrow fuselage to minimize drag and weight of fuselage structure (or use the same weight in a smaller area to support the point loads imposed by those heavy weapons). This is why the B-52 and Tu-95 look so similar to each other, and the B-1 to the Tu-160, but why the 767, A330 and Il-96 look so different from the bombers.
Le's say you did go through all of the work to modify a C-46 to have bomb bay doors. The JASSM-XR is expected to be 16 feet long, so you are getting 3 bays (two ahead of the wheels, one behind). You could get 4 missiles across at the width of the 767 cargo bay floor, and then find a way to get two high (or design to cut a hole in the main deck for an 8 weapon rotary launcher). So 24 missiles. You're already at 62,400 lbs, about the current KC-46 cargo weight, and you haven't even used the entire volume of the cargo bay let alone ANY of the volume above the main deck. All that volume above the main deck IS A LIABILITY, not a feature. You are wasting fuselage and structure enclosing a cylinder of air that you will not use, and in exchange getting an RCS 100 times larger than a B-1, let along the 1000+ times larger of a B-2 or B-21. This is not a good tradeoff.
You could make the same argument about using airlifters for the standoff munitions role, and you would be correct, because airlifters are designed to move cargo that is usually heavier than people but not as dense as bombs. But airlifters have a ramp at the back, which is both good for pushing things out while flying (like standoff missiles) and loading things on and off on the ground. So airlifters can make use of that volume when not dropping missiles, while a BC-46 cannot.
Once again, if you want a non-stealthy bomber to replace the B-52, design a non-stealthy bomber (as I have noted above, I think that a modern combat aircraft without stealth or at least low-observable design is foolish). With all of the experience now from the F-117, B-2, F-22, F-35, B-21, RQ-170 and various test articles (X-36, X-45, X-47, Polecat, RQ-180?) designing a flying wing or blended body aircraft with reduced signature, even if not edge of the envelope stealth, will not be a huge deal. And you can actually use it as a bomber instead of having it detected at maximum range by the crudest enemy radar like the "BC-46" would be.
Or again save all of your R&D costs (including R&D to modify the KC-46) and spend what you would spend on procurement on additional B-21s, whose flyaway costs only go down as procurement goes up. There are 75 B-52s. Were you going to replace them 1 for 1? 3-4 KC-46s buys a B-21. Your BC-46 will be more expensive than a KC-46. Just getting 20-25 more B-21s would be supremely more valuable than 75 BC-46s, and to make up any difference in max missile capacity activate the 26 mothballed C-17s for use with Dragon Cart.
I can't find any pictures of the B-2 rotary launcher, but I know both the B-1 and B-52 use MAU-12s on the rotary launcher. It's not all of the hardware you need, but I was trying to make the point that if you build a system that can carry JASSM, it can also carry JDAM basically for free.
Obviously, the MAU-12 is an ejector, not a teleportation device. If I didn't state we needed bomb bays earlier, it's because I assumed all of the people reading this were smart enough to figure that out without me needing to state it.
Ooh, that's a good point. I really didn't know that...
Sorry, that's from an alternate universe where I didn't spend a couple of years as the lead engineer on a weapons integration program. I know how much of a pain it can be. It's an amount probably measured in the tens of millions.
Look, I work with this stuff for a living, so you can't just baffle me by throwing names around. The AGM-158B is JASSM-ER, not JASSM-LR (that's not a thing). Also, P-8s are certified to carry LRASM, which I'm pretty sure weighs the same.
All of the ones I can think of were due to control cable damage, not gross structural failure of the aircraft.
You were the one who was just lecturing me about the need to test capabilities. If "optionally manned" isn't taken that seriously, then they won't build and test the B-21s system to make sure it can do everything. Saves probably a couple hundred million.
OK. I think I'm going to call it here. Ignorance is forgivable and curable. Aggressive ignorance that refuses to listen to people who have been paid to do the thing under discussion (on at least two different facets here) is not, at least not in my comment section. If you want to apologize, you can find my email.
@onux
Using a drone as a replacement for the RC-135 seems to make very little sense. One of the biggest advantages the RC-135 has is that the people analyzing signals have direct access to the equipment and there's like 20 of them right there who's entire job is just managing the equipment, who aren't hamstrung nearly as much by every bit of information needing to be passed halfway across the world through potentially multiple relays.
As to the BC-135 idea, one of the biggest reasons the modern tube-and-wing design is as universal and has stuck around as long as it has is because of upgradability. A flying wing bomber based on the B-2 can't take advantage of much of any design at all because the B-2 production line has been dead for 20 years. Even if the base 767 fuselage design was entirely unusable you could redo it from scratch and still have massive amounts of the design work reusable from the 767, or even a 777x if you wanted to go bigger.