Reddington777's BWB Project

[Reddington777]

Those images are very close to a cranked-kite (X-47B) shape, which is pretty solidly LO.

Keep the canted ruddervators, shift to non-tapering wings, bury the engines, and sharpen some chines. That should give you 4 major glint angles in the front arc, plus another glint off the ruddervators abeam the aircraft.

Buried engines will cost you a big chunk of interior volume, however. Could an inlet spike work for RCS at subsonic speeds?​

So as I'm working on this, the problem with having a transport in a stealthy triangular planform is that you are basically flying a plane the size of a C-17 but with a useful cargo hold of a C-130 unless you start introducing less LO features.

In a triangular planform like this, if you try to stay in the same volume, then you are already trading length for width here. Then if you try to bury the engines, the ducting around the engines is going to further eat into width (which is all you have). So a fully stealthy blended wing transport in a stealthy version of a JetZero planform may end up having much less cargo space than a C-17 while still having a comparable size - that is unless the planform is so much better that it requires much smaller engines.

The best work internal arrangement I can think of is this:






The cargo bay sacrifices a full width ramp opening to accommodate two engines inside the fuselage. The intake will be blended into the forward fuselage. in the center bay section, the width is twice as wide as the C-17 bay. but the ramp itself is the same or slightly wider than the C-17 bay. It's not particularly convenient for the loaders, but this is the best usage of space I could come up with. You'd have to load something, then scoot it sideways to fit into the main bay - and this is without the massive landing gears yet. The engines I've used are still the TrentXWBs used before, but from the looks of it, JetZero's design has engines larger proportionally to the rest of the airframe than pictured here, so to even have this configuration work you'd have to sacrifice even more cargo space.

With tail mounted engines sitting up high, you'd be hard pressed to bury them in a good LO way. You can make the airframe wrap around it, but that seems sketchy to me still. The only way to not sacrifice storage space is leave it the way JetZero has - just sitting atop the fuselage, which is not going to be LO really.

 

[Scott Kenny]

Yuck, that's even worse than I thought!

Would it be possible to stick the engines above the rear ramp instead of beside it?

 

[Reddington777]

Yeah I know right.

I think Ill have to go back to using ventral ducting to make that work.

 

[Moose]

I don't think anyone has seriously proposed such a strangely compromised configuration. A transport/tanker is going to be more "reduced signature" than "broad spectrum stealth," for example LM's recent concept had the engines pushed far forward, JZ artwork usually sticks to having 2 conventional turbofans above the fuselage, etc.

 

[Brett Davidson]

Some of the aerodynamic jiggery-pokery that went into the B-21 overwing inlets and format of this Lockmart sorta-blended tailed design might work (just cut the tail off). Also, here's Boeing's blended design with the enormous greenhouse for reference. Yes, it would have to be wider in proportion for the cargo bay you're proposing.

The Lockmart transport apparently draws on the same research that went into their collaboration with Boeing for the NGB. The inlets are closer together and higher than those of the B-21, indicating an even more extreme S-duct in the vertical plane.

 

[Reddington777]

I don't think anyone has seriously proposed such a strangely compromised configuration. A transport/tanker is going to be more "reduced signature" than "broad spectrum stealth," for example LM's recent concept had the engines pushed far forward, JZ artwork usually sticks to having 2 conventional turbofans above the fuselage, etc.

In case my response wasn't clear enough -

While I was modeling this anyway, my whole point was (and continues to be) to show that trying to VLO a transport requires some crazy shit that probably isn't possible.

I've commented in the past (in the NGAL thread) that I find for the most part that a stealthy air lifter probably doesn't work. This (and the other NGAL model) was just having some fun playing around with planforms.

 

[Reddington777]

Boeing's blended design with the enormous greenhouse for reference. Yes, it would have to be wider in proportion for the cargo bay you're proposing.

Huh. That one has engines sandwiching what I assume to be the ramp.

The Lockmart transport apparently draws on the same research that went into their collaboration with Boeing for the NGB. The inlets are closer together and higher than those of the B-21, indicating an even more extreme S-duct in the vertical plane.

I've seen some 3d models of what people think is the B-2 / B-21 ducting and it was pretty extreme too given the relatively short length of the intake and exhausts. It's a subsonic aircraft so the ducting can be a bit more extreme.

 

[Brett Davidson]

Huh. That one has engines sandwiching what I assume to be the ramp.

Yeah, Boeing has studied a 'clam' ramp. Egad, zounds and Bozhe moi, it's from way back in 2017!