H-20 bomber (with H-X, JH-XX)

[Nx4eu]

I tried my best to overlay the scales on top of each other for layout A the cranked kite versus Layout D like the B-21. We can see that on average Layout D has lower dbsm across most angles, all except from the peak at 30 degrees where all the edges line up for Layout D.


Apart from a hopeless diamond, Layout D is the most optimal planform for observability reduction. It's not at all a surprise that the B-21 is shaped exactly like this.

 

[Gloire_bb]

You know, IDK why the artist draws it like that, is it for the cool factor? They always show H-20/PAK DA with cranked config or misaligned edges. It's infuriating and almost like they think Chinese/Russian do not know how stealth works.

I think - don't quote me on that, I am no engineer, - there's a choice there; ultimately GJ-11, S-70 as well as other demonstrators are misaligned.

What's that? Hell I know. I thought that for sure frontal rcs(over number of additional small spike elsewhere), sharper leading edge is more beneficial, but graph shows otherwise.

But clearly there's something, because all engineers from different nations(all with access to silent rooms and rcs ranges) do it over and over for some reason.

 

[latenlazy]

B-21 is the last one, along with basically every other uncranked flying wing drones.

I don’t think you guys understood what I was pointing out. Profiles C and D have the exact same frontal aspect shaping but do not have the same RCS on at frontal aspect. The same is true for A and B My point is “edge alignment” is not the explain all heuristic you’re making it into.

 

[gelgoog]

You can forget about an XB-70. That used metallic honeycomb composites to keep weight down. They never got them to work properly. So the plane crumpled like an accordion. That is why it was canceled.

The fashion now in terms of materials is carbon fiber composites. Those use resins to glue the fibers together. The resins melt at high temperatures in Mach 3 flight.

At best you would get a Mach 2 aircraft. Anything higher and you need new materials. The HGV and HCM programs might lead to such materials eventually but it should not happen soon.

 

[Gloire_bb]

You can forget about an XB-70. That used metallic honeycomb composites to keep weight down. They never got them to work properly. So the plane crumpled like an accordion. That is why it was canceled.

It was cancelled long before, for entirely different reasons. And honeycomb planes were long since fully operational by that point (B-58).

 

[gelgoog]

Well I got that straight of the horse's mouth from someone who worked at Rockwell. They never got a viable XB-70 design due to materials challenges.
The stainless steel honeycomb was a flop.

 

[Gloire_bb]

They never got a viable XB-70 design due to materials challenges.

That's true, and in many ways. But in any case, Convair did it in late 1950s.
Making big supersonic bomber (be it high supersonic cruiser or dasher) is totally doable, including one with huge bays. With some fever, you can make it stealth shaped. With more creative fever, you can develop materials just for that.
The question, of course, is what's the point.

Supersonic giants don't come free even before you add edge material science and suboptimal aerodynamics. Even without that, it's expected that, say, pak-da will be massively cheaper than tu-160m, for similar range/payload at least at longer ranges, and same time to target.

 

[Tomboy]

I think on't quote me on that, I am no engineer, - there's a choice there; ultimately GJ-11, S-70 as well as other demonstrators are misaligned.

What's that? Hell I know. I thought that for sure frontal rcs(over number of additional small spike elsewhere), sharper leading edge is more beneficial, but graph shows otherwise.

But clearly there's something, because all engineers from different nations(all with access to silent rooms and rcs ranges) do it over and over for some reason.

If you look to highly stealth long range drones/bombers like B-21/B-2, RQ-170 and the WZ-X. They all feature fully edge aligned trailing and leading edges. I personally think tactical drones/UCAVs have their own set of mission requirement that either require good speed and flying characteristics hence the tradeoff with planform. If I remember correctly someone here said that the beaked/cranked arrow design was used because it increased low speed performance and manuverbility hence makes it valuable for carrier based drones albeit at the tradeoff of some amount of stealth.

I don’t think you guys understood what I was pointing out. Profiles C and D have the exact same frontal aspect shaping but do not have the same RCS on at frontal aspect. The same is true for A and B My point is “edge alignment” is not the explain all heuristic you’re making it into.

That's probably because of edge diffraction from the trailing edge which are *not* aligned with the leading edge

 

[gelgoog]

That's true, and in many ways. But in any case, Convair did it in late 1950s.

That was aluminium, not stainless steel.
The Hustler operated at much lower speeds so thermal expansion was less of an issue.

 

[latenlazy]

That's probably because of edge diffraction from the trailing edge which are *not* aligned with the leading edgeView attachment 159157

Sure, and if actual real life planes were only these 2 dimensional shapes the sweeping conclusions about RCS you’ve been drawing using this diagram might be more valid.