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0 pointsdr_orpheus3y ago0 comments

> There is some crazy public belief that it is more fuel efficient

There are a number of engineers at NASA and Boeing working on the X-48 who would disagree with you on this one.

The main advantage of the blended wing body is to reduce the skin friction drag [0] of the aircraft relative to the typical fuselage and wings. You have less surface area in contact with the air relative to the amount of internal volume. There may be some increase in the profile drag (i.e. the cross section of the aircraft) but is made up for by the reduction in the skin friction drag.

> The fuel burn of a B2 is far higher pound for pound than a 737.

This isn't really a fair comparison. They are two aircraft optimized for entirely different things.

[0] https://en.wikipedia.org/wiki/Skin_friction_drag

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jcampbell13y ago

Skin friction drag is a drop in the bucket compared to parasitic and lift induced.

I’m willing to accept that a gold bullion transporter can look closer to a flying wing, but with any reasonable cargo density you are back to the standard design.

Trying to intuitively explain CFD results is apparently just as hard as dispelling the Bernoulli nonsense about airfoils.

I’m right and high aspect ratio wings are a harder materials science and design challenge than blended wings. There is a reason 10000x as much engineering effort is going into folding carbon fiber wings for passengers/cargo. The folding is to increase fuel economy through aspect ratio and fit in terminal box.

Everything I have said is trivial to prove with CFD and experimentally. I get that popular science articles need to entertain the masses.

Let me ask you this, why is the tail of passenger aircraft upward sloping?

dr_orpheusOP3y ago

One, I'll admit I'm not an expert in this, I have an aerospace degree and took some aircraft classes but it was 90% on the space side of things. But I'm trying to be devils advocate here since its not just pop-sci articles.

> Skin friction drag is a drop in the bucket compared to parasitic and lift induced

I'm trying to rectify it with papers that say "In civil aviation, skin-friction drag accounts for around 50% of the total drag in cruise conditions" [0]

> I’m right and high aspect ratio wings are a harder materials science and design challenge than blended wings

I understand that higher aspect ratio reduces drag too and that the planes should all look like scaled up gliders with their long skinny wings. But as you said, it is harder. So is it a clear cut answer that exploring blended wing designs is a waste of time?

> Let me ask you this, why is the tail of passenger aircraft upward sloping?

To prevent tail strike during take-off and landing when you are at a high angle of attack.

[0] https://www.sciencedirect.com/science/article/pii/S037604212...

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