<<  As Vance recently pointed out it is nearly impossible to build a light
 > > weight pressure vessel that looks like a Burnelli fuselage.
 > >
 > > Structurally efficient pressure vessel tends to look like a sphere or
 > > a tube.
 > >
 > > Also, low aspect ratio lifting bodies have high induced drag if
 > > in fact they indeed reach a high enough angle of attack to generate
appreciable
 > > lift. If they don't they merely have excess skin friction drag due to an
 > > unfavorable  surface area to volume ratio. In short the Burnelli flies
 > > in the face of aerodynamic and structural principle :-) >>

Should Boeing give up on it's blended wing research before it's too late?

Lynn E. Hanover
lehanover@aol.com

I think so. The Boeing project prompted Vance's response to the pressurization
problem in the first place as I recall. I agree with Vance.

To give one a feel for this lets say the passenger compartment is 50 feet wide
and 50 feet long or 2500 square feet. At 144 square inches per square foot that 
is 360,000 square inches. At 10 psi pressurization differential 3,600,000 pounds 
is trying to rip the roof (top of the blended wing) off or blow the floor 
(bottom of the blended wing) out from under you. 

Let's compare this with the pressure due to fuel weight in a conventional wing.
Let's say fuel weighs six pound per gallon and there is 232 cubic inches in a gallon.
That is... it weighs .0258 pounds per cubic inch.
If the wing/fuel tank is four feet or 48 inches thick that would be a column of fuel 
one inch square by 48 inches high or 48 cubic inches of fuel.  
At .025862 pounds per cubic inch that would be only 1.2 psi on the bottom
wing skin by my calculations. At 3 G's that would still be only 3.6 psi.

If we break the big 50 foot square  room into smaller 
rectangular rooms say ten feet wide to tie the roof and floor together you have 
cyclical stress concentrations in the corners. In other words the rectangular 
rooms want to become tubes. In addition the blended wing skins will have waves in
them due to the deflections.  A structural engineering nightmare.
Is all this worth what ever small aerodynamic advantage one can eke
out of a blended wing design? I don't think so. Perhaps there could be
columns every couple of feet or so tying roof and floor together.

I also like to look out of the window. I don't like flying around in 
a large flat room without being able to see what is going on from time to time.

Paul Lamar
 
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