lehpron
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Difference Between Flying Wing & Lifting Body?

Thu Dec 29, 2005 6:02 am

I credit Starlionblue and LeanOfPeak for inspiring this thread. Here is their portion from the 'how high a 747 can fly' thread:

Quote:
Quoting LeanOfPeak (Reply 44):
Quoting Starlionblue (Reply 42):
Hmmm, but the X-15 cheats! The thing needs to take off and land under it's own power, wouldn't you say?

Far more relevant than that is that the X-15 is a rocket.

Oh yes indeed. Non-airbreathing. But then again the X-15 is a winged craft... On the other hand even capsules like Apollo generate some lift. The argument could go on for a while

There is something I still don't get with regards to that arguement: Where is the line between a lifting body and a flying wing? It is the cross section or leading edge sweep or aspect ratio? Or is it an arbitrary parameter like the 80m box for VLA's? Or is it just a preception, i.e. people think flying wings should only be wider than their length??

Imagine a plane with a 75-degree delta wing but the thickness ratio being 20% of the chord. Imagine that within the thickness volume is where the payload and fuel is kept. What is that classified as?  irked 
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Starlionblue
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RE: Difference Between Flying Wing & Lifting Body?

Thu Dec 29, 2005 11:34 am

Quoting Lehpron (Thread starter):
Where is the line between a lifting body and a flying wing?

Arbitrary. It's all arbitrary. Apollo capsules generated lift by having an offset center of gravity. Essentially anything will generate some lift right? What I actually meant was that Apollo could (to some degree) control re entry with a shifted CoG. The capsule will generate lift in any case as long as the orientation is correct.

So pretty much anything that flies is a lifting body? Hmmm. Here are my definitions:
- Flying wing is when the wing and body are completely blended such that there is no visible distinction between the two. Eg B-2, Ho-229, etc...
- Lifting Body is a wingless structure, such as the Apollo capsule, the X-24 and those weird Russian experiments in which the fuse was the wing. Unlike the flying wing, the fuse (useable for payload) extended all the way out to the edges of the craft.
"There are no stupid questions, but there are a lot of inquisitive idiots."
 
LeanOfPeak
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RE: Difference Between Flying Wing & Lifting Body?

Fri Dec 30, 2005 9:29 am

I don't think anyone's ever considered it important enough to make a hard and fast rule.

Personally, I'd say that:

If it looks like a fuselage:


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Photo © Javier F. Bobadilla - Iberian Spotters



(Like this X-24A) it's a lifting body.

If it looks like a wing:


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Photo © George Canciani



(Like this B-2) it's a flying wing.

I'd say thickness-to-span ratio and aspect ratio would weigh heavily in any conclusion.

Your hypothetical 20%-thick, 75-degree-sweep delta sounds a lot like the X-24B. NASA considered that one a lifting body, and I'd have to agree with them.

Quoting Starlionblue (Reply 1):
Unlike the flying wing, the fuse (useable for payload) extended all the way out to the edges of the craft.

This guideline also makes a lot of sense.
 
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Starlionblue
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RE: Difference Between Flying Wing & Lifting Body?

Fri Dec 30, 2005 1:43 pm

Another fun lifting body:

The Vought XF5U: http://www.unrealaircraft.com/wings/cv_flapjack.php
"There are no stupid questions, but there are a lot of inquisitive idiots."

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