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enter image description here

This is what some people think the SR 72 will look like.

If a plane wing was attached to the whole fuselage, couldn't it have a shorter wing span? If it had a shorter wingspan it would be less of a lever so could be less strong and therefore lighter. I don't mean a blended wing.

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You are right, a short wing span is a blessing for the structural design and the wing will be nice and light. But since you need a certain wing area to keep the aircraft in the air, the wing will have a long chord as well, and that won't be good for aerodynamic resistance.

For subsonic aircraft, you want the longest, narrowest wing possible: the lift create by the wing is caused by air accelerating downwards. The amount of air streaming in is a function of the span, so a long span accelerates a lot of air downwards only a little bit; a short span wing has to accelerate much less air much more. That creates induced drag: the horizontal component of the backwards tilted lift vector.

From the wikipedia entry for Induced Drag

Another source of drag is the tip vortex, where air 'flips over' from high pressure below to low pressure on top of the wing. So for subsonic aircraft, the longest, narrowest wing is the most beneficial from an aerodynamics standpoint. It will add constructional weight and therefore increase weight induced drag, but will compensate for it by a reduction in aerodynamic induced drag.

Supersonic aircraft have an additional source of drag: shock waves. The air gets no warning that an aircraft appraches. The nose arrives first, and a shock wave streams off of the nose in the form of a cone. Inside the cone, the air has lower velocity - if the wing can stay within the cone, it creates much less supersonic drag.

enter image description hereImage source

The higher the supersonic speed, the more the shock cone bends backwards, and the widest bit of the wing needs to be more towards aft to remain within it. So for supersonic aircraft, the delta wings that you draw are in use. They create a relatively huge drag when flying subsonic though.

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One of the issues with flying wings / blended wing bodies is ground servicing. All kinds of people or vehicles require all kinds of access to all kinds of systems which is more difficult to arrange (not impossible, but more complex) than the ubiquitous tube-and-wing design.

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  • $\begingroup$ What I'm trying to describe is not a BWB or flying wing. In those designs the fuselage is surrounded by wings. I mean if you made a normal (747 for example) jet have it's wing start at the front end at the back and maintain its thickness therefore engines etc would be equally accessible. The one harder thing would be loading but that could be done. $\endgroup$ – SRawes Jun 29 '17 at 12:36
  • $\begingroup$ @SRawes can you draw a sketch or link a picture? $\endgroup$ – user7241 Dec 25 '17 at 17:24
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Consider also skin effect. In your scenario, the larger wing surface would create more drag than a typical configuration.

Edit, ok I see what you are saying now. And yes, your assumptions are correct.

Your question seems to be, why isn't this more common place?

If that's correct, the answer is stability and controllability. These designs are inherently less stable than what you would consider "conventional"

There are plenty of examples of aircraft that have attempted to overcome the hurdles, the verhees delta comes to mind.

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  • $\begingroup$ @Jim The wing surface area would have to stay about the same, because with about the same weight your lift force would have to be about the same, and this is proportional to surface area of the wing. You don't need more surface area, so increasing the wing chord goes along with decreasing the wingspan. $\endgroup$ – user7241 Dec 25 '17 at 17:28

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