I have been a fully paid up member of the RAeS for over sixty years, but as I don't want to be accused of nit-picking (post#8) I will refrain from any direct comment on the HyperJumbo as presented and confine myself to remarks on the general concept.
The box-wing has been around for a long time and although the details differ the HyperJumbo under discussion has noticeable similarities to the 1995 Lockheed Boxwing.
This latter was put together by a professional design team so we can assume it to have been properly thought through. It was assessed by a NASA/Boeing/Stanford group as having achieved the minimum theoretical vortex drag in a configuration with "reasonable" high speed performance (it had favourable transonic area ruling) and some structural advantages.
The problem areas identified, but not resolved, included landing gear integration, maximum lift penalties, fuel volume and low sectional Reynolds Numbers.
The general concept of drag reduction by use of non-planar wings has been studied in detail by Prof. Ilan Kroo of Stanford University. There are a couple of papers worth reading if you want more detail.
Highly Nonplanar Lifting Systems: Ilan Kroo, Stanford University; John McMasters, Boeing Commercial Airplane Group, and Stephen C. Smith, NASA Ames Research Center: Transportation Beyond 2000: Technologies Needed for Engineering Design: September 26-28, 1995
Nonplanar wing concepts for increased aircraft efficiency. I Kroo Stanford University USA; VKI lecture series on Innovative Configurations and Advanced Concepts for Future Civil Aircraft. June 6-10, 2005
The more important conclusions are summarised on the following chart, extracted from one of those papers.
Down on the bottom right Configuration "A" is the closed wing arrangement proposed for the HyperJumbo. It offers the maximum reduction in theoretical vortex drag.
However, Kroo established that you do not need to close the wing to get this drag reduction. Configuration "C" has pretty well the same drag reduction but without the problems associated with the complete boxwing. Kroo developed this thinking into a "C wing" design as shown.
You may, or may not be a convert of the blended wing philosophy, but it does look plausible.
Before getting too excited it might be worthwhile reflecting that the drag reductions being claimed relate to the theoretical vortex drag; that is to the inviscid drag produced by the particular distribution of vorticity over the wing. This theoretical vortex drag is a large part of the total drag due to lift, but is by no means the whole of it.
Staying with the American practice of using Oswald efficiency to describe induced drag, the Oswald efficiency of a modern wing in cruise is of the order 0.8. The theoretical vortex drag contribution would be around 0.9 to 0.93, the rest comes from lift (or aoa) sensitive viscous flow effects giving rise to minor flow separations which in turn produce drag.
Until we know how these viscous effects will operate on unconventional configurations such as the Hyperjumbo we cannot be sure how much of the theoretical drag gains will actually be achieved.
Note also that modern wings are NOT designed to cruise with the theoretically optimum vortex drag. The objective is to produce the best wing not simply the most aerodynamically efficient. It generally pays to back off the theoretical optimum, have a span loading with a more inboard centre of pressure than an elliptic loading and cash the weight saving. That is without winglets of course.
This general thought must be carried over to any new proposals - the object is the best overall design not necessarily the most aerodynamically efficient.
Go back to the second chart and consider Configuration "B". This has less potential gain than A or C but it is a much simpler arrangement. In fact the reduction in theoretical vortex drag is 90% of the theoretical maximum reduction, but the only change to a planar wing is the addition of Longhorn style vertical winglets.
Now if, and it is a very big IF, a viable market emerges for an aircraft with more capacity than be squeezed out of an A380, would you tear up everything and go for an untried unconventional layout or would you chicken out and adopt a simple vertical winglet modification to the A380 for slightly lower potential gains but much less commercial risk?
PS I have just discovered that the illustrations may not appear. They were OK on my PC but not on the ipad. I seem to have a problem with Dropbox which I will attempt to sort out. Meantime, if anyone is desperate to see the pictures they are lifted directly from the two papers I cited. For the first illustration see the Kroo/McMasters/Smith paper p338, for the second see the same paper p346 or p 353, or a slightly different presentation in the Kroo paper Fig 18 (p.18) and for the third illustration see the Kroo paper Fig 13 (p. 15)
Last edited by Owain Glyndwr; 12th Feb 2016 at 12:02.
Reason: Retry at inserting illustrations