World Surveillance Group Inc (fka WSGI)

[imawswami]

Skunkxstox...maybe Kroplin explains better

Skunkxstox thanks for the response, am always glad to share and discuss what is going on with our company so as to gain a greater understanding. In that vein, you wrote:
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"I see the Air Chain vs rigid airship approach a little differently however when it comes to the relative drag of each.

Total drag is not as much a function of the cross section of a body as it is of the total surface area and the nature of the airflow over it. For example, a round teardrop-shaped object can have several times less drag than a spherical object of smaller diameter because a sphere is a much higher-drag shape. That's why footballs look like water melons. The key is to not disturb the boundary layer which in turn maintains attached airflow which is needed for low drag. The shape of the Air Chain cells is not conducive to low drag IMO, even though it has a slimmer profile."
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Sure would agree with your description as one would relate a single ball to a slick teardrop-shaped airship. Airship would win the drag/volume contest.

Problem with this example is that it does not apply to the airchain, which is comprised of a narrow conical front and a series of cones designed and aligned to improve drag/volume through it's length and further, actually reduce a major source of drag not mentioned in the example you've provided: the tail.

A tail is especially large for a teardrop shaped airship.

Refering back to the aspect ratio of the respective crafts. Longer (more volume) and leaner (airchain) airship beats out wider/shorter traditional airship in the critical Drag to Volume ratio.

But Kroplin explains it best here. And, yes weight is a problem, especially as we read how the traditional airship approach to over-building to compensate for design deficiencies.

http://books.google.com/books?id=k9ifqUt5CvIC&pg=PA52&lpg=PA52&dq=airworm+airship&source=web&ots=O6MCSCwUE8&sig=OIEYm24hP0h-eXX5l9Kv3RusjmE#PPA55,M1

Here is an excerpt from the above Kroplin work:

"It follows that the normal blimp design used for High Altitude Platforms leads to an unfavourable scaling and an increasingly large part of dead mass. This can be compensated by using stronger materials and all the problems associated therewith, or it can be overcome by an improved design.

Structurally seen, the most lightweight blimp should be a cluster of spheres made from the thinnest possible material arranged in a spherical cloud in order to minimize the Munk load and the empannage mass.

But what about the drag? Drag results fromt the airship body itself and from the empennage. The lowest drag per volume for the single body is achieved with an aspect ratio of nearly six. If the empennage (which can be relatively smaller for
slender airships) is also taken into consideration this shifts to around eight. An aspect ratio within this range cannot be achieved with a conventional blimp design since it would lead to a very high differential pressure and Munk Loads.

This contradiction cannot be solved with a convential blimp design. A lightweight airship has to be made of a number of spheres, a low drag airship has to be elongated with an aspect ratio in the range of eight.

7.1 The Airworm concept and its advantages:

The Airworm concept solves the problem of slenderness versus low differential pressure and combines the advantages of both by creating a chain of spheres (or almost spheres) and stablizing each one individually. This is the most lightweight structure possible.

Aerodynamically the overall shape corresponds to a slender elongated airship with low drag.

Moreover, if every segment is stablized in itself, a central empennage at the tail is no longer necessary, neither is one needed for every single segment. "
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Kroplin goes on to write that all the above was proved out through numerous trials with the segmented airships. -Pete


Skunkxstox, thanks for your comments. Am always glad to respond.

pete