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Evolution and Theory of Cellular Kites

Kites are often classed between flat kites and boxes, as well as between single and multi-kites. Although highly three-dimensional and/or multi-unit kites are ancient, Hargrave invented the modern box kite in the late 19th century, naming the individual box sails as "cells". We can also define multi-kite architectures such as stacks, trains, arches, and clouds as cellular.
Numerous box kite and kite train variations emerged in the golden age of manlifting and meteorological kiting. The box kite evolved directly into the early biplane. The most visionary box kite R&D was by Grahm Bell, whose "cellular kites", as he dubbed them, fully realized the modern tetrahedral spaceframe of identical units. Unfortunately the otherwise efficient structure was poorly adapted to fly. Bell crowded his wings into small cells and proved that even superior spaceframes do not scale well for flight; no brittle flying structure really does.

Far more successful box-cell kites tended to have fewer larger cells supporting projecting wings. The French Military and Delta Conyne kite variants represent a mature simplicity, stability and performance in the classic cell-kite lineages. Multi-sled and parafoil kites gave new life to cellular kite design by eliminating need for rigid sparred structure. Ram-air inflated structure progressively stiffens at higher speeds, maintaining a quality wing shape with no brittle-failure. Highly multi-cellular parafoils currently dominate the power kite space.

A "secret life of cell kites" is also occurring. Wholly new classes of cellular kites are bursting onto the scene. Hot niches include single-cell 3-D box kites like the Triangle Box, Pop Can, and so on. These types tend not to foul on ganglines and to self-relaunch easily. There is a lot of ferment in the soft Bag Kite design space. KiteLab's cellular arrays are another frontier.

Modern high-wind versions of popular kites are cellular arrangements of fabric holes, woven strips, or porous mesh panels. This stability effect owes to cross-linked cellular hole structure acting to damp rather than couple turbulence. Sub cells reduce a kite's total Re characteristic length, allowing larger "metakite" dimensions of equivalent lift at a lower fundamental harmonic. Similarly we understand how loosely cross-linked kites cancel chaos by an "aggregate stability" effect.

Some of the new cellular kites are tricky to define precisely (like our metakites). A major hobby-kite class goes by names like "Star Box", "Facet", "Flair", or "Snowflake" kites. I just finished cataloging for WKM Bill Godel's personal creations along these lines. One sees winged-box and common flair kite DNA mutated into baroque assemblies that fly rather well (i was permitted to briefly test a Gobel masterpiece in a playful breeze).

The key to these designs is "textbook tensegrity" whereby a spar is guyed othogonally from its neighbors. In the case of kites, tensegrity guys are replaced by "flairs" of fabric that act as wings. A kite arch of diamond kites looks very different, but works by the same principle; each of its wings uni-sparred at a right angle to its gangline. Within this design pattern-language, it does not take a great leap to imagine vast flying honeycombs of wings arched across the wind. To only need isolated battens or ram-air airbeams allows megascaling of kite structures.

Multiple types of cell kites in fractal dimensioned multi-cell arrays may be the ultimate large-scale AWES architectures. The cellular principle, with its cloning and mutation dynamics, could be as fundamental to AWE as it is to biology.

CoolIP*                      ~Dave Santos                 4Jan2012                 AWES5294     

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