DRAFT Version 05/18/2001
Mega-Scale Free-Space Polymer Engineering
Case Study: Super-Density Kite-Energy Arrays
Kites offer a wonderful chance to power our world by tapping clean renewable geoflow energy. Upper wind is an estimated 3500 terawatt resource & ocean currents harnessed by water-kites are a comparable opportunity. Civilization needs only 20 terawatts to thrive. The modern kites required are a blend of aviation & industrial rigging technology. Kite Energy is also widely known as AWE (Airborne Wind Energy), with many small demonstrations & lots of great introductory information online. This report describes the next conceptual frontier of AWE, the aggregating of capacity to mega-scale by rigging dense arrays. Rigging with lines is the ancient universal engineering language of sustained action at a distance & the spanning, crossing, or filling of free-space volume with robust tensile infrastructure. Endless 3D configurations of rigged presence are practical in airspace, outerspace, & undersea free-space, with unlimited choice of subcomponents. A "String Revolution" that began in the Upper Paleolithic propelled human culture to its present complexity. Fibers twisted into cordage & woven into canvas made practical tents, clothing, fishing tackle, hunting gear, baskets, megalithic architecture, & seafaring. We can build on mature technological models with billions of hours of operational success, from fishing to classic kiting. Sailing, mega-construction, cableway tech, & even puppetry are examples of instructive real-world rigging traditions. Instructive rigging principles are found in molecular arrangements & biology, from cytoskeletons to spider webs. Diverse break-through applications are emerging, but safe low cost AWE is presented here as the most urgent case. Intensive complex automation, E-Flight, & LTA methods are not key enablers, but mostly avoidable expense & complication.
Fundamental Rigging Properties
Idealized kite rigging occupies maximal space-time by minimal mass-energy because it is made of line & membrane, quasi one & two dimensional objects. Strength & simplicity are prime virtues of rigging. "Captivity Factor", especially for stability, is the basic rigging effect. Untethered, an object is free to translate & rotate in undesirable ways. A single tether begins to constrain motion. Multiplying tethers progressively constrains until an object is as fully bound as Gulliver. Matter itself is bound in molecular latticework, our very flesh hangs in place by sinews. Lattices cancel chaos & create certainty.
Ordinary compressive structure is expensive & unwieldy to fly as a kite, but compressive resistance is available from fluidic compression of the medium or the ready natural substrate of Earth's surface. Masses secured aloft by more than one line have a lowered chance of breakaway; less danger to life & property. A powerful property of an extensive string latticework in Free-Space is IsoPresence, direct mechanical presence in all regions of a volume. Isopresent wireless sensor/actuator networks are easily rigged with modern microelectronics.
Less "rigging-dependent" single tether designs make quite sparse use of land footprint, about a hundredth of ideal potential. A proposed 2mw AWECS operating under a US regulatory ceiling of 2000 ft needs a circular tether scope about 3 km across. The same land area can host about 50 MW of conventional turbine capacity. Geometric analysis suggests latticed "superdensity" arrays might yield over 200 MW from the same land & airspace.
The advanced 3D free-space rigging described here is informally referred to as "latticework", "meshes", "nets", & so on, or formally as "Fress-Space Tensile Latticework" (FSTL). The ongoing rigging revolution is not just knowledge-driven, but also propelled by the incredible performance of modern super-fibers like UHMWPE. Bountiful energy is just a start to the magic possible with string & rag.
Wind, Kite, Tether, & Anchor Principles
Wind is a chaotic combination of fossil momentum from the Big Bang, solar convection, & terrain effects. The kite is a paleo-cybernetic (autonomous) wind-powered flying robot. It generates Newtonian reaction force as lift to cancel gravity & provide excess energy to tap. Kites, tethers, & anchors are elemental building blocks of airborne latticework, just as transistors, resistors, & capacitors are digital building blocks. A tether on an anchored winch is a poor man's tractor beam. Towing force transfers energy at almost superconducting efficiency. A kite's tether transmits reaction over distance by coupling to an anchor. Wind momentum is processed into useful power by the interactive physics of the kite. In AWE wind momentum transfers as a stress wave from a typically membrane wing's loadpaths to ropes that then transfer the captured momentum to work a generator shaft.
Every day sees wild new AWE experiments. Its an era of naive jury-rigging & dynamic ad-hoc results resembling "spider on acid" experiments. Latticework design variants are "rigs". Essential rigging is rope & rope-handling components like anchors, reels, winches, capstans, pulleys, swivels, & so forth. Membranes add powerful flow processing to rigging. Membrane is also a basic FSTL element, for wings, reflectors, containers, etc. Engineering with wire-rope is giving way to modern super-polymers with over ten times the strength-to-weight.
Geological Surface & FreeSpace Media Compression as Fundamental Structure
Conventional compressive structure is a hopeless basis for megascale airborne engineering, but there are better sources of compressive resistance. The earth's surface is a "free" compressive anchor medium to react against. FreeSpace mediums, like air & water are also suited to compress against. A pressurized bag is efficient compressive structure, but tends to leak in hard use. With wind or currents, a partial membrane angled correctly generates enough pressure to build with. In principle, the entire atmosphere could be filled by this special sort of engineered structure.
Aggregation into Arrays
Kite stacks, trains, & arches aggregate great power by individually manageable elements. A toy kite stack launched from a small box once even pulled up a fire-hydrant, to the mortification of the hobbyist, who made a quick get-away.
Flocking aerial vehicles is a popular concept, with many identified advantages. Simple rules enable simulated flocking behavior, but real-world robotics is a far more demanding & robust flocking aircraft will take decades to refine. Many of the benefits of dynamic flocking are realized by simply harnessing kite elements together as a "team". Semi-capture enforces flocking rules of aggregation, orientation, & following behavior.
Gigawatt mesoscale kite structure is a "meta-kite" with standard kite dynamics in a slower timeframe. A small human flight crew can pilot a vast meta-kite by a few massive winches as a single control process, with passive automation regulating cells distributed throughout the lattice. Latticed arrays tolerate local perturbation & self-recover like "ruffled feathers". Freeflying elements foul each other without complete clearance.
KiteLab Ilwaco has identified a key array advantage, aggregate stability, where crosslinked kites as a group are more stable than any one kite. Local failure hardly affects an overall array-
A Meta-Kite is one big kite made of many sub kites, a sort of fractal kite. A classic instance is Bell's Cellular Kites: They looked futuristic but suffered by excess rigidity, weight, & aero-solidity. Cellular configuration again advanced by Bucky's exploration of tensile cellularity, especially tensegrity. Jalbert's fully soft cellular wings were a crowning invention. Mandelbrot's fractals figure as a mathematical model for cellular, where the surface (& mass) is increasingly cut away by pattern at finer scales. A meta-kite acts much as a porous kite in classic kiting, an expedient to fly stably in high wind.
A typical kite on a tether is anisotropic; it must orient to the wind dependent on the tether rotating around its compass & the kite weathervaning. Similarly, a metakite can rotate as a whole to follow wind direction, but there is a limit to how big an arch or 3D array can be & still rotate in real-time. A related space utilization limitation is for the anchor point to be fixed at the center of the "rose" (or in the arch case, abeam of the center), rather than the anchor point shifting fully windward, allowing higher flight while staying within tight bounds if forced to land. On cannot merely stake out a kite or array radially without excessive slack of the downwind lines & suboptimal AoA. Another problem is reliance on a single tether that when it parts results in a breakaway event, a general worst-case scenario.
A KiteLab tabletop demo showed a solution to these problems. A Tri-Tether pulley or winch anchor triangle allows an isotropic kite or kite array to adapt & receive wind from any direction; to passively tune its AoA & fly from windward anchors, without rotating. While the demo used a common paper plate as a "Sedgwick UFO" style kite element, the intent was to suggest a vast kite array, possibly a fractal Play-Sail or "Ohashi-Mesh". During the test session in fluky wind the plate self-launched every time, adapted without fuss to rotating the tabletop, & flew with decent stability. This concept can be envisioned at an early full scale of 2000 ft regulatory altitude within a rose approximately 1 km across, or as an ultimate version 10,000 m high by about 20,000 m across, able to span a major city.
A modest Isotropic Array could land its center (or legs) on a tower(s) or hill(s) and a giant version center on a mountain to keep array elements clear of the ground. The versatile tri-tether is also suited to tow a kite or array in circles, for persistence in calm. One can also imagine this adaptive mechanism as a cellular unit in a larger fixed lattice, compliant to array-scale turbulence. A hybrid design option is anisotropic kites on an isotropic lattice using classic kite train connections like thru-bridling and tri-swivels.
Despite a low dimensionless wind velocity, a single giant kite still operates at a high Reynolds Number (Re), due to its large spatial characteristic-dimension. High Re flight demands a fine airframe combining high performance & stability. Its just not yet practical to make conventionally shaped aircraft at giant scales, given cubic-mass structural scaling penalties. Giant soft-kites do fly, but they are ominously unstable in turbulence. A Meta-Kite mitigates this limitation by breaking up the giant kite into a mesh of many small sub-kites of lower Re. One can thus potentially make well behaved Meta-Kites kilometers across, up to the working limits of the polymer fiber structure. There are several stabilizing effects at play: Each Sub-Kite is semi-captive, compliant to local turbulence, acting to damp the overall mesh dynamics. A Meta-Kite is porous; thru-flow creates, in effect, a thick wing of higher stability. A Meta-Kite is somewhat larger than an area-equivalent monolithic kite, but the stability gained is well worth it, now actuation need not struggle to maintain flight. These effects are seen even in hobby kites stabilized by varied porosity. I recently noticed my net hammock flying out almost horizontally in a gale, but with gentle stable motion, whereas any solid membrane would have thrashed constantly. One can design a membrane to progressively open up in high velocity flow, just as banners are cut to "let the wind through". This is not just bleeding pressure, but also reducing the Re characteristic-dimension.
KiteShip's giant "OL" traction kites can be arrayed in meta-configurations. Three OLs sewn together radially form a super varidrogue with heart valve geometry. A fractal OL geometry, where many sub OLs form the open mesh of a vast super OL, would scale hugely, each sub OL tailored for local trim within the matrix, flown semi-captive. The super OL would be controllable by three lines. The superkite would be towed/hauled aloft & deployed sequentially from a pack, parachute style.
Airborne structure is naturally mobile, a free-space lattice is suited for travel, either by packing small or moving fully configured. Ground towing is a simple expedient & aerotowing liberates an airborne system to go anywhere in the world.
Kites have long been used to span gaps, like famously initiating bridge construction over gorges. A variation developed by KiteLab Ilwaco to routinely cross obstacles, like overhead wires, uses two lines. One line flies the kite as the other drifts beyond the obstacle, where it is retrieved. The first line releases & the kite moves onto the second line. The cycle repeats by alternating lines. By careful scouting & flight planning a kite makes cross country progress flexibly & reliably, even upwind. The coolest version would be a kite centered human platform that flies out pseudopod lines to selected anchor points & thus walks across the land. This is a real-life Seven League Boots & Flying Carpet hybrid device.
Functional LatticeWork (Mesh) Layers-
Control Layer/ Control Mesh
following section concerns megascale potential as based on Surface Layer
The lesson of these varied clues was that the major scaling limit to kite structure is insufficient passive stability. A huge soft kite can be built & flown, but one cannot count on active actuation to be either powerful or fast enough for "five nines" reliability, especially with airborne actuation. The only way to get powerful passive stabilization is to stake-out the kite. The challenge is to see that the stake-out mechanism scales to tens-of-km across, with the top of the kite arch structure easily able to reach our "ultimate" 10,000 m altitude. Smaller megascale kites can be rotated by "compass belay", but the largest sizes require a radial line stake-out pattern with phase tracking (Iso methods). In effect the kite arch now becomes a kite dome & can be angled for any wind direction or "wobbled" to sustain flight in calm. Various means exist to operate safely over populations & other surface conditions.
Stake-out involves "captivity factor" & also exploits the ground surface as "free" megascale compressive structure. Ground based actuation allows the fastest most-powerful response using industrial winches & no regard for flying-mass limitation. Bulk industrial actuation evades the aerospace component pricing trap. Megascale kite structure, as single control thread, eases realtime latency control computation challenges. Its pretty cool that we are not limited to dinky mesoscale single megawatt AWECS concepts, when what we really need is gigawatts.
Fan-in, Nexus Points, Gang or Bus Lines
Persistent kite flight backed by energy from the ground is a low-tech way for com hubs to station-keep in the sky. RF energy saved by high altitude transmission & reception offsets energy cost of airborne station-keeping. AWE based com hubs can piggyback on bulk power generation.
Basic FreeSpace Rigging
Rigging Vertical Lines
Vertical kitelines are set by windward guy-lines. A wide-format airspace can be rigged to consist mostly of vertical lines with only a single row of windward angled lines needed. Vertical lines can be halyards to suspend turbines & membrane wing-wills directly over their surface work-cells. Many such uses are enabled by the unique properties of vertical lines. They are gravity-aligned, wind-direction-neutral, & the shortest path to altitude. Vertical tethers are ideal for membrane wingmills to passively accept wind from all quarters. Surface work-cells can be turret-less.
Vertical is an overlooked "crosswind" geometry for a tethered-foil to follow, as a vertical zip-line, pulley loop, or elastic-return line. Far more wings can operate in the same airspace, by plunging up & down as pumping-trains, than common back-&-forth figure-of-eight AWE schemes allow. A light enough wing easily climbs a vertical line faster than the wind. The plunge back down is a high-speed dive, but under captive control, especially with elastic-return. Vertical self-oscillation, triggered by line-bow phase, is an elegant passive steady-state wing tacking mechanism.
The "Austrian" theatre curtain is an upside-down vertical rigging model, with drawlines gathering or deploying material along sewn-in rings. Vertical line arrays lifted by pilot-lifter kites can guide complex 3D meshes aloft, just as traditional circus canopies ran up erected tent-poles by their bail rings. Unlike a circus tent, multiple levels of AWE structure can be raised in orderly sequence according to conditions, especially to conform to calm & storm. Return loops in the array interstices allow every flying component to be hot-swapped freely
Multiple kites can reside on a vertical line, providing self-lift (see next) to the line without fuss, regardless of wind direction or line length. According to vertical tension, this is not the weak lift of a high L/D kite near zenith. Vertical kite towers can displace rigid towers in many applications. Vertical-trains can rise from a packed stack in a small box & return there passively, by gravity.
All inner cells of an elevated mesh can deploy vertical tethers & even tethers tilted windward for lift & reduced drag. The wider & deeper downwind a meshed array is proportioned, the more low flying-angle penalties are avoided. A meshed array can have its entire margin consist of low angled tethers, independent of wind direction. Such an array need not rotate if its lifters swivel in place or on short leaders.
The simplest vertical-line case is a single guy set at an angle shallower than the pilot-lifter's leader to pull a second line into vertical position. A vertical line can be dynamically anchored by by a castored cart or hanging teabag-mass, typically water or sand-bag free to be briefly lifted & dragged around ("tea-bagging").Three guys rigged as a shallow tripod can hold a fourth line vertical, as wind freely veers. Let a kiting Whiskey-Line be defined as a special case of guy-line; an adjunct or improvised guy-line to haul a vertical line or array into shape. This usage is from commercial fishing where an extra trolling line was set over & beyond the standard lines "to pay for the whiskey".
Planar Symmetric Arrays (PSAs) do not veer around the wind compass like single-anchor AWECS. Vertical lines are natural PSA feature. Non-rotating arrays do not sweep large areas like single anchor AWECS, but are constrainable to narrow corridors for forced-landing containment.
One & two dimensional kite arrays are well developed as classic trains & arches that gang multiple kites on common lines. Adding the third dimension & increasing operational density extends these methods. Putting wings all along a tether structure raises the flying angle. Wings all over a net maximize airspace by optimal frontal solidity. A self-lifting string latticework can accept wind from any direction without need to rotate.
Many kite array designs only work for a specific tether orientation, crosswind or downwind, so a kite for a towering train may not work in an arch & vice versa. The common Flat Kite is a sparred wing that can be set on a tether thru its CP (Center of Pressure) without a bridle. Thus its free to orient to the wind in almost every direction independent of the tether's angle. The key is for the junction of kite & tether to act as a balanced gimbal or ball joint. The toy method of simply tying across the kite's central spar creates small imbalances in the kite's trim. KiteLab has found that a well rigged Flat Kite does indeed reliably orient, trim, & lift properly even as the tether angle varies in almost any directions (a narrow interference zone in the single element state-space hardly affects array flight). This is basically Dave Culp's "Flying Rope" idea realized. A nice instance of this trick is a self-lifting string tripod from three fixed anchors, with many potential uses.
Self-lifting tethers have kitewings all along them. Self-orienting kite-elements adapt to wind from any quarter. Sparred flat kites work best, tether passed thru the center of pressure. The crossing-point can be a gimbal or ball-joint allowing the wing to orient in its lifting position even as the tether axis varies in direction. Eddy arches along these lines are called (Eiji) Ohashi Arches. Another key eddy arch method is by (Gerhard) Blattert Arch with eddies with out the lateral stick set all along the arch. Combining Ohashi elements at the sides & Blattert elements along the top would be a superior hybrid arch. Blattert's diamond pattern can double-up into an Allison Sled plan, or multiplied even further, but without reverting to a (Etienne) Veyres arch, which does not have the distributed AoA compliance of the Blattert & can bow-tie.
Its proposed that "Super Density Operations" (SDO) of AWECS is required to maximize airspace, that systems incapable of close formations will not be competitive for utility scale AWE. Most of the ideas needed for SDO already exist in fun kiting & have been mentioned on the forum. This post adds more detail, particularly advances in recent decades.
Classic kiting has long flown trains & arches, either for pure delight or to aggregate power in a manageable way. The highly evolved stacked train is seen in tradtional Chinese Dragon Kites. Eddy rediscovered branched trains 120 yrs ago. The two types are comparable in power, but very different in handling & flight character. Branched arches, basically a branched train bent across the wind, have existed for over a hundred years, & are used by modern kite shows to pack the most kites into a small field.
A new kind of arch emerged in the 80's when Etienne Veryes invented the Skybow, a ribbon-like arch. There were two enabling tricks; curving the overall ribbon in plan so that the trailing edge was slightly longer & spacing cross-battens along its length. Meanwhile Eiji Ohashi found he could take a train stack of diamond kites & bend them over into an arch, with half the kites flipping face. It was not perfect, as the kites in the center tended to interfere with the line. Then Gerhard Blattert found that an arch could be made by removing the horizontal spar of the diamond kite & running the arch line in its place. This removed the defect of the ribbon arch, that it does not gracefully adjust AoA everywhere along its span. This is the arch that has become popular at kite festivals: its so easy to make & flies quite well. There is nothing to stop such arches from being many kilometers wide.
A variation is to set several arches concentrically from common anchors into a "rainbow". Here we see a close approximation of what AWE SDO might look like if it is to truly tap the most power from a given volume. No monstrous single kite can compete in scalability. Combining Ohashi elements at the sides & Blattert elements along the top would be a superior hybrid arch. A common kite-rigging trick is to let every wing to swivel independantly on a continuous gang-line, so the wings do not twist the line or "bow-tie" fail. Blattert's diamond pattern can double-up into an Allison Sled plan, or multiply further toward a Veyres arch, subject to bow-tie failure. Multi-arched structure is well suited to host membrane wingmills or turbines underneath to harvest wind energy, or even to lift "architectural" payloads.
GeoFlow Energy Fan-In to Gigawatt-Scale Generators
Biological cells are size-limited & must aggregate to scale up; just so, kites have practical scaling limits & aggregate to scale. Lattices can naturally aggregate power input by fan-in to ground-based WorkCells at high density. Fan-in models include animal draft teams, tree structure, & so on. Diffuse wind energy requires a large harvesting area & concentration into powerful high-speed motion to drive the largest generators. Simple fan-in patterns of synchronzed pulsed lines can sum forces to any any scale. Unsyched pulses can be aggregated by multiple sprags on a shaft. High speed driven-loops can deliver aggregrated airborne & ocean power "the final mile" to drive the largest (gigawatt-scale) generators on the surface. Many existing generator plants might be cheaply retrofitted to accept airborne power, especially as a boosting force.
When many identical wing elements are tied together they phase lock into synchrony or metachrony as harmonic systems, as galloping meshes of kite elements self-excited or resonant with turbulence. Partial interfering or canceling as damping for power extraction. Flow-field/Membrane entrainment creates phase lines like sand ripples the waves in flags. A feature of large AWE FSTL operation is its atmospheric-wave compliance. The oscillation spectrum is wide-band- Array-scale, element scale, subelement scale.
A compelling possibility is that many kites set in vast aerial latticework of polymer line (megascale engineering) can display dynamics of Cellular Autonoma BZ reaction style self-oscillations, which can be tapped to drive generators on the ground. Such a 3D lattice acts as a true gel on a giant scale, with air as the pressurizing fluid, a nicely excitable highly scalable medium to transfer wind momentum to generators on the ground. Its phononic field-computing able to process wind-field chaos into synchronous grid power. Self-oscilliating kite elements called membrane wingmills have been recently developed that can be ganged into firing in synchronous sequences. Numerous small-scale experiments validate the potential of these ideas to scale greatly.
Progress in Aero-Synchrony is driven by a fairly mature applied chaotics science. Passive synchrony phase-modulate modulate many kites as one for powerful power cycles. A tree in a high wind is a damped model whereby each leaf's motion is mostly asynchronous, but by the fan-in of oscillating momentum the swaying trunk shows a bulk synchrony.
Year span of 2006-9 was a period of intense review & fresh research into converting chaotic mechanical motion into regulated motion. A classic toolkit of flywheels, pulleys, sprags/rachets, cranks, gearing, & so forth does the job. A KiteLab Ilwaco demo of a self-winding chronometer accepting chaotic input was a real-world instance.
Latticework that acts as network of mass-spring elements naturally enables synchrony, the phase-modulation of many kites as one, especially for powerful power cycles. The simplest method is to tie elements together so they are forced to act together. With kite wings, for lower darg & more lift, its desirable to allow each individual some freedom to comply with turbulence, much as a bird's feathers ruffle asynchchronously, then recover. synchtrony. SE Asian fireflies are a famous example of emergent synchronicity. At first the insects blink in random phases in a Gaussian (Bell Curve) distribution of frequencies, but gradually they begin to fire together in great flashes. As we get our kites to do that they can pull on a gang-lines together for powerful tensile pulses that may in turn drive massive generators in phase. Metakites might even end up flapping like great birds.
Electronics & musicology have the conceptual tools needed to design synchronous kite systems. The goal is phase-locked loop harmonics where every kite "fires" at the desired moment for an overall pattern. There are endless variations on this theme; paired "dancing kites", looping stacks, & so on, but the best configurations for power production are perhaps yet unimagined. A useful principle is that two kites crosslinked to each other phase-lock. The problem is that undamped matched kites resonate so strongly that they tend to chaotic divergence. A more stable system of two kites is for one to be the initiator/leader of the phase loop as the "timekeeper" & the other is a phase detector with some feedback of phase information. An example of such stable synchrony is a looping kite under a pilot kite: Observed closely it is seen that the pilot is Dutch-rolling in phase-lock with the looping wing. The harmonic is part unison & part octave, which promotes stability. In a stack of kites any individual kite may tend to tow the stack or be towed, just as networked generators & motors shoulder work. This mechanism absorbs turbulence acting on the kite stack.
Biomimetic studies find self oscillating aeroelastic elements oscillate best at the fundamental harmonic. Higher harmonic modes tend to be parasitic damping, but in a megascale array higher harmonic modes are working states. Jumping between internal modes tends to be awkward, like shifting gears. Large stacked-kite trains spontaneously exhibit strong synchronous motion, typically Dutch-rolls that move up & down the train according to wind & harmonic circumstance. If such a train begins to loop in rising winds it comes down, but not if the top of the train is somehow held up, say by a top train of non-looping kites. Train loops create spiral waves along them that can drive a crank or tri-tether
Spiral waves traveling along a tether is an interesting directed energy mode. The bimodel of flagella is spiral wave driven. Its lossey, mostly due to low Re. What is proposed is an aggressively looping train to create spiral waves. If the train has a looping middle, but a synchronously Dutch-rolling top pilot section, it is stable. This is how easy synchrony turned out to be- a looper & pilot pair are in naturally in octave synch. Kite trains naturally exhibit strong spiral waves along them. Tethers of enough mass can transmitt energy easily by looping one end jump-rope style, creating a spiral traveling wave to the other end that can turn a crank at fairly high efficiency. Combined mass & aeroforces along a kite train emerge spontaineously & optimized designs greatly enhance the effect. One can drive the train as well, pushing against its natural frequency much like an AC gen on a grid.
With wings all along a line driving the spiral waves, damping loss is exceeded by wind excitation. The driven cycling is steady & robust, as seen by the looping kite under a pilot set-ups, but also in festival trains a fresh breeze. Its nice to have use for unavoidable kite mass, which in the spiral wave case acts as flywheel mass. On the other hand, weakness & instability plague in low-mass slack lines. Tight lines with higher mass higher frequency winged lines seem quite powerful, with lift forces far greater than drag & internal friction loss. That's the test-based prediction for what a simulation should show. What is proposed is an aggressively looping train/stack to create spiral waves. If the train has a looping middle, but a synchronously dutch-rolling top pilot section, it is stable. This is how easy synchrony turned out to be- a looper & pilot pair are in naturally in octave synch.
Line drag is also somewhat mitigated by many kites along one line, just as kite trains reach higher altitudes at a higher flying angle than single kites. Every other scheme has transmission loss too.
A classic kite train dutch-rolls (transverse eight wave) more than loops (transverse spiral wave) in normal wind.
Single Kite & Looper- In dying wind, the AWECS naturally descends the surface wind gradient, its looper stops looping to hang stably under its pilot (2nd metastable state) & lands gently (3rd metastable), in seqence, & relaunches in reverse order.
Turbulence scales larger than the tensile aero-structure is not so disruptive as turbulence on a similar scale.
State transitions can misfire
locally, but in a consistent trend the whole train
soon synchronizes in a desired metastable state.
FSTL embodies solid-state physics at the edge of solidity: Gels. A kite-based 3D lattice is a gel porus to flow. The unit of flow volume thru a lattice is the Sverdrup.
The newest frontier in AWE thinking is vast kite-based lattices that exhibit powerful bulk harmonics to tap, sort of like turning the sky into wiggling Jello. A gigwatt scale AWE plant of this sort would fit into a volume roughly 1km x 1km x 1/2km high & sing a monstruous song.
Some branches of computational physics usefully describe active rigging. Soft Body Dynamics based on aeroelastic/mass-spring methods is a popular model. Tensioned string lattices trace calculable minimal energy geometries. What layered structural honeycomb geometries work best in a given application is an open study. The tetragonal disphenoid is the simplest space-filling lattice; a nice blend of diagonal shear-resistence & horizontal function planes. Other interesting structures are the bitruncated cubic & disphenoid tetrahedral honycombs. Hypercubic Structure is as natural to 3D network structure as it is to topological computer nets.
Gigawatt-Scale Kite Energy by Dense Arrays
An intuitive kite energy scaling strategy is to fly many kites in dense arrays. Numerous experiments  have revalidated classic kite methods like "stacks", "trains", & "arches"  for aggregation of airborne capacity with enhanced safety & reliability. "Airborne latticework" concepts emerging from this experience mitigate kite cubic-mass scaling penalty & low stream-tube efficiency of sparse kiteplane concepts. Dense arrays are a path toward maximal energy extraction from a given airspace volume, reduced surface sprawl, & integrated control. The experiments also showed that a "minimal-mass-aloft" approach facilitates tapping high-altitude wind, persistent flight in calm, & inherent flight stability. It was found that actuation & avionics can be kept on the ground to great advantage. Simple solutions were tested to many subproblems of gigawatt operation, like persistent kite flight by phased radial tugs or towing. Launching & landing challenges were routinized by self-cascaded sequences. Self-oscillating power harvesting wingmills & ultralight turbine modules operate nicely from ganglines & halyards without local flight controls. High L/D kiteplanes were shown resistant to mishap incorporated semi-captive into dense arrays. Depowering, killing, & hot-swapping of arrays & elements was shown practical. Even "far-out" ideas, like mass synchrony of aero-elements, were made to work by classical kite methods. Given dense array historical precedent & steady progress, no critical barrier prevents rapid scale-up of kite energy toward gigawatt scale, even the retrofitting existing generation plants as kite hybrids. Pioneering gigawatt scale operations are workable under existing aviation regulations . Early large scale control operations will likely consist of a supervised automation environment overseen by a Pilot-In-Control, Visual Observer, & Field Operations crew rotated in watches. Economy-of-scale in conventional electrical generation suggests that lowest AWE capital & OM cost may depend on arrays able to directly drive the largest conventional surface-based generators. Utility scale airborne wind energy production in 2025 will likely involve Super-Density Operations (SDO) governed under NextGen Airspace .
 Findings of KiteLab Group (KG), a circle of aerospace & kiting experts working on a creative-commons IP basis, with five years of scale-prototype AWE experiments (links below).
 Archival resources: Drachen Foundation & World Kite Museum. Many domain-experts directly helped KiteLab survey & master classic techniques of kite stacks, trains, & arches.
 FAA Flight Regs, incl. draft sUAS guidelines.
 FAA/NASA NextGen Airspace Plan, AWEIA Tethered Aviation ConOps Draft.
This kite trick can scale up as a "millipede array"-
Seven League Boots & Flying Carpet Hybrid
Kites span gaps, even initiating suspension bridges over gorges. A KiteLab nethod to cross obstacles like overhead wires, uses two lines. One line flies the kite as the other drifts beyond the obstacle, where it is retrieved. The first line releases & the kite moves onto the second line. The cycle repeats by alternating lines. By careful scouting & flight planning a kite makes cross country progress flexibly & reliably, even upwind.
The coolest version would be a kite centered human platform that flies out pseudopod lines to selected anchor points & thus walks across the land. This is a Seven League Boots & Flying Carpet hybrid device. One can print a Persian carpet pattern on the kite & ride on top.
Dynamic Assembly of Large-Scale Airborne Structure
Skydivers can pour out of airplanes individually & under canopy link together into vast geometric arays resembling a common kite, hold a controlled glide, then unlink for separate landings. Future flight automation should be capable of comparable operations. The modern parachute, paraglider, & power kite are fundamentally the same parafoil invention. Perhaps the best way to make a vast AWECS is to fly many individual aircraft into linked formations like the complex kite arches the forum recently considered. In routine calm or storm the many pieces would unlink to land on a small field. Malfunctioning units will be hot-swappable. An array of this sort could even reconfigure continuously for conditions, including load demand. Dynamic assembly in free-space allows vast structures not otherwise practical. Diverse pieces made anywhere in the world might even fly together into a composite system & fly apart to specific maintenance locations. Ships & trains might serve a mobile bases for airborne dynamic assembly.
NextGen Airspace is a major upgrade of the US Air Traffic Control system lead by NASA & the FAA, due to be fully operational in 2025. The R&D has been seriously underway for about five years. A core concept of NextGen is Super-Density Operations (SDO), the ability to crowd the most operations into an airport to meet peak air-traffic demands. NextGen & AWE share many common sub-issues such as trajectory planning & wake turbulence. A spin-off SDO application will be AWE dense-arrays that take-off, link, separate, & land in large numbers. AWE R&D can piggy-back on the NextGen bandwagon.
Why wait for 2025 to dynamically assemble AWECS in mid-air? There are already many easy methods to "build in the sky".
Those who fly branched trains are familiar with the routine of launching a single pilot kite & subsequently building out a towering train by clipping on kites & lines as it rises. Cody used a method of stopper rings & cones whereby kites were added at the bottom of the line & rose to take specified places. KiteLab Ilwaco, in numerous experiments. showed that docking & undocking kites aloft is easy with just simple tow-hooks. Hot-swapping kites & lines while maintaining flight was also shown easy. One can use a pulley aloft to support a halyard to hot-swap any element. A halyard "loop" allows itself to be switched at will. Useful tricks include stopper knots, pin-releases, & tension-switching. Those who sew kite arches could even fly an arch from the sewing machine as it grows...
"There is a limiting condition when (AWE) elements are a significant distance from the base unit and sweep a large scope. This...tends towards a power restriction based only on the isolated performance of the aerodynamic unit as the retardation of the mean free stream flow through the swept ring tends to zero. This arises from the exceptionally low disc solidity and mean disc loading associated with this operational configuration. " Howe & Macnaghten's AWE Feasability Study
"An arch is a collection of kites linked on a common line (that) minimizes space needs and maximizes chances of a successful fly." David Gomberg, Giant Kite Showman
In AWE, non-latticed single tether systems make very sparse u se of land & airspace, requiring a wide circular scope to avoid interference. A kite farm made up of such units demands an expensive sprawling network of distributed infrastructure. FSTL methods organize large numbers of elements over a wide area. FSTL is the practical alternative to loose aggregations (swarms, flocks) with high individual losses & interference.
Power elements operate nicely semi-captive, in close proximity, without interfering. Super-Density Operations (SDO) is a NextGen Airspace concept descriptive of dense peak operations around hub airports, but also well applies to any extreme density of aircraft such as formation flying, "flocking UAVs", & AWE Dense Arrays. Utility-scale Airborne Wind Energy SDO is desirable on economic & operational grounds. Early array concepts presumed rows of single units flown from individual anchor points, but such geometries can only sparsely tap a wind-field; low frontal area solidity & high tether-scope consumes inordinate amounts of land & airspace. Crosslinked airpborne structure by extended classic kiting methods enables dense packing of elements without collisions. These string structures include arches, meshes, trains, & 3D lattices. Dense configurations maximize footprint & airspace. Safety & reliability is enhanced while easing control. Super density & high solidity are relative terms. Airborne latticework is tenuous structure in in capacious airpace. Latticed arrays will be like "coral reefs in the sky", dense islands of activity. Systems will be mixed captive-array & free-flight elements. Small free-flight platforms might serve as tenders & karger aircraft as tugs or serviced units. One might, for example, fast-charge an electric-transport aloft from a captive-array.
Dense-Array techniques have been developed & tested over years of experiments on the Pacific NW Coast by KiteLab Ilwaco. Solutions emerged to remediate previously problematic AWE concepts. The linked video shows an arch of tailless deltas flying robustly in turbulent wind over the Ilwaco cove. They soon enough crash flown singly in these conditions, but have yet to fail as a group. Current experiments fly mini AWECS off halyards hung between the kites. Airspace Infill Factor is very high.
Super-density lattices have many secondary advantages, like far greater inherent visibility than sparse configurations.
Tall ships are a dense line thickets controlling a megawatt or so of arrayed sail power. Fish trolling & trawling culture long ago developed effective arrays.
Manageable gigawatt arrays can consist of Lifter-Kite cells of about 1000sq m & densely spaced multi-megawatt Membrane WingMills 200m long.
Lattice Launching & Landing
String rewards mastery. Its a marvel to see how a spider begins a web in free-space & by a definite sequence assembles a complex structure. A century ago Sam Cody devised a clever system of graduated rings & cones on kitelines as programmable stops & passes for sequenced launching of his manlifters. Layered Latticework can self-launch & settle down by stages in lulls, by common kite methods. Launch can be a cascade event across the array beginning from a single launched element. Initiation of a launch can be by high-speed winching against a pilot aerostat, circling tow-pane, or ballistic pilot lifter.
Kill sequences can generally proceed by furling from bottom to top, then the furled train is pulled down. Cody's graduated cones & rings system was used to build a train. A system of kite-killers should allow the reversal of the build sequence.
A KiteField AirSpace is cylindrical volume of Restricted AirSpace. Kite mesh is a lenticular volume inside the cylindrical no-fly zone, the empty "rim" is a natural flight separation safety factor. 2000 ft is an initial default AWE airspace ceiling above most surface inversion & ground boundary-layer turbulence. KiteMesh scales are a good fit. KiteField cells of 2km across well proportioned for a 2000 ft ceiling. Ten such cells across a Class 4 wind resource is a gigawatt class installation.
More lines better capture tethered foils & tame them, while too few make for an unstable system. Tangle & snag are manageable; avoid designed-in inversions (true knots), maintain tension (false knots, "bird's nests" & "line showers"), & fair away all snags in the operational environment)
A kite-arch is a simple way to to stretch a lot of kite across the sky. Generally kite-arches set crosswind, but can be run in any direction with kites that self-orient on leaders. Vast arrays can thus be rigged as a "rose" of arches radiating from a central aggregation station to a circle of passive pulley-anchor points. The geometry resembles an skewed umbrella skeleton.
Weathercocking Array or Subelements
An entire array can veer with the wind by means such as a circular track or belayable anchor circle. A kite-arch rose is easily automated from a center point. It can be trimmed to prevailing wind by simple adjustment of the arches without resort to belaying, vehicles, or tracks. It helps for upwind anchors to let out some line as downwind anchors take in some, ideally as crosslinked partially buried pulley loops. Arches upwind of the center point are best flown lower; downwind arches best flown higher, maximally infilling projected airspace with minimal shadowing or gaps. An added aerostat, kite, or
kitetrain can even be flown from the center point, at a higher angle clear of the arches, & provide pilot lifter function.
Latticed-arrays need not rotate with wind-veer if the semi-captive lifter, drogue, & powerwing elements are locally free to weathervane. Non-rotating latticework can translate a controlled distance in any direction, with rotating ground workcells following the motion. The whole mesh can be snugged upwind to keep in vertical register.
Horizontal & vertical set-lines are easiest to design kite lift elements for, to accept any wind-direction. Along a wide string arch many lines kites can fly on a short leaders from a tri-swivel. Another type is kites designed to be strung on a train thru their centers. Power harvesting is nicely done by membrane wing-mills arrays hung vertically or leaned slightly upwind for a bit of lift.
Aerial Architecture & Vehicle Platforms
A point-to-point "zip-line" tether is a rail for winged shuttles to traverse cheaply & reliably; precise aerial navigation without high-tech. Fishing longlines are set out to 100km, similarly, one can envision flying tow-lines cross-country hauling trains of cargo gliders. A triangle route can harvest its power from any wind direction along favored legs & transfer drive power to unfavored legs.
The more we look at AWE-driven winch-towing of gliders the more it seems like a potential foundation for extensive fueless aviation. It works at all scales, from model to jumbo aviation.
Fast tow a L/D30 gliderliner to 10,000m & it will glide some 300km a hop. Repeating the tow XC (bounding mode) can go any distance. Aircraft could even be slingshot into the upper stratosphere for very fast ballistic XC travel. A simple mechanism is bow-string geometry where a short powerful fairly slow longitudinal tug on the "bowstring" creates high speed transverse travel. I have studied Wayne's hypersonic kite concept for feasibility & find that a tungsten cable could resist even orbital re-entry heat, although some sort of ceramic anti oxidation coating would be needed for long life. Nano tubes will be even better for extreme performance towing.
A future-tow key is a little airplane at the end of the tow rope to fly the tow rope for docking & back during retracts, sort of like the winged mid-air refueling pods. All sorts of variations would work; a major hub airport might have a continuous tow rope to launch transports at a high rate. Folks have already towed many gliders in gangs; the record is like nine at once & could be far higher. E-train-based ground towing is attractive.
There are two main options in applying the AWE. We could power electric winch-towing as a separated utility, or direct power the winching with kites. E-flight aerotow would also have a place, but be fairly limited by the battery requirement.
Spanning Atmospheric Waves with Tethered Foils is possible by long horizontal trains of dual-mode (towed/towing) AWE kiteplane gliders. Cross-country transport was one application identified. Virtues & methods of vertical lines were recently explored & in a similar spirit one sees unique properties of horizontal tensile structure & motion. Horizontal is the general direction of both wind & human transportation, but is orthogonal to gravity. A tether run axial to apparent wind develops minimal drag of any tether orientation, & run crosswind, maximal drag.
An interesting possibility with horizontal glider trains is maintaining flight across wind "deserts", areas of calm that would otherwise force grounding. The basic idea is to transfer energy from windy to calm zones as needed by kite-elevated long-lines. Dale Kramer tells us that a high performance glider can be towed with just 25 kilos of tug (at about 120kmh). This is a baseline model for long polymer train tethers with high L/D gliders spaced every few kilometers. The toy kite train that reached the stratosphere gives us a rough proportion for tether to kiteplane. Presume the toy kite model to be about 1/20th scale, so full sized gliders flying about 4km will be spaced about 8km apart to carry the tether well off the ground. These are crude estimates & hopefully the ignored dimensions mostly cancel.
Wind blows by combined mechanisms in a complex spectrum of wavelengths. The waves are everywhere & the challenge for AWE systems is to persist thru common lulls between wind wave peaks, without constant forced motoring or landing & relaunching. The lightest kites are clearly favored. The biggest wavelengths are planetary waves & the lulls between peaks are typically thousands of kilometers across & commonly take several days to pass overhead or even park for a season as persistent High Pressure zones.
It might be possible to span moving planetary calm zones with horizontal long-lines of towed tethered-foils. A hundred gliders spaced at 8km would span 800km, with a towing force requirement of 2500 kilos, plus tether drag; which we can guess will approximate or well exceed 50% of total drag before scale-limiting. The largest continental summer Highs are a tough challenge for AWE & are generally better suited for solar-power. Another post will consider migrating "clouds" of tethered foils, as enabled by horizontal trains to follow wandering Jet Streams, while hop-scotching across fixed groundgen fields.
Rossby Wave spacing determines how redundant a persistent wide-area airborne net needs to be. Imagine an airspace 2000km across, On average, at any given moment about 60% of the space is windy enough for generation from cut-in to rated-power; another 20% is break-even lift, & the last 20% is calm requiring back-driving to loiter aloft.
The kite is an engineering basis for a new civilization. Persistent tensile infrastructure of wind & wing anchored with string has protean potential. Land, air, & water spanned with essential services like bountiful green energy, transport, housing, & communications. On a global scale, such submarine to airborne architecture is a planetary "TetherSphere". Maybe we get live in a New Olympus over a restored Earth.
Earth is easily bound in string, end-to-end, from deepest abyss to highest zenith, in as yet unimagined uses; great caution is needed to avoid bad use, like long-line fishing or tethered "perpetual" predator-drones. Recall H. G. Wells epitath, "...damn you all, I told you so," should you be tempted by "the merchants of death". Beyond refined energy, Lift is seen as a elemental commodity that based on fueled aviation is far too expensive. Vast tonnages can be raised aloft & delivered by wind energy, entire infrastructure flown into disaster-zones, even bulk water delivered to drought-stricken watersheds. We can live aloft like gods with these methods, in cooler purer air, in the brightness.
Notes Toward Further
Life imitating art (monkey-in-a-mirror)
The material basis for these schemes is the now common super-fiber-
My bloated conference abstract (accepted) paints the picture leading up to the FlubberSphere concept-
A breakaway school of robotics, Morphological Computing, has progressed to conferences in Venice. My lost years in field-computing with rags & string honed methods such as using a naturally excited traveling wave in a pennant flag to regulate the metachronal firing of powerful membrane wing-mills, all hung from kites. Wind fields are canonical chaos, so the rag-flaps effectively process chaos into useful work, like commodity energy production. There are endless mechanisms to find using a growing list of logic functions.The kite is a pure morphologic flying robot & its just a start.
We have seen chaos science go overnight from rain-forest butterflies & Peter Max BZ reactions to spooky Oobleck (after Dr. Seuss) Dynamics. Consider that a basis for a future Standing-Wave Engineering is seen in these "Cornstarch Monsters" growing out of wounded Faraday-Wave Fields. UltraLowDensity atmospheric Flubber is not the only comedic polymer in the Airborne Latticework recipe, but Oobleck, a Suess (Clarke-Magic) morph of rain, is essential. Seuss warned darkly about misuse, starting in kindergarten-
Dr. Suess discovered Oobleck while stationed in Belgium, presaging the famous Belgium School of Chaos Theory & an Austin connection, but first remember how Carrol posed modern Nonsense Theory in a passing note, judged by critics, "philosophical gibberish" (duh, or it would have been inconsistent), but it was Norm Steenrod (funny name?) who properly formulated Nonsense science within Category Theory. The great Belgium Chaotician, Prigogene, mostly made nonsense, no one in Texas could understand him which accelerated progress in Chaos. It was Oilbleck $ what bought Ilya for UTexas in order to found the Center for NonLinear Dynamics, out of which Cornstarch Monsters duly emerged (Borges also was drawn to Austin & "Many Worlds" Everett too). Meanwhile, Dr. Seuss dreamed atop a tower on a hill in La Jolla, California, & gazed off on Mexico ("most surreal country", Breton) across a fictive border, & wrote. Dr. Seuss is classed as a Mexican Writer of the Magic Realist School, a regular shaman.
Anyway, Mori's robotic "uncanny valley" traces back to Jentsch & Freud's classic analysis of the uncanny. Early chaos theorists right away found transitions between metastable states evoked uncannyness, Twilight Zones, "the sleep of reason", productive of (Cornstarch) Monsters even, Goethe's homonculus, true golem, a glimpse at an Aleph into a future tech of standing-wave engineering (Oobleck Physics). Artaud, the greatest surrealist of all, clearly saw the same tortured humanoid orgies in rock formations in the Tarahumaran Wilderness, just west of where Ambrose Bierce dissappeared & a bit father west where the Beats visited Burroughs on his South Texas farm. My grandfather ended up with part of Burrough's land when Billy had enough of the place, but back on topic, this whole spooky phenom of faraday waves tearing & quasi humanoid monsters emerging from prolonged oscillon also recall the Russian sci-fi classic where the astronauts go mad staring at chaos. In the rock formations we see a reversed flow of energy & information as an eon of erosive weather worked on the figures.
A beautiful example of Kite Chaos-
Paul Nylander modeled this elastic disc vibrating in its 31st Mode. A aerial lattice excited by wind can vibrate just like this, its static nodes on a string scaffold would connect to the surface & to lifter kites to hold it in place & the active nodes could be tapped in alternating phases. Imagine the disc as being the middle slice of a sandwich structure of a kitefield a few kilometers across & maybe a kilometer thick. Wing-mills would be natural transducers to tap the wind & drive the mesh structure. Properly cross-linked, they naturally entrain & fire in phase.
Ever eager to learn from any kitemaster, i helped Terry to beat his own record (39 fighters on one line, WSIKF09). The principle shown is aggregate stability of massed chaotic elements. The KiteLab demo is less gnarly, a stable arch of crazy toy deltas-
Phononic Alfven Wave Tranmission of Atmospheric Momentum to Surface Generators
Alfen Wave is a borrowing into Phononics of spiral wave energy transmission as seen in solar flare plasma. So we are now talking of inertio-acoustical spiral waves, such as Will Rodgers used to twirl his lariat, as a projected energy beam, in the reverse direction the rope is a phonon tractor beam. My looping wings under kites work by this principle.
Can CAPOW do wandering sets? That seems to the tool to model weirdness on top of grandmother's CA.
Faraday Waveguides, Oscillons in string media, Cymatic Zoo, Phonon Holes,
Travelling waves self propagate along a shear field, like the moving billows of a flag in wind, a basis for downwind sequencing of really powerful Metacronal Waves, wonderfully simple & practical. Large scale metacronal waves are called Mexican Waves; Carambas! Synchronous waves are easy, just crosslink anti-nodes.
Airborne string lattices are properly defined as gels, jiggly aerogels on a grand scale, continuous 3D structure nourished by flow thru its tissue, a Turing Pattern Reactor, a "breatharian" creature. Phasma- is a sci-fi ghost medium or, technically phonized gas or plasma. Early Ectoplasm was slobbery mess of gauze mesh, but these "mediums" had conjured something much like Oobleck. Like, Orgone is Sizzle, not Steak. Slime, the new smart material...