No, the chance of all lines breaking is far smaller than depending on one line, Go ahead and provide any evidence of all-lines failure. I have never seen it. What kite expert has? What cases are recorded?
Kite-killing works great with multilines. The kite goes nowhere. A runaway M600 can go a long way. Good luck convincing FAA reviewers. I was able to get them to take Makani risk seriously. No kite killers, or multilines, or low density low velocity advantages for them.
Below is a kite-killer:
That’s just a drone.
Pierre, Compare kite accidents with rigid aircraft accidents, to distinguish relative hazards better.
Luke, To the FAA, its not a “drone” even in runaway mode. Its a fast massive UAS, highly regulated as such.
Statistics is better by taking account of the traffic.
Well, being an idiot in charge of a soft kite is very dangerous. I beheaded an anemometer last night with my, now very old, single line lifter.
As for the M600, what were the stats on how fast it was going and the height of the bottom of the loop… Scary… But there is a little braking available.
Yes, giant soft kites are dangerous. Let the power-to-hazard performance of soft power kites vs rigid kites be tested carefully.
Agreed, there won’t be much “braking available” in an M600 control-loss crash.
Let me add a thought to the discussion which seems to be focused around «soft» vs «rigid» kites. What if it turns out that both are feasible? Perhaps even one will not displace the other, but both have their place (togeter or in separate rigs) in a future AWE?
Both rigid and soft wing AWES are feasible, but with stark choices of capital cost, crashworthiness, scalability, and so on. Rigid wing should work fairly well at ~3m WS, for those who want that sort of fast platform for some specific reason, and soft wing already has reached ship-kite scale. There is also a niche for rigid looper under soft lifter, but soft looper under soft lifter is competitive.
Turning distance is emerging as a critical design factor.
It would be great if even only one is viable.
Both are already proven viable in real-world cases, and it is great.
Rigid wing transport aircraft save ~5% fuel burn by AWE tailwind seeking and headwind avoidance. Kite sports already prove power kites viable in that domain. When I charge cell-phones with KiteSat, the viability is not in question; it works, a child can do it.
It will just get better. We are nowhere near a limit on viability.
To be more specific: What if both soft and rigid wings were both viable as parts, either separate or together, for competitive power production for a normal grid.
The analysis got as far as proving that the rigid part still sets a lower scaling limit. So a ~3m rigid wing under a soft lifter is about as good as it gets, if cost, safety and performance of scaling to utility-scale is accounted for.
There is always Wubbo’s Principle, that we choose whatever AWE we want. Carrying on his thought, that means many oddball designs in low numbers, and a few optimal designs in large numbers. That’s “the best of all possible worlds”.
kPower’s power-kite bias is clear, but the company will pivot if the power-kite stops working for us. Hoping KiteMill pivots the other way, if facts warrant.
Having noted the famous “kitegod” inventors of modern power kites, that’s not the actual statistical evidence of Power Kite dominance in AWE. In the small AWE R&D world, claims of a “trend” toward rigid wings and E-VTOL as “Energy Drones” are fading; a mere drop-in-the-bucket compared to explosive Power Kite sports progress. Given kite sports count as Darwinian AWE R&D, the mega-trend is vastly in favor of the Power Kite.
Energy Drone efforts are not flourishing. No one shares their power-curves proving scaling barriers, nor crash statistics, nor realistic costs, and so on. Despite venture PR for Energy Drones, only the Power Kite is able to progress on its own, in or out of AWE R&D. Its the only TRL9 COTS technology. The same low complexity dynamic holds in flight control. Only human piloting is practical, with some mix of inherent stabilities, and simple PIC-supervised auto-pilotage and alarms.
Its a very disruptive situation for the high-complexity venture players with little to show. As the Power Kite is simply harnessed like a draft animal to drive generators, almost anyone with kite skills will be able to get into the AWE game and win. For all its quirks, the “rag and string” Power Kite is closest to perfection as de Saint-Exupery defined it-
“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away”
Thanks to Joe Faust for finding this great historical documentary about the birth and early triumph of KiteSurfing.
The pioneers express almost unlimited expectation of future power kite glory-
AWE notes- DonM, as seen in the video, only a year or so later was putting together Makani for LarryP.
Over a decade later, kite sports have continued their rapid evolution. Foilboards with non-LEI (parafoil) race-foils have popped up big; not suspected in 2005.
Hardham should have figured more as KS pioneer, apparently not available to production, but there he is in the visual record of the early Hood River Era. The week before his tragic death at his Makani desk, he had jumped over a large Great White Shark.
The power kite vs energy drone AWE race is just as dramatic a kite story, and we are in in it.
Regarding how many AWE developers may not see kitesurfing as AWE proper, its necessary to recall how MIT-Boeing aerospace engineer, Billy Roeseler, and his son, Corey, first invented the sport on the Lower Columbia River. Billy had produced a landmark AWE proposal internally at Boeing, that did not get developed, so he turned instead to inventing kitesurfing. A true genius.
The connection between kite sports and AWE R&D is inherent and essential.
Not Necessarily. Quite possibly only so far as what you think. Like so many of your blanket declarations, subject to being totally inaccurate. Blanket statements are one thing. Showing anything working is another. I also, like the people you refer to above, was inventing AWE systems in the 1970’s, years before drawing a kite pulling a ship as my first AutoCAD drawing in the 1980’s, before kite-surfing. As you point out, AWE was being explored before kite surfing, not the other way around. AWE would seem to be more puzzling for the average person than kite-surfing, which was more easily achievable.
I believe it is possible that the above statement will turn out not to be true.
An analysis from Dave Santos below:
Furthermore, power-to-mass of a soft kite design is sensitive to scale, not just subject to non-dimensional geometric (spatial) topology linearly.
Higher L/D parafoil or LEI is only favored over a narrow range bounded by minimum fabric thickness at the lower end (~1m2) and square-cube law at the upper end (200m2 parafoil, 30m2 LEI). Single-Skin (SS) scales best at smallest (<1m2) and largest scale (>500m2).
Insofar as an AWES kite seeks to be “a truck, not a sportscar”, lower L/D can deliver higher power-to-mass by higher area at lower velocity. kPower first worked all this out around 2012.
An interesting theorem is that highest theoretic power comes from 100% polymer kept at working load. This is surprisingly constant across a kite quiver consisting of various designs tuned to their ideal scale. Thus an SS kite can dominate in lowest wind or greatest scale, and a parafoil race kite dominate in a central wind range.
How odd that AWE developers depend on LEI kites intended to float on water, but heavier, less aerodyamic, and prone to deflation elsewhere. Valved parafoils now work well on water and dominate in elite kite racing.
Dave Culp figured out that a simplified NASA Power Wing rules for AWE, by cost and power-to-mass, as proven in Polar Exploration. An Iso-radial SS kite properly rigged is almost as good and an aniso-polarized NPW of similar scale, but scales even further as a unit (~1000m2) and beyond in isoradial networks. See MSE (Mass Scaling Exponent) flight physics.
It depends it depends it depends.
What is actually this analysis saying that anyone who did some initial thinking about the subject did not identify?
How about how to produce a useful single skin kite? How about Skysails already made huge foils? How about Kitepower using LEI is of course less scalable than a single skin, but look at details maybe they may scale far enough for a LEI to make sense before said scaling limit occurs?
I am a bit harsh but we have heard all of this now numerous times. It gives the impression of deep understanding when in reality its just some thoughts thrown together. If we want to proceed in AWE we can’t base it on generic statements like this.
Let me be more specific: The way the kite looks depends on which plant you want to use it in. If you are building “The Pyramid”, a truck will not work. The design thrives with high lift-to-drag kites. If you are building something to work on a really long tether, you already have so much tether drag that using a truck can make sense both to limit the tether speed through the air and because an efficient wing will anyway not fly fast with that tether attached to it.
There is no one size fits all, thus the above analysis is false