Isotropic kite

Lounge
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Dave Santos posted this file on Yahoo forum some years ago: isotropic
an expected advantage can be avoiding rotating to face the wind direction, acting on the bridle.

Last days I experimented this ugly round parachute as a kite. But a parachute without holes is perhaps not as stable as a parasail with slots for what I saw, or the altitude was too low to avoid turbulence. A kite lifter like Peter Lynn’s single skin pilot-kite would perhaps be better than a parachute if it is quite round in order to face any wind directions without rotating, but losing also some stability (?). For this I prefer avoid implementing tails or cones.
This parachute was realized using XF-film. The wind speed was 6 to 12 m/s.
Photos and a video:

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parachute en vol paysage.JPG3264×2448 1.84 MB

parachute%202%20m%20en%20vol
parachute 2 m en vol.JPG3264×2448 1.82 MB
parachute%20en%20vol%20complet
parachute en vol complet.JPG3264×2448 1.87 MB
https://forum.awesystems.info/uploads/default/original/1X/d25422ddf38d00058eb39170993b061d36af3f9b.mp4

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I am not quite sure of it. Parasails contain drive and turn slots for lift and steering left and right. For my use slots could be useless, excepted for some variants.

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I’d like to add to this topic that there are other methods by which to make an isotropic kite
(Kite which takes wind from any direction)
a single line kite already does, but it’s land use is huge on it’s own, and the chance of it colliding in urbulence is high. But by being stayed by with wide topnet network formation, as in the video below, you have stability, seperation and isotropic behavior from single line kites…

You see the simulated effect of a changing wind field in this video.

Other isotropic network forms were also proposed

Still more exist where a tensile ring (or fractal ring array) is flown or tethered such that a kite (or kite net) can be flown with a rotary anchoring set, held on the tensile ring forms… The rotary anchoring set e.g. turns with the kite and wind

Kites with a wide spread rotary anchors could be set and added to the inside the ring forms of a


Or the triangle patches themselves could maybe be set as lift surfaces.
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The video I put on my initial post shows a chaotic motion due to the turbulence close to the ground, but without major crash, with the possibility to take-off after a minor crash. Lines can act on the kite deformation in order to steer it. As it scales up, this single kite should keep its unity. The question of the unity of the network remains as to the possibility of a control with different winds on the same sector.

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Some videos of istropic kites are linked.

Santos’ isotropic kite below:


Lee Sedgwick and his UFO below:

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Video of the oscillating parachute.

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Nice to see such a simple arrangement tested
Thanks Pierre

I guess there will be ways to extract the pulses of energy available at the anchoring
I shouldn’t think the output will be stable nor powerful or easy to coordinate

I saw this arrangement today


It reminded me of this post even though your anchors are fixed location here.
This simple linear relationship between intersections from moving points may have an interesting application
Yet again though I doubt it will be powerful
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Thanks @Rodread.

My video is not quite new but I rather envisaged yo-yo use. Here another use is evoked as an oscillating parachute (in Dave Santos’ style) could act at each anchor on its respective generator via its respective winch or hydraulic accumulator, and by short strokes. Returns are made by springs according to the parachute moves. The generators will not work quite at the same time because the parachute does not pull all of them simultaneously. I think such a system could scale without requiring any automated control, but rather by stochastic playing on numerous anchors regulating chaos.

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I doubt also, because the motion of the kite is limited. The kite moves little and only based on random turbulence near the ground. Another (not too good) possibility is to use an unstable kite like my parachute. So there can be no substantial wind energy collected.

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I dont see the huge benefit as most kites will align nose into wind inherently. The only benefit otherwise is having a «divergent» bridle, meaning that the bridle is fastened to a larger ground area rather than a single point.

A huge disadvantage is that most airfoils have a front and aft and they are not symmetric. So by doing this, you are getting less lift per wing area.

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The main claimed advantages of isotropic kite networks are dense, safe and stable deployment in all conditions. Shared load line efficiency. And a further claim is the advantage of combining the work output of multiple kites on a large single generator. Sounds worthwhile investigating.

The forms of kite network which enable Isotropic action are varied.
The kites (Often referred to as kixels (kite-pixels)) on the network are either
set aspect e.g. tied to the network and unable to rotate relative to the network
or
themselves isotropic. e.g. the kixels either mount via a standard single bridle point on a thrust bearing able to rotate with respect to the net
OR
the kixels are able to rotate within a cell (a net hole) within the network. For this the kixels have their ends mobile tethered to net holes via a clamping pulley trolley set.

For many Isotropic network forms (especially where the net is not tight over a valley or the kixels are fixed) all of the bridling would actively have to be altered to reshape the whole net surface as a lifting body.

You can see videos of basic designs of these types in the post above

For a really brave use of isotropic kite network
How about travelling on a kite bridge?

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A more or less isotropic form can be approximated on the basis on steerable triangular and cruciform rescue parachutes which are the advantage to have a very high drag coefficient, increasing the power during reel-out phase, while the lift coefficient is correct enough to assure an elevation angle of about 30-35 degrees.

Triangular shape:

Cruciform shape:

Multi-anchored steerable triangle and square rescue parachute-based AWES
Multi-anchored steerable triangle and square rescue parachute-based AWES1004×959 232 KB

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In addition to the initial shape of Isotropic kite, Dave Santos previously developed triangularly anchored concepts.
This concept was investigated on: Assessment of an Alternative Concept for a High-Altitude Wind-Power Generator (authors: Max Langbein, Maja Ruby, Nicolas Gauger), * DOI: 10.1088/1742-6596/1037/4/042023, * License CC BY 3.0.

These are essentially concepts of crosswind kite acting pulleys, while the concept I present is a drag-based kite working in pumping mode.

I thank Dave Santos for opening up the concepts of multi-anchors and isotropic shapes.

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I am not following you here. I think the reason though is you need to provide a consise description to what you are talking about rather than links to Santos’ confused sketches. It is not clear what part is of importance

I think also the naming you are using is a bit confusing. A drag based kite is a kite producing most downwind force and only a little lift? The possibility for confusion is huge. maybe «A kite with a very low L/D ratio [or glide ratio]». Also I prefer «bounding» to Yoyo, but then I am not completely sure what you are talking about yet

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My two last comments here are perfectly clear.
To understand them, however, you must read my latest comments on A (train of) parasail(s) as AWES ? and High drag coefficient : the link on X-triangle (which is not quite a Rogallo) is also here, and also on an previous comment by @AweEnthusiast ; and the link on Charly rescue system is on my preprint which is linked on this comment.

It is easy to understand that I was talking about high drag coefficients. On parasails and the latest developments from steerable Rogallo and square rescue parachutes, I have mentioned the existence of lift which allows them to be extrapolated as kites, and provided links to calculations on my preprints already connected, and which show that drag predominates, which is not a scoop.

So I wrote “drag-based kites” because that is what they are.
And drag-based kites are named regardless of the downwind movement of the swept area in yo-yo mode. This has all been discussed several times. “Bounding” term is not used in accredited environments: the terms yo-yo, pumping mode, reeling, reel-in/out are already used. One more term only adds to the confusion.

See also the Book of Abstracts (AWEC2024), page 37:

In the parachute based AWES, the shape of the parachute and the distance
between neighboring parachutes are key factors affecting the flow field, the aerodynamic drag force, and hence the efficiency in harvesting wind energy.

But the current topic is about Isotropic kite. I thought of configurations already discussed or linked in the comments cited above, because allowing steering leading to adapt to various wind directions, without having to move the anchoring, is one of the sought-after characteristics of Isotropic kites.

My previous comment noted the differences between our two respective concepts, Dave Santos and me. Do you also need a definition of crosswind kite?

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It seems clear that you are not looking for my involvement here, pointing out how clear this all is even in between a quite convoluted explanation of what you are thinking about that is still not clear to me. But maybe we both are content with this… My door is ajar if you want my involvement, just explain what you are thinking of.

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It becomes true, especially since it would take more than 2 minutes to read all I wrote, quote, and linked about high Cd, steerable rescues as kites with high Cd, and a possible application for Isotopic kite. I repeat again Dave Santos used a multi-anchored crosswind kite, while here I investigate about a multi-anchored drag-based kite in pumping mode.

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So let me kick off with my first query about your proposed system; It seems you are thinking about using a kite with multiple tethers to travel mostly downwind and upwards, then I guess depower for the return by making some lines slack. I am thinking Zhonglu style but with multiple tethers (though I also think they must have at least two tethers to implement power and depower).

The difference between this and Zhonglu seems to be every tether could carry the main load?

The good thing about such a design would be achieving high altitudes without worrying about tether drag. But I think it is probably infeasible (or at least very hard) to control a multi line kite on very long tethers.

Also the notion of having multiple tethers on such a design carries some issues with it; you need to scale each tether for the maximum load it should hold, but in normal operation, some tethers will be unloaded or less loaded. So they will contribute to drag, but more importantly, because of your low glide number kite, they will fall on the ground if they are long enough.

I dont see much potential in this avenue of ideas unfortunately. Foregoing crosswind flight if foregoing more pull per kite area and an option of controlling the pull by controlling the speed of the kite.

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First of all, I think we need to separate the concept of multi-anchoring from the concept of a very high drag coefficient and a high lift coefficient due to the very high angle of attack, and coming from steerable rescue parachutes and some parasails, for an elevation angle of 30-35 degrees, which is that of an AWES crosswind kite.

Note that even with a low elevation angle, the kite is closer to vertical, which still allows it to access high altitude winds if it is gigantic.

There is a considerable advantage of a Cd greater than 2 and almost 3 for the devices I’ve investigated, notably the reserve parachutes (based on the sink rate and the load), and a thrust coefficient Ct of over 3, which multiplies the power in yo-yo mode by around 3, while the AWES remains tether-aligned, keeping its corridor, unlike a crosswind kite which would have a power/kite area of around 3 times more: don’t forget the losses due to power variations (above all in figure-eight) as the kite moves away from the zone of near-maximum power while consuming a large space area to fly correctly. I calculated that with an elevation angle of 50 degrees or a little more, the Ct of a Rogallo rescue as a kite would be about two times less, becoming almost close to that of the Zhonglu device, although with an autonomous lift instead of the lift by a lifter kite or a balloon at the top.

The depower would be controlled by a central tether, akin to the third line in kitesurfing.

The two concepts can operate independently. Why multi-anchoring? The idea is to move the anchors further apart in order to preform a kite of very large dimensions and to facilitate its take-off and landing, and whose tethers will be relatively short.

From what I have seen, steerable parachutes can be steered (and therefore extrapolated into kites) using the brakes installed on two opposite sides.

As I indicated, if you want to benefit from winds from more or less all directions, you should implement a brake on each side (3 for a triangle, 4 for a cruciform), then choose two brakes according to the current wind direction. Depower is ensured via a central station controlling the central depower tether.

Of course it can be interesting if gigantic dimensions of the kite can be achieved. Otherwise, it is better to stay on a single line and still benefit from the high coefficients.

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