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Makani had huge amounts of capital from Google to work with. As you point out there are other much smaller players in the field who keep the generator on the ground and generate power from the upward pull of the tether. I worked at one of these startups. But after Google canceled Makani it became very difficult to find funding because angel investors figured that if Google got out of the game it must not be viable. And so we folded.

> - On the edge, possibly near to commercialization: https://www.ampyxpower.com

A CGI video does not convince me that they're near to commercialization.

The ampyxpower website claims they translate tether tension into rotational energy to drive the generator, but how does that work?

The tether is rolled up on a drum, whose axis is connected to a generator.

You are right, I used the wrong wording:

"possibly near to commercialization"->"they have something flying"

Many others should be mentioned, i.e. https://www.kitemill.com/

Making flying things lightweight is a means to an end, not the goal or a hard requirement. Makani experimented with a wide variety of solutions before settling on their final model. The initial work on soft kites had serious durability issues, IIRC. What they ended up with looks a lot like a very lightweight airplane, for good reason.

[Former Makani software engineer, here. I wasn't involved in the early stuff, or the design trades, but I heard a lot about it.]

I'm realizing my phrasing was too critical. I think it's a very good thing that Makani explored that "design path" and shared the knowledge acquired with that level of details. I would also say that rigid wing has more potential for AWE, but I am pessimist toward 'fly-gen'/'energy-kite' solutions, because when dealing with a gas as bearing medium reducing weight seems a reasonable and trending rule of thumb. It's difficult/too-vague to compare designs with substantially different ramifications, some of which are still hypothetical, but it's maybe worth if it leads to a better understanding or general awareness.

I am curious, do you know why Makani went 100% 'fly-gen'? From by biased point of view I would say that it was easier to bootstrap (more control agency, easier take off and landing) but harder to scale.

I tried to skim through the 1k+ pages 3 part report available from Makani (https://x.company/projects/makani/), but it doesn't seem to speak much about the considerations which when into that early design choice. Do you know more?

Is it possible to summarize them or it's an organic set of reasons which cannot be untangled nor simplified like often happen when dealing with complex systems?

[Mechanical Engineer here]

Because Makani was by far the best funded startup in this space and they got very far. Very easy to understand why I'd say.

As to fly-gen, it has several benefits, like continuous power delivery and not least an easy way to launch and land - you already have the propellers.

The main downsides are complexity, weight, and the weight and girth of the tether needed to transfer the power. The drag from the tether is significant. Plus the sound of the blades.

What's the reason for the emphasis on weight? From reading the technical reports (from Makani), there were larger issues with the design unrelated to the weight.

As an example, Makani's Y-bridle design to attach the tether to the kite introduce stability issues during hover, and limited their control when the kite was aloft making circles, which in turn limited their power generation.

> What's the reason for the emphasis on weight? .... As an example, Makani's Y-bridle design to attach the tether to the kite introduce stability issues

It's quite possible that if their kiteplane was much lighter that these tether issues would have been much less of a problem. Remember that the Makani tether also had to include some copper cable for power transmission to the ground. That makes the tether itself heavy as well.

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