Hacker News new | past | comments | ask | show | jobs | submit login
Makani source code released (github.com)
449 points by johmathe 11 days ago | hide | past | favorite | 123 comments

From https://x.company/projects/makani/:

> In 2020 Makani’s journey as a company came to an end [0]. To share the lessons and insights the Makani team gained from their 13 year journey developing an entirely new kind of wind energy technology, the team created The Energy Kite Collection, a portfolio of resources including a technical report, Makani’s entire avionics, flight controls and simulation code repositories [1], flight logs [2] for every crosswind flight of the M600 prototype, technical videos [3], a new simulation tool called KiteFAST [4] created with the National Renewable Energy Laboratory, and a non-assertion pledge [5] for the free use of Makani’s worldwide patent portfolio.

I just wanna say that this -- all of it, the entire paragraph! -- is absolutely amazing (well, except for the end of the company, of course).


[0]: https://blog.x.company/a-long-and-windy-road-f8e09d02c9e1

[1]: https://github.com/google/makani

[2]: https://console.cloud.google.com/marketplace/product/bigquer...

[3]: https://www.youtube.com/playlist?list=PL7og_3Jqea4VRCZmMNK4L...

[4]: https://github.com/rafmudaf/openfast/tree/kitefast

[5]: https://storage.googleapis.com/x-prod.appspot.com/files/Maka...

IEEE Spectrum did a story on us a few days ago that you might want to check out too:


X is what Google used to be.

X is still X and Google is still Google.

Outside of X, Google was never known for crazy moonshots. Google was always an ad platform with a search engine.

X was Google X, now it's Alphabet X. Google was Google, now it's Alphabet Google.

Google was the name of the search engine and the company. Now the company name has changed, everything is restructured and Google is an ad platform with a search engine.

"X Development LLC. is an American semi-secret research and development facility and organization founded by Google in January 2010, which now operates as a subsidiary of Alphabet Inc. X has its headquarters about a mile and a half from Alphabet's corporate headquarters, the Googleplex, in Mountain View, California."[0]

[0]: https://en.wikipedia.org/wiki/X_(company)

"X is what Google used to be." didn't strike me as a comment about the paperwork of corporate restructuring, but rather a comment on how Google isn't doing interesting things anymore. And I don't think anything changed in that regard. They just pulled non-core businesses such as X into Alphabet Inc. That doesn't mean that what X is doing used to be more important to Google than it is to Alphabet now, it's just paperwork.

> Google isn't doing interesting things anymore.

I think they've founded X because Google's interesting ideas got too big for a single department, so they spun it off.

We don't know how many smaller X inventions get into Google ecosystem. I'm sure that some of that research got integrated back into their data centers or networking hardware, etc.

That's the name of the legal entity. The actual name, if memory serves, is "X, the moonshot factory".

Gmail seemed kind of crazy at the time.

The only crazy part when it launched was the growing storage space aspect, which only seemed crazy because all the other mail providers were so ridiculously stingy. Email as a fantastic data gathering and ad platform made sense from day one.

I don't think they risked anything significant to build gmail. Nor was there any significant risk of gmail not succeeding due to hard technical problems. Compared to X projects like autonomous cars or power kites the original gmail was nothing crazy at all. Was it good software? Yes. Crazy? Hell no.

There's also (quite surprisingly!) a feature-length film that talks about Makani's work over the last 13 years: https://www.youtube.com/watch?v=qd_hEja6bzE

Beautiful documentary, thanks for sharing.

Amazing stuff. Just made my Saturday night.

Very enjoyable documentary, thanks!

Incredible document about a fascinating workplace!

All of their assets were liquidated in their Alameda location. I bought some power tools from the auction went to pick it up and saw this really long wing span in a hangar. I asked the people with the liquidators what it was and they told me it was used for power. Then I remembered reading about this company in Wired many years ago and felt it would be something cool. Well I own some power tools they used to use so that’s as close to having their history with me.

I heard that one of our wings (SN1) will be incorporated into a playground somewhere on the Big Island of Hawaii (where someone bought it at auction). It would be fun to hear what comes of our other stuff.

How do you find out about these auctions, generally speaking?

There's websites for disposition of company assets when they go under. The Makani auction was advertised on the Silicon Valley Disposition website [0] for a while.

[0] https://svdisposition.com/

This site is fascinating, thanks!

I guess this means that this project is dead or not viable for some reason, and they're being nice and releasing their work. Good job Google!

As an aside, it should be law to release any firmware, code, and backend services code for any device that is no longer fully supported by the manufacturer.

Let other people play with your dead things and reduce the barrier for new innovation on top of them.

Google stopped funding Makani several months back.

I'm not sure how applicable most of this code will be for other kite power companies. The Makani "kite" turbine was 2000 lbs. It definitely required Google-level funding to develop which is now gone. None of the remaining kite power companies that I'm aware of have the kind of significant funding required to develop this - ours ran out of money late last year.

> The Makani "kite" turbine was 2000 lbs.

Essentially the same code could run Makani's smaller machine, the 20 kilowatt "Wing 7", with a 7.8 meter wingspan and a mass of 60 kg. Many of the existing kite power companies are working on machines of this scale.

But we did have the luxury to design and build the system from the ground up, whereas scrappier startups might have to cobble together existing components. Hopefully they will be able to utilize some of the materials we've just released.

So what's to stop me cobbling together something like the Wing 7 and just leaving it unattended in a field to launch and generate whenever the wind conditions are suitable?

If I did, and I got typical government subsidies for wind power, I might earn $10k/year. That ought to pay for all the machines parts if I buy everything hobby grade from AliExpress. The 2nd year is pure profit assuming the craft lasts that long.

So that leads me to suspect the key issue is the various control algorithms can't be made reliable enough to run for years and years without crashing under any combination of gusts and wind conditions. Am I along the right lines of the issues?

The issue is the tumbling cost of regular wind turbines, even offshore. If you have such a field, you would build a turbine, not a kite.

So yes, you could make a profit. But there is an alternative source of technology that makes the same power and has become really profitable in the last 10 years.

The FAA (or your local alternative) might want to check your paperwork and licensing too.

While it stays tethered to the ground, I don't believe the FAA would be interested? Am I mistaken?

Makani engaged early with FAA and we had a great working relationship. This enabled us to move out of China Lake (where we were using the military's restricted airspace, which didn't require FAA approval) and out into the public airspace in Hawaii. We did several test flights in close collaboration with FAA observers, developing a color scheme for the tether and a lighting system for the kite and ground station that were deemed adequately conspicuous. We also held a round-table with local pilots to get their input. Ultimately we operated under a "determination of no hazard" that classified the Makani system as an obstruction, something like a large radio tower.

Our COO gave a talk on the FAA approval process at the Airborne Wind Energy Conference (AWEC) a few years ago: https://repository.tudelft.nl/islandora/object/uuid:ea8256a2...

A tethered unmanned aircraft is still considered an aircraft by the FAA and subject to FAA regulations:


It depends on how high it gets, because even high buildings/structures can be problematic. (They need a blinky light of course, but maybe more importantly a radar reflector.)

I think the main obstacle is these things often contain licensed code the company does not have permission to open source.

That's right; or the IP gets sold to someone and never sees the light of day. Think of BeOS (sold to Palm Inc) etc.

Neat! If I'm reading the repository right, it looks like the avionics firmware ran on a TMS570 Cortex-R microcontroller made by TI:


I'm pleasantly surprised to see that instead of a big Cortex-A or x86/64 chip. It's cool to read well-funded code for a small realtime SoC.

you don't see them too often outside of things like memory controllers and safety-critical products, but Cortex-R chips can have some cool features like ECC memories and mirrored CPUs:


Apparently the next generation Cortex-R82s will also have 64-bit options with an MMU, which should make it easy to run a "real" OS.

Too bad that the company didn't work out, but it was nice of them to publish this stuff.

Not entirely true. The actual autopilot (the controller + estimator) runs on an imx6. The tms570 are the sensor / actuator nodes.

Edit: just to add some detail. The autopilot and aio (avionics io, i.e. the tmd570s) communicate over a ring ethernet topology.

Oh, that makes sense. It did seem like a lot for such a small processor to handle.

Still, that sounds even cooler; a reference for how to set up a local network of MCUs controlled by a big processor? Awesome.

This topology is very common. Hard real-time sensor nodes feeding softer real-time big iron that does the estimation and control.

The TMS570 has a decent amount of computing power on it for a microcontroller. The CPU core itself seems pretty solid. Unfortunately, the peripheral set is incredibly painful to develop for because it's riddled with poorly thought out registers and silicon bugs.

For low volume stuff, the chance of a detectable miscalculation occuring in the field is low, while the chance of a firmware bug causing a failure is high. Using a TMS570 for a hobby project would be a very poor choice. With a sufficiently high volume project, though, the development pain can be worth it.

The redundant cross checked CPU cores gives you piece of mind that the thing will self-diagnose a miscalculation and report it, rather than go off into the weeds. It enables you to responsibly design safety critical fault tolerant systems based on explicit handoff from one MCU to another. Without the cross checking, you can't trust a single MCU to act rationally; in designs like that, you typically need more than two MCUs with majority voting circuitry. So the TMS570 can help reduce total system complexity at the cost of lower level firmware pain.

Former Makanite, and current abc employee here. Happy to answer questions.

What sort of control methodologies were you using for the autopilot? Classic linear negative feedback or more modern techniques? How much of the autopilot problem was novel? Could you use existing designs from other aircraft or do these tend to be kept secret?

The top-level autopilot used a nonlinear path controller, which produced position, attitude, and rate commands for an inner-loop controller that used linear feedback and gains computed using LQR and a linearized model of the system.

Because the maneuver the kite must fly is very dynamic (always turning, but not at constant rates), control with feedback alone would lead to pretty sloppy flight, since feedback requires an error to develop before the system can respond to it. Good feed-forward was crucial to flying well; from the desired flight path, wind speed/direction, and desired aerodynamic quantities (airspeed, angle of attack, and angle of sideslip), we could compute the required rates and feed-forward actuator displacements needed to execute the trajectory.

For more details, check out my paper titled "The Makani Autopilot: A Critical Retrospective", available here: https://storage.googleapis.com/x-prod.appspot.com/files/Maka...

How did you feel about the project being shut down? Did you feel like you still had work to be done or was there a feeling that this just isn't going to work?

The usual disclaimer: these views are my own, and do not represent Makani, abc, etc.

I was terribly disappointed the project was shutdown. The engineering problems were unique and challenging. And the team was absolutely world class.

I felt like we could do it. And I wish we were still at it. But that's purely from the technical side. I wasn't involved in things like budget, and whether it would be economically viable.

I never knew about this project. It would have been my dream job.

It was a dream job! Not sure what to do next.

What are some of the surprising/unforseen aspects of working on this hard tech problem?

why wasn't the turbine hung off an airship?

This is actually a good question as it addresses the common misconception that the purpose of the kite was just to hold the propeller blades high up in the sky. In fact, having the kite fly like an airplane is a crucial part of the principle of operation. The documenary film (https://makanifilm.com/) might help make this clear.

There are airborne wind turbine concepts that use an aerostat (blimp/balloon). However, these suffer from at least two effects: (1) the largest practical turbine aperture is quite limited, and (2) the drag of the turbine will push the whole balloon/turbine contraption downwind and downward.

Where did everyone go? I wanna work with people who do stuff like this.

Some people stayed in Alphabet, either working at Google, X, or one of the bets. Other people left Alphabet and went to work somewhere else. Some are still searching for jobs (covid made the job search somewhat difficult)

I ran the code and took some screenshots of the really nice web UI. Simple and inspiring since I've been working on a robot web UI recently. Here's some screenshots of the Makani interface: https://imgur.com/gallery/NMjBJSY

Awesome! You might be the first outside of Makani to run the code. :-) I'm glad you were able to get it up and running. Please let us know if you have any questions or run into any trouble.

Hah cool! Yeah I was hoping the simulator was a 3D sim environment I could use with my off road robot, but it was actually still really helpful even though it wasn’t that. I have been making a robot web UI and all your graphs and debug data give me ideas on more data I want to pipe up to the UI, and some improvements I can make to allow automatic UI elements from certain data structures. :)

Here’s one of my robots: https://reboot.love/t/new-cameras-on-rover/

That rover is super cool - good work!

We were just beginning to experiment with computer vision to augment/replace GPS at the time we were shut down.

Thank you! You can certainly get a lot done with RTK, but computer vision is a big fun technical whale.

That’s awesome! What OS did you use to run it? Did you do native installation or use docker?

Ubuntu 18.04 host but I ran it from docker.

It's cool that they open sourced this, but as someone who worked at a kite power company (a much smaller company with a much smaller kite) I'm not sure much here will be transferable to other companies. Makani was making a huge 2000 lb "kite" turbine. That requires the kind of money that Google could back them with - and since Google isn't funding this anymore I just don't see where this can go as none of the remaining kite power companies have much funding (ours ran out of money late last year).

While our code might be too specialized to help out other crosswind kite power companies in particular, I think the technical document might be quite impactful:


The chapter "Airborne Wind Turbine Performance" contains some sobering lessons for the field and deserves a close read.

Thank you so much for that document it's so interesting. Interesting lesson from the exec summary: The real world kite underperformed the model by nearly half, and from the numericals it seems like the main reasons we're that the turning radius was about double that what you were trying to get, and that the tether drag was a significant loss that was not accounted for. The next gen model would be the same span but with a larger area and with a shorter tether, the turning radius would be a lot smaller and it would effectively halve the drag and increase performance by 30% but it would still underperform the initial model by about 20%.

The general big conclusion as I get it is that because of these losses even though the kites are capable of getting more wind per kite, when area is constrained a conventional turbine seems to have better density.

The idea that the kites have lower installation cost offshore does seem interesting to me, but I only skimmed it so maybe that's offset by something else.

The Airborne Wind Energy section is general, and discusses energy kite performance in a broad way - the tether drag was well predicted and wasn't a surprise for our prototype.

The inability to turn the necessary tight paths and some degraded aero performance are responsible for most of the performance miss. Also hugely concerning was the struggle to saturate power at high winds.

It is important to separate and highlight tether drag in the context of the purported big benefit of airborne wind turbines accessing higher, faster winds. While they do indeed access higher winds, they do so via tether length and elevation angle, both of which carry losses. The net effect in almost all scenarios isn't a win.

> ...tether drag was a significant loss that was not accounted for...

I wonder if some of the losses to tether drag could be made up for by re-purposing some of the wave energy tech to capture energy from the base of the tether as the kite pulls and slackens on the base, or if the tether could be made rigid on demand with some tech in the future.

There isn't a large amount of energy stored in the tether catenary or elasticity. Any hardware to recoup it probably wouldn't pay for itself.

Offshore, there can be a lot of energy stored in buoy motion, and utilizing this can help, but probably in a resonant way that doesn't require additional hardware.

"Rigid" is a relative term. The tether already utilized a carbon fiber core. It doesn't get much stiffer, short of going to exotic fibers or more of them, both of which degrade performance in other ways.

The optimum is going to be closer to a strength limited tether than an overly stiff one.

I don't think the goal here is to help other kite power companies. If google thought there was still something there they'd still be funding the project in all likelihood. But who knows what this might teach someone trying to move into a related space? Also it's just freaking cool that this stuff is available.

It was very much a blue-sky project. A very highly ambitious one. Other kite power companies are generally taking much more affordable routes by necessity.

Does code released have to have commercial applicability to other organizations to be relevant?

It seems like a post-mortem code dump.

We hope that others find the code useful. There are a lot of goodies in there. A full-fledged flight simulator that could be used to simulate a variety of physical systems. A Kalman-filter-based state estimator. Math libraries. Firmware to run high performance electric motors. We also understand that it's typically very hard to adapt and re-use other people's code, especially when it's no longer actively supported.

Aside from the "code dump" portion, we have published 400 pages of entirely new documentation describing the system, plus about an equal amount of technical document artifacts.

Hopefully someone can use it and realize the kite power dream someday. Right now funding in this space is tough especially, it seems, after Google stopped funding Makani. We used to be able to say "Look, Google is funding this kind of thing" - it lent a certain legitimacy, but now potential funders seem to be nervous about Google dropping the funding.

Totally agree! And for what it's worth, sorry it didn't work out.

My reply above was to the parent who seemed to think it wasn't all that useful. I looked through the code and found a lot of goodies in there. :)

If nothing else, looking at how you've approached problems can help inspire solutions related problems.

That's not totally true. While there are certainly custom control laws and gains, almost everything is parameterized in terms of the kite's configuration.

Edit: to clarify, I was responding to: "I'm not sure much here will be transferable to other companies"

Dude, that's totally true. Just for one example: I.MX, TMS570, and ethernet of all things are all very expensive and extravagant solutions for the application. Those decisions are only supportable if you can hide the cost behind the price tag of a system the size of Makani (preferably much larger). Almost anyone else would be looking at Cortex-M and CAN bus and be quite satisfied with those selections.

The use of those processors and ethernet were not major cost drivers.

There's a very nice technical document describing the network topology titled "A Low-Cost Fiber Optic Avionics Network for Energy Kites" in the collection of technical documents:


At this scale, no of course not. But at 100 kW or 10 kW? Remember that the argument is about applicability to other kite energy systems. Margins get very thin when power electronics costs only 0.03 USD/watt for the entire system. It gets harder to hide signal processing costs as the size of the system decreases.

System scale is a crucial component of a cost competitive energy system. I lay out the argument for this in the early part of my section - Airborne Wind Turbine Performance - of the released documentation.

A 100 kW system may prove useful to some niche, but I don't think can be competitive with the utility energy market at large, even if you give away the system for free.

At the larger scales, these electronics are not meaningful cost drivers at all.

That's true - and it was always tempting to reach for another expensive sensor when we knew that ultimately we would have to simplify and rely on simpler/cheaper components.

Opening it up makes it available to people who might look at it and get an idea. Sometimes the thing has to be available before someone figures out what to do with it.

Oh sure, I completely understand that. The point I was trying to make was that all of this flight control & simulation software is very specific to the characteristics of their particular kite. I'm not aware of anyone else in the industry making a kite that large and heavy - most of these companies are operating on a shoestring budget. Sure, it's possible that maybe some general ideas could be obtained from their autonomous control software - but they would need to be heavily adapted to a different kite with different flight characteristics.

We were starting to think about using reinforcement learning to develop an autonomous controller for our kite. That would have involved recording lots of real-world in-flight data for our particular kite which we were starting to do. Similar flight data for a different kite wouldn't have done us much good when it came to training as each kite has very different flight characteristics.

We don't mention this at all in the technical report, but there was a lot of interest in applying reinforcement learning to the control problem, and there was some work done in this direction. (I was one of several who groaned whenever we were admonished to "just use machine learning." )

Ultimately we couldn't afford to dedicate much effort to the rather speculative RL approach (our team was small and we were always scrambling to meet our rather ambitious milestones - you know, the usual story :-) ). Instead we chose to continue to pursue tried-and-true controls techniques.

Blog post from February when Alphabet withdrew funding: https://blog.x.company/a-long-and-windy-road-f8e09d02c9e1

(Disclosure: I work for Google)

To be accurate, partner Shell choose not to re-up its investment after exactly one year, from 2019 Feb 12 to 2020 Feb 18 as indicated in the blog post you linked (actually https://link.medium.com/KBxNNZGcK9 since your link didn’t work for me). It seems unfair to blame Alphabet solely, or even Larry, as one comment below did.


Like half of all people on this site are at FAANG+MS so it's not a flex but some people always flip out when you're at one of the big ones and you don't say so when linking to company media.

Maybe not? But I've seen people here get mad at other employees for not disclosing, so I do it to be on the safe side.

I’ve never seen anyone from my company disclose, which has way more engineers.

...only because other folks implicitly look down on me

Why this failed? I would love to learn more if anyone has more insider knowledge

I highly recommend watching the documentary they produced, https://t.co/y70yeZ3ZjY?amp=1 . My takeaway is that it took 14 years to produce a working kite and in that time conventional wind turbines became much more economical and efficient. After realizing this, they pivoted to doing off-shore wind generation because the cost for competitor products was higher. They had one somewhat successful test but were out of money and couldn't find any other investors.

This was my take away as well.

What was somewhat surprising to me though was that, for all their technical ability, nobody at Makani foresaw the future of conventional wind turbine efficiency?

It just kinda seems like all of a sudden (in the documentary), they lifted their heads up, and 10 years had passed and conventional wind energy was dramatically improved. Case closed, that's it.

> Why this failed?

Well, I think the main TLDR is that it would require significant additional investment to reach MVP. Also- the energy sector lacks the huge margins of the tech sector. Renewables have long been subject to a boom-bust cycle driven by the prevailing price of energy.

Our released technical report "The Energy Kite" is intended to help answer this question, and to explain what we would do if we had the opportunity to continue our work. Check it out here: https://storage.googleapis.com/x-prod.appspot.com/files/Maka...

One major learning is that it ultimately appeared to us that crosswind kite power currently offers little benefit over traditional horizontal axis wind turbines for onshore applications, except perhaps niche applications such as small-scale generation allowing rapid deployment. There may still be a viable opportunity for large-scale crosswind kite power in the deepwater offshore environment. In that environment, conventional wind requires huge floating platforms to deal with the overturning moment arising from the turbine drag acting at the top of the tower. In crosswind kite power, only a small buoy is required to support the tether tension.

Finally, the M600 failed to meet its performance specification (the "power curve" which shows how power generation scales with wind speed). The reasons for this are detailed in the technical report (starting on page 231 of the above link). (We designed a follow-on system called MX2 which we believe would meet its performance objectives but the project was cancelled before it was built.)

Clean small scale rapid deployment power generation sounds like such a good thing for emerging countries! :sob-emoji:

But then again, so does solar. It's tough to compete when there are existing options.

Full respect to everything you and your team built!

There are several companies working on this application. One that I know if is called WindLift: https://windlift.com/ based in North Carolina.

Not an insider but isn't it obvious? Too expensive and it can only crash once. Regular wind turbines are probably cheaper and failsafe. Should have pivoted but it is a make it work at all costs kind of vanity project. Once you go big pivoting is not an option. Investors don't want to hear that. They just want a delivery date.

I was on one of these multi-billion boondoggle projects. Basically people keep it going even though it is not viable. Telltale sign is the project is spun off or 'cut loose' to die.

The product can be totally amazing though and parts of it could be a viable company on its own. Maybe these projects should be structured in a way that each component is a business entity.

The tether replaces one set of problems with a different set of problems. Some of the new problems had promising solutions, but others were more marginal.

1) Land use. The small props are loud, and the setbacks relative to populated areas are pretty high for tether and crash safety. Solution: offshore. Now you have two problems :)

2) The tether's weight is a factor. Its hard to build in much margin on this component before it gets too heavy to fly. What happens if a gust temporarily reduces tension on the tether? Can it handle a shock load from the kite hits the end again if it comes off its sphere? How many conductors can you run down the tether? IIRC, they were running DC+ and DC-... with no ground. Now, what exactly happens during lightning strike? At the time they believed that they were just barely on the "feasible" side for this component on a feasible-infeasible axis, but it was pretty darned close.

3) The power system was complex. Tether weight biases you strongly towards a medium voltage power system (a few kV pole-to-pole) to cut down on the weight of the conductors. However, the size of the turbine was smaller than any medium voltage application I had ever heard of. Maybe the ground side could be COTS, but the flight side almost certainly couldn't. So now you are also in the business of building bespoke medium-voltage switching power converters and motor/generators. There's nothing fundamentally infeasable about this, its just a bunch of hard work that detracts somewhat from the main mission. A startup would much rather buy this tech, but they were forced to build it instead.

I mention the power system explicitly because that's particularly in my bailiwick, but I think it was really a microcosm of the project as a whole. They were building an airplane for the purpose of energy production. So they had to solve all of the problems that an airplane company has to solve. Also, since electricity is so cheap, you can't afford to pay human operators for all of the generators, so you also must solve many of the problems that an autonomous airplane company has to solve. In salty air to boot.

Overall, there's just a staggering amount of NRE that must be spent chasing a market that is already commoditized. 50 USD/MW-hr is a typical benchmark for wholesale electricity. Meanwhile, solar panels are iterating and getting cheaper and traditional wind turbines are iterating and getting cheaper. Eventually, the bean-counters start to notice.

There's an alternative explanation: Makani (and Wing, and Titan, and the robotics initiative, and other things) were initiated when Larry was still young and excited about the technology itself. We used to morbidly joke that Ruth Porat (hired CFO) was going around the company asking questions like, "Airplanes, Larry? Really?" (taps clipboard, raises eyebrow). Eventually the long years of almost-but-not-quite-success wore them down past the point of endurance, and the projects started dying off when the leadership got bored of them.

IMO, both explanations are likely to be true.

Having worked in the industry a bit, yes, likely both are true. There are very complex engineering problems to solve and Makani was taking one of the more complicated approaches to the problem. Some other kite power companies (including the one I worked at) have the generator on the ground and use an ascending figure 8 pattern of flight to pull the tether thus generating power (at the top of the cycle the kite goes into a sort of controlled stall to lose altitude, the tether is rewound and the cycle continues) - that approach certainly has issues as well.

I often think that maybe most of us were taking a much more complicated approach than is actually needed. Perhaps (thinking out loud) something much simpler like a soft kite with a sort of trap-door which closes as it ascends and opens to let it fall to a lower altitude would be a much simpler approach - essentially a bag kite with an end that can be opened and closed - obviously it would be smaller scale, but most of the kite power companies are working at a much smaller scale than Makani was.

The tether was indeed medium voltage, but the motors and controllers were not, through use of a fairly novel stacked architecture.

There were still hard problems to solve there, but ultimately the power system worked well, and out performed it's original design targets. It was not responsible for the projects demise.

From what I hear the robotics initiative is still going. I left in early 2019 and the project has its challenges (robotics is hard), but from what I could tell they still had support of leadership.

For everyone saying "land wind turbines were cheaper".

Ok, but doesn't mekani have the advantage of being out of sight? Many people find wind farms unsightly.

Incredibly ambitious project. I watched the whole documentary.

I'm surprised they were 'unable to secure additional funding'.

Considering how many crackpot app-of-the-month companies have gotten cash thrown at them over the last decade, you would think a company doing real engineering would be drowning in money. It's a bummer to hear that they folded.

Speculation abounds, I suppose, as to why investors started (or kept) saying "no."

When investors look to invest, they want a fast ROI. Engineering company likes this typically takes many years to fruition or maybe not. It's much easier to justify dumping money on these "tech" companies like WeWork, AirBnb hoping to get another facebook unicorn than putting money into real engineering company like Makani.

Personally I find that troubling for the progress of humanity. We need big money (resources) to solve real challenging engineering problems.

Unfortunately it seems like a lot of the big money is going towards less critical 'problems' if problems at all, like social media companies.

Any chance on board schematics, or even just some basic block diagram of the avionics hardware? It's hard to understand this firmware without having any idea what it ran on.

Ask away and I'll tell you what I can. :-)

You'll find some description here (but no schematics): https://storage.googleapis.com/x-prod.appspot.com/files/Maka...

the system overview slides in... part II?

pretty sure there is a top level avionics layout in there.

What happened to the Makani refugees at G?

Many found new positions in Alphabet/X, and others found new positions at outside companies. Yet others still are either taking a break or still looking.

And you?

I had the privilege of being part of the documentation team preparing some of the materials that were released yesterday (in particular: the code and the chapter on the autopilot/control system). Now I'm taking a little break but I hope to start something new around January. Definitely open to ideas. :-)

Some of the code for the tools is fun to read https://github.com/google/makani/blob/c421e4497dd09c86b01725...

This is not proper Java, at all. But it's what a lot of Java code looks like because it's a good choice for inexperienced devs or rushed projects.

The commenting here is actually pretty dope. I really enjoy the small notes saying _why_ the code exists:

    // because all low speed wind tunnel cases are overset and all high speed are 
    // fixed with a remesh, we only rotate in the presence of overset domains.
This is something that personally I strive to do but isn't always repeated in my team. It's important as 6 months later you struggle to remember the nuance that lead to your code being written.

Whoever this is seems to have experience with this, so I definitely wouldn't say this is an inexperienced dev.

According to GitHub this project is less than 3% Java. It's mostly C++, C, and Python

That's right; the real-time autopilot is written in C, and the flight simulator is written in C++. We have a really slick configuration system written in Python that compiles down to a Python dict and then a C struct at build time.

Example production C code (the crosswind flight controller): https://github.com/google/makani/tree/master/control/crosswi...

Example production C++ code (the "wing" model in the simulator): https://github.com/google/makani/blob/master/sim/models/rigi...

Other than it being a 2400 line file, what's wrong with the Java code?

I wonder if this could be repurposed to kite sail large cargo ships.

That was indeed an application investigated by Makani! I think some companies are still pursuing this.

I wonder why it didn’t go anywhere. But maybe a difficult industry to interrupt. Google or an org with that kind of money should buy an cargo ship and just make it happen.

What was the back of the envelope calculation that suggested this would work?

To be clear: crosswind kite power does work. The question is whether it is economical or competitive.

The paper that started it all is this one by Miles Loyd from 1980. It's short enough it could fit on the back of a large envelope. :-)


In the film they explain that since wind turbines extract power based on the area they sweep, their kite would be able to sweep a bigger area more easily. (No need for so much material, no need for a 150m tall tower, etc.)


I am waiting for them to release the google earth source.

Self Flying Energy Kite Self Flying Energy Drone

Interesting stuff.

Larry cancelled Makani meanwhile he lands his helicopter on his yacht?

Applications are open for YC Winter 2021

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact