Failure is an option


It's raining robots-

That will be the headline all of us will cringe at, when the Media goes manic over the first commercial drone crashes of any significance. The same way they do anytime something new takes a stumble (or two).

The thought of my craft hitting somebody really haunts my mind. I'm sorry to be a downer, this topic is definitely a buzz-kill from the heady intoxication of being in the midst of the next great economic boom, but I can't let it go.

So the topic is failure. Despite what your high school sports coach told you, failure is not just an option, it's a guarantee. Yes- our thrust makers, power systems, flight controls, and firmware will get better quickly. However, even if we could magically achieve 100% reliability with all of our flight critical components, failure will still be there. The most random shit is always going to happen.


 The project-

I'm focusing on multicopters in particular with this project, but I feel that a similar strategy would be effective with fixed wing craft as well, in fact it's used all the time.

The specific type of failure scenario I want to tackle here is a total loss of thrust and/or control. Deployable parachutes are being developed, and seem to be working well. I would like to pursue a more passive system, an aerodynamic design built into the airframe itself. Inspired by watching Marcy fly around and wingsuit pilots, I hope to achieve a passive "auto-rotation" or glide of the entire airframe. If the the craft looses thrust, the actual act of falling makes the conversion into an alternate flight mode. A slow spiraling glide to the ground, with a gear down orientation maintained. Energy absorbing landing gear, maybe even a supplemental air bag would compliment the design. The key in my opinion is making the recovery mode completely non-dependent on any system other than gravity and wind resistance. Time is so critical in a recovery scheme for these types of failures at the altitude multis usually work. No sensors, servos, or firmware required, just a thoughtful arm and frame design. The challenge will be to prevent undesired flight characteristics while in normal powered flight, in fast controlled descents we don't want to be induced into a flat spin! Can the free fall decent rate be slowed enough to usefully lower the risk of damage on the ground and airframe itself?

Step one- Get to the sewing machine and build a Bat suit for one of my quads


To be continued.


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  • Hehe... Joshua, now you've piqued my interest again... I'm assuming by your analogy to Ukemi that you'll deploy the landing gear at just the right moment to apply a good, controlled strike against the ground...

    I'm very curious as to how you'll stop an essentially semi-rigid (presumably hinged) body from recoiling from this strike... human bodies are wonderfully good at absorbing and redirecting energy (back into the ground)... the  key to Ukemi.

  • Sounds very interesting Joshua. Make sure to update us! :)

  • Just to jump ahead a bit. The landing gear I've been working on is based on Judo Ukemi techniques. The breakfall. That's right I'm teaching my bot martial arts. Sorry Isaac : /

  • Phil,  Ballute! That's the word I have been looking for, thanks! 

    Jesper,  First step would be to just get a reliable gear down descent that maintains a relatively constrained path, the slower the better. The helical path would minimize wind drift keeping it close, and also give someone underneath a chance to see a pattern in it's descent so they could get out of the way, hopefully. Protecting the craft itself would be a second level, but still important, priority.

    I'm almost done with the deployment scheme mock-up.This nylon is very slippery, very hard to sew neatly, it wants to wad up into a ball in an instant : (

  • Does this "system" have to bring the craft down nice and neat? What if the criteria simply was to slow the decent and making sure that what ever part of the craft that could sustain the most energy at impact was facing downwards(the landing gear i suppose)? 

  • I suspect a ballute like drag device would inflate faster than a parachute could deploy, would not need spring stored energy (in itself pretty nasty) to launch/unfurl the parachute, would be more reliable in it's deployment, more tolerable to poor packing than a parachute and do just as good a job as a parachute.  Ballutes and parachutes have better packaging potential than any other device.  Deployment based on separate Z direction accelerometer only board run by a rechargeable cell - with solar panel charge/condition.  Accelerometer detects 9.81m/s vertical and triggers the cylinder (or it could be a gas generating reaction).

  • Just a 7 second video. 

  • After pondering since last night, I sat down with some heavy paper and a sharp knife. I have enough of the concept figured out to make the first test platform.

    It's always a hard time trying to explain the image in the mind, it seems to take several tries before it is articulated clearly. So let me try one more time, with pictures now also.

    I'm not trying to auto-rotate the props. This has nothing to do with the props.

    (That's Italics, Underlined, and a touch of Bold)

    Two things need to happen- first is a sustained yaw in a gear down orientation, then, while maintaining the yaw, a helical glide path is initiated.

    Anyone who has thrown a piece of plywood or roof shingles off of a building has seen this. Paper pinwheels, falling leaves, these are the things I'm talking about.

    3692586829?profile=originalShapes like this are interesting because the can morph.

    3692586976?profile=original3692586913?profile=originalThis little guy flies nicely from the height of my outstretched arm to the floor, I'll post a video of it next.

    Of course this particular shape is not the final product (it needs to fold flat in a different way). It's just a sketch.

    I was able to find my stash of rip-stop nylon leftover from my fathers kite making days.

    3692587003?profile=originalA mock-up for the airfoil deployment scheme begins in the morning.

    Thanks for all the feedback and opinions.

    I love this place, you're all just a bunch of hopeless nerds!

    Here is some math type stuff

  • Dwgsparky: Planes are great, until the elevator servo fails full down. ;)

  • I like your post, and idea. NASA developed the bouncing balloon ball for landing rovers on mars. through my research when something is falling and your want to make it slower attach  a lighter than air balloon to an object that best represents an envelope with a point facing down. With helium becoming increasingly harder to produce (and our reserves, the final and last reserves going dry)  perhaps argon or something like wise filling balloons on the arms when it looses power automatically. just like an airbag deploying on impact. This idea would be to your requirments and would still work in a total failure scenario, also your idea of an "air diode" could be incorporated into it. its not a bad idea, and testing has been done before, its just a use for it has never been found...until now. cheers and fair flying friend!

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