Hybrid Aerial Underwater Drone – Bachelor Project [video] | Hacker News Reader

Hybrid Aerial Underwater Drone – Bachelor Project [video]

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66 pointsnhma33 comments

https://www.energy.aau.dk/aau-drone-can-both-fly-and-dive-un...

Any ideas how the signal is transmitted once the drone is underwater? Typical RC transmitters run 2.4 GHz. Some systems use 700 MHz. The former wouldn't penetrate at all, the latter might penetrate to a shallow depth, but I think that what's shown in the video is deep enough that the signal would get attenuated. There doesn't seem to be a tether and the drone doesn't seem to have any computer vision capabilities to fly itself whilst under water. I wonder how they solved this.

IMU that determines rotation rates and acceleration without vision. A drone can fly and hold attitude with some accuracy without any outside help, it doesn’t need cameras or outside control. Only GPS to counteract drifting but that can be neglected in the very short term.

As far as I can tell from their report (https://gitlab.com/hybrid-drone/paper), the authors did not consider underwater RF transmissions in their prototype design and simply use standard COTS components typically used for DIY UAVs.

Variable pitch! Waterproof! This thing is awesome. Surely there is different tuning when it's in water vs when it's not, right? How do you detect the transition? Motor currents? This is a really neat project!

In their report (https://gitlab.com/hybrid-drone/paper) the authors mention that they implemented one controller for flying and another for diving. The transition seems to be initiated manually, but they propose a few ways of automatic detection and transition.

> Hybrid drones offer great potential in many industries due to their ability to operate in air and water.

"Hybrid" usually means a combination of features from two different things.

For instance, a car with electric & internal combustion engines.

But here they are using "hybrid" to mean a combination of capabilities. That's different than features.

Also, "hybrid done" already has a meaning:

https://en.wikipedia.org/wiki/Hybrid_drone

Looks to me like it is a hybrid of an underwater drone thing and an aerial drone thing, and that you have a good opportunity to expand that wiki page to include the other meanings of the term.

As an undergrad project this is rather impressive. But those motors do not look very water resistant. We all know that that shape and those blades are not very efficient in the water. And as others mention the RF signal probably cuts out at a few meters (probably worse in salt water).

Definitely impressive as a proof of concept. A lot of the other problems can be solved with iteration. There are some IP67-rated drone motors meant to both fly and run underwater (available from Westmag for example).

There might be less that can be done about the underwater drag, but if it doesn't need to go long distances underwater that's not as much of a problem. For the RF signal, it can either run autonomously underwater, or use a fibre-optic umbilical, or even convert from an umbilical to wireless when it takes to the air.

Very impressive. I assume that underwater propulsion uses a lot more energy per meter moved?

that is the thing here. While the project is cool, the drone's underwater drag is very high, while typical such drone of that size is foldable, and thus one can fold it (even if a bit, Star Wars X-wing style) to decrease drag and use say only one or two motors with much greater efficiency as result. Though high speed drone like this https://www.youtube.com/watch?v=7PTsHDFMams may be ok without collapsing.

But you use spend much less energy fighting gravity.

I’d expect it to have more range underwater than a typical quadcoter has through air. And much longer “flight” time.

But I doubt it gains enough to compete with a fixed wing drone using the same battery.

>I’d expect it to have more range underwater than a typical quadcoter has through air.

I would expect the opposite, with the higher drag being much more of an issue than gravity. But I would be interested to hear a definitive answer.

It's interesting how simple this looks, off the shelf parts, and 3D printed components. I'm almost surprised this doesn't already exist after looking at it.

If this what can be done with off the shelf parts and 3D printing, imagine what DARPA and the like have been doing for the past 20 years.

Makes the UFO/UAP stories about "it transitioned from the water to the air and back to the water!!" seem way more plausible.

> imagine what DARPA and the like have been doing for the past 20 years.

People always say this, but anyone I know who's ever worked in one of these companies that contracts for the DoD or DARPA always complains about how behind the market government tech is. Obviously private industry isn't producing competitors to the F35, but for less complicated kit the government doesn't seem to be doing anything super sophisticated. In fact a bunch of people I knew who went to Iraq bought supplemental gear on the private market.

> In fact a bunch of people I knew who went to Iraq bought supplemental gear on the private market.

Like, photography gear?

No, like armor and rifle optics.

Oh, the people you're talking about were deployed military personnel?

> I'm almost surprised this doesn't already exist after looking at it.

What's the use case? We have very good dedicated aerial drones and very good dedicated submarine drones. If something is technically possible but no one makes it usually it means it's not that interesting

If your mothership is low-observable/submersible you could park it in a harbor and when time is right unleash a swarm of hybrid aerial underwater drones with mission payload.

This design uses 1 swashplate server plus 1 brushless drive motor for each prop for a total of 8 motors. Designs in Ukraine are now using 1 brushless drive motor to synchronously drive all 4 props and 1 swashplate servo each prop, reducing total number of motors to 5, which might be a natural path of optimization for this type of hybrid aerial underwater?

Why do the drones need to be able to work underwater? Can’t you just connect some floats to them and launch the drones once they’re at the surface?

The floats would mark the location the mission originated

I feel like I've seen some of these before without the variable pitch part

ex. https://www.youtube.com/watch?v=jlMDabBfJp0

You can waterproof regular fpv quads with silicone coating on the pcb. https://www.youtube.com/watch?v=WzUy6Wk86-A

Right I remember this spray stuff like rusteoleum or something. I always flinch when I see a motor run underwater ha.

I suppose that pool is the ~max RF range under water? Is prop pitch mandatory for underwater use?

Getting closer to the well documented amphibious UAP drone I guess..

The manhunt from a drone becomes more of a nightmare.

in some sense it isn't nightnmare, it is already a reality, just non-uniformly distributed. Sounds like you just haven't watched hours of footage from Ukraine. The drones there - in the 10-30km zone from the frontline - are onmnipresent like birds, just the birds of the killing-humans-on-sight kind (and with IR cameras it is 24x7, at night it is even more effective as you don't see it coming, only hear a slight buzz of the props, while the drone sees a warm human even better at night, like a kind of a flying rattlesnake :).

Unprepared NK soldiers in Ukraine facing drones first time https://youtu.be/9BQKfSHqRDk?t=117

SciFi becomes reality.

Maybe you will be able to use these to defend Greenland?

Obligatory: https://xkcd.com/2128/

Or for the more cynical, replace "search and rescue" with "military covert ops".

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