Drone Propulsion

From cycle rotors to jet power, and even artificial wanes, we take a look at some of the strangest propulsion systems out there for drones.

As most of you know, Leonardo da Vinci came up with some very fascinating aerial screw designs over 500 years ago, and finally, this idea has been modernised. First modeled in this simulation, this design demonstrated some very interesting vortexes. After several months in testing, the University of Maryland actually came up with a drone which could fly on this design. With the right optimisation, the craft could reduce now wash and potentially operate quieter than a typical propeller. The downside is that this is a pretty complex design. Without gaining any efficiencies in lift, it's fairly safe to say that this is not going to displace propellers anytime soon. But it is fascinating to see something like the aerial screw actually work for drones.

So, there are many different ideas out there, and a newer idea was likely derived from the Marine Cheryl propeller. The original selling points were faster planning and more efficiency at a particular RPM. MIT transitioned this idea over to the multi-rotor, and there's some very interesting improvements, with the most notable being that there were less audible spikes at specific frequencies. Now, of course, many people have tested this propeller design, and there's still debate on performance gains. Basically, this prop has to be optimized for every multi-rotor out there. The argument is that this will likely not have any improvement because you can already configure a propeller to have three or four blades with different flying characteristics. Ultimately, I think the toroidop is a very niche thing, and it's not going to break numbers anytime soon.

I'm going to digress a little bit and get into a different type of propulsion system called the cycle rotor. You can kind of think of this as a paddle boat going through water. The cycled water works by accelerating fluid with a perpendicular rotating mechanism. In this orbital motion along with pitch angle, generates a relatively high thrust. Individual blades can also be pitched, providing rapid thrust vectoring. There are several downsides to the cycle motor, but the most prominent being complexity and higher cost, although with being a heavier setup. However, you could use a cycle motor for different hybrid applications. The Austria is an excellent hybrid example. Unlike a multi-rotor, which has to pitch to change its horizontal position, the Astra can just use a cycle rotor on top, and it doesn't pitch at all, making it very useful for certain applications like inspection or even working on remote equipment. In conclusion, cycle motors are probably not going to displace propeller-based systems anytime soon, but they could be used in hybrid applications where there is more stabilisation required.

Probably the most obvious and extreme idea is to retrofit the multi-rotor with a jet engine. Many startup electric vehicle companies have revealed their own concept with a jet engine simply due to the extreme performance gains. In reality, there are very few jet drones simply due to cost. The Jackpot is a perfect example, as it has very extreme abilities, such as going over 300 miles per hour with a 40-pound payload, but it's also going to be priced at around $250,000. Will we ever see cheaper models come out? Well, it's kind of hard to say because this is dependent on innovation and fabrication techniques. So, until we get multi-material 3D printers out there, which can build jet engines, I highly doubt that we will see jet drones flying around everywhere. However, jet engines have one of the highest thrust ratios compared to all the different propulsion systems, and there will always be a high