What is the one detail you expect to see when you hear about consumer drones?
Propellers!
The first time you see them, drones remind you of helicopters; and that is because of their rotors (or propellers).
Propellers are the ultimate iconic detail of drones in our collective consciousness, and this is also how they achieve their vertical lift-off and directional flying abilities.
One could even say it is the most important part of the drone. And it’s most vulnerable.
How many times have we seen a propeller snag a tree branch after which the drone plummeted to the ground?
In other instances, the drone ends up flailing around with no direction, defying your flight commands.
To counter this problem, some manufacturers install propeller guards. Some of the more advanced models come with obstacle avoidance systems and collision avoidance technology.
All these help to keep a drone’s propellers free from getting tangled up.
And they work to varying degrees of success.
But what about taking out the propellers all together?
Can Drones Work Without Propellers?
A student at the Royal College of Art, Marcus Kung, has taken an approach to design a drone that may prove the most creative solution against propeller entanglement so far. His drone ditches propellers altogether.
How does this drone work without propellers?
Marcus Kung’s Impeller Drone uses centrifugal fans or impellers in place of axial fans.
Centrifugal fans are the sort you would come across in leaf blowers and hair dryers. They pull air from the back. But instead of pushing the air out through the front like a regular fan, they push the air out sideways.
The centrifugal fans in the Impeller Drone are arranged in such a way that they are like the wheels on a car.
The air is pulled from the sides, and pushed downwards. The design of the cover around the fans make this possible by directing the air-flow where it needs to go.
The cover also protects the impeller from coming in contact with anything outside, protecting the air inlet formed inside.
The advantages of this impeller setup are not hard to see. Your drone is much safer from object collision and irreversible damage to important components.
The protective housing around the impeller also allows the air to be pushed more forcibly through the outlet. This means the drone flies higher with lesser power.
The one disadvantage nobody can escape, though, is the noise that will be made when the drone operates. It’s the same situation as when you switch on your leaf blower, so no surprises there.
The Science Behind Drones That Don’t Use Propellers
So now we know a drone need not necessarily have a propeller to fly. To understand how this is possible, we need to understand how drones fly in the first place.
How Does a Drone Fly?
Drones are lightweight aircrafts that are unmanned and capable of flying at high altitudes, and usually, though not always, they are directed with a remote control.
Now, the motors and propellers are responsible for getting the drone to the lofty heights it can reach. And these usually come in pairs even though some drones come with 3 or fewer.
Why Propellers?
It is easy to underestimate the role which propellers play in ensuring your drone does not crash.
In the case of helicopters, they need at least 2 propellers, and these have to be mounted strategically to prevent a crash.
Likewise, a drone needs at least two propellers to operate smoothly, otherwise, a tail prop needs to be in place. Usually they’ll have four, hence the quadcopter name that most drones go by.
Each propeller on your drone spins in a direction opposite to the propeller it is paired with. This keeps the drone steady up in the air and maintains a manageable speed.
So, in the case where you have 2 propellers, you can expect one propeller to spin in a clockwise direction while the other spins anti-clockwise. In the case of a quadcopter you can expect to see two propellers spinning clockwise, while the other two spin anti-clockwise.
What role does the motor play in all this?
The propellers spin because the motors they are attached to spin.
This causes a downward displacement of wind. The force of the wind blowing downwards is able to push the aircraft upwards since according to the laws of physics, for every force in any direction, there is an equal force pushing in the opposite direction.
This is how the lift force is created that takes your drone to the heights you love to fly it.
When flying your drone at these heights, you are able to control its direction thanks to the propellers.
In order to cause your drone to descend, all you have to do is slow down the motors which will cause the propellers to slow down as well.
This slowing down means less wind will be sent downwards and the lift force of the drone will become less powerful than the gravitational forces pulling it down. This causes the drone to descend.
In this manner, a drone’s propellers and motors are absolutely crucial to its flight and control.
Does the Material and Design of Propellers Matter?
The material, design, and even length of propellers matter, and have a direct impact on the way a drone flies.
The propellers of high-performing drones are not just manufactured on a whim. Much thought is put into this part of the drone because manufacturers understand the impact of these factors on performance and flight.
For example, you may realize that some propellers are made of hard fiberglass such as those on the Phantom 4. Other propellers are made of carbon fiber like those on the industrial Matrice 600. These materials are all chosen for their high-performance.
As for design, that is usually decided after a lot of modeling and simulations have been carried out to ensure aerodynamic efficiency and maximum thrust.
The Role of Manufacturing
The manufacturing process is designed to ensure the highest quality propellers are produced for enhanced performance of the drone during flight.
Uniformity and quality control are enforced by using injection molds.
Each propeller must be perfectly balanced with the others, and still be dynamic enough to function freely. This is essential for peak performance during flight.
The vibration control is also smoothened out during the manufacturing process to ensure minimum vibration when the drone is operating. This ensures that image and video quality is not compromised during flight.
The importance of proper manufacturing really comes to the fore when the drone has to fly during harsh weather. For example, some drones are specifically made for rigorous tasks like chasing tornadoes and other natural weather conditions, providing live coverage.
Drones Operating Without Propellers
We have already seen one drone design that exists without the use of propellers. That is Marcus Kung’s Impeller Drone.
But what about a drone that operates without blades at all?
A bladeless drone.
What Is a Bladeless Drone?
The bladeless drone was designed by Edgar Herrera, and was featured in Yanko Design.
The technology behind this drone uses propellers, but has no need for the blades for drone flights.
This aerodynamic design is similar to how modern airplanes are designed, but with a somewhat different body.
The main body is equipped with a large air duct which helps in ascending and descending.
The air utilization happens through the internal ducts. Smaller propellers on each side of the body suck the air through the four intake valves, which is then directed towards helping the drone ascend.
When the drone is in the air, the three smaller propellers are used to generate downward flow that keeps the device afloat.
As you can imagine, the absence of blades means this drone makes much less noise than you would normally associate with a drone. Noise pollution could really be mitigated should this design ever become widespread among hobbyists and commercial drone pilots.
Militarily, it would also enhance the stealth ability of drones that are sent to infiltrate hostile territory.
For his design, Edgar Herrera earned an international award for concept design, the Red Dot Award.
But the technology has yet to be incorporated into any drones being used today. Until that situation changes, you can expect to keep seeing drones that remind you of helicopters because of their propeller blades.