To get off the ground, a drone must be able to generate lift, a force that pushes air out from underneath the drone, allowing the drone to gain height. Generally, this is handled by propellers mounted on the drone, which spin with tremendous speed, pushing air from above towards the ground, and in the process lifting the drone into the air. More propellers mean more air is being pushed towards the ground, and over a wider area of land. The effect: added stability. Thus, unlike their helicopter counterparts, drones employ multiple propellers (often 4 or more), to gain the stability they need to function autonomously.
However, this raises the issue of weight, as although the propellers can generate significant lift, this lift is only useful if it can get the drone of the ground. A drone that is too heavy for the amount of lift generated by the propellers will not fly. Thus, propellers that are too heavy in and of themselves cannot lift the drone. Further, batteries used to power these propellers weigh down the drone, causing tremendous difficulties in sustained power. Added accessories, such as cameras, GPS systems, etc. weigh down the drone even more so. Heavier drones require more energy, but since batteries also take up space and add weight to the drones, heavier drones generally have lesser flight times. Hence, engineers are left with a difficult balance when designing drones: increase functionality but decrease fly time, or increase fly time but decrease functionality.
The issue is often solved in drone design by implementing lightweight battery cells and replenishable power sources, such as solar cells. Only lightweight accessories are used, and only those that are absolutely necessary. Further, lightweight materials are used in the construction of drone bodies, such as carbon fiber and nano-tubing, to maximize both functionality and flight time.
The key differentiator of an unmanned aerial system, hereby referred to as a drone, it its ability to sustain flight without input from a pilot or operator. However, taking off and landing does require the use of a controller, whether that controller be human or automated. Generally speaking, drones require the use of a launch pad or runway, a space large enough to stabilize the drone as it lifts into the air. Non-windy conditions, especially for smaller drones, allow for maximum stability.
To initiate launch, a controller, automated or operated by a human, must send a message to the drone’s control system that it is to lift the drone into the air. Typically 2.4 gigahertz radio waves are used to communicate between drone and controller, however more modern drones also rely on wifi signaling. Upon receiving a signal, a drone generates lift by spinning its propellers, and is able to lift into the air. Controllers range from simple smartphone apps, to radio wave controls, to full scale military mission control rooms.
The uniqueness of a drone lies in its maneuverability and ability to stay airborne. As in any multi-propeller aircraft, a drone turns when one set of propellers spin faster than the other. For example, spinning the right set of propellers faster than the left would cause a drone to fly in the left direction, vice versa, and a similar principle for forwards and backwards. Gyroscopic sensors, in conjunction with computer programs designed to keep a drone stable, allow for a drone to remain airborne without human interference while maneuvering. Through the use of realtime data (via wifi), location services (GPS sensors), and gyroscopic sensors, drones have the capability to stay balanced in the air and adjust to changing conditions. These advantages make the operation of a drone extremely cost effective, as the operation of the aircraft is essentially automated, save directions on where to go.
The ability of a drone to stay balanced on its own is a tremendous safety advantage over other aircraft, such as helicopters and airplanes. While human error may lead to disastrous consequences in the latter, drones are entirely automated, eliminating a serious source for disaster.
As in takeoff, the landing of a drone requires the use of a controller, an interface which instructs the drone when and where to land. Often, drones will employ special landing gear, which minimize shock upon impact with the ground and keep all aspects of the drone safe and reusable.
As previously mentioned, drones are composed of lightweight materials to maximize the lift produced with the least energy. An aerodynamic body, with curves rather than sharp edges ensures a drone minimizes drag as it flies through the air. The body is completed by a full electrical system, which, upon receiving information from controllers and sensors, helps keep the drone stable.
The most common accessory seen upon modern drones, besides necessary sensors and data transmitters, is the camera. This simple tool, mounted upon a flying aircraft, allows for never-before-seen footage of the Earth at a low cost. Further, the use of cameras upon drones allows for increased control by the operator, and has tremendous other practical applications. Other accessories include weapons systems, for military use, robotic components (ex: a robotic arm for picking up samples), and GPS tracking systems. However, there is no limit on the accessories that can be placed upon a drone, if the drone can generate the lift necessary to get off the ground with the accessory, the accessory is viable.
The most significant research being done with regards to drone usage is the most effective way to maximize the lift:weight ratio. As more research is done with new battery types, lightweight batteries made possible by aluminum and carbon nano tubing are emerging as a possible way to extend the flight time of lightweight drones by hours. New materials, such as graphene, also have the capability to revolutionize the ability for drones to stay in flight for longer. As this technology progresses, research into gyroscopic sensors, and GPS data is being revisited, to further improve the stability and safety of drones, as the industry shifts towards commercial applications.