This article explains how the four branches of aerospace engineering – structural mechanics, aerodynamics, propulsion, and controls – are applied to the design of airplanes and rockets. It covers the role and importance of each branch, and highlights the elements that are essential to the design and operation of airplanes and rockets.
Before we get into what aerospace engineering is, we need to talk about engineering. Aeronautical engineering is a branch of engineering, as it is part of the College of Engineering. Engineering is more than just a collection of technologies; it is the result of human creative thinking combined with scientific principles. Engineering plays an essential role in our daily lives. Our electronics, cars, buildings, and even medical equipment are all products of engineering. Engineering is the artificial creation of things that don’t exist in nature. Does that mean that cavemen making stone axes is engineering? No, it’s not. Engineering is not something that can be created haphazardly, but rather systematically using natural sciences, especially mechanics. Mechanics literally means the study of forces, which is the calculation of what happens to an object when a force is applied to it. Performing these force calculations is crucial to engineering. For example, the principles of mechanics were used by architects in ancient Rome when they designed and built their huge amphitheaters. They didn’t just stack stones on top of each other, they calculated weights and pressures to ensure the stability of the structure. Modern engineers also use complex calculations and simulations to design safe and efficient structures. As a building designer, you need to calculate the many forces acting on a building. They’ll have to calculate the weight of the building, the strength of the wind, the shaking of the ground, and more, and then design a structure that won’t collapse in spite of them. In this way, engineering is the study of creating artifacts based on the knowledge of mechanics.
Now, let’s talk about aerospace engineering. Aerospace engineering is the engineering of aviation and space, so it’s all about creating artifacts for use in the sky and space based on knowledge of mechanics. What are the objects that are used in the sky and space? Airplanes, helicopters, rockets, missiles, satellites, and more. Aerospace engineering is the pinnacle of modern technology, and there is significant research and development in this field around the world. Satellites are responsible for global communication, and the GPS system has become an indispensable tool in our daily lives. None of these technological advances would have been possible without aerospace engineering. So what kind of mechanical knowledge is needed to create them? There are four main ones: structural mechanics, aerodynamics, propulsion mechanics, and control engineering. These are called the four branches of aerospace engineering. To explain what each of these disciplines does, let’s use the example of building an airplane.
To build an airplane, you basically need to have an airplane structure. You’ll need wings to keep the airplane afloat, a body for people and luggage, and a tail fin for balance. To do this, you need to calculate how much force the airplane’s bones can take without breaking, and how far it will turn if it does. Furthermore, it’s important to know how long it can last. An airplane is made up of many parts, and how each of them withstands and distributes specific forces is important. In particular, it’s essential to design materials and structures that can withstand the pressures and temperatures that occur during high-speed flight, hence the need for structural mechanics, the subject that calculates these things. Airplanes, in particular, unlike other man-made objects, contain highly irregularly shaped structures called wings. For this reason, structural mechanics in aeronautical engineering is much more important than structural mechanics in other engineering disciplines because it involves calculating the forces acting on irregular shapes.
Once the structure of the airplane is built, the next important thing is to fly it. An airplane uses its wings to create a pressure difference between the air above and below the wings. This pressure difference creates a force that keeps the airplane aloft, called lift. The science that studies this lift is aerodynamics. Aerodynamics means the mechanics of air, and it’s the study of calculating all kinds of forces caused by the motion of the wind around a wing, including lift. The forces acting on a wing depend on the shape of the wing, and the main goal of aerodynamics is to develop a wing shape that produces as much lift as possible. Aerodynamics isn’t just about keeping the plane aloft, it’s also about maximizing the efficiency of the plane. Examples include designing a plane to fly farther while using less fuel, and optimizing the shape of the wing to reduce noise.
Once an airplane is airborne, the next thing it needs is to move forward, or propulsion. The means by which an airplane gets propulsion include propellers, jet engines, and rocket engines. The science of designing these propulsion engines is called propulsion engineering, and it’s based on thermodynamics and fluid dynamics. Thermodynamics is the study of how heat from fuel is used to generate force. Fluid dynamics is the study of the flow of fluids, such as fuel and air, that are necessary for combustion. A propulsion engine basically mixes compressed air with fuel, burns it, and uses the heat to generate thrust. Advances in propulsion are one of the keys to aerospace engineering. Recent research has focused on developing engines that can provide more powerful thrust while reducing carbon dioxide emissions by using cleaner fuels. These two dynamics are essential in propulsion engineering.
Now that the airplane is flying and moving forward, the last thing it needs is control. Control means directing an object to a desired state. To do this, we first need to know what state the object is currently in, which is where sensors come in. Sensors detect external stimuli such as temperature, pressure, velocity, tilt, and so on, and represent them as electrical signals. This tells us what state the object is in. Once we know the state of the object, we need to make it move to the desired state, which is what we call an actuator. The combination of sensors and actuators is called a controller, and designing a controller is what control engineering is all about. Control engineering plays a key role in many fields, not just aircraft, but also self-driving cars, drones, and more. The principles of control engineering are essential for the reliable operation of complex systems, and they contribute to the safety of flight in aerospace engineering.
In this article, we’ve explained the four main branches of aerospace engineering: structural, aerodynamic, propulsion, and control. You might think that an airplane is governed by different dynamics than a rocket, but that’s not the case. Rockets, like airplanes, spend time in the atmosphere before reaching space. Within the atmosphere, the forces on a rocket are similar to those on an airplane. However, once it leaves the atmosphere, the situation is completely different. Movement in zero gravity and propulsion in outer space must be based on completely different principles, leading to a new field of study called space dynamics. So, rockets are no different from airplanes. The only difference is that once the rocket reaches outer space, its trajectory must be calculated based on the universal gravitational force. Therefore, we can say that both airplanes and rockets are based on the above four systems of mechanics.
