Learn Aerospace Engineering

Alternative Theories of Lift ARE THERE ALTERNATIVE  EXPLANATIONS OF LIFT? The explanation of lift favored by this website states that lift is created by an imbalance of pressure against a wing—lower pressure on the top surface and higher pressure on the bottom surface. This "pressure distribution" can be calculated accurately for both subsonic and supersonic flight. But there are other ways of explaining how lift is created. Title: Propeller Downwash image Downwash is especially noticeable beneath a helicopter's rotating blades. Credit: United Technologies Sikorsky Aircraft THE MOMENTUM EXPLANATION OF LIFT According to this explanation, the slight downward deflection of the air leaving the trailing edge of a wing is what produces lift. Since for every action there is an equal and opposite reaction, the downward push on the air must result in an upward push on the wing. But this “downwash” results from air pressure differences on the wing—it is an effect of lift, not the c...

THE OUTER SPACE TREATY OF 1967 AND THE MAIN PRINCIPLES OF SPACE LAW For this new Space Law article on Space Legal Issues, let’s have a look at the Outer Space Treaty of 1967. What are the main principles of space law? How do the international texts organise the Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies? FOREWORD The UNITED NATIONS TREATIES AND PRINCIPLES ON OUTER SPACE are “ Text of treaties and principles governing the activities of States in the exploration and use of outer space, adopted by the United Nations General Assembly ”. The United Nations has the responsibility, in the legal field, to develop and codify international law. Because outer space was an environment of a new nature, “ extraordinary in many respects ” and “ unique from the legal point of view ”, and because its human conquest started in the tense climate of the 1950s, the international community had to rapidly legislate ab...

THE LAWS OF SPACE With this new Space Law article on Space Legal Issues, let’s have a look at the laws of space and outline the field of international space law and explain its main principles, focusing on the five UN space treaties. It will present the international law‐making process and examine the ability of existing international legal instruments to address current and future space activities and challenges. THE LAWS OF SPACE Space law emerged soon after Sputnik 1 was launched into outer space in 1957. Several  legally binding international instruments  (treaties) governing the use of outer space for peaceful purposes have been adopted within the framework of the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), with the 1967 Outer Space Treaty (OST) at its core. The OST contains the basic rules that define the behaviour of States in conducting activities in outer space, and has resulted in more than sixty years of peaceful cooperation in space that ...

Factors Affecting Lift WHAT FACTORS AFFECT LIFT? The size and shape of the wing, the angle at which it meets the oncoming air, the speed at which it moves through the air, even the density of the air, all affect the amount of lift a wing creates. Let’s begin with the shape of a wing intended for subsonic flight. WHY DOES A WING HAVE A ROUNDED FRONT? Air divides smoothly around a wing’s rounded leading edge, and flows neatly off its tapered trailing edge. You might think a sharp leading edge would be better. However, air cannot turn a sharp corner, so tilting a sharp wing even slightly would disrupt the smooth airflow over the wing. This would cause a loss of lift and increase drag. A rounded leading edge divides the airflow smoothly, even as the wing is tilted up or down. WHY DOES A WING HAVE A SHARP REAR EDGE? If the trailing edge were rounded, the higher-pressure air flowing along the lower side would try to follow the rounded surface and spill upward into the lower-pressure air abov...

Aerodynamics   Subsonic Wings Learn Aerospace Engineering, WHAT MAKES A WING WORK? Let's use a wing to help get a better understanding of lift at subsonic speeds. With a typical subsonic wing, the upper surface is more curved than the lower surface. The curved upper surface constricts the flow of air more than the flatter lower surface, causing the air above the wing to speed up more than the air below. The faster the air speeds up, the lower its pressure becomes. So the faster moving air above has less pressure than the slower moving air below. (Remember, this relationship between pressure and speed is called Bernoulli’s principle.) The higher air pressure below pushes the wing up—lift.  Any further increase in the speed of the air will increase the difference in pressure and increase the lifting force on the wing.    

Aerodynamics Air in Motion Learn Aerospace Engineering, FLIGHT BEGINS WITH AIR IN MOTION As an airplane moves through the air, its wings cause changes in the speed and pressure of the air moving past them. These changes result in the upward force called lift. To understand lift, you first have to understand how air (a gas) behaves under certain conditions. BERNOULLI PRINCIPLE Let's start with the Bernoulli principle. The Bernoulli principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in the pressure exerted by the fluid. WHY DOES THE AIR  SPEED UP? When moving air encounters an obstacle—a person, a tree, a wing—its path narrows as it flows around the object. Even so, the amount of air moving past any point at any given moment within the airflow is the same. For this to happen, the air must either compress or speed up where its flow narrows. While air can be compressed more easily than water, freely flowing air acts much like water—at least ...

Aerodynamics Aerodynamics of Automobiles Learn Aerospace Engineering, Aerodynamics of Automobiles Automobiles started using aerodynamic body shapes in the early part of their history. As engines became more powerful and cars became faster, automobile engineers realized that wind resistance significantly hindered their speed. The first cars to adopt improved aerodynamics, or streamlining, were racing cars and those attempting to break the  land speed record . "Dreamers, engineers, racers and entrepreneurs were lured by the potential for the profound gains aerodynamics offered," wrote Paul Niedermeyer, author of " Automotive History: An Illustrated History Of Automotive Aerodynamics ," on the website Curbside Classic. "The efforts to do so yielded some of the more remarkable cars ever made, even if they challenged the aesthetic assumptions of their times." Regarding the  aerodynamics of a racing car , Dr. Joe David, professor of mechanical and aerospace engi...