Aerospace Engineering

Aerospace Engineering Day One- History of Aviation

Definition • Aviation, • Is the science and practice of flight in heavier-than-air craft, (Airplanes; Gliders; Helicopters), which are distinguished from lighter-than-air craft (Airships; Balloons).

Classes of Aviation • Aviation is grouped broadly into three classes: • Military, • Military aviation includes all flying by the armed forces, • Commercial, and • Commercial aviation includes primarily scheduled and charter airlines, • General. • General aviation includes all other flying, such as instructional, private, and corporate flying,

History • Human beings have long dreamed of flying, • The first aircraft made was the kite, in about the 5th century B.C., • Italian artist and scientist Leonardo da Vinci (1452-1519) gathered data on the flight of birds and developed concepts of the propeller, the parachute, and heavier-than-air craft,

The 19th Century • During the 19th century researchers and inventors explored flight in Great Britain, Germany, France, Australia, and the United States, • They experimented with kites and gliders, and they designed various models of flying machines, • Experimental craft were powered with steam engines, rubber bands, and even compressed air, • Other craft had flapping wings designed to fly using the muscle power of the pilot, but none were successful for more than short times and short distances,

19th Century • Aeronauts who studied gliding were more successful in their flying attempts, • German flier Otto Lilienthal was very successful in his two years of glider flights, but he died in a glider crash in 1896, • American engineer Octave Chanute also flew gliders, but his most notable contribution was his compilation of aviation developments, Progress in Flying Machines (1894), • In 1896 American astronomer Samuel Pierpont Langley became the first to fly a heavier-than-air craft powered by a steam powered engine,

Kitty Hawk & After • On December 17, 1903, near Kitty Hawk, North Carolina, American brothers Wilbur and Orville Wright made the world's first successful flights in a heavier-than-air craft powered by a gasoline engine, • Not until 1906 did anyone else fly in an airplane, • In that year, short hops were made in Europe by several different fliers, • By 1908 Americans and Europeans were making great advances in aviation, flying increasingly longer, faster, and farther, • American aviator Glenn Hammond Curtiss won the first international speed event, at about 75.6 km/h (47 mph) in 1909, • The first successful seaplane was made and flown by Henri Fabre, of France, in 1910,

After Kitty Hawk • During the period before World War I (Pre -1914), design of both the airplane and its engine showed considerable improvement, • The propeller was moved from behind the wing to in front of it, • The first official U.S. airmail was flown in 1911, • The first flight across North America was also made in 1911,

World War I & After • During World War I, both airplanes and lighter-than-air craft were used, and designers constructed specialized planes for: • reconnaissance, • attack, pursuit, and Bombing, • Huge biplane bombers with more than one engine were introduced, • Advances in aviation continued following the war. Notable flights included a nonstop flight from Chicago to New York City in 1919 and a flight from Cairo to Cape Town, South Africa, in 1920, • The first flight completely around the world was made from April 6 to September 28, 1924,

Transoceanic Flights • Transoceanic flying began in 1919 when a huge flying boat flew from the United States to England, with intermediate stops at Newfoundland, the Azores, and Lisbon, Portugal, • The first nonstop transatlantic flight was made by two British aviators from Newfoundland to Ireland in 1919, • The first nonstop solo crossing of the Atlantic Ocean was made by American aviator Charles A. Lindbergh, from New York City to Paris in 1927, • Later that year two Americans made a nonstop flight from California to Hawaii, and two other Americans flew from Newfoundland to Japan,

The 20’s, 30’s & 40’s • In the 1920s airlines were established for mail and passenger routes both within the United States and between the United States and other countries in the Western Hemisphere, • Between 1930 and 1940, commercial air transportation expanded greatly, and frequent long-distance and transoceanic flights were undertaken, • Most of the major countries of the world developed commercial air transportation, with the United States in the lead.

World War II • The further development of aircraft was greatly accelerated during World War II (1939-1945), • Important advances were achieved in the development of planes for: • bombing, • for combat, and • for the transportation of parachute troops and of tanks and other heavy equipment, • Toward the end of the war, airplane production attained an all-time high, • air warfare increased in intensity and extent, and • domestic airlines established new passenger- and cargo-carrying records,

After World War II • After the war, • U.S. military aircraft production dropped; • civilian aircraft orders increased considerably; and • international commercial services resumed, • After World War II, a marked increase took place in the use of company-owned airplanes, and, • Larger, faster aircraft with pressurized cabins were made available to the airlines, • Improved airports, • more efficient weather forecasting, • additional aids to air traffic control, • and public demand for air transportation, all contributed to the postwar boom in airline passenger travel and freight transportation, • Experimentation with new aerodynamic designs, new metals, new power plants, and electronics resulted in the development of the high-speed turbojet, which changed aviation considerably,

After World War II • by the early 1980s such craft numbered more than 90 percent of all aircraft active in the United States, • General trends in the U.S. air transport industry included airline deregulation, mergers of airlines, and fluctuating air fares and so-called price wars,

Aerospace Engineering Day Two - Glider Technology

The Development of Gliders • A glider is a special kind of aircraft that has no engine. Paper airplanes are the most obvious example, but gliders come in a wide range of sizes. • Hang-gliders are piloted aircraft that are launched by leaping off the side of a hill. The Wright brothers perfected the design of the first airplane and gained piloting experience through a series of glider flights from 1900 to 1903. • More sophisticated gliders are launched by ground based catapults, or are towed aloft by a powered aircraft then cut free to glide for hours over many miles. • The Space Shuttle flies as a glider during reentry and landing; the rocket engines are used only during liftoff.

Gliders • In order for a glider to fly, it must generate lift to oppose its weight. To generate lift, a glider must move through the air. But the motion of a glider through the air also generates drag. • In a powered aircraft, the thrust from the engine opposes drag. But a glider has no engine to generate thrust. With the drag unopposed, a glider quickly slows down until it can no longer generate enough lift to oppose the weight.

Gliders • So how does a glider generate the velocity needed for flight? • The simple answer is that a glider trades altitude for velocity. It trades the potential energy difference from a higher altitude to a lower altitude to produce kinetic energy, which means velocity. Gliders are always descending relative to the air in which they are flying.

Gliders • How do gliders stay aloft for hours if they constantly descend? • The answer is that they are designed to be very efficient, to descend very slowly. If the pilot can locate a pocket of air that is rising faster than the glider is descending, the glider can actually gain altitude, increasing its potential energy. • Pockets of rising air are called updrafts. Updrafts are found when a wind blowing at a hill or mountain has to rise to climb over it. Updrafts can also be found over dark land masses that absorb heat from the sun. The heat from the ground warms the surrounding air, which causes the air to rise. • Rising pockets of hot air are called thermals. Large gliding birds, such as owls and hawks, are often seen circling inside a thermal to gain altitude without flapping their wings. Gliders do exactly the same thing.

Design Brief #3 • You will build a model fighter jet and test it in the wind tunnel, • Choose either the F-15 Eagle, or MIG 29, • Build the Paper model, • Build the Prototype from Aluminum sheet, • Test your Prototype fighter in the wind tunnel, • As you construct the model and prototype keep a log of design changes/adaptations that you make.

Aerospace Engineering • Day Three –Aerodynamics of Powered Flight

Powered Aircraft • Compared to a powered aircraft, a glider has only three main forces acting on it: lift, drag, and weight. • Forces are vector quantities having both a magnitude and a direction. • The weight acts through the center of gravity and is always directed towards the center of the earth. • The magnitude of the weight is given by the weight equation and depends on the mass of the vehicle plus its payload. • The lift and drag are aerodynamic forces and act through the center of pressure. The drag is directed opposite to the flight direction, and the lift is directed perpendicular to the flight direction. There are many factors that influence the magnitude of the lift and drag forces.

Finding the area of a wingspan • To figure out how much lift a wing will generate, you must be able to calculate the area of an airplanes wing • The area is the two-dimensional amount of space that an object occupies. • Area is measured along the surface of an object and has dimensions of length squared; • for example, square feet of material, or centimeters squared.

Rectangular Wing • For a rectangular wing, the distance from one wing tip to the other is called the span - s and the distance from the leading edge to the trailing edge is called the chord - c. The area of a rectangle is equal to the height h times the base b; • A = h * b • so the area of a rectangular wing is • A = s * c

Triangular Wing • For the triangular wing, we use the semi-span length s and the root chord length cr. The area of a triangle is equal to one half of the base b times the height h; • A = .5 * b * h • so the area of a triangular wing is • A = .5 * cr * s

Trapezoidal Wing • For a trapezoidal wing, we need to know the semi-span s, which is the distance from the root to the wing tip, and the chord length at the root cr and at the tip ct. The equation for the area of a trapezoid is one half the sum of the top t and bottom b times the height h; • A = h * [ t + b ] / 2 • so the area of a trapezoidal wing is • A = s * [ ct + cr ] / 2

Elliptical Wing • Though not shown on the figure, some wings or control surfaces are elliptically shaped. For an ellipse with a semi-axis a and semi-axis b, the area is given by: • A = pi * a * b • where pi is the ratio of the circumference to the diameter of a circle and is equal to 3.1415. A special case of the ellipse is a circle, in which the semi-axis is equal to the radius r. The area of a circle is: • A = pi * r^2 • For a compound configuration like the Space Shuttle, you have to break up the wing into simple shapes which you can compute.

Calculating Lift • Lift depends on • the density of the air, • the square of the velocity, • the air's viscosity and compressibility, • the surface area over which the air flows, • the shape of the body, • and the body's inclination to the flow. • In general, the dependence on body shape, inclination, air viscosity, and compressibility is very complex.

Calculating Lift • One way to deal with complex dependencies is to characterize the dependence by a single variable. For lift, this variable is called the lift coefficient, designated "Cl." • This allows us to collect all the effects, simple and complex, into a single equation. • The lift equation states that lift L is equal to the lift coefficient Cl, times the air density r, times half of the velocity (speed of the aircraft) V squared, times the wing area A. • L = Cl * A * .5 * r * V^2 • Or, you can use NASA’s FoilSim software to calculate it for you,

Calculate Areas and Lift • Use the following information to calculate the wing area, and lift, • A rectangular wing that is 24’ high and 6’ wide, remember your formula is A= height x base, • Select “Size” in the Input drop down box, • Input your Info into the “Wing Size”, • What happens when you increase the speed? • What happens when you increase the altitude?

Aerospace Engineering