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Courses

The Science of Flight

YEAR: ???? | LENGTH: 29 parts (~29 minutes each)  |  SOURCE: TGC

description:

Many of us board a plane without understanding what a truly extraordinary experience flight is: suspended 30,000 feet or more in the air, propelled to our destination at close to the speed of sound, protected from extreme cold and low pressure by the thin skin of the aircraft. We realize it’s complicated, but few of us know how it works. Even more remarkable is space flight, the “rocket science” that we use as a benchmark of difficulty or complexity.

episodes:

How did two world-class pilots coax their glider to a new altitude record? Focus on this feat as a lesson in the key principles of winged flight—including angle of attack, lift, drag, thrust, and weight. Also explore “the miracle on the Hudson,” when airline pilot Chesley Sullenberger glided his jet to an emergency water landing. Close your first lesson with an investigation of the control inputs: yaw, roll, and pitch.

Balloons were the first vehicles to fly and Archimedes' principle is the secret of their lift-carrying power. Use the ideal gas law to determine air density and the hydrostatic equation to chart air pressure versus altitude. Then apply these concepts to lighter-than-air craft to learn how the Breitling Orbiter balloon was able to circumnavigate the globe non-stop.

Lift is the fundamental force involved in winged flight. It is also fraught with misunderstanding. Debunk a popular but incorrect explanation of lift, known as the equal-time theory. Then gain a deep appreciation for the power of air flowing around an airfoil at differing angles of attack. Also examine Albert Einstein's misguided attempt to design a better airfoil.

Focus on parasitic drag, a byproduct of moving an aircraft through the air, which has no practical benefit and is therefore like a parasite. Zero in on two aspects of parasitic drag: skin friction and pressure. Observe how these phenomena arise and how they can be reduced, which is a key goal of aircraft design. Learn about laminar flow as well as golf ball design.

Aerodynamic stall occurs when lift suddenly decreases, causing drag to rise steeply. Consider the role of stall in several notable air accidents, and see a demonstration in which Professor Gregory deliberately pilots a plane through a stall, showing how to recover. Also look at technological measures to combat stall and the problem of induced drag.

Starting with the Wright brothers, trace the role of wind tunnels for studying lift and drag on aircraft structures—research that sparked the rapid advancement of aviation. Aerodynamic research also involves analysis and computations. Get a taste of this process by analyzing conservation of mass, momentum, and energy as they relate to lift and drag.

Apply concepts of lift and drag to propulsion, focusing on the internal combustion engine and propeller—still the most efficient power plant for aircraft flying at low speeds. Study the four-cycle engine and the design of propellers, which are rotating wings twisted to present an optimum angle of attack across their entire length.

Propeller-driven aircraft drop sharply in efficiency at high fractions of the speed of sound. For sustained high-speed flight, a different propulsion system is needed—the jet engine. Trace the history of jets and their super-efficient variant used on commercial airliners—the high-bypass turbofan, a machine so intricate and beautiful that a piece of one is on display at the Museum of Modern Art.

For anyone who gets the jitters during heavy turbulence, fear not: the plane is designed to take it! Follow the evolution of airframes from wood to metal to today's composite materials. Consider the problem of designing a sturdy structure that is still light enough to fly efficiently. Also look at tragic accidents that revealed the limits of certain materials and led to safer planes.

Trace the quest for stable, controlled flight back to aviation pioneers Samuel P. Langley, the Wright brothers, and Glenn Curtiss. Stability means producing forces that restore an aircraft to equilibrium when perturbed, while control entails deflection of control surfaces to alter the pitch, roll, or yaw effects that act on the aircraft's center of gravity.

Enter the realm of extreme flight, exploring how fast and how high a plane can go. The answers are remarkably precise and help define a given aircraft's flight envelope. Learn how aeronautical engineers calculate parameters such as airspeed for best climb angle, service ceiling, absolute ceiling, time to climb, stall speed, maximum speed, and speed for optimal cruise.

During and just after World War II, the quest for ever faster fighter planes reached an apparent natural barrier—the speed of sound. On approaching this limit, aircraft became unstable and uncontrollable. Discover how a new approach to aircraft design solved the problem of compressibility and shock waves in this transonic region, paving the way for supersonic flight.

Planes take off with only the fuel required for the planned trip—plus a safety margin. Since there are no filling stations in the sky, the calculations must be precise, taking account of the plane’s performance characteristics, the weather, and other factors. Learn the equations that pilots use and hear a riveting story about what happens when they get it wrong.

Dogfighting is not just about stick-and-rudder skills; a pilot must understand the physics behind aerial maneuvering. Focus on turn performance, which is the key factor that limits maneuverability and is the cause of many fatal loss-of-control accidents. Learn how energy management is the secret of success in aerial combat, and get tips on performing a barrel roll.

Roll up your sleeves and learn how to design an aircraft, using an approach that has hardly changed in a century of building new airplanes. Start out by determining the weight values, maximum lift coefficient, wing loading, and thrust-to-weight ratio. Next lay out a configuration. Finally, iterate, making modifications and adjustments to perfect your vehicle.

Focus on the science and engineering of the flight instruments. First, look at the hazards faced by even experienced pilots in the era before the altimeter and attitude indicator, learning how these vital instruments work. Then consider the importance of the airspeed indicator, turn coordinator, heading indicator, and vertical speed indicator.

On a typical weekday, five to ten thousand aircraft are in the air over the U.S. at a given moment, flying to different cities at varying speeds and different altitudes. Survey the methods, tools, and jargon of air traffic controllers, who keep this traffic moving safely and expeditiously. Also look ahead to next-generation enhancements in the air traffic control system.

Automated flight systems are increasingly used in human-piloted aircraft, where their nearly fail-safe expertise creates some unusual problems. Also look at remotely piloted vehicles, also called drones. Pioneered by the military, these are taking to the sky for a variety of practical civilian missions, including recreational uses.

Helicopters are so unlike fixed-wing aircraft in appearance and operation that it's hard to believe they work on the same aerodynamics principles. Focus on their ingenious rotor blades, which are rotating wings. Explore the challenge of flying a chopper, and learn why it's safer to lose power at altitude in a helicopter than in an airplane.

Fly beyond the atmosphere with the only vehicle now capable of reaching space—the rocket. Discover that rocket science is not “rocket science,” in the sense of being extraordinarily difficult. It’s just basic physics and chemistry. Review the fundamentals of solid and liquid propellants, thrust, specific impulse, stability, nozzle design, and the advantages of using multiple stages.

Having ascended into space in the previous lecture, now investigate your orbital options. Whether you go into a circular, elliptical, or Earth-escape orbit—or make it into orbit at all—depends on your cutoff velocity. Calculate different orbits, including the Hohmann transfer ellipse needed for efficiently changing orbits. Also relive the orbital rendezvous exploits of Gemini 8 and Apollo 11.

Venture beyond Earth to the realm of the planets. Interplanetary trajectories require exquisite timing so that the target planet is in exactly the right spot when the spacecraft arrives, often by a Hohmann transfer ellipse. Consider two fuel-saving approaches to these marathon journeys—gravity assists and ion propulsion.

Now return to Earth, analyzing the problem of decelerating from orbital or escape speed to a gentle touchdown on land or water. Calculate the amount of energy that must be lost during the plunge through the atmosphere, and consider three approaches to reentry, including that of the Space Shuttle, which unfortunately ended tragically for Columbia in 2003. Also look at the dire reentry scenario faced by Apollo 13 in 1970.

Close by probing future developments in air and space flight. See these two realms combined in two vehicles: the White Knight aircraft that launches the Space Ship One capsule, and the proposed Mars atmospheric flyer. Consider technically possible devices such as the space elevator, solar-powered aircraft, and personal air vehicles. And that's just the beginning, for the sky is truly the limit!

Interview with Dr. John Anderson regarding Gustave Eiffel's Wind Tunnels and his career as an applied scientist in the field of aerodynamics. Dr. Anderson is the Curator of Aeronautical Engineering, Aeronautics Department at Smithsonian's National Air and Space Museum.

Interview with Dr. John Anderson regarding flight speed engineering.

Interview with Dr. John Anderson regarding how and what contributed to the success of the Wright Flyer.

Interview with Dr. Tom Crouch regarding the many innovations of the Wright Brothers. Dr. Crouch is the Senior Curator, Aeronautics Department at the Smithsonian's National Air and Space Museum.

Interview with Dr. Roger D. Launius, Former Associate Director of Collections and Curatorial Affairs with Smithsonian's National Air and Space Museum.