ADTO # 87 - November 19, 1999
QuestChats require pre-registration. Unless otherwise noted, registration is at: http://quest.arc.nasa.gov/aero/chats/#chatting RESCHEDULED Friday, November 23, 1999 10 AM - 11 AM Pacific Ray Oyung, Research Coordinator for the Fatigue Countermeasures Program Ray Oyung is part of a team that tries to find ways of reducing the effects of fatigue, sleep loss, and disruptions to the body's internal clock on flight crews during flight operations. Read Rays' biography at http://quest.arc.nasa.gov/aero/team/ray.html Friday, December 17, 1999 10 AM - 11 AM Pacific Aerospace Team Online QuestChat with the Wright Brothers Step into the QuestChat "time machine" to chat with Orville & Wilbur Wright in celebration of their 97th anniversary of the first successful, powered, piloted flight in history.
The Aerodynamics of Things That Spin A WebCast /Chat from NASA Ames Research Center featuring Dr. Earl Duque and Joe Jordan Wednesday, December 1, 1999 10 AM PST Join us for a fun-filled hour of demonstrations, videos and explanations about things that spin. You can ask questions in the chat room and Earl and Joe will answer them. Dr. Duque is a research scientist who uses computers to study the aerodynamics of helicopters, rotorcraft, and wind turbines. Go to http://quest.arc.nasa.gov/aero/events/spin for more information on this event.
Editor's Note: David Sauders is a computational fluid dynamicist. He uses computers to design airplanes. I thought I would share his answer to an email question with you. Read his biography at http://quest.arc.nasa.gov/team/saunders.html This is just a sample of of what you can find in our question archive. http://quest.arc.nasa.gov/aero/question/
QUESTION: Why were airplanes designed the way they were?
ANSWER from David Saunders on November 12, 1999:
As we approach the 100th anniversary of the first powered manned flight (still just 96 years ago, but close to 100), this is perhaps a timely question. Would the answer be the same if it had been asked 50 years ago? 75 years ago? Clearly the "this way" would be different but perhaps the "why" would not. Before attempting to answer "why", a quote from the Chairman of the San Francisco Section of the AIAA (Stephen Jaeger, American Institute of Aeronautics and Astronautics) can provide perspective: [Referring to a visit to the Moffett Historical Museum at Moffett Field, which is open most afternoons:] "Deep in the museum is an intriguing collection of old newspapers tracing the important events of the last 100 years, particularly those related to aviation. In the editions dating from the first and second decades of the 20th century, you will come across articles and cartoons postulating what the future of flight will be like 50 or even 100 years in the future. They are completely wrong. Yes, these guesses were often invented by writers and artists who had little knowledge of basic aerodynamics, but they also completely missed key developments such as monowings [monoplanes], all metal fuselages, rocket flight, and jet engines. Glaringly absent from our history [from what ACTUALLY happened] are hovering cruise ships bristling with multiple wings, squadrons of nuclear-powered airplanes, and fleets of sleek, supersonic transports trailing sonic booms over the continent. How could they have known what our reality would really be like? I can't wait to see how wrong our best guesses will be as we enter the 3rd Millennium." Earlier in the article, Jaeger mentions three Bay Area pioneers who died recently (Harvard Lomax, R. T. Jones, and Charlie Hall). Not only did these "modest giants" contribute in their own right, they were also "conduits to earlier pioneers such as Schlichting, Buseman, Goddard, Wilbur and Orville Wright, Prandtl, and even Sir George Cayley. They were like miners tunneling through time looking for gold. The pick-axe keeps getting handed off to the younger miners, but the tunnel continues to grow. This path appears to us in textbooks as a logical procession of events: A discovered this, B discovered that, then C came along and put them all together. But to these pioneers it was not history but the demands of their [era]: determine the equations of flight, design us a flying machine that will carry a man, build us a faster airplane, build us a more powerful engine, exceed the speed of sound, put a man on the moon, fly a probe past Saturn." The article concludes as follows: "One's day-to-day contributions can seem small compared with history, but that is a short-sighted attitude. Each event that erupts around us, each development in the field, can have a dramatic and far-reaching influence on the future, no matter how inconsequential it may appear to be at the present time. Being mindful of our legacy, even if only considered at fleeting moments, sets our place in history and carves that tunnel through time even further. What we do now will be handed off some day to those still in elementary school or yet to be born. What sort of legacy will we leave for them?" A little abstract, perhaps, but relevant to the question of why airplanes are the way they are. Their designs have been influenced by the demands of more effective travel (speed, capacity, range, economics), and of war (as ever-more devastating weapons). Bombers begat fighters begat air-to-air and air-to-ground missiles. The V-2 ballistic missile provided a weapon from which cities within range had no defense - surely a leading motivation for wartime inventions. Then V-2s led naturally to satellite launchers and moon rockets. More recently, military aircraft shapes have been influenced by stealth considerations. Initially, the (F-117) results were angular, faceted shapes that were decidely UNaerodynamic (having higher drag at high speed). Yet they flew well enough to be tolerable given their advantage of being difficult to see and shoot down. Most recently, the shapes (e.g., B-2) have become more aerodynamic and have managed to do without tail surfaces, thus saving weight as well as being more stealthy. For a civil transport example, consider the configuration that Boeing established with its B-47, B-52, and 707 designs - that is, the slender airliners have used since the 707 (aft-body-mounted engines being an occasional alternative). Why so common? Among the reasons are the wing weight-saving afforded by the engine weight counteracting wing bend, the fact that the lower wing surface is much less critical to wing efficiency than its upper surface, the improved engine location with respect to centers of gravity or lift, and slo with respect to the wing spars: no interruption, unlike the British examples of the De Havilland Comet and the three V bombers, which (quite remarkably, in retrospect) all had their engines buried in the wing root with all sorts of undesirable consequences in terms of structure and safety in the event of turbine blade failures. Historical success tells us that Boeing got it right, yet aerodynamicists are arguing that it is high time for a whole new paradigm, and large blended wing/body transports appear to be on the horizon for improved aerodynamic and load-carrying efficiency. Can the costs of abandoning decades of vital experience be kept under control? Only time will tell. In the case of supersonic transports, we have a pretty good handle on what they should look like, yet making them quiet enough to meet ever-more stringent airport regulations, let alone building them to have sufficient range (trans-oceanic) and affordable operating costs, remains beyond the present technology and economic climate, as evidenced by Boeing's 1999 decision to abandon development of the High Speed Civil Transport as a successor to Concorde. Every design involves compromise among myriad conflicting requirements. Human ingenuity in the days long before computers achieved remarkable successes and rapid advances. Evidently it is the gifted engineer's capacity to balance these demands while pushing the boundaries based on solid theory and experiment that has made each advance possible. We can see, looking back, that the significant developments occurred for logical engineering reasons. Looking forward is not so easy. As Mr. Jaeger says, it will be interesting to see how wrong our best guesses at future developments will turn out to be.