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ADTO # 87 - November 19, 1999

PART 1: Upcoming Chats
PART 2: Special Events
PART 3: "Why were airplanes designed the way they were?"


UPCOMING CHATS

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.


SPECIAL EVENT


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.
 
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