|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 62
OCR for page 63
ADOLF BUSEMANN
1901-1986
BY ROBERT T. JONES
ADOLF BUSEMANN an eminent scientist and world leacler in
supersonic aerodynamics who was electect to the National
Academy of Engineering in 1970, stied in Boulder, Colo-
racto, on November 3, 1986, at the age of eighty-five. At the
time of his death, Dr. Busemann was a retired professor of
aeronautics and space science at the University of Colorado
in Boulder.
Busemann belonged to the famous German school of
aeroclynamicists led by Ludwig PrancitI, a group that in-
cludec! Theodore von Karman, Max M. Munk, anct Jakob
Ackeret. Busemann was the first, however, to propose the
use of swept wings to overcome the problems of transonic
ant! supersonic flight ant! the first to propose a cirag-free
system of wings subsequently known as the Busemann Bi-
plane. His "Schock Polar," a construction he describer! as a
"baby hedgehog," has simplified the calculations of aerody-
namicists for decacles.
Aclolf Busemann was born in Luebeck, Germany, on April
20, 1901. He attendee! the Carolo Wilhelmina Technical Uni-
versity in Braunschweig and received his Ph.D. in engineer-
ing there in 1924. In 1930 he was accorcled the status of pro-
fessor (Venia Legendi) at Georgia Augusta University in
Goettingen. In 1925 the Max-Planck Institute appointed him
to the position of aeronautical research scientist. He subse-
63
OCR for page 64
64
MEMORIAL TRIBUTES
fluently held several positions in the German scientific com-
munity, and during the war years, directed research at the
Braunschweig Laboratory.
In the late 1920s Italy was producing the fastest airplanes
in the world and had won the famous Schneider Trophy in
competition with American racers. To further development
in this arena, the Italian government, under Mussolini, de-
cidect to hold an international meeting on the problems of
high-speed aeronautics the ~ 935 Volta Congress. The
American delegation, which included Eastman N. Jacobs of
the National Advisory Council on Aeronautics's [Langley Lab-
oratory and Theodore van Karman, traveled to the meeting
on the luxurious Conte de Savoia, courtesy of the Italian gov-
ernment.
At this early period, the maximum speed that had been
achieved, even by the Schneider Cup racers, was less than
300 miles per hour, and the idea of flying at supersonic
speeds was far from the consciousness of the aeronautical
community. Yet it was at this meeting that Busemann pre-
sented his first theory of the effect of sweep in reducing the
drag of a wing at supersonic speed.
In his Volta Congress paper, Busemann used the so-called
independence principle, which states that the air forces and
pressures on a sufficiently long and narrow wing panel are
independent of that component of the flight velocity in the
direction of the long axis. The air forces, then, depend only
on the reduced component perpendicular to the long axis.
The independence principle had been used previously by
Munk in a discussion of the effect of sweep on lateral stability,
but no one had thought of using it to reduce the effective
Mach number of the wing.
Busemann's 1935 theory was incomplete in the sense that
only wings having supersonic sweep were considered; the
component velocity perpendicular to the eclge, although re-
duced, remained supersonic. In this configuration a wave
drag would still exist, although the force would be directed
partly inward by the inclination of the wing panels. Later,
OCR for page 65
ADOLF BUSEMANN
65
cluring the war, Busemann extencled his theory to inclucle
subsonic sweep, placing the wing panels inside the Mach
cone and thereby reducing the effective component velocity
to a subsonic value. In this configuration the wave ctrag
wouIc! disappear completely in the limiting case.
During the war years, communication with German scien-
tists was lost, ancT my own somewhat belated discovery of the
sweep effect, which emphasized subsonic sweep, was not im-
mediately accepted by American aeroclynamicists, including
those who hac! attended the Volta Congress. Consequently,
the first American supersonic airplane, the X-l, had no
sweep. However, the National Advisory Council on Aeronau-
tics decided to test the idea, and Robert Gilruth was able to
show experimentally that the drag of a wing having forty-
five degrees of sweep can be as little as one tenth that of a
straight wing at Mach one.
At the enct of the war, a group of American scientists trav-
eled to Germany to learn what progress hac! been made in
aerodynamics during the preceding years. The group in-
cluclect von Karman, H. S. Tsien, H. L. Dryden, anct George
Schairer of the Boeing Company. Schairer relates that the
validity of my proposal was a principal topic of discussion
during the twenty-six-hour flight to Europe.
On arrival, the group found that much research had been
clone on the sweep effect. When the group finally met with
Busemann, van Karman asked, "What is this about wing
sweep?" According to Schairer, Busemann's face lit up and
he saicl, "Oh, you remember, ~ read a paper on it at the Volta
Congress in 1935." Busemann went on to remind them that
at a dinner following the meeting, Luigi Crocco, the promi-
nent Italian aerodynamicist, had sketched an airplane having
swept wings "and a swept propeller," labeling it "the airplane
of the future."
Schairer recalls that five of the 1935 dinner guests were
present at the 1945 interview, anct all remembered the inci-
clent, although they had completely forgotten about the wing
sweep concept during the ten-year interval. How could this
OCR for page 66
66
MEMORIAL TRIBUTES
have happened? Clearly, Busemann's thinking was ahead of
its time. Perhaps also, as a true scientist, he hacT emphasized
too much the limitations of his theory.
In his biplane concept, Busemann disclosed an arrange-
ment of airfoils in which the wave system would be com-
pletely trapped between the two wings of a biplane, resulting
in zero wave drag but also, unfortunately, zero lift. In prin-
ciple, one coup form a lifting system with no wave drag by
flying the upper wing of the biplane in close proximity to a
flat reflecting surface. In one experiment at the National
Aeronautics and Space Aciministration's Ames Research
Center, we enclosed the streamlines of a Busemann biplane
within a tube bounded by a circular cylinder ant! clemon-
stratect the absence of wave drag.
Among the most interesting ant] important of Busemann's
ideas revealer] at the end of the war was his theory of super-
sonic conical flow. By means of a transformation, which he
attributer! to Chaplygin, Busemann reduced the flow around
triangular wings ant! around wing edges to a problem of con-
formal mapping in the complex plane. The conical flow
theory has played an important role in subsequent studies of
wing theory.
After coming to the United States in 1947, Busemann cle-
votec! considerable effort to analyze the sonic boom made by
a supersonic transport. The sonic boom phenomenon was
for a time not well understooct, being attributed to a focusing
along a caustic curve produced by the accelerated motion of
the airplane. Of course, everyone knew that a supersonic
plane wouIct make waves, but who would think of the waves
reaching all the way to the ground from 60,000 feet? Buse-
mann analyzer! this problem carefully and for several years
sought a means to eliminate the boom. The fact that he couIcI
not find a satisfactory solution probably means that none ex-
ists.
Outwardly Adolf Busemann seemed an intense, almost as-
cetic figure. His scientific discussions, however, frequently re-
liecl on slightly humorous, sometimes outrageous, but very
OCR for page 67
ADOLF BUSEMANN
67
concrete analogies. Thus, writing on the occasion of Buse-
mann's seventieth birthday, Professor Milton Van Dyke of
Stanford University saict:
Others of his friends will certainly praise his areas contributions to
.
, ~ ~
fluid mechanics. I would like to recall a peripheral aspect of his genius
that gives us a glimpse of how that inventive mind works. He thinks
always in concrete images. Thus in extending our knowledge of fluid
motion he has created a fantastical Alice in Wonderland world filled
with imaginary animals, shapes, and people. Has any bestiary a more
lovable animal than the "baby hedgehog" or any utopia a shape more
pleasantly named than the "apple curve"? My favorite character in all
this magical kingdom is the "ingenious pipefitter," endlessly fitting his
stream tubes around a body in the hope of constructing a transonic
flow and then, like Sisyphus, starting over again when he fails to match
the condition at infinity. I hope that these charming creatures will
thrive in the literature as long as Busemann's ideas and equations
themselves.
Representative terms from entire chapter:
wave drag
