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代写英国硕士论文-HAROLD EDGERTON IN WORLD WAR II( The Structure of E(5)

时间:2012-05-23 14:02来源:未知 编辑:留学生作业 点击:
28 Harold Edgerton Papers, Box 51 Folder 3, p.148. Figure 13: Joe Louis Vs. Arturo Godoy27 Figure 14: MIT Exhibit at New York World's Fair28 14 WORLD WAR II CHANGES RESEARCH AT MIT To understand the r

28 Harold Edgerton Papers, Box 51 Folder 3, p.148.
Figure 13: Joe Louis Vs.
Arturo Godoy27
Figure 14: MIT Exhibit at New York World's Fair28
14
WORLD WAR II CHANGES RESEARCH AT MIT
To understand the reasons behind Edgerton抯 direct involvement in the war effort, it is important
to understand the environment and time period in which he lived and worked. In particular, it is
helpful to examine MIT抯 attitude towards the military during World War II. As soon as the
United States entered the war, MIT transformed from an industry-dependent institute, to an
entity increasingly funded by the federal government. In Compton抯 eyes, MIT needed to
mobilize all of its resources and intellectual power to help in the war effort:
We are fortunate to serve as an institution whose objective in respect to national needs is
so clear-cut and constructive?In a time of military crisis, technological efficiency in
production as well as in design of instruments of defense and offense is the basic element
of national defense?We should make [best evaluation of national importance] possible
by postponing less urgent research projects, by internal rearrangement of teaching
schedules, and by carrying out a more than normal per capita burden of work.29
Both the students and the staff redirected their research and goals to meet the needs of the war
effort. In line with what was expected of MIT, Edgerton was ready to contribute. Major
Goddard, the leader of the aerial reconnaissance team from Wright Field in Dayton, Ohio visited
Edgerton during the summer of 1939 and presented him with the project of developing an
electronic flash unit for nighttime aerial photography. For Edgerton, this opened a whole new
dimension to his research that was grander in scale than his pre-war consulting endeavors.
AERIAL RECONNAISSANCE PHOTOGRAPHY
The original impetus for soliciting Edgerton抯 involvement in World War II was the need for a
more advanced system of nighttime aerial photography. Aerial reconnaissance was a tactical
operation used by the Allied forces to track enemy movements of supplies, weapons, and their
locations. During WWII, the Germans anticipated aerial reconnaissance operations. As a result,
much of the their movements occurred at night, under the blanket of darkness. Hence, there was
a need for nighttime aerial photography.
WORLD WAR I AERIAL PHOTOGRAPHY
Aerial photographs were first being used for reconnaissance during World War I. After the war,
development of cameras for aerial photography continued as nations began to see the importance
of aerial reconnaissance. In an army wide general memo, Captain Lynfold Bright wrote,
The importance of air reconnaissance cannot be overemphasized and its effect upon the
enemy抯 morale cannot be overstressed, let alone the military importance of the
information obtained through these night photographs.30
By 1928, the Royal Air Force was using aerial cameras that could photograph regions up to 4
square miles from 30,000 feet, beyond the reach of anti-aircraft guns. These cameras were
equipped with electrical heating systems to prevent the shutters from freezing at high altitudes.31
29 Burchard, 6.
30 Harold Edgerton Papers, Box 77 Folder 2.
31 British Journal of Photography 1928, Vol. 75, No. 3553, p.334.
15
The technological advancements in the United States?aerial photography research coincided
with research in Europe.
FLASH BOMB
In the United States, Major George Goddard played a
critical role in the advancement of aerial photography.
As aerial reconnaissance photography grew more
prevalent, the military learned to move at night in
order to avoid being seen by enemy reconnaissance
operations. In order to be able to track enemy
movements at night, Goddard began to investigate
night aerial reconnaissance methods. He took the first
night aerial photograph in the U.S. (Figure 15) over
Rochester, NY in 1925, using the flash bomb
technique he invented. A bomb of magnesium powder
was dropped from an airplane and triggered the
camera shutter to coincide with the flash caused by the bomb抯 explosion. The time at which the
flash bomb detonates was regulated by a time-delay fuse. When the flash illuminated the ground
below, a photocell fixed to the plane would trigger the shutter of the camera. While flash
powder made night aerial photography a reality, it was not an ideal solution. The flash powder
was dangerous due to the risk of the bomb igniting while still on the plane. Goddard narrates
many incidences in his book Overview: A Lifelong Adventure in Aerial Photography indicating
the dangers involved with the powder of the flash bomb as well as the primitive release
mechanism. In addition, the number of photographs that could be taken was limited by the
amount of explosive powder carried on the plane. In an article published in the Journal of
Physical Society of America, Edgerton described the disadvantages:
In spite of apparent success, the flash-bomb method of
night photography had several disadvantages. The flash
bomb is dangerous because the powder is easily ignited.
The number of reconnaissance operations is restricted
since the number of bombs that can be carried is limited.
The plane can operate only at a given altitude because
the time-delay fuses are set before take-off [for the
bombs] to be dropped from a pre-determined altitude.34
Because the flash bomb fuses are set before take-off, this
system has no flexibility in the operating altitude. For this
reason, inclement weather may cause problems for night
photography using flash bombs. Encountering unexpected
clouds may prevent the operators from being able to
photograph at the pre-set altitude. However, they cannot
32 Brigadier General George W. Goddard, Overview: A Life-Long Adventure in Aerial Photography, (New York:
Doubleday & Company, Inc., 1960), 179.
33 Harold Edgerton Papers, Box 80 Folder 6.
34 Harold Edgerton, "The Past, Present, & Future of High Speed Photography" Journal of Physical Society of
America July 1947, 13. Harold Edgerton Papers, Box 105 Folder 32.
Figure 15: First Aerial Night Photo, Taken
over Rochester, NY32
Figure 16: Flash Bombs Being
Loaded33
16
simply fly below the clouds, since the flash bomb would not explode at the right time. Inclement
weather in the form of wind or rain may also be problematic, since they could blow the flash
bomb off course or prevent the flash powder from igniting.
Anticipating increased use of nighttime aerial reconnaissance in World War II, it was clear to
officials in the armed forces that a safer and more versatile aerial photography technology was
needed. Edgerton was asked by Goddard to adapt his stroboscope technology for use in
nighttime aerial photography. In theory, the electronic flash system addressed most of the
disadvantages of the flash bomb:
?The equipment was inherently non-explosive.
?The electronic nature of the flash meant that it could provide a reusable and limitless
source of light.
?The light source itself was controlled internally and was contained within the
reconnaissance aircraft, meaning that it could be operated at any altitude.
These advantages were inherent to the flash equipment itself. However, the size of the system
needed to accomplish aerial reconnaissance was much greater than the systems for close-up
photos like those used to analyze milk drops and motors.
EDGERTON JOINS THE WAR EFFORT
Because of the possible advantages of an electronic flash, Goddard
approached Edgerton in 1939 with the proposition to develop a more
advanced night aerial reconnaissance than the flash bomb:
While my photoelectric system automatically opened the camera
shutter when the bomb went off and therefore assured greater
photographic dependability, the disadvantages remained and even
though the Ordnance people worked long and hard at overcoming
them, I began looking for a better method by which to light up the
sky. I found it at MIT at the electroscopic laboratory of Dr. Harold
Edgerton. I knew that Dr. Edgerton and his assistants had come a
long way in methods of generating bright light using electricity. 36
DEVELOPMENT OF ELECTRONIC FLASH FOR NIGHT AERIAL RECONNAISSANCE
Edgerton抯 work on his flash technology during the war focused primarily on creating strobe
equipment that could generate a flash with enough power to illuminate a target more than a mile
away and withstand the amount of energy such a flash would generate. At first glance, it would
seem as if the technology used to take pictures from miles in the sky would differ greatly from
that used in Edgerton抯 pre-war work in sports photography and industrial consulting. However,
a comparison of a pre-war handheld unit (Figure 18) with a wartime aerial flash system (Figure
19) shows that the basic architectures were nearly identical. In both units, the system
architecture is comprised of a flash bulb, the camera used to take the pictures, a power source
35 Harold Edgerton, "The Past, Present, & Future of High Speed Photography."
36 Brigadier General George W. Goddard, Overview: A Life-Long Adventure in Aerial Photography, (New York:
Doubleday & Company, Inc., 1960), 244.
Figure 17: Major
Goddard35
17
and capacitors to store the energy discharged in
the flash, and a control unit to trigger the system


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