2009 Issue 1 - Raytheon

Cossor company together with fate.
Experiments in 1935, which included A.C.
Cossor personnel, proved that radio waves
could be “bounced” off aircraft and the
“echo” picked up and interpreted by a
receiving station to determine the bearing
and distance of the aircraft. The secret
technology was the RAdio Detection And
Ranging system, a device more commonly
known today by its acronym … RADAR.
A.C. Cossor was selected by the Air
Ministry to build the critical receiving units
and operator displays that made Britain’s
“Chain Home” air defense radar network
usable and the first operational radar system
in the world. At the onset of the Battle
of Britain, Chain Home included 19 transmitter
and receiving stations, providing a
protective umbrella from the Shetlands to
Lands End. With Chain Home, the Royal Air
Force had a precious 20-minutes warning
to deny the German Luftwaffe the element
of surprise and scramble fighter squadrons
to form “welcoming committees” for their
uninvited visitors.
1940s: Mass-producing Magnetrons
Born from necessity, the World War II years
were a period of tremendous innovation,
spawning technological changes that continue
to reverberate into the 21st century.
One of Raytheon’s first innovations of the
1940s would significantly improve the capability
of radar to detect enemy planes.
Laminated magnetron anode with cooling
fins, early WWII
In 1940, British scientists brought their new
magnetron tube — a device for producing
high-power microwaves used in radar protecting
their country’s coastline — to the
United States. They hoped to draw on
Americans’ manufacturing ingenuity and
find a better process for producing these
magnetrons.
The visiting scientists had planned meetings
with industry leaders in microwaves —
General Electric, Westinghouse and Bell
Labs; all were dabbling in lower power
radar work.
Dr. Edward L. Bowles of the Massachusetts
Institute of Technology’s Radiation Lab recommended
that the British bring their magnetron
to Raytheon. “It is not good to give
a large company an exclusive … It should
always be pitted against a smaller one.
Small firms are mobile, and can be quick in
an emergency,” Bowles later wrote.
The cavity fabrication was a complex
machining operation from four-inch copper
bar that required skilled labor and many
hours to produce, with an output of only
several magnetrons per week. Percy
Spencer wrote of that Friday afternoon
meeting, “The technique for making these
tubes, as described to us, was awkward
and impractical.” After asking, and then
arguing, to take the highly secret device
home for the weekend, Spencer began to
ponder the problem. A man with no formal
education, he had many past successes
improving radio tubes.
Monday morning Spencer came in with a
simple solution: To make the cavity from
multiple stamped 1/8-inch sheet metal copper
plates, stack them in a fixture with silver
solder layers in between, and finish the
process in a hydrogen brazing oven. The
thermal properties of the stacking fixture
would expand faster than the copper and
lock them into conformity.
This was a tremendous breakthrough for
British radar production. Because this technique
employed two mass production
processes, “Out were coming magnetrons
Legacy of Innovation
like sausage!” said Charles F. Adams, president
of Raytheon from 1948 to 1950.
Raytheon received the contract in 1941 and
was soon producing an astonishing 2,600
magnetrons per week.
Before long, Raytheon would be producing
80 percent of the U.S. and free world’s
magnetrons. For his work, Spencer received
the Distinguished Public Service Award, the
U.S. Navy’s highest award for excellence.
1940s: Developing Subminiature Tubes
for the Proximity Fuse
Raytheon did not invent the highly accurate
fuse using radio waves to trigger a
time at distance detonation. However, in
1945 the company perfected the integral
subminiature tubes to survive the harsh
environment of acceleration force 20,000
times stronger than Earth’s gravity and a
centrifugal force set up by approximately
500 rotations per second until the projectile
reached its target.
Subminiature tubes
Many scientists did not want to use the fuse
because if it was captured by the enemy, it
could be used against the Allied Powers. It
was so secret it was considered “fantastic
secret” — higher than top secret during the
war because of its scientific importance.
Years before the fuse was put into use,
Spencer had been working to add radio
controls to an airplane model for his son.
Using several types of receiving tubes and a
heavy battery, it could not get off the
ground. So he was already miniaturizing
tubes that use lower power.
Continued on page 30
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