Fifty years ago today, the U.S. Army Ballistic Missile
Agency (ABMA) sent America's
first satellite, Explorer 1, into outer space. The successful launch of the 30.7-lb.
satellite lifted a heavy weight from the shoulders of American rocket scientists William H. Pickering and Wernher von Braun, who had been alarmed by the success
of the Soviet Union's Sputnik program and
humbled by an embarrassing launch-pad failure a month earlier. Explorer I also validated
the work of James Van Allen, a University
of Iowa space scientist who argued
that America's
first satellite should carry a Geiger counter to detect charged particles.
Today, the Van Allen Radiation Belts bear his name.
Sputnik Succeeds and
Vanguard Fails
The successful launch of Explorer I ended a painful
four-month period for American space scientists. On October 4, 1957, the Soviet Union had trumped its Cold War rival by launching
the world's first artificial satellite, a basketball-sized spacecraft named
Sputnik 1. The launch vehicle, an R-7 rocket, could double as an
intercontinental ballistic missile (ICBM) – a fact not lost on American
military planners. One month later, on November 3, 1957, the U.S.S.R. sent the
first payload, a dog named named Laika, into space aboard Sputnik 2. Laika died
while in orbit, but the Soviets had proven that more than metal could survive outside
of Earth's atmosphere.
On November 8, 1957, the U.S. Secretary of Defense ordered
Werhner von Braun to build a rocket that could put a satellite into space in 90
days. As von Braun's team of scientists toiled at Alabama's
Redstone Arsenal, the former director of Germany's V-2 missile program was soon
summoned aboard the U.S.S. Forrestal.
After three days of secret meetings, the National Advisory Committee on
Aeronautics (NACA) formed the Special Committee on Space Technology - the
forerunner to NASA. The 16-member group that was named on November 21, 1957 included
Redstone's von Braun as well as William H. Pickering, director of the Jet
Propulsion Laboratory (JPL).
In the days before NASA, the development of rockets and
satellites were functions of the U.S. military. Inter-service
rivalries were (and are) also a fact of life. On December 6, 1957, the U.S. Navy
launched Vanguard, a satellite that was designed to take some of the sting out
of Sputnik's bite, aboard a three-stage rocket. The margin of extra lifting
power in the first stage was too small, however, and Vanguard failed to rise
more than four feet in the air before falling back to Earth. After learning
that Vanguard's three-stage rocket had toppled and burned on the launch pad,
newspaper reporters labeled the failed launch as "Flopnik".
U.S. Space Scientists Turn the Tide
 As the space historian Gregory P. Kennedy has written, the
prestige of the United
States now rested on Werhner von Braun and
the U.S. Army. But William Pickering and James Van Allen had an important role
to play, too. Just 84 days after the Secretary of Defense ordered the Redstone
team to put a satellite into space, a four-stage Jupiter-C rocket thundered
into the skies above Cape Canaveral,
Florida. The rocket's payload, a satellite
designed and built by Pickering's
JPL, had been completed in less than three months. Its instrument package,
designed in part by Iowa
State's Van Allen, would
provide science with its first major discovery of the space age.
Shortly before midnight on January 31, 1958, the U.S. Army's
twenty-ninth Jupiter-C put Explorer 1 into an orbit with an apogee of 1,575
miles and a perigee of 224 miles. As America's first satellite orbited
the Earth once every 115 minutes, scientists at mission control noticed that Van
Allen's Geiger counters would stop working periodically, but then resume
operation. Although Explorer 1 did not include a data recorder, its nickel-cadmium battery powered a pair of transmitters which relayed these
anomalies to Earth. Two months later, when the U.S. Army launched Explorer 3, scientists
would learn that the Geiger counters stopped working whenever the satellite
passed through a pair of radiation belts that encircle the planet.
Other components of Explorer 1's instrument package also
sent valuable information back to Earth. The 11-pound unit featured internal
and exterior temperature sensors, micro-meteorite erosion gauges, and a micro-meteorite
impact microphone. The satellite's high-power transmitter sent signals for 31
days, and a low-power unit remained in operation for 105 days. Years later, on
March 31, 1970, Explorer 1 made the last of its approximately 56,000 orbits
around the earth. With its transmitters silent and its orbit decayed, America's first
satellite re-entered Earth's atmosphere and burned up.
Resources:
http://spacefellowship.com/News/?p=4367
http://www.nasm.si.edu/exhibitions/GAL100/exp1.html
http://www.phy6.org/stargaze/Spacefly.htm
http://www.astronautix.com/lvs/jupiterc.htm
http://www.ispyspace.com/Explorer_1.html
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