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 Fifty years ago today, Sputnik 1 re-entered the Earth's
atmosphere as the result of orbital decay, a process which gradually reduces
the height of a satellite's orbit. When Sputnik 1 re-entered Earth's atmosphere
on January 4, 1957, aerodynamic friction caused the world's first artificial
satellite to burn up like a meteor. Drag, the type of aerodynamic friction that
caused Sputnik's demise, is caused by the skin friction between the molecules
of the air and the molecules of a moving body. When skin friction is an
interaction between a solid (e.g., a satellite) and a gas (e.g., the
atmosphere), the magnitude of the aerodynamic friction depends upon the
properties of both solid and gas.
Although Sputnik 1 spent only three months in space, its
successful launch started the Space Race and triggered a series of events which
culminated with the landing of men on the moon in July 1969. Made of aluminum
and weighing just 184 lbs., Sputnik 1 was just 23 in. (58 cm) in diameter –
about the size of a basketball. The satellite's elliptic orbit carried it to an
apogee of 588 mi (946 km) and a perigee of 141 mi (227 km). A radio transmitter
made by the Soviet Ministry of Radiotechnical Industry relayed data about cosmic
rays, meteroids, and the temperature and density of Earth's upper atmosphere. While
traveling in the vacuum of space, Sputnik circled the globe in 96 minutes at
17,000 mph.
The return of the Soviet satellite ended a three-month
period in which anxious Americans had gazed skyward, alarmed at the military
capabilities of their Cold War rivals, whose R-7 intercontinental ballistic
missile (ICBM) had served as a rocket. For 21 days in October, amateur
radio operators had listened to Sputnik's telltale "beeps" at 20.005 and 40.002
MHz. Although the Soviet satellite was too small to be seen with the naked eye,
one future astronaut remembered Sputnik's launch of October 4, 1957. "I saw the
booster, not Sputnik, flying by", said Wally Schirra, "and I said, maybe this
is the way we should be going, not just sitting back waiting for something to
happen.
Resources:
http://www.zarya.info/Diaries/Sputnik/Sputnik.php
http://en.wikipedia.org/wiki/Sputnik_1
http://www.sciam.com/article.cfm?articleID=0001D591-A0ED-1C76-9B81809EC588EF21
http://exploration.grc.nasa.gov/education/rocket/rktaero.html
http://www.brainyquote.com/quotes/quotes/w/wallyschir325671.html
http://en.wikipedia.org/wiki/Sputnik_1
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