Launching Satellites
Kelly D. / Physics # 337 / 19 May 1997
Everyday, satellites are either being launched , repaired, or retrieved
in space. Satellites help transmit communications at the speed of light,
serve for navigation for the military and help in exploring the universe.
They are very important to the world of communication, but it takes a great
deal of work to get them in and out of orbit. Launching is essential to
satellites , but many problems might be encountered during the launching
or retrieving of a satellite, which might cause for repairs to be made
in space.
Where Are They Launched From?
The government uses a number of launching areas around the country
depending upon the type and orbit of satellite that is to be launched.
Most launches occur from Cape Canaveral, Florida for regular satellites.
NASA's (National Aeronautics and Space Administration) Wallops Flight Center,
located in Virginia is used to launch regular satellites. To launch polar
orbits, or satellites which orbit over the North and South Poles, these
take place from the Vandenberg Air Force Base in California.
Putting Satellites Into Orbit
Satellites are carried into orbit by shuttles, where they go through
a process of being launched. Shuttles flying into an orbit are inclined
at 28.5 degrees to the Equator (Broad, A22). Even though a good number
of satellites are carried into orbit by space shuttles, most satellites
are carried by rockets. The rockets fall back into the ocean after they
have launched the satellite and their fuel has run out. Sometimes they
are retrieved and are used for other launches. Rockets have the capability
to put satellites into orbit which are 120 miles above the Earth. Satellites
which need to be put into higher orbits are first put into one orbit around
the Earth and then with their motors, are pushed into higher orbits. Once
the satellite gets away from the rockets own protective shroud, they are
then controlled by signals from ground controllers in the launching center.
Space shuttles can carry a maximum of 3 or 4 satellites. These satellites
are either pushed into orbit by a space arm or can be gently pushed out
into orbit while spinning.
Types of Launching Vehicles
Different types of launching vehicles are used to put satellites into
orbit. Two types of launching vehicles used are either solid or liquid
fuel propellants, or motors. The solid propellants can be compared to a
rocket used in fireworks displays and the liquid propellants, which are
forms of kerosene and liquid oxygen are used to provide movement for launching.
Another type of launch vehicle includes the use of volatile hydrogen and
oxygen combination as fuel. At liftoff, the three large liquid motors are
assisted by the solid rocket boosters. The two solid boosters burn out
after some time and fall back into the ocean. The other liquid motors are
used during the rest of the flight to put the satellite into the proper
orbit, to control the satellites orbit and to return the rockets to Earth.
Problems Involved With Launching
Problems such as vibrations and the emission of gasses cause problems
during a launch. During launching, vibrations which are transmitted from
the launch vehicles and shock loading take over the launching process as
they enter the upper stages of launching. To add to the problems, some
of the materials, in the launch vehicles, can emit gas or give off particles
of their substance such as kerosene or liquid oxygen under a vacuum (How
It Works, 2038). This transmission of particles has to be avoided because
the particles could be confused as stars or they might contaminate the
solar system atmosphere. Satellites which require minor adjustments due
to launching difficulties must be adjusted otherwise they will not function.
Thrusters or built in rockets have been placed in satellites to assist
in making these minor adjustments.
Another problem at launch time is the weather at the launching pad
and tracking stations around the world. Unless weather is ideal, where
there is very little wind and no rain to affect the rocket, a launch will
not take place. Further the tracking stations must be able to follow the
rocket into orbit.
During the countdown prior to actual launch, a major problem can occur
while the computers are checking all the systems. If the computer encounters
an error, the countdown is stopped to fix the problem so the launch can
either go on, be scrubbed, or canceled to take place at a later date. To
launch with the problem could mean the loss of a satellite and millions
of dollars invested in the launch, and the lives of the astronauts who
are flying the mission.
Life Span
Once in orbit, satellites may last for a few years to a few hundred
years depending on its' size and its' orbital distance from Earth. Since
outer space has become crowded with satellites, meteors, and space junk
from failed launches and non-working satellites, many of the working satellites
might have to be raised to higher orbits by the ground controllers with
the use of the thrusters to escape the crowding in various orbits to extend
their lives.
The Death of a Satellite
Many factors can contribute to the slowing down or even the death of
a satellite. Even before some satellites reach space, 1 in 20 are rendered
useless by either being jolted on lift-off, perish in fires of defective
rocket blasts or are put into improper orbits (Canby, 282). The atmosphere
in space is less dense than on Earth and approximately 124 miles above
the Earth. There is no part of the space's atmosphere which is an absolute
vacuum. In time, a satellite will lose velocity or speed and won't be able
to go high enough and will eventually fall out of orbit and disintegrate
falling towards Earth because of the tremendous speed and friction. Some
satellites will begin to lose the balance in the pull of the Earth's gravity
and will fall toward the Earth. Friction will be a major cause for the
death of most satellites. The friction of air particles in the high atmosphere
and the gentle pressure of the sun's energy will cause a satellite to fall
back in the Earth's atmosphere. Falling into the atmosphere means that
the satellite will be exposed to intense heat as it collides with large
numbers of molecules and ions and this causing the satellite to burn up
in flames even before it reaches Earth. Satellites that escape the Earth's
gravitational field have a good chance to crash with the moon or planets
and they might even begin to orbit the sun.
International Killings and Repair Rescues
Satellites in orbit might be killed on purpose while others need to
be rescued to get repaired. Since satellites can cause interference with
other orbits or are just not needed anymore, countries such as the United
States and the Soviet Union have taken actions to kill these satellites.
The United States uses a F-15 fighter which fires a two stage missile at
it's target, the satellite. Using telescopes as it's eyes, the 50 pound
warhead adjusts it's flight path so that it might intercept the path of
the satellite. The Soviet Union uses a heavy satellite, the hunter-killer,
which is boosted to the same orbital path as the target satellite. The
hunter-killer, when in the same orbit as the target satellite , closes
in and explodes destroying the target satellite (Canby, 333). Satellites
in need of repair and rescue are assisted by shuttles while the satellites
are in low orbits. Many satellites get repaired while other satellites
in the wrong orbit get returned to Earth to be launched into the correct
orbit or to be repaired.
Conclusion
Satellites are a very important part of our communication system and
without them, the lives of many people would be totally different. The
life and death of satellites are a very crucial factor to the world today.
Everyday, new discoveries are being made on how to make the launching and
retrieving process a little more easier, while at the same time, technicians
are learning new ways on how to extend the life span of a satellite.
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