Chemistry Reference
In-Depth Information
space elevator—a tall structure from which satellites and other objects
could be launched. The conventional means of launching payloads is
with a rocket propelled by chemical fuel. Rocket launches are risky, and
malfunctions are common. They are also tremendously expensive—the
cost per pound is about $10,000 ($22,000/kg)! Instead of costly chemical
rockets, a space elevator would simply haul the object up to the needed
altitude. Having a functional space elevator could reduce this cost by a
factor of about 50 or even 100 times.
The difficulty with space elevators is that they would need to be
thousands of miles high. A common orbit for satellites is geosynchro-
nous orbit, where the satellite moves at a speed that matches the Earth's
rotation. In this situation, the satellite stays in one point of the sky, since
its revolution matches that of Earth. The speed of an orbiting satellite
depends on its altitude, and the altitude at which the speed of a satellite
matches the Earth's rotation—in other words, a geosynchronous or-
bit—is 22,240 miles (35,784 km). Several designs have been considered
for space elevators, with a height reaching 62,000 miles (100,000 km).
Compare that with the tallest freestanding (self-supported) structure,
Burj Dubai in Dubai, United Arab Emirates, which is still under con-
struction as of May 2009, and is expected to reach a final height of about
2,684 feet (818 m)—slightly more than 0.5 miles (0.8 km).
To reach the fantastic heights required by a space elevator, new
materials are essential. Skyscrapers of today are usually composed of a
steel framework, but steel is too heavy to use for the space elevator—the
tower must be so high and needs so much material that it could not
possibly support its own weight if it was made of steel. One possibility
for a new material is related to the fullerenes discussed in the text. Car-
bon nanotubes are cylindrical fullerenes composed of sheets of graph-
ites rolled into tiny cylinders with a diameter of roughly 0.00000004
inches (0.0000001 cm)—a nanometer. The structure and bonds of car-
bon nanotubes could potentially be used to create a material with about
50-100 times the strength of steel. A slender ribbon of carbon nanotube
could be the key to bringing the dream of a space elevator into reality.
A functioning space elevator would drastically change the world,
allowing the placement of factories, research laboratories, and even ho-
tels into orbit. Other new materials and medicine could have similar
affects, altering the way people live and work in a multitude of interest-
ing ways.
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