Lead-In 4
Space Elevators
Task 14. Discuss the questions:
What do you think is a space elevator and how could it be used?
How do you think a space elevator would work?
What technical challenges would it face?
How seriously do you think the concept of space elevators is being taken at present?
Reading and Speaking 4
Photo courtesy LiftPort Group: satellite at GEO
Space Elevators
When the Space Shuttle Columbia lifted off on April 12, 1981, from Kennedy Space Center, Fla., to begin the first space shuttle mission, the dream of a reusable spacecraft was realized. Since then, NASA has launched more than 100 missions, but the price of space missions has not changed. Whether it is the space shuttle or the non-reusable Russian spacecraft, the cost of a launch is approximately $22,000 per kg.
But many years prior to these events, in his 1979 novel, The Fountains of Paradise, Arthur C Clarke had written about an elevator connecting the earth's surface to space. Three decades later, this science-fiction concept is preparing to take off in the real world. NASA has launched the Space Elevator Challenge, a competition with a generous prize, and several teams and companies are working on serious research projects aimed at winning it.
As its name suggests, a space elevator is designed to raise things into space. Satellites, components for space ships, supplies for astronauts in space stations, and even astronauts themselves are examples of payloads that could be transported into orbit without the need for explosive and environmentally unfriendly rockets. A new space transportation system like this could make travel to geostationary Earth orbit (GEO) a daily event and transform the global economy. As researchers predict, space elevator would be able to carry cargo and humans into space at a price of only about $220-$880 per kg.
However,
the altitude of orbital space – a colossal 35,790 km above the
earth – is a measure of the challenge facing engineers. How could
such a height be reached? The answer is by using an incredibly
strong and lightweight cable,
strong enough to support
its own weight and a heavy load. It would be attached
to a base
station
on earth at one end and a satellite in geostationary orbit (fixed
above a point on the equator) at the other. Lift vehicles would
ascend
and descend
the cable, powered
by electromagnetic force and controlled
remotely. The design of such a cable is still largely theoretical
but current m
aterial
that could be used for this purpose iscarbon
nanotubes.
Carbon nanotubes have the potential to be 100
times stronger
than
steel and
are as
flexible as
plastic.
The
strength of carbon nanotubes comes from their unique structure. Once
scientists are able to make fibers
from carbon nanotubes, it will be possible to create threads
that will form the ribbon
for the space elevator. A ribbon could be built in two ways:
Long carbon nanotubes -- several meters long or longer -- would be braided into a structure resembling a rope. As of 2005, the longest nanotubes are still only a few centimeters long.
Shorter nanotubes could be placed in a polymer matrix. Current polymers do not bind well to carbon nanotubes, which results in the matrix being pulled away from the nanotubes when placed under tension.
The ribbon would serve as the tracks of a sort of railroad into space. Mechanical lifters would then be used to climb the ribbon to space.
The space elevator could replace the space shuttle as the main space vehicle, and be used for satellitedeployment, defense, tourismand further exploration. To the latter point, a spacecraft would climb the ribbon of the elevator and then would launch toward its main target once in space. This type of launch would require less fuel than would normally be needed to break out of Earth's atmosphere. Some designers also believe that space elevators could be built on other planets, including Mars.
Task 15. Match the verbs from the text to the definitions.
|
a) carried (objects, over a distance) b) hold something firmly / bear its weight c) climb down d) provided with energy / moved by a force e) joining f) driven / have movement directed g) flat cable h) climb up i) lift / make something go up j) fixed |
Listening 4.1
Task 16. James, an engineer, is giving a talk on space elevators. Listen to him and complete his short notes.