Space Elevator たぶんいらん

If I were an astronaut, I could go into space!

A lot of people dream of traveling to space, but not everyone can be an astronaut.

Many distinguished people try to get into space flight programs, but only a few of them are selected.

Even if they are selected, they must succeed in the hard training.

In the end, only a small number of people can achieve this dream.

However, we should not give up too easily.

Now there is promising scientific technology that may make traveling to space simple.

It is called the space elevator.

According to Ohno Shunichi, the president of the Japan Space Elevator Association, anyone will be able to ride the elevator into space, just like traveling abroad.

This sounds like something out of a science fiction story.

However, he says, this could become a reality by the middle of this century.

How will the space elevator be built?

See A in Figure 1.

First, a stationary satellite will be launched to a point about 36000 km above the Earth’s equator.

This is the place where the Earth’s gravity and the centrifugal force are in balance.

Next, as B in Figure 1 illustrates, a cable will be stretched downward from the satellite to the Earth’s surface, and upward to space to keep the balance.

When the elevator is attached to this cable, it will be able to climb up and down, as shown as C in Figure 1.

How long will it take to go to space on the space elevator?

The elevator is expected to run on electricity at a speed of 200 to 300 km per hour.

Therefore, the elevator will take one or two hours to reach the height of the International Space Station, about 400 km above the Earth.

In order to reach the stationary satellite about 36000 km above the Earth, the elevator will take about one week.

The space elevator needs an extremely long cable.

It must be about 100000 km long.

That is about eight times longer than the Earth’s diameter.

Such a long cable might be broken by the pull of the Earth’s gravity and the centrifugal force.

Therefore, the cable must be more than 100 times as strong as steel.

Until the 1990s, no one knew what kind of material would be strong enough for this cable.

This was the biggest problem in the development of the space elevator.

In 1991, Dr. Iijima Sumio, a Japanese scientist, discovered a potential material for the space elevator cable.

It is called carbon nanotubes.

If this material did not exist, the space elevator would remain only in science fiction.

Carbon nanotubes are made of carbon and are the lightest and strongest material on Earth.

They are about 50000 times as thin as a human hair and about 20 times as strong as steel.

Researchers are now working hard to produce a long and tough carbon nanotube cable.

Today’s rockets require huge amounts of fossil fuel.

However, the space elevator is energy-saving and eco-friendly.

The space elevator may use a lot of electricity when it goes up, but it can also produce electricity when it comes down.

That electricity can be stored in a battery and used when the elevator goes up again.

The cost of a single trip may be about a hundred times lower than that of a trip on a rocket.

Unlike rockets, the space elevator will not produce any carbon dioxide.

The space elevator has even more potential.

We may be able to build space elevators on other planets such as Mars, too.

By using them, it may be possible to send things back and forth between the Earth and other planets.

See Figure 2, Like a hammer throw, we could use the rotation of a planet to send things into space without using fuel.

The space elevator may soon become a reality.