THERE has been a lot of interest recently in going back to the moon. Currently, the only way to do so is via rockets. These are very costly and use up a tremendous amount of fuel. One alternative is not yet technically possible although efforts are underway to make it happen.
I’m talking about space elevators! These elevators feature a cable that extends from the Earth upwards towards the moon or vice versa. This is not a pipe dream. In 2003, Nasa released a report detailing a possible design for this.
The concept of a space elevator is a lot older than you’d probably expect. Konstantin Tsiolkovsky first described a kind of space elevator in 1895. He had proposed building a tower from the surface of the earth up to the geostationary orbit. The problem with his idea was that such a structure would collapse under its own weight.
But this idea still cropped up regularly in science fiction. For example, in 1979, Arthur C. Clarke wrote an entire novel The Fountains of Paradise about the construction of such a space elevator. Today, 40 years later, many scientists believe this is not just a science fiction concept but one that could actually work.
Modern concepts of space elevators envision an elevator that would be built using a cable attached at one end to the Earth's surface and to a massive counterweight at the other end (which will be in geostationary orbit, about 36,000 kilometres above earth).
The earth’s gravity would pull downward on the cable while the centrifugal force from the orbiting counterweight would pull upward. These opposing forces would reduce the stress on the elevator itself.
The space elevator would rely on “crawlers” that travel along the stationary cable to transport items and potentially humans. Power would most likely be supplied by solar power. |
Travel time would be much slower than that of a rocket though. If the climber were to move at say, 300km per hour, it would take five days to reach geostationary orbit.
BUILDING SPACE ELEVATORS
Another approach does not involve attaching the cable to a platform on earth but rather to one on the moon. In this scenario, a cable would be run from the moon and out into space.
That’s basically the idea behind Spaceline, which was described in a report recently published by researchers at Columbia University and Cambridge University.
Under the Spaceline concept, astronauts would only need to reach the end point of the cable and latch onto a solar-powered shuttle (or crawler) that would climb along its length.
The reason for connecting the cable to the moon rather than the Earth is that the latter’s stronger gravitational pull and rotation would cause the cable to break. There’s far less risk of that happening if it was tethered to the moon.
Although no current material can be used to build such a cable, many scientists believe that carbon nanotubes is the answer, with the cable being extremely narrow at either end (so it doesn’t collapse under gravitational pressure) but thickened at the middle (to prevent snapping).
Prior to1991, there didn’t exist any material strong enough to construct such a cable. That changed when physicist Sumio Iijima of Japan discovered the mechanism of the carbon nanotube, a material with the theoretical strength to be used as a space elevator cable. Only 30 per cent denser than water, carbon nanotubes are said to be 1,000 times stronger than traditional steel cables.
The problem is that these materials have yet to be able to be made to scale in such a way that they could be used for such an endeavour. The longest carbon nanotube that has ever been constructed is only a few inches long and a nanometer in width. So, a lot more work needs to be done on this material before it could be used for a space elevator.
Perhaps it’s not surprising that the leading corporation working on a space elevator comes from Japan. Obayashi Corporation announced its Space Elevator Construction Plan to connect Earth and space by 2050.
Its plan is to have six elevator cars move between a platform in the sea and a space station orbiting the Earth. A trip from the sea to the sky would take about eight days. The idea relies on creating carbon nanotubes at the scale that’s necessary. Obayashi believes the cable problem could be resolved by 2030. Meanwhile, scientists at the Kanagawa University have begun designing robotic cars, which are expected to carry around 30 people.
If Obayashi is successful, it would radically change space travel due to the dramatic change in costs. Currently, it would cost something like US$22,000 per kg (RM 92,000) to get a package from earth into the geostationary orbit using rocket technology. Space elevators are believed to be able to cut that cost down by a whopping 95 per cent.
“The space elevator is the Holy Grail of space exploration,” says Michio Kaku, a professor of physics at City College of New York and a renowned futurist. “Imagine pushing the ‘up’ button of an elevator and taking a ride into the heavens. It could open up space to the average person.”
Rockets are a proven way to get people to the moon but they are impractical if the idea is to make moon-travel mainstream. They are ridiculously expensive, require a huge amount of fuel and leave behind a lot of space junk. Whether it’s a cable from the Earth or the moon, space elevators could be the solution.
Oon Yeoh is a consultant with experiences in print, online and mobile media. Reach him at oonyeoh@gmail.com.