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| Artwork of a space elevator ferrying people as it ascends through the planet’s atmosphere |
What is the biggest obstacle facing space exploration today? What is preventing us from establishing extensive settlements, venturing further into the Solar System, and opening the universe not only to the ultra-rich, but to all of us with the desire to travel deep into the cosmos? It is not about understanding physics or engineering. We already know exactly what we have to do. The biggest problem preventing us from colonizing our star system is cost.
Depending on the estimates you use, shipping something into space costs around $ 10,000 per pound. This equates to more than $ 1 million per person. Part of the reason this number is so high is due to the inefficiency of the rockets.
Think of it this way: is it more efficient for you to carry little fuel with you on a long road trip and refuel at gas stations along the way, or is it more efficient to carry tons of fuel with you up front so that no No need to stop and refuel? Of course, it is much more efficient to carry little fuel and stop at gas stations along the way. Starting off low on fuel means that most of the weight can be the car and its passengers, and the energy from the fuel will go into getting them moving. However, if you carry a large load of fuel up front, not only does this make the vehicle much heavier, but most of the energy in the fuel will simply go into moving more fuel, greatly reducing the efficiency of the system.
Unfortunately, there are no rocket fuel stations in space yet. This means that the propellant, a mixture of fuel and oxidant, occupies 80% of the initial mass of a rocket. Only 16% of the mass is the rocket itself and a paltry 4% is the payload. But it is not the propellant that costs a lot of money. It only takes a few hundred thousand dollars out of the average cost of $ 150 million per rocket launch. Most of the cost is used by the rocket itself. This rocket is discarded after a single use.
Proposals on how to reduce the cost of space exploration include the recovery and restoration of rockets, the development of space planes that can use multiple types of engines to achieve Mach 25 (orbital speed), and the use of a series of controlled explosions to reduce the need for fuel on board.
But one technology in particular shows the most promising of all, as it has the ability to open up the universe and reduce the cost of exploration by 100 times. It is a technology imagined for centuries, although we are only now developing the necessary materials to make it a reality.
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| The US space shuttle was designed to be a reusable launch vehicle that would dramatically reduce the cost of space exploration. However, the cost of reconditioning the vehicle ended up being more expensive than simply building a whole new rocket. |
The technology in question is a space elevator. The strong but lightweight cables would stretch 62,000 miles (100,000 km) into the upper atmosphere for a quarter of the distance between Earth and the Moon. A climber would transport people from the planet's surface to the interstellar sights above, capable of carrying up to 40,000 pounds of cargo at a time. If the ISS weighs around 900,000 pounds, this means that the space elevator could carry enough material to build a new space station every month.
The idea itself seems to border on the fantastic, but there is nothing too complex about the space elevator system. It consists of only 4 basic parts: a base station on Earth, cables, a climber to lift the load, and a counterweight in space that will tension the cable. Various objects can serve as a counterweight. A collection of space junk, a space station, or even an asteroid close enough for us to capture it would be enough. This counterweight should be at least 22,000 miles (36,000 km) from the Earth's surface, but ideally it will be 62,000 miles away. At this distance, the counterweight can ensure that the center of mass of the entire system remains around the geostationary orbit, a position in which objects remain stationary relative to the Earth's surface.
The elevator's biggest challenge isn't the counterweight, it's the cable itself. Never in the history of the world has there been a material strong, light and flexible enough to fill the position. It wasn't until we started using carbon nanotubes in the 1990s that we found a true candidate for our cable.
Pure, perfect carbon nanotubes are more than 100 times stronger than steel, yet remain thin, flexible, and chemically stable. They are also excellent electrical and thermal conductors. Unfortunately, we still don't know how to make carbon nanotubes at the thousands of kilometers we need. The longest nanotube ever built is only a foot and a half long, although Japanese researchers made great strides by developing a forest of nanotubes last year. The forest, which is a delightful collection of carbon nanotube growths, reached 14 cm in length, far surpassing the previous record of just 2 cm.
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| Japanese researchers cultivate the longest carbon nanotube forest in history. Image by Hisashi Sugime, Waseda University. |
