How space elevators work
In this artist's concept, the lift will be able to carry up to 13 tons of cargo into space, propelled by a laser beam. More space exploration pictures. (Source: LIFTPORT GROUP)
On April 12, 1981, the Space Shuttle Columbia lifted off from the Kennedy Space Center in Florida and began its first spaceflight mission, which meant that the dream of reusable spacecraft was realized. Since then, NASA has completed more than 100 launches of space missions, but the cost of aviation missions has not changed much. Whether it's a space shuttle or a non-reusable Russian spacecraft, a single launch costs about $10,000 per pound ($22,000 per kilogram).
A new space transport system being developed could make travel to static earth orbit (GEO) more sparse and ordinary and could transform the global economy.
The space elevator, made of carbon nanotube composite tape, is fixed to an offshore platform and extends into space by a small counterweight and is about 62,000 miles (100,000 kilometers) long. Mechanical lifters attached to the cable then climb along the cable, sending cargo and humans into space at a cost of just $100 to $400 per pound ($220 to $880 per kilogram).
In this article, we'll learn how the concept of a space elevator went from science fiction to real life.
Space elevator cable belt
The counterweight at the end of the space elevator will keep the carbon nanotube cable strip tight. (Image source: LIFTPORT GROUP)
To better understand the concept of a space elevator, let's associate a rope ball game in which one end of the rope is tied to a pole and the other end is tied to a ball. By this analogy, then the rope is a carbon nanotube composite cable, the rod is the earth, and the ball is the counterweight. Now, imagine the ball constantly spinning at high speed around the pole, keeping the rope tight. This is the general idea of the space elevator. The counterweight rotates around the earth at high speed, keeping the cable straight, and the automatic lift moves up and down the cable.
According to the design proposed by LiftPort, the height of the space elevator is about 62,000 miles (100,000 kilometers). LiftPort is one of several companies that design and develop space elevators and their parts. Teams from around the world competed for the first prize of $400,000 in the X Trophy Space Elevator Competition in October 2006, Las Cruz, New Mexico.
The core component of the elevator is a carbon nanotube composite cable tape, which is only a few centimeters wide and almost as thin as a piece of paper. The discovery of carbon nanotubes in 1991 led scientists to believe that space elevators could be built. According to Dr Bradley Edwards of the Space Development Foundation, "In the past, the challenges in materials were too great. But now we're getting more advanced in making carbon nanotubes and building machines that can stretch materials long enough to make cables that extend into space. ”
According to some early plans, the remaining building materials will be used to make counterweights. (Source: LIFTPORT GROUP)
Carbon nanotubes may be 100 times stronger than steel and have the flexibility of plastic. This intensity comes from its unique structure similar to that of a soccer ball. Once scientists are able to fiber the carbon nanotubes, it is possible to make the wires used to make the cables of space elevators. Previously available materials were either weak or flexible enough to make cables and break easily.
Tom Nugent, research director at LiftPort Group, said: "Their elastic modulus is very high and their tensile strength is also very high, which all shows that this material should theoretically make the construction of space elevators relatively easy." ”
A cable can be made in two ways:
Long carbon nanotubes — a few meters long or longer — are woven into a structure similar to a rope. As of 2005, the longest nanotubes were still only a few centimeters long.
Shorter nanotubes can be placed in the polymer matrix. Current polymers do not bind well to carbon nanotubes, which causes the matrix to be pulled away when carbon nanotubes are under tension.
If a long carbon nanotube cable tape can be made, it will be rolled into a spool and sent into orbit. When the spacecraft carrying the spool reaches a certain altitude, such as low Earth orbit, it will begin to untie the spool and lower one end of the cable back to Earth. At the same time, the spool will continue to move to higher heights. When the cable tape descends into the Earth's atmosphere, it is captured and then landed and anchored on a moving platform in the ocean.
This cable could serve as the track for a railroad to space. The lift module will climb along the cable into space.
How high is the space elevator
If built, the space elevator cable would represent a modern world wonder and would be the tallest building ever built. The tallest freestanding tower in the world in 2005 was the 1,815-foot-5-inch (553.34 m) CN Tower over Toronto, Canada. The space elevator will be 180,720 times taller than the CN Tower!
The 62,000-mile (100,000-kilometer) space elevator will be much higher than the average orbital altitude of the shuttle (115-400 miles/185-643 kilometers). In fact, it would be equivalent to a quarter of the Earth-Moon distance (237674 miles/382,500 km).
Take the space elevator to the top
The lifting chamber will climb up the cable belt at a speed of 200 miles per hour. (Source: LIFTPORT GROUP)
While the cable is still a conceptual construct, all other components of the space elevator can be built using existing technology, including an automatic lifting chamber, ground base stations, and a laser-powered system. By the time the cable belt is complete, the other components will be almost ready for launch sometime around 2018.
Lifting cabin
The automatic lifting module will be guided into space by using cables. The towing wheels on the lift cabin clamp and pull the cable, allowing the lift cabin to climb up the elevator.
Ground base station
The starting point of the space elevator will be set on a mobile platform in the equatorial Pacific Ocean, which will hold the cable straps to Earth.
Counterweights
A heavyweight counterweight will be fitted to the top of the cable. Early plans for space elevators included capturing an asteroid and using it as a counterweight. However, programs like LiftPort and the Institute of Science are preparing to use artificial counterweights. In fact, the counterweight may have been assembled by the equipment used to make the cables, including the spacecraft used to launch the cables.
Laser power system
The lifting chamber will be powered by a free electronic laser system located at or near a ground base station. According to the Institute of Scientific Research, the laser will emit 2.4 megawatts of energy to a photovoltaic cell made of gallium arsenide on the lifting chamber, and then the photovoltaic cell will convert the energy into electrical energy for use by conventional niobium magnetic DC motors.
Once put into use, the lift module can climb the space elevator almost every day. The weight of these lifts and lowers varies from the initial 5 tons to 20 tons. The 20-ton lifting chamber will be able to carry up to 13 tons of payload and have 900 cubic meters of space. The lifting cabin will climb the cable belt at 118 miles (190 kilometers) per hour, carrying everything from satellites to solar panels, as well as humans.
Maintenance of space elevators
The space elevator cable will be fixed to a mobile platform in the equatorial Pacific Ocean. As part of a system that helps space elevators avoid orbital debris, mobile platforms can be repositioned. (Source: LIFTPORT GROUP)
Space elevators are 62,000 miles (100,000 kilometers) long, so they are vulnerable to many dangers, including weather, space junk, and terrorists. As space elevator design initiatives advance, developers are evaluating these risks and looking for ways to overcome them. In fact, to ensure that there is always one space elevator to work on, the developers plan to build multiple elevators. In terms of construction costs, each one is cheaper than the previous one. The first space elevator will serve as a platform to assist in the construction of more space elevators. In doing so, the developers wanted to ensure that even if one space elevator had a problem, other elevators could continue to deliver payloads to space.
Dodge space junk
Like space stations or space shuttles, space elevators also need to be able to avoid orbiting objects such as debris and satellites. Ground base stations will use active avoidance to protect space elevators from such objects. Currently, north American Air Defense Command (NORAD) can track targets larger than 10 centimeters (3.9 inches). Protecting the space elevator requires an orbital debris tracking system that can detect objects about 1 centimeter (0.39 inches) in size. Other space programs are currently developing the technology.
"Our plan is to anchor the cable to a mobile platform in the ocean," LiftPort's Tom Nugent says, "in effect, you can pull the cable off satellite orbit by moving a ground base station." ”
Responding to terrorist attacks
The isolated location of the space elevator will greatly reduce the risk of terrorist attacks. For example, according to LiftPort, the first ground base station will be set in the equatorial Pacific Ocean, 404 miles (650 kilometers) from any route or channel. Only a fraction of the space elevators are within range of each type of attack, i.e. 9.3 miles (15 kilometers) or less. In addition, space elevators will be a valuable global resource, likely protected by the military forces of the United States and other countries.
The impact of space elevators
Conceptual drawing of the sun perspective made by the artist. (Source: LIFTPORT GROUP)
The potential global impact of space elevators can be compared to another great transportation achievement, the Transcontinental Railroad in the United States. The transcontinental railroad, built in 1869 on Cape Utah, connected the east and west coasts of the United States for the first time, accelerating the development of the american west. Travel across the Country has been reduced from months to days. It also opened up new markets and spawned entirely new industries. By 1893, the United States had five transcontinental railroads.
The concept of a space elevator has many similarities with a transcontinental railway. The space elevator will create a permanent and never-closing ground-air connection. While it won't make space travel faster, it will make space travel more frequent and will usher in a new era for space development. Perhaps the biggest factor driving the space elevator project is that it will drastically reduce the cost of sending cargo into space. Although slower than the chemically propelled space shuttle, the lifter can reduce the launch cost from $10,000 to $20,000 per pound to about $400 per pound.
According to Bradley Edwards, author of NASA's Phase II Final Report (who is also president and founder of Carbon Designs), current estimates show that the cost of building a space elevator is $6 billion and the legal and regulatory cost is $4 billion. For comparison, the Space Shuttle program was expected to cost $5.2 billion in 1971, but ultimately cost $19.5 billion, and in addition, the cost of flying each space shuttle was $500 million, more than 50 times the original estimate.
Space elevators can replace the space shuttle as the main means of transportation in space for satellite deployment, defense, space tourism and further exploration. For that last point, the spacecraft can climb up the cables of the space elevator and then launch in space toward its main target, a type of launch that requires less fuel than launches from earth's atmosphere. Some designers also believe that space elevators can be built on other planets, including Mars.
NASA funded Dr. Edwards to conduct three years of research. In 2005, however, it only allocated $28 million to companies working on space elevators. While they are still interested in the project, they are more willing to wait for its more substantial development for the moment.
BY:KEVIN BONSOR
FY: Gin
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