With the development of science and technology, people’s lives are more and more convenient, and the degree of mechanization is getting higher and higher. As long as the elevator is installed on a slightly higher level, the elevator can be seen everywhere in the city, saving us time and effort.
As people’s demand for space exploration increases, we often use launch vehicles. However, the cost of launching rockets is huge and time consuming. If you build an elevator in space, it will be much more convenient, and the space elevator can not only transport goods, but may also take humans to space for sightseeing.
In fact, as early as the end of the 19th century, the scientist of the former Soviet Union, Konstantin Tsiolkovsky, proposed this idea. Later, Russia and the United States also explored and studied space elevators. Now, Japanese scientists have officially started experimenting with space elevators, and plan to realize the idea of space elevators by 2050.
How to build a space elevator?
The space elevator consists of five parts: the base, the cable, the elevator cabin, the space station and the counterweight.
The construction principle of the space elevator is actually very simple, it combines universal gravitation and circular motion. When we were young, we probably did this. We used a rope to hold a heavy object (perhaps a stone or a sandbag) and pulled the rope. If the speed is fast enough, the weight will not fall.
When building a space elevator, one end of the cable connects to the base on the Earth’s equator, and there are two options: fixed (fixed on the surface) and drift (flight platform in a large offshore platform or stratosphere). The other end of the rope is a space station in geostationary orbit. In the geostationary orbit, the angular velocity of the space station is equal to the angular velocity of the Earth’s rotation (synchronized with the Earth), that is, the space station is relatively stationary with respect to the Earth; the centripetal force of the satellite is equal to the attraction of the Earth to it, and the space station does not fly away from the Earth nor fall. Back to Earth, the cable was fixed.
The height of the geostationary orbit is fixed, about 36,000 kilometers above the equator. In fact, in order to ensure the stability of the entire cable and space station, the center of gravity of the whole system should be placed in the geostationary orbit, but the cable itself has a certain weight, so we have to add a heavy object and put it behind the whole system, that is, Its position is higher than the space station (the geostationary orbital height), which is called the counterweight.
Although the idea of building a space elevator has been around for nearly a hundred years, its principle is simple, but it has not been realized. The key to construction is on the cable.
The materials used to build tens of thousands of kilometers of space elevator cables must be very light, very strong, and the material cost is very low. The development of human technology to date, there are only a handful of materials that can achieve such standards, the most promising material is carbon nanotubes. According to current technology, we may need 7 million kilograms of carbon nanotubes to make elevator cables.
However, there are still two problems: First, the current technology cannot produce so many carbon nanotube cables; second, the materials are not light enough. Moreover, cable materials also need to face cosmic radiation, atmospheric corrosion, space debris, etc. These are the problems that need to be solved when building space elevators.
In addition, the researchers also need to solve the problem of the power of the elevator. We can’t use electricity to provide the energy needed for the lift, and because of the length, the overall wire resistance is huge. In response to this, a method of boosting by laser emission has been proposed. Solar panels are installed at the bottom of the lift and then illuminated with laser light on the ground to provide energy from the laser, but the higher the lift, the less light is reached. At the same time, the sun’s light will increase with height, so adding some upward-facing solar panels to the lift will be more advantageous.
Mini elevator approach
In 2007, Japan established the “Space Elevator Association” and began research on space elevators. According to their design, the space elevator has a cable length of about 96,000 kilometers. It is equivalent to a quarter of the Earth’s distance from the moon. In order to achieve the ultimate goal, the researchers began a phased trial.
On September 22, 2018, with a loud bang, the H-IIB launch vehicle (a large Japanese launch vehicle) was launched from the ground and began a five-day international space station tour. The rocket carries two small cube satellites with a side length of 10 cm. The two satellites are connected by a 10 meter long steel cable. On the cable, the researchers will try to use a motor to drive a box that simulates the elevator’s lift to move it back and forth over the cable.
When the micro-elevator moves between two satellites, it will provide scientists with important information about the force of the cable. The test will also reveal the interaction between the elevator and the cable so that scientists can design better elevators. Through Bluetooth, the micro-elevator will continuously send data on its location and cable status to one of the satellites, which will then transmit the data to scientists on Earth.
Space logistics line
If one day the space elevator becomes a reality, it will be a much cheaper space vehicle than a rocket. At present, 90% of the total weight of the launch vehicle is fuel, 5% is the hull, and the last 5% is the astronauts, satellites and other effective payloads. Compared to the large amount of fuel consumed, the effective load is too small and the efficiency of the rocket is too low. The current market price is: $20,000 for every kilogram of payload loaded into space. Space elevators are different. The lift can recover the energy (potential energy) accumulated during the ascent, and it can be powered by solar energy. Therefore, it is much more efficient than the rocket.
Now when we launch the spacecraft, the rocket needs to provide power so that the spacecraft can get rid of the gravity of the Earth. Since the space elevator rotates around the earth synchronously, as long as the spacecraft is transported to the space station and gently released, the spacecraft will be able to get rid of the gravity of the earth. Once the space elevator is built, it will effectively solve the problem of high rocket launch cost.
In addition, according to Japanese researchers, the elevator cabin they plan to design can transport 30 passengers to a space station of 35,000 kilometers from the Earth at a speed of 200 km/h in 7.5 days. And because the cost of space elevators is low, ordinary people can also go to the space station to watch the space scene.