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A mathematician and a mechanical engineer at Johns Hopkins University in the United States proposed that as long as elevator manufacturers adopt more biological techniques, adjust risk assessment, and build some robots for automatic maintenance, a space will be built in the near future. The elevator is entirely possible.
On June 11th, Beijing time, according to foreign media reports, space elevators have long been separated from real life and have appeared in one of the themes of science fiction. At the same time, this is also the subject of feasibility studies conducted by NASA and other agencies. . The current consensus reached by engineers is that space elevators are a very good idea, but the construction process involves tremendous stress and pressure, and existing materials cannot meet their requirements.
However, a mathematician and a mechanical engineer at Johns Hopkins University in the United States proposed that as long as elevator manufacturers adopt more biological technologies, adjust risk assessments, and build some robots for automatic maintenance, one will soon build one. Space elevators are entirely possible.
In a research report, authors Dan Popescu and Sean Sun simulated the design of space elevators. They were based on biological structures (such as ligaments and tendons) and found maximum stress and maximum pull. The ratio of tensile strength is calculated. This is much higher than the stress-strength ratio used in the project, and the ability of the material to absorb the force is at least twice that of the damaging force.
Researchers point out that stress-strength ratios such as this are acceptable for normal civil engineering projects, but for large buildings, this ratio is too strict to control failure probability. It is worth noting that space elevators are very large and may be the largest building structures built by humans.
The construction of space elevators enables humans and space supplies to be transported out of the Earth's atmosphere. In some space elevator designs, there is no mention of the necessity of using rockets. The earliest idea of a space elevator was proposed by Russian scientist Konstantin Tsiolkovsky in 1895.
From 1895, scientists began to refine and update the space elevator design, but the basic design of the elevator has not changed. The space elevator contains a solid cable on the earth. Usually the elevator extends up to the geostationary orbit - about 35,786 kilometers from the ground.
At the top end of the cable is a counterweight. Gravity and centrifugal force in the outward direction tension the cable. A cargo tank is placed along the cable and can be moved up and down along the cable. The main problem with this space elevator is that the pressure on the extra long cables is so great that there is currently nothing to withstand it.
In the past few decades, there have been a number of large design competitions and proposals to solve this problem, but so far, no one program has been successful. The most recent solution was the “Google X” project launched by Google in 2014. However, no one was able to manufacture ultra-strength carbon nanotube cables longer than one meter long. The plan for the construction of space elevators was shelved.
It is understood that carbon nanotubes are a great hope for space elevator engineers, but this hope may be shattered. A research model in 2006 predicts that certain defects must exist in about 100,000 meters of nanotube cable, which will reduce the overall strength of the cable by 70%.
Pupescu proposed a different solution in the research report. Although carbon nanotubes are theoretically the best choice for space elevator cables, current technologies cannot produce carbon nanotubes that are more than a few centimeters in length, so carbon nanometers are used. It is impossible to manufacture space elevators. However, he proposed using some composite materials—carbon nanotubes combined with other materials. Although the strength is weaker than pure carbon nanotubes, we are using self-repairing mechanisms to enhance the strength of materials and ensure the stability of super buildings.
This self-healing mechanism is crucial, and researchers have proposed a cable design that divides its direction into two, upwards, into a series of "stacked segments"; laterally, into a series of "parallel." "Hair filaments". When any of the cable filaments fails, the fact is that this happens often and its influence is limited to its own stack segment. The weight of the load is immediately shared by the parallel cables until the repair robot arrives for replacement.
The researchers pointed out that with this "autonomous repair mechanism", space elevators can ensure reliability at high stress levels, and at the same time, they can also be made of materials with slightly lower strength, making practical feasibility closer.
Pupescu pointed out that the foundation of all these space elevator models is the gradual reduction of the stress ratio, the combination of engineering design standards and biological principles. He emphasized that the human Achilles tendon and the spine can be subjected to great stress, very close to their tensile strength, which is greater than the stress intensity of steel engineered.
The main reason is that, at least to some extent, the tendons and spine have the ability to repair themselves, which is missing from the steel material. Researchers believe that adding the biological mechanisms of tendons and spines to space elevator design means that we don't have to wait for futuristic new materials.
Pupescu said: "We believe that the design of super-large building structures such as space elevators must fully consider that components may fail, and also need a self-healing mechanism to replace damaged components, so as to ensure that space elevators are under high load. Running down without compromising its integrity means that it is possible to build superstructures using existing materials!"