A mathematician and a mechanical engineer at Johns Hopkins University

Update:30-08-2018
Summary:

A mathematician and a mechanical engineer at Johns Hopk […]

A mathematician and a mechanical engineer at Johns Hopkins University in the United States suggested that as long as elevator manufacturers adopt more biological techniques, adjust risk assessments, and build some automated repair robots, they will build a space in the near future. The elevator is completely possible.
Sina Technology News Beijing time on June 11th news, according to foreign media reports, space elevators have long been one of the themes of science fiction in real life, and this is also the feasibility of NASA and other institutions. The subject of research. The current consensus reached by engineers is that space elevators are a very good idea, but the construction process involves enormous 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 suggested that as long as elevator manufacturers adopt more biological techniques, adjust risk assessments, and build some automated maintenance robots, they will build a future. Space elevators are entirely possible.

In a research report, authors Dan Popescu and Sean Sun simulated the space elevator design, which found maximum stress and maximum pull based on biological structures (eg, ligaments and tendons). The ratio of the strength of the extension is calculated. This is much higher than the stress-strength ratio used in engineering, and the material's ability to absorb forces is at least twice the breaking force.

The researchers point out that stress-intensity ratios like this are acceptable for normal civil engineering projects, but for large buildings, this ratio is too strict to control the probability of failure. It is worth noting that the space elevator is very large and may be the largest building structure built by humans.

The construction of space elevators allows humans and space materials to be transported outside the Earth's atmosphere. In some space elevator designs, there is no mention of the need to use rockets. The earliest space elevator concept was proposed by the Russian scientist Konstantin Tsiolkovsky in 1895.

Since 1895, scientists have continued to refine the design of space elevators, but the basic design of the elevator has not changed. The space elevator contains a cable that is solid on the earth, usually extending upwards into the geostationary orbit – about 35,786 kilometers from the ground.

At the top end of the cable is a balance, gravity and outward centrifugal force put the cable in tension, placing a cargo compartment along the cable that moves up and down the cable. The main problem with this space elevator is that the pressure on the extra-long cable is so great that nothing is currently enough to withstand it.

In the past few decades, there have been some large design competitions and proposals to solve this problem, but so far no one has been successful. The recently proposed solution was the Google X project launched by Google in 2014, but no one was able to manufacture super-strength carbon nanotube cables over 1 meter long, and the space elevator construction plan was put on hold.

It is understood that carbon nanotubes are a great hope for space elevator  word brand elevator engineers, but this hope may be dashed. A 2006 research model predicted that there must be certain defects in the nanotube cable of about 100,000 meters long, which reduced the overall strength of the cable by 70%.

Propscu proposed a different solution in the research report. Although carbon nanotubes are theoretically the best choice for space elevator cables, current technology cannot produce carbon nanotubes over several centimeters in length, so carbon nanometers are used. It is not possible to manufacture space elevators. However, he proposed the use of some composite materials - carbon nanotubes combined with other materials, although the strength is weaker than pure carbon nanotubes, but we are using self-healing mechanisms to enhance the strength of the material to ensure the stability of the super building.

This self-healing mechanism is crucial, and the researchers proposed a cable design that splits its direction into two, up, into a series of "stacked segments"; laterally, into a series of "parallel Cable filaments. When any cable filament fails, this situation will often occur, its influence is limited to its own stack section, and the load weight is immediately shared to the parallel cable 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 be made of materials with lower strength, which makes the actual feasibility closer.

Propscu pointed out that the basis of all these space elevator models is the gradually decreasing stress ratio, the combination of engineering design standards and biological principles. He emphasized that the human Achilles tendons and the spine can withstand tremendous stresses, very close to their tensile strength, which is greater than the stresses that engineers design steel.

The main reason is that, at least to some extent, the tendons and spine have self-repairing power, which is lacking in steel materials. Researchers believe that adding the biological mechanisms of tendons and spine to space elevator design means we don't have to wait for futuristic new materials.

Propscu said: "We believe that super-large building structures such as space elevators must fully consider the possibility of component failure, and also need a self-healing mechanism to replace damaged components. This will ensure that the space elevator is under high load. Run down without damaging its integrity. This means that it is possible to build superstructures using existing materials!"

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