The development of rocket technology, it seems, is nearing the limit of its capabilities, so that scientists and engineers are engaged in the development and research of new methods of launching cargo into low-earth orbit and beyond. Among the most promising is the idea of a "space elevator" put forward back in 1895 by the Russian scientist Konstantin Tsiolkovsky. Until recently, it was believed that the current level of development of technology does not allow its implementation, but a group of American scientists does not agree with this opinion.
The proposed Tsiolkovsky project of the "orbital tower" was developed in the 1960s by the Soviet engineer Yuri Artsutanov. In his writings, he proposed a structure modified in relation to the experience accumulated since Tsiolkovsky's time. It is noteworthy that Artsutanov published his article "Into Space on an Electric Locomotive" almost a year before Yuri Gagarin's flight. In it, he proposed using ropes attached to satellites in geosynchronous orbit to deliver cargo and people to orbit. Thus, freely flying ropes (rotovators) rotate with the speed of the Earth or other celestial body, which ensures their tension. In this case, transportation by cables is carried out with significantly lower acceleration than with a rocket start. The novel of the famous British science fiction writer Arthur Clarke "Fountains of Paradise" is also dedicated to the construction of the "space elevator".
In theory, a much safer, cheaper and more reliable way of developing near-Earth space for implementation requires, first of all, the production of cables with a strength of more than 65 gigapascals (for comparison: the strength of steel is 1-5 GPa, silica fiber is about 20 GPa). Even ultra-strong graphene-based carbon nanotubes have not yet reached the required strength (despite the fact that the length of existing samples usually does not exceed several centimeters). However, an article submitted for publication in Space Policy by American researchers Eubanks and Redley (the original is available at arXiv.org) proves that the construction of a space elevator on the Moon is most likely possible using polymers available in commercial circulation today.
On the tightrope
The first phase of the project, called the Deep Space Tether Pathfinder (DSTP) by the authors, should simultaneously become both a prototype of a commercially exploitable space elevator between the Earth and the Moon, and an important tool for researching our satellite. Rotating the DSTP will allow enough samples to be captured for scientific research in Shackleton Crater, after which, about half of the rope rotation, the capsule with the samples will go to Earth, thanks to the acceleration that allows you to select the optimal return trajectory. The device, in simple terms, will act as a catapult, allowing you to move cargo from the Moon to Earth. DSTP will be able to make only one shipment of samples, after which it will go into outer space - and itself will become the object of studying the influence of micrometeorites on the state of the tether and other factors,important for understanding the operation of the space elevator. The DSTP cable will be 5,000 km long and weigh 2,228 kg.
If successful, the next step could be the construction of the infrastructure of the Lunar-Space Elevator (LKL) proper for moving into the Moon's orbit from the satellite surface and further to the Earth. The system should be a super-long cable attached to the surface of the Moon passing through the Lagrange point (in which the weight fixed on the cable will remain motionless relative to two celestial bodies) between the Moon and the Earth, approximately 56 thousand km from the Moon. LKL will be able to lift approximately five tons of rock per year from the Moon and lower equipment of the same combined weight to the lunar surface.
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Available means
As the authors of the article point out, for the implementation of the project, given the lower gravity on the Moon, it is possible to use synthetic polymers that already exist and are commercially available in commercial circulation, such as ultra-high-molecular-weight high-density polyethylene (UHMWPE; used, in particular, for the production of bulletproof vests, lining of shipbuilding berths In Russia, there are two pilot plants for the production of such material) and polyphenylene-2, 6-bezobioxazole produced in Japan (PBO; trade name Zylon, is used, in particular, for reinforcing concrete building blocks).
Photo: nasa
According to the calculations of scientists, one flight of a space mission of the NASA Discovery class will be enough to implement the project. After the delivery of 58.5 tons of Zylon polymer to the Lagrange point, a "warehouse" of the materials necessary for the operation of the elevator will be equipped there. From there, a descent vehicle will be lowered onto the moon's surface, into the Central Gulf, on a cable, which will become the base station for lifting and lowering cargo. A counterweight will be fired into open space to keep the system in balance; the total length of the cable will thus reach 278.5 thousand km. Samples of regolith, lunar soil weighing up to 100 kg will be sent to the intermediate base at the Lagrange point using a reusable capsule powered by solar energy. Fuel for further transfer of samples to Earth is not required, since,Having detached from the cable at a distance of approximately 220.67 thousand km from the Moon, the capsule will continue to move by inertia and will enter the Earth's atmosphere in about 34 hours at a speed of about 10.9 km / s. To estimate the possible volume of cargo turnover, it is enough to remember that during all the Apollo lunar missions only 382 kg of regolith were delivered to Earth.
If successful, the second LKL can be built on the far side of the Moon, with a base station in the Lipsky crater area. As the researchers point out, such a position will, among other things, be an ideal place for radio astronomy research, since the far side of the moon is completely isolated from radio waves from Earth. The authors of the project estimate the lifespan of the lifts at five years. In addition to scientific research and hypothetical use for mining, lunar elevators could play an important role in the implementation of a manned mission to Mars. According to a report published in the fall of 2015 by an international research group from the Massachusetts Institute of Technology, Keio University and the Jet Propulsion Laboratory of the California Institute of Technology,the launch mass of the spacecraft to Mars can be reduced by 68 percent due to the use of oxygen contained in the regolith for engines (41-46 percent of the specific gravity). Eubanks and Redley point out in their work that an additional factor may be the use of the LKL counterweight on the far side of the Moon to accelerate and launch cargo ships into Mars orbit to supply future colonies on the "red planet".
Vladislav Krylov