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Since the dawn of the space age, more than six decades ago, there was only one way to get to the moon and come back: rockets. But two graduate students say that we should now be able to transport humans and goods between Earth and our natural satellite via a kind of high-tech elevator.
The idea of space elevators is not new; Space visionaries have been talking about it since at least 1895. But Zephyr Penoyre and Emily Sandford envision a system that would not be used to transport human beings and cargo from the Earth's surface to Earth's orbit – the goal of so-called conventional concepts Space elevators – but provide transportation to and from the moon.
In a study published Aug. 25 on arXiv online research archives, students claim that it is technically and financially feasible to build such a "lunar space elevator", described for the first time by space flight scientist Friedrich Zander in unpublished notes of 1910.
"It shocked me how cheap it might be," says Penoyre, co-author of the study, a postgraduate astronomy student at the University of Cambridge, adding that the $ 1 billion that It would be necessary to build such a motivated billionaire elevator. "
A very long cable
Penoyre and Sandford, a graduate student in astronomy from Columbia University and co-author of the study, call their Spaceline lunar spatial lift concept. Its central element is a cable that would be anchored in the Moon and extend over 200,000 miles to a point above the surface of the Earth – perhaps an orbit about 27,000 miles from our planet. (The cable of a lunar elevator could not be anchored to the surface of the Earth because the relative movements of the Moon and our planet would not allow it.)
As explained in the document, the simplest version of the Spaceline cable could be only slightly thicker than the pencil lead and weigh about 88,000 pounds – within the payload capacity of one. NASA rocket or SpaceX of new generation. It could be made from Kevlar or other existing materials rather than exotic, hard-to-fabricate carbon-based materials that have long been considered the key to building a classic space elevator.
Future space travelers would use a spacecraft to travel from Earth to the end of the suspended cable, which would be held taut by Earth's gravity, and then move on to solar-powered robotic vehicles that would wind up the cable to the ground. To the moon. The trip can take days or weeks. Return trips would simply reverse the process.
Why spend hundreds or even billions of dollars building a lunar space elevator instead of relying on proven rocket technology? Penoyre and Sandford say in their article that the former could ultimately be more economical, especially for bringing back to Earth raw materials from moon-based mines.
An article published by the American Institute of Aeronautics and Astronautics estimated that a system of lunar space elevators could self-finance in 53 journeys by carrying cargoes. lunar material to a space station between the Moon and the Earth.
Miner the moon
For years, experts have envisioned the moon as a potential source of valuable raw materials, ranging from helium-3, a heavy version of the well-known gas that can be used in fusion reactors, rare earth minerals such as neodymium and gadolinium. used to make cell phones, medical scanners and other high-tech devices.
"A space elevator, it's like a railroad. You do not build it unless you expect a lot of rail traffic, "says physicist Marshall Eubanks, chief scientist at Space Initiatives, a satellite technology company in Palm Bay, Florida. He calls the calculations used in the Spaceline paper, but warns that satellites in Earth orbit could collide with the colossal cable – a potential problem that could be mitigated by keeping the cable out of the orbital space paths of the Earth.
Despite their potential benefits on rocket transport, neither lunar space elevators nor conventional space elevators have captured the attention of space agencies or aerospace manufacturers. NASA has funded occasional studies on the classic concepts of space lifts since the late 1970s. But to date, there is no SpaceX for space lifts, although Chinese and Japanese companies have launched proposals for space lifts. the construction of conventional space elevators by 2045 and 2050, respectively.
"What's frustrating is that the idea of lunar space elevators is not very successful, and yet it's a feasible and economically-minded idea." said Charles Radley, CEO of Space Initiatives.
Debate elevator
Some experts claim that a classic space lift could make more sense than a lunar lift, at least initially, as it could make exploration easier. For example, a classic space lift could be used to assemble a huge space ship into Earth orbit and launch it from there. Experts say it would probably be easier than launching the spacecraft from Earth, where gravity is so intense.
But the conventional space elevator would require a much stronger cable to withstand the high forces on the cable – and it is unclear whether materials that are strong enough and of sufficient length to make an adequate cable will be available.
"The classic space elevator is a really difficult problem because the Earth's gravity field is so big that you need such powerful materials that we do not have at the moment," says James Pearson, aerospace engineer and president of Star, Inc. an aerospace company in Mount Pleasant, South Carolina, and author of several articles on space elevators. "On the other hand, you could build a lunar lift with existing equipment currently."
Given this concern, Pearson endorses the idea of moving forward with a lunar space elevator as a precursor to the construction of a conventional space elevator. "There are a lot of benefits with a lunar lift," said Pearson. "And with this new NASA program to return to the moon, there could be additional interest."
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