Everyone who's been to the moon so far has travelled there in a rocket. But soon they might be taking the elevator.
Space elevators have remained in the realm of science-fiction since they were first proposed in the 1890s, before anyone had even flown a plane, let alone a spaceship.
It essentially involves hoisting a cable from the ground up into the sky, held in place by centrifugal force. Payloads can climb the cable without having to worry about being pulled down to Earth, and once at the top have enough speed relative to Earth to escape its gravity without the need for massive amounts of fuel.
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None have ever been built because no one's yet figured out how to make one that wouldn't break.
But new research by a couple of astronomers has suggested how one could work - build it on the moon.
"By extending a line, anchored on the moon, to deep within Earth's gravity well, we can construct a stable, traversable cable allowing free movement from the vicinity of Earth to the Moon's surface," grad students Zephyr Penoyre and Emily Sandford from the universities of Cambridge and Columbia wrote in a new paper.
"With current materials, it is feasible to build a cable extending to close to the height of geostationary orbit, allowing easy traversal and construction between the Earth and the moon."
Their 'Spaceline', made of kevlar rather than next-gen carbon nanotubes, would need to be barely any thicker than the lead in a pencil, and despite being more than 340,000km long would only weigh about 40 tonnes - light enough to fit aboard a SpaceX rocket. The cable would be held in place not by centrifugal force - the moon spins far too slow for that - but by the Earth's strong gravity.
The moon always faces the same side towards Earth, so its rotation wouldn't be a problem.
"The classical space elevator is a really tough problem, because the Earth's gravity field is so great that you need such strong materials that we don't have right now," aerospace engineer Jerome Pearson told NBC. "On the other hand, you could build a lunar space elevator with existing materials right now."
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And the cost wouldn't be an obstacle - Penoyre suggesting it could be as low as US$1 billion (NZ$1.6 billion), "within the whim of one particularly motivated billionaire".
It wouldn't reach all the way to Earth, as that would put it in danger of being hit by satellites and other space debris. And it can't attach to the Earth, for obvious reasons - the Earth spins around 29.5 times for every revolution the moon makes.
But even if you still need a spaceship to get to the elevator, the cost of getting to the moon and back would be lowered so much, the economic benefits of mining the moon would quickly pay for it, one expert told NBC.
"Many important questions remain unanswered, many technological and sociological challenges stand between the idea and its execution," Penoyre and Sandford write.
"But if the logic presented here holds up to scrutiny it can be done. With concerted effort and investment, it may be a reality in decades, perhaps even years. We hope it will inspire others to question, calculate, discuss, and to take a long view on our ambition and path to becoming a sustainable spacefaring civilisation."
The paper, uploaded to research site arvix.org, has not been peer-reviewed.
Newshub.
