Rare earth elements and helium are just some of the resources scientists believe are abundant on the Moon. The problem is how to get them here. Rockets are not cost-efficient, otherwise, we would have already colonized our natural satellite. Yet there is an alternative to rockets and it might have just got doable: a lunar elevator.
Two astronomy students from the University of Cambridge and Columbia University recently published a paper on an invention dubbed Spaceline – a space elevator they say could be built with existing technology and would cost only about $1 billion. And it would be easy to build.
“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. 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,” Zephyr Penoyre and Emily Sandford write in the abstract of their paper.
A cable to the Moon may sound like something out of a cartoon, but Penoyre and Sandford are not joking. According to their idea, travellers to the Moon would fly to the end of the cable on spacecraft and then transfer to solar-powered autonomous vehicles that would climb the cable to the Moon. The cable itself could be no thicker than the lead of a pencil and made from Kevlar, which is much cheaper than other materials considered for a space elevator.
Of course, the question everyone would ask is, why bother building a space elevator to the Moon. True, there are potentially valuable minerals on the Moon, but we have yet to determine if their mining is commercially viable. But there is another reason a cheap enough space elevator could make sense: helium-3.
Helium-3, many believe, is the solution to the nuclear fusion problem, that is, how to make it work. The element is scarce on Earth but thought to be abundant on the Moon, with several governments eyeing lunar mining to get their hands on it. The reason is helium-3 is a potentially much more efficient fuel for nuclear fusion reactors than what researchers currently have access to on Earth. Combined with deuterium—already used in nuclear fusion reactors—it turns into regular helium with a single proton as a by-product, meaning a lot less energy waste than other elements. What’s more, a deuterium-helium-3 fusion reaction would be much easier to contain.
Yet not everybody shares the enthusiasm about helium-3. One critic, planetary science and astrobiology professor Ian Crawford, for example, has likened helium-3 to fossil fuels.
“It’s a fossil fuel reserve. Like mining all the coal or mining all the oil, once you’ve mined it … it’s gone,” Crawford told Space.com a few years ago. According to him, mining helium-3 on the Moon would require massive investments that do not justify the whole endeavor. With technology moving relentlessly forward and previously expensive infrastructure becoming cheaper thanks to this fact, the investment in helium-3 mining may not need to be that massive.
However, the Spaceline has yet to prove its viability.
“A space elevator is like a railroad — you don’t build it unless you expect a lot of railroad traffic,” physicist Marshall Eubanks told NBC News. And that’s just a commercial concern. A much more serious one has to do with safety: satellites orbiting the Earth could collide with the cable.
These are just a couple of potential problems with the Spaceline and other lunar elevator ideas. Because of these problems, it’s no wonder space agencies have not been all too enthusiastic about the whole idea of linking the Earth with the Moon via an elevator. It seems despite the promise of such ideas, it will be a while before we get our hands on the lunar helium-3.