Traveling to the Moon aboard a space elevator is possible using modern technology

One idea is to build a space elevator, a cable that runs from Earth to orbit to take you into space. (CREDIT: Creative Commons)

Perhaps the biggest obstacle to humanity’s expansion into the solar system is the prohibitive cost of escaping Earth’s gravitational pull. So think Zephyr Penoyr from the University of Cambridge in the UK and Emily Sandford from Columbia University in New York.

The problem is that rocket engines work by shedding mass in one direction to create thrust for a spacecraft in another. And this requires huge amounts of fuel, which is eventually thrown out, but it also needs to be accelerated along with the spacecraft.

As a result, putting one kilogram into orbit costs about tens of thousands of dollars. Flying to the moon and beyond is even more expensive. Thus, there is considerable interest in finding cheaper ways to reach orbit.

One idea is to build a space elevator, a cable that runs from Earth to orbit to take you into space. The big advantage is that the climbing process can be powered by solar energy and thus does not require onboard fuel.

But there is also a big problem. Such a cable must be incredibly strong. Carbon nanotubes are a potential material if they can ever be produced long enough. But the options available today are too weak.

Similar stories

Enter Penoyre and Sandford, who have revisited the idea with a twist. They say their version of the space elevator, which they call the spaceline, can be built from materials that are commercially available today.

First, a little background. A space elevator in the traditional sense would consist of a tether attached to the ground and extending beyond geostationary orbit at an altitude of about 42,000 kilometers (26,098 miles) above the Earth.

Such a cable would have a significant mass. Therefore, to prevent it from falling, it would have to be balanced at the other end by an equally rotating mass. Then the entire elevator will be supported by centrifugal forces.

For years, physicists, science fiction writers, and visionaries have been excitedly calculating the magnitude of these forces, but the results have unfortunately been disappointing. No known material is strong enough to handle these forces—not spider silk, not Kevlar, not even the strongest modern carbon fiber polymers.

So Penwire and Sandford took a different approach. Instead of fixing the cable on the Earth, they propose to fix it on the Moon and extend it to the Earth.

The big difference is due to centrifugal forces. A typical space elevator would make a complete rotation every day in accordance with the rotation of the Earth. But a lunar-based space line would only rotate once a month—much slower, with correspondingly smaller forces.

Moreover, the forces are distributed differently. Stretching from the Moon to the Earth, the cosmic line will pass through the region of space where the earth’s and lunar gravity balance each other.

This region, known as the Lagrange point, becomes the center line of the space line. Beneath it, closer to Earth, gravity pulls the cable toward the planet. But above it, closer to the moon, gravity pulls the cable to the lunar surface.

Penoir and Sandford were quick to show that extending a cable from the Moon to the Earth’s surface creates forces that are too great for today’s materials. But the cable doesn’t have to stretch all the way to be useful.

The main result of the researchers is to show that today’s strongest materials – carbon polymers such as Zylon – can comfortably support a cable that stretches from the Moon to geostationary orbit. They further speculate that an experimental device made from a cable as thick as a pencil lead could be dropped from the moon at a cost measured in the billions of dollars.

This will reduce the amount of fuel needed to reach the Moon’s surface. (CREDIT: LIftPort)

This is clearly ambitious, but by no means over the top for today’s space missions. “By extending a line anchored on the Moon deep into Earth’s gravity well, we can build a stable, traversable cable that allows free movement from Earth’s neighborhood to the Moon’s surface,” Penoyre and Sandford say.

The savings would be huge. “This will reduce the amount of fuel needed to reach the lunar surface to a third of the current value,” they say.

And this would open up a completely new area of ​​space for research – the Lagrange point. This is of interest because both the gravity and the gravity gradient in this region are zero, making it much safer for construction projects. In contrast, the gravitational gradient in low Earth orbit makes orbits much less stable.

“If you drop an instrument from the International Space Station, it will rapidly move away from you,” Penoyre and Sandford note. “The Lagrange point has an almost negligible gravitational force gradient; a dropped tool will stay at hand much longer.”

There is also no significant debris in the area. “The Lagrange point has been largely untouched by previous missions, and the orbits passing through it are chaotic, which greatly reduces the number of meteoroids,” they say.

For these reasons, Penwire and Sandford say access to the Lagrange point is the main advantage of the spaceline. “The base camp at the Lagrange point is what we consider the most important and influential for the early use of the space line (and for human space exploration in general),” they say. “Such a base camp would enable the construction and maintenance of a new generation of space experiments—one could imagine telescopes, particle accelerators, gravitational wave detectors, vivariums, power generation stations and launch points for missions to the rest of the solar system.”

This is an interesting work that suggests a renewed focus on the idea of ​​a space elevator. Cheap access to the Lagrange point, the Moon, and points beyond it could become much cheaper and more likely.

For more science news, visit our New Innovations section at The bright side of the news.

Note. Materials provided above by Emerging Technology from the arXiv archive. Content can be edited for style and length.

Do you like such pleasant stories? Receive Brighter Side of News Newsletter.