Penoyre and Sandford, a graduate student in astronomy at Columbia University and a co-author of the study, call their lunar space elevator concept Spaceline. Its central element is a cable that would be anchored to the moon and span more than 200,000 miles to a point above Earth’s surface — perhaps an orbit about 27,000 miles from our planet. (The cable of a lunar space elevator couldn’t be anchored to Earth’s surface because the relative motions of the moon and our planet wouldn’t permit it.)
As explained in the paper, the simplest version of the Spaceline cable might be barely thicker than the lead in a pencil and might weigh about 88,000 pounds — within the payload capacity of a next-generation NASA or SpaceX rocket. It could be made from Kevlar or other existing materials rather than the exotic and hard-to-make carbon-based materials that have long been seen as the key to building a classical space elevator.
Future space travelers would use a spacecraft to fly from Earth to the end of the dangling cable, which would be held taut by Earth’s gravity, and then transfer to solar-powered robotic vehicles that would climb up the cable to the moon. The voyage might take days or weeks. Return trips would simply reverse the process.