![]() ![]() The big hurdles to building a space elevator are: 1) it sounds like a physicist stoner fantasy and 2) for Earth there are only a few things you can build a space elevator out of and we can’t manufacture any of them on the scales we need. Basically, space elevators turn Earth into a giant space weed wacker. ![]() ![]() If you swing a rope around over your head it will point straight away from you and for exactly the same reason space elevators stay upright (as long as enough of its mass is above geosync). If you run a cable from the equator straight up, below geosync it will want to fall, because it will be traveling slower than orbital speed (that’s why ropes don’t stand up on their own), but above geosync it will want to fall up, because it will be traveling faster than orbital speed. If you ever see a satellite dish that’s nailed to a wall, it’s pointing at a satellite in geosync, because only those satellites sit perfectly still in the sky with respect to the ground. In between is “geosynchronous orbit”, where objects can orbit the Earth in exactly one day, allowing them to stay over a single point on the equator indefinitely. Near the surface (within a few hundred km) orbits around the Earth take about 90 minutes, while the Moon (385,000 km away) takes about a month. The higher something is, the longer it takes to orbit. Since the tether is anchored to the ground, the rotation of the Earth supplies sideways velocity to anything attached to the tether and (like anything that rotates) that sideways velocity adds up to a lot if you get far enough out. While the trip will be much slower and controlled, more like travel by train than roller coaster, the real advantage of space elevators is infinite free energy forever and a safe, convenient way to get to and from the surface of Earth and literally anywhere else in the solar system. Vehicles that climb up and down a space elevator can be as small as you like, run on electricity, and don’t suffer from the burning/exploding snafus native to rocketry. It’s good that the lower stages are now being reused, but it’s bad that they exist at all. And then of course are all of the usual issues that crop up when you ride an explosion into space. And since a rocket needs to carry all the fuel it burns, the first (and largest) stage of a rocket is almost entirely fuel used to lift other fuel. Rockets are powered by rocket fuel, which means that there’s a whole extra process for supplying them energy. But even with reusable equipment, rocket flight has a number of drawbacks that are unlikely to ever be fixed. The cost of sending stuff to space has dropped precipitously in the last few years, as people of staggering genius discovered not-throwing-your-rocket-away technology. Once it’s anchored, we’d get new cables into place by running them up the old cables like a flag pole. In order to build a space elevator we’d first send a bundle of cable to geosync (or manufacture it in space) and then lower one end to the ground. Above geosynchronous orbit, 42,000 km up, the tether will swing fast enough that it will “fall up”, keeping the whole system upright. ![]()
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