[eli5]Building a sky elevator



Why instead of launching rockets from the ground, we don’t build a high platform above the sky and launch from there?

In: Earth Science

Wind, temperature, high costs, complexity. There are many reasons why that’s a bad idea. A space elevator however could be a futuristic way to bring things into orbit. But even that is currently not exactly do-able.

In concept launching a rocket when it is already outside the atmosphere would save a lot of fuel and be easier to reach orbit.

All you need to do is build a structure at least 200 times taller than the tallest building ever made. Simple, no problem, why don’t you get right on that.

But if we are serious about sending equipment on Mars, we need to find better delivery system than the one we have now. And money is not important if it’s a humanity effort instead of country effort. Even if we start launching from the stratosphere it will save us a ton of space on the rockets because the rockets will use less fuel because of lower air density which means less friction. Also Burj califa costs 1.5 billion because its a luxury building with glass and tiles and furniture. For sky elevator we would need just steel and concrete

The wind sheer from our atmosphere would be near impossible at our current technology.

However, the next best thing is going to be sending things from the moon. I expect to see a moon colony in my kids lifetime.

It’s possible, but not financially feasible. According to current estimates, even if a space elevator exists, it would move so slowly that it wouldn’t be worth it. We’re talking about several days of transit, because of the forces involved. If the elevator tried to shoot up at high speed, it would pull on the structure and possibly topple it.

There also are things to consider like storms, temperature changes, and so forth; highways are built with seams to allow them to expand and contract when the temperature changes, and those sections are just 50’ long or so. If those seams aren’t there, the roadway buckles, arches, cracks, and sometimes violently shatters. A space elevator would be up to *150 miles long*, and would expand and contract by *up to a mile* when temperatures change!

Then there’s maintenance. How do you send someone up to fix a thing 40 miles in the air? We currently send workers up 1700’ radio towers, which takes several hours and is absolutely terrifying, and pays tens of thousands of dollars to each of the 2-4 workers who climb, just to replace a light bulb every so often.

Compare all of this to our current strategy; we have rockets we can move inside when the season turns or a hurricane forms. The rockets can reach orbit in just a few minutes, and can be aborted if something goes wrong before ignition; a crew eight miles up on a space elevator traveling 3/4mph would be screwed if a storm suddenly formed underneath them.

Then there’s the fact that we don’t even have the mechanics or materials to build a space elevator, or an upper-atmosphere launch platform.

For now, this is the best we have. But in the future, the next big change they’ll have to make to allow for long-distance space travel is launch fuel reserves into orbit, so once in orbit a spacecraft could switch out an empty/partial tanks for a full one en route to Mars or Europa.

There is a great podcast on this from SYSK. The biggest limitation is we don’t have any material strong enough to make a space elevator. Once carbon nanochains can be mass produced this is a entirely realistic probability, but you would have to contend with space debris and orbits

The concept you’re asking about is usually called a [space elevator](https://en.wikipedia.org/wiki/Space_elevator) and was first suggested way back in 1895.

It’s theoretically a conceptually sound idea. The main problems are practical engineering problems. For a space elevator on Earth, you’d need to build it out of a very strong, very light material. Which we simply don’t have.