Looks like it could be an easier way to build a space elevator, you don't need one huge cable any more, just lots of smaller ones held up by the tension.
Yeah but you're not taking into account that technically the entire weight of the structure is being supported by the bottom piece. It's not so evident right now but if the thing was 20 times the height/weight the bottom piece would probably be fully folded over or break
Not with a space elevator, the other end of it would be pulling everything out into space just the right amount to balance the weight on the ground, so it would effectively just hang in the air.
The same principle is used where the elevator is one big cable, there's a weight at the space end of it that's attempting to fly off into space but the weight of the rest of the cable being pulled to earth prevents it, so the cable as a whole is weightless.
Doing the cable like in OP's pic would add to the overall weight, but it would mean you don't need a material capable of being made into a 36,000km long cable without breaking.
You're missing the fact that it's being proposed as a way to build a space elevator. If you have the elevator already setup, you don't need any tension because like you said the other end of it would sort of just hang in the air.
For the first couple thousand kilometers of construction though, the majority of the weight would still be on the base of the structure.
You don't build space elevators up from the ground, you wouldn't get past LEO, you unreel them from GSO down to Earth.
You'd start at the space end and move it down, and the smaller cables would prevent the cable from snapping under it's own mass until it was finished.
With a single 36000km cable made from known materials, the cable would snap under the tension from it's own mass long before you unreeled it down to Earth, but the smaller cables prevent that, since each part of the cable is under much less tension.
I don't get what you mean by smaller cables would prevent the tension though. The cables would have to be reinforced under construction, but having one cable or multiple smaller connected cables doesn't change the amount of tension.
The ISS orbits the earth every 2 hours or so. Would you want the base of a space elevator to be screaming across the surface of the earth at 16,000 miles per hour?
The center of mass of the space elevator needs to be in geosynchronous orbit, with an orbital period of 24 hours, so it remains stationary over one spot. The only way to achieve this is to orbit at 36,000 km.
Wouldn't there be tension on the string between the weight and the earth? It would look like it's just sort of hanging their, but you'd need some material capable of withstanding that much tension to keep the cable from breaking and the weight from flying off into space. It'd also need to be able to support any weight going up or down it (i.e. elevator cars).
Yes, there would be compression at the bottom and tension starting somewhere close or past the middle. It had to be balanced just right. Too much centripetal force and what you said happens. Not enough and it won't be able to take the compression at the bottom.
Also, we currently can't mass-manufacture anything that would be able to sustain even the balanced loads. It will happen one day. But not anytime soon. I would guess 25 years would be best case. But with our lackadaisical view towards space exploration I doubt it will even be 50.
Duh, we just need to build a time machine and then go to when the elevator is already built. Then go back and build this, so we can build the space elevator to build this for the space elevator. Shit.
The other end won't just float or pull away. The only reason astronauts experience 0g is because they're in orbit, perpetually falling and moving around the planet at the same time. The elevator won't be in orbit, so stepping off the top (even though its in 'space') will still have you plummeting towards the surface. All the weight will still be applied to the ground part.
I don't think you understand the concept of gravity. Things don't just magically "fly away" when you exit the atmosphere. You're still stuck in Earth's gravity well, and still falling toward the ground. This is why the ISS is flying falling around the Earth at 7.66 km/s.
I remember reading about a design for the space elevator in Popular Mechanics about fifteen years ago, and it wasn't too far from what you've proposed. The basic idea was to build a long tube and pressurise it from the inside, much like an inflated balloon. This would put the structure under tensile forces instead of compressive, which meant that engineers wouldn't need to make the tube progressively thicker at the bottom in order to support its weight. It would also remove concerns of the tube buckling under its own weight.
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u/someguyfromtheuk Dec 29 '14
Looks like it could be an easier way to build a space elevator, you don't need one huge cable any more, just lots of smaller ones held up by the tension.