4 ms·

What I never seem to see addressed, is the following: As the elevator ascends the cable, it's "ground speed" must continually increase. What is the source of th

What I never seem to see addressed, is the following: As the elevator ascends the cable, it's "ground speed" must continually increase. What is the source of the force that provides that acceleration (parallel to the ground)? A traditional rocket expends a great deal of energy firing its rockets with a component parallel to the surface of the earth to gain acceleration in that direction. Where is the equivalent coming from w/ the space elevator?

CapitalistCartr 11y ago
That is not at all how it works. The elevator does not go into low-Earth orbit(LEO). It is part of the elevator system whose center of gravity is at Geostationary Orbit. So the craft itself, and the ribbon, is always over the same spot on the Equator.
Retric 11y ago
The earth's rotation. Much like how your rotational velocity increases when you climb stairs. Also, the cable is not vertical, you want a large mass past geostationary orbit which pulls the cable fairly thought though there is some bend. PS: Try and calculate just how much energy is in earth rotation it's a rather large number.
- willismichael 11y ago
  > climb stars I love this typo.
parenthephobia 11y ago
That's caused by the Coriolis force. Rising elevator cars would leach the Earth's angular momentum, whilst lowering cars would replenish it.
- deleted 11y ago
  [deleted]
johngalt 11y ago
> As the elevator ascends the cable, it's "ground speed" must continually increase That is backwards. The higher you are the less speed you need. This is true in all orbits. Contrast the orbital velocity of Mercury vs Neptune. The rocket is aiming for low orbit. I.E. you go fast enough that you fall around the earth rather than into it. The only reason a rocket's ground speed increases as it's altitude increases because it's hard to add a lot of speed while still in the denser sections of the atmosphere. Altitude is needed merely to clear the drag imparted by the atmosphere. We go fast and low because it's the easiest way to get something to stay in orbit using rockets. But mechanically as we gain altitude we go slower relative to the ground. Eventually when you go high enough you are standing still relative to the ground (geosynchronous orbit) or even go backwards relative to the earths rotation (high orbit). A space elevator is aiming to go so high that there is no parallel acceleration necessary. The rotation of the earth provides all the acceleration needed. A space elevator that ends in geosynchronous orbit requires no parallel acceleration relative to the ground. A space elevator in high orbit could get something of a free ride out of earth's gravity well powered by the rotation of the earth.

CapitalistCartr 11y ago

That is not at all how it works. The elevator does not go into low-Earth orbit(LEO). It is part of the elevator system whose center of gravity is at Geostationary Orbit. So the craft itself, and the ribbon, is always over the same spot on the Equator.

Retric 11y ago

The earth's rotation. Much like how your rotational velocity increases when you climb stairs. Also, the cable is not vertical, you want a large mass past geostationary orbit which pulls the cable fairly thought though there is some bend. PS: Try and calculate just how much energy is in earth rotation it's a rather large number.

willismichael 11y ago
> climb stars I love this typo.

parenthephobia 11y ago

That's caused by the Coriolis force. Rising elevator cars would leach the Earth's angular momentum, whilst lowering cars would replenish it.

deleted 11y ago
[deleted]

johngalt 11y ago

> As the elevator ascends the cable, it's "ground speed" must continually increase That is backwards. The higher you are the less speed you need. This is true in all orbits. Contrast the orbital velocity of Mercury vs Neptune. The rocket is aiming for low orbit. I.E. you go fast enough that you fall around the earth rather than into it. The only reason a rocket's ground speed increases as it's altitude increases because it's hard to add a lot of speed while still in the denser sections of the atmosphere. Altitude is needed merely to clear the drag imparted by the atmosphere. We go fast and low because it's the easiest way to get something to stay in orbit using rockets. But mechanically as we gain altitude we go slower relative to the ground. Eventually when you go high enough you are standing still relative to the ground (geosynchronous orbit) or even go backwards relative to the earths rotation (high orbit). A space elevator is aiming to go so high that there is no parallel acceleration necessary. The rotation of the earth provides all the acceleration needed. A space elevator that ends in geosynchronous orbit requires no parallel acceleration relative to the ground. A space elevator in high orbit could get something of a free ride out of earth's gravity well powered by the rotation of the earth.