# Gravity on a space evelvator

• jack5000
In summary, the space elevator would be very long, have a fast climber, and be able to reach high speeds.

#### jack5000

I've been reading a lot about space elevators being built from carbon nanotube thread and having lifters powered by lasers. I'm imagining it to be 50,000 long. Obviously this is fiction at the moment, but i was wondering...

if there was such a structure, what would be the effects of gravity on someone in a lifter?
At what point would the effects be felt?
As the lifter was pushed/pulled further along the ribbon, how would gravity's force change along the journey.

Also what kind of speed do you think would be reached on a 50,000 km long cable?

The passenger would weigh less and less, reaching weightlessness at the height of ~35800km(geosynchronous orbit), and then get heavier again, with the upper limit depending on the cable length.

The maximum speed of the climber would be constrained by the thermal tolerance of the climber/ribbon.
This publication:
http://www.mill-creek-systems.com/HighLift/contents.html
describes a climber going at 200km/h, but that is the cable-deployment vehicle, so perhaps the payload-carrying version could have a different, faster design.

Thanks the reply and for that publication, looks very interesting.

Bandersnatch said:
The passenger would weigh less and less, reaching weightlessness at the height of ~35800km(geosynchronous orbit), and then get heavier again, with the upper limit depending on the cable length.

Is the 35800km the point where Earths gravity has lost effect?

Also what if the ladder was going toward the moon? would the passenger feel the weight again as he got closer to the moon?

Would there be a Lagrangian point and would that effect?

jack5000 said:
Is the 35800km the point where Earths gravity has lost effect?
That point does not exist, the gravitational force from Earth is everywhere (but quite weak in large distances).
35800km is the point where the gravitational force is just enough to keep an object in an orbit with a period of 1 day (= the movement of the space elevator itself)

Also what if the ladder was going toward the moon? would the passenger feel the weight again as he got closer to the moon?
The moon needs much more time for an orbit, you cannot connect a space elevator to the moon (or extend it so far that the moon's gravity becomes important).

Lagrangian points refer to objects with the same orbital period - which would be about one month for moon, and not one day for the space elevator.

Doesn't the upward velocity of the elevator itself create an artificial gravity that has to be factored into these calculations?

Only if it is accelerating.

## 1. What is a space elevator and how does it work?

A space elevator is a hypothetical structure that would be used to transport people and materials from Earth's surface to space. It consists of a long cable or ribbon attached to a counterweight in space, and the rotation of the Earth would keep the cable taut. Similar to an elevator, a climber or vehicle would travel up and down the cable using mechanical or electrical power.

## 2. How does gravity affect a space elevator?

Gravity plays a crucial role in the functioning of a space elevator. The cable is held taut by the counterweight's gravitational pull, which is balanced by the Earth's gravitational pull on the climber. As the climber moves up the cable, it experiences a decrease in gravitational pull from the Earth, allowing it to continue its ascent. Similarly, when the climber descends, it experiences an increase in gravitational pull, aiding in its descent.

## 3. What are the challenges of building a space elevator?

There are several challenges associated with building a space elevator, including the engineering and materials required to construct such a large and long cable, as well as the effects of weather and atmospheric conditions on the structure. Additionally, the cable would need to be able to withstand the extreme forces of gravity and tension, as well as potential impacts from space debris.

## 4. How does the location of a space elevator affect its functioning?

The location of a space elevator plays a crucial role in its functioning. It needs to be located near the equator to take advantage of the Earth's rotational velocity, which aids in keeping the cable taut. Additionally, the location should have a stable and predictable climate to minimize the effects of weather on the structure.

## 5. Could a space elevator be used to transport people and objects to other celestial bodies?

The concept of a space elevator has been proposed for use on other celestial bodies, such as the Moon or Mars. However, the unique conditions and gravitational forces of each body would present new challenges and require different designs. Additionally, the construction and maintenance of a space elevator on another planet would be significantly more complex and costly compared to one on Earth.

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