Gravity and Acceleration on a 50,000 km Space Elevator

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Discussion Overview

The discussion centers around the theoretical implications of gravity and acceleration on a hypothetical 50,000 km space elevator, including the effects on passengers in a lifter, the variation of gravitational force along the cable, and potential speeds of the climber. The conversation explores both conceptual and technical aspects of this idea.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that a passenger would experience decreasing weight until reaching weightlessness at approximately 35,800 km, after which they would feel heavier again, depending on the cable length.
  • Another participant questions whether 35,800 km is the point where Earth's gravity has lost effect, noting that gravitational force exists everywhere but weakens with distance.
  • A participant clarifies that 35,800 km is the altitude where gravitational force allows for a geosynchronous orbit, not a point of zero gravity.
  • There is a discussion about the implications of extending the elevator towards the moon, with questions about whether the passenger would feel weight again as they approach the moon.
  • One participant introduces the concept of Lagrangian points and their relevance to the discussion, noting that they pertain to objects with the same orbital period.
  • A participant raises the idea that the upward velocity of the elevator could create artificial gravity, prompting a response that this would only apply if the elevator is accelerating.

Areas of Agreement / Disagreement

Participants express differing views on the effects of gravity at various altitudes and the implications of extending the elevator towards the moon. There is no consensus on the specific points of gravitational influence or the feasibility of connecting a space elevator to the moon.

Contextual Notes

Some assumptions about gravitational force and orbital mechanics are not fully explored, and there are unresolved questions regarding the effects of acceleration on perceived weight.

jack5000
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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?
 
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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?
 

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