Can a space elevator be stabilized without reaching geostationary orbit?

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Discussion Overview

The discussion centers on the stability of a proposed space elevator and whether reaching geostationary orbit (GSO) is necessary for enhanced stability. Participants explore the implications of tower height, gravitational effects, and engineering challenges related to constructing such a structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a tower reaching geostationary orbit would be more stable than one that does not, pondering the existence of a gravitational pull from orbit versus reduced downward pressure at higher altitudes.
  • Another participant mentions the impact of ground vibrations and wind forces on stability, citing an example of a skyscraper's oscillation due to wind.
  • Some participants assert that a tower would be more stable if built to geostationary orbit, noting that the portion of the tower above GSO contributes to stability, but this requires precise equatorial placement.
  • A later reply suggests that if the tower does not extend to geosynchronous orbit or higher, it would collapse, as parts of the cable at lower altitudes would not maintain their position and would fall to Earth without a counterweight beyond GSO.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of reaching geostationary orbit for stability, with some supporting the idea while others highlight the engineering challenges and potential collapse of a shorter tower. The discussion remains unresolved regarding the optimal height for stability.

Contextual Notes

Participants mention various engineering challenges, including the effects of environmental factors like hurricanes and tsunamis, as well as the need for a counterweight beyond GSO, indicating limitations in current technology and assumptions about structural integrity.

Andrew S
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Hi.

This may be really basic, but would appreciate your help. Is a tower whose height reaches a geostationary orbit at 35,000km's altitude or so more stable that one which doens't quite reach that height? So, say you are building a tower, decide you'd like it more stable, so should you go to the effort of making it a bit taller in order to take advantage of some sort of low gravity pull from the top?

I guess the question is whether there is such a 'pull' from orbit, or if the downward pressure is just less on the higher portions...

Thanks heaps.
Andrew
 
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Andrew S said:
Hi.

This may be really basic, but would appreciate your help. Is a tower whose height reaches a geostationary orbit at 35,000km's altitude or so more stable that one which doens't quite reach that height? So, say you are building a tower, decide you'd like it more stable, so should you go to the effort of making it a bit taller in order to take advantage of some sort of low gravity pull from the top?

I guess the question is whether there is such a 'pull' from orbit, or if the downward pressure is just less on the higher portions...

Thanks heaps.
Andrew

Are you taking into account ground vibrations and wind force? A number: The highest skyscraper in Madrid is 200 m high (not too high by the way), but its top part oscillates about 1 m in a normal wind day. Definitely I think that building such an "space elevator" is "engineerably" impossible.
 
Yes, the tower would be much more stable if you built it out to geostationary orbit. Just keep in mind, though, that the top of the tower would have to be built beyond GSO to achive this added stability. Whatever portion of the building's weight is above that altitude, that's the portion that will help steady the tower (kind-of the way a string gets steadied when you pull on both ends). Also, this only works if the tower is spot-on the equator.
 
great, thanks.
:biggrin:
Understand this is impossible with today's technology - it's a sub-plot in my book.

The figures I'm thinking are that they were building the tower to 25,000km, found that it would be more unstable than they thought (due to frequency of hurricanes and Tsunami in the projected future), and therefore decided to build it up to 40,000km, to stabilise in the way described.

Does this figure out okay?

Thanks for the equator tip . . . will have to locate it in Africa or something, as I'm planning on most of the Pacific islands having sunk...

cheers,
Andrew
 
If the tower is only to Geosynchronous orbit or lower, then it will collapse. Every part of the cable which is at an orbital period of 1 rotation/day (like the entire elevator would be) and an altitude less than Geo-synch will eventually fall to earth. You need a counterweight past GEO to hold that part up.
 

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