Energy savings with space elevator

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Discussion Overview

The discussion revolves around the energy savings associated with using a space elevator to transport payloads to geostationary orbit. Participants explore the formula presented in a paper and the underlying physics of energy requirements for reaching orbit, comparing it to traditional rocket propulsion methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the formula for energy savings provided in the paper, suggesting it may be incorrect.
  • Another participant asserts that reaching orbit necessitates increases in both potential and kinetic energy, which they claim are invariant regardless of the method used (rocket or space elevator).
  • A later reply clarifies that the equation in question represents the percentage savings of energy compared to rocket propulsion, linking it to the use of centrifugal force from Earth's rotation.
  • One participant challenges the notion that escape velocity is necessary for achieving geostationary orbit, arguing that such velocity would prevent the satellite from being stationary.
  • Another participant draws an analogy between the energy savings from a space elevator and using renewable energy sources instead of conventional power sources.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the formula and the fundamental principles of energy requirements for reaching geostationary orbit. There is no consensus on these points, indicating ongoing debate and uncertainty.

Contextual Notes

Some assumptions about energy requirements and orbital mechanics remain unaddressed, and the discussion reflects varying interpretations of the energy savings concept.

bksree
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Hi
I read in a paper that the energy saving in taking a payload to geostaionary orbit with a space elevator is (R/Rg)*(2-R/Rg) where R- radius of earth, Rg - radious of geostaionary orbit.

How is this obtained ?

TIA
 
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bksree said:
Hi
I read in a paper

Please make a complete citation of the paper!

Zz.
 
It's easy enough to calculate, and the formula you give is wrong, but more importantly the premise is wrong. Reaching orbit requires an increase in potential energy and an increase in kinetic energy. These are the same regardless of how you get there, whether you use a rocket ship or a space elevator.
 
Thanks for the replies. The paper is : P.K Aravind, 'The Physics of the space elevator', Am. J. Phys., 75(2), Feb 2007.
The eqn actually gives the percentage saving of energy w.r.t that required if rocket prpoulsion is used. I think it is related to the energy required to accelerate to escape velocity with rocket propulsion wheras the space elevator uses the centrifugal force ofthe rotating Earth to accelerate the satellite.

TIA
 
You don't need escape velocity to put a satellite in geostationary orbit. If it has this much velocity it won't be neither geo- nor stationary.

The paper may be about the energy "saved" from the point of view of not using fuel but rather some other way to get the energy required.
Similar to the energy "saved" by connecting an appliance to a solar cell or wind generator rather than the wall plug.
 

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