Re: LEO tethers


"Alain Fournier" <alain245@xxxxxxxxxxxx> wrote in message
news:yhtAf.22506$xk1.657690@xxxxxxxxxxxxxxxxxxxxxxxx
>
>
> Tater Schuld wrote:
>
>> the problem with tethers (and space elevators) is station keeping. apply
>> newtons laws and explain to me how you gain any advantage. you are
>> applying energy to increase your vehicles position in a gravity well.
>> that energy has to come from somewhere.
>
>
> For space elevators the energy comes from slowing down the rotation of the
> Earth. The energy transfer happens because the elevator is anchored to
> Earth.

In some variants i assume, since one or two anchors i've seen dont use
tension from earth anchorage for nothing but to keep the elevator cable
taught.

so how does this slow the rotational rate of the earth? I can see how it
would shift the center of earths mass, and cause another wobble to the
orbit, but i cannot see how it does not cause the far point from getting
pulled to the earth.

> For tethers you gain by either using very high ISP propulsion to
> raise the tether. You can use ion drives to raise the tether's orbit at
> a very slow pace. It is also possible to transfer energy from incoming
> traffic. You can use the tether to lower cargo or passengers, which
> will raise the tether (and reduce the heat shield requirement).
>
so in other words, there is no benefit to using a tether then, unless you
can get your propulsion power directly from the sun


.

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