From: g_d_pusch_remove_underscores@xnet.com
Dr John Stockton writes:
> JRS: In article , seen in
> news:sci.space.science, Gordon D. Pusch et.com> posted at Tue, 6 Apr 2004 21:08:29 :
>
>> Your proposal is not _totally_ implausible. The energy required to climb
>> a beanstalk is only a small fraction of the energy required to accelerate
>> a payload into Low Earth Orbit; the fuel and oxygen tankage required
>> would be large, but not prohibitively so.
>
>
> Earth radius is 7 Mm, GSO radius is 42 Mm, so in units of the Earth's
> radius 1 and 6.
>
> Potential energy in an inverse square field is inverse linear, so with
> it being zero at infinity, it is 1/6 at GSO and 1 on the ground,
> difference 5/6.
>
> But the energy required for LEO is half that for escape, so climbing the
> stalk to GSO requires 5/3 of the energy to LEO.
>
> "Centrifugal force" will supply a significant part of that energy (by
> lengthening the day), but not enough to leave only a small fraction.
>
> Much of the fuel and oxygen will need to be lifted, though there is the
> advantage that the exhaust need only carry a little energy other than
> that of height.
The significant difference is that, when climbing a beanstalk, one only has
to supply the change in _energy_, not the change in _momentum_, which is
is instead provided by the lateral force exerted by the beanstalk, which
very efficiently extracts momentum from the angular momentum of the Earth.
By contrast, much of the energy stored in the propellant of a rocket is
uselessly wasted, because it goes into accelerating the _rocket exhaust_,
rather than the _payload_...
-- Gordon D. Pusch
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