Re: Value of a tower into space?

Wasn't it Mad Bad Rabbit who wrote:
>Mike Williams <nospam@xxxxxxxxxxxxxxxxxx> wrote:
>
>> At 120 miles high, the orbit speed required is about 17000mph. You
>> either need a centrifuge and satellite that are ridiculously strong to
>> withstand the g forces, or you need a centrifuge with a ridiculously
>> long arm.
>>
>> Even with method 1, the size of the rocket required to accelerate
>> the satellite to 17000mph isn't going to be much cheaper than one
>> that would launch from the ground, climb through the atmosphere and
>> accelerate the payload to 17000mph. Your x dollars per pound would
>> have to be very low to attract any customers.
>
>Since the top is above the atmosphere, what about method 2a:
>Payloads are flung a short distance upwards by a catapult and
>grabbed by the orbital tether that swoops by every N minutes?

You still have the problem that any mechanism that accelerates the
payload from 0 to 17000mph in a few seconds is going to apply
ridiculously large g loads to it. So the payload has to be able to stand
ridiculously high g loads, and the tether (particularly the bit that
attaches to the satellite) has to cope with extreme forces.

I think the only way to get reasonable forces is to have a ridiculously
long tether so that its centre of gravity is near geostationary orbit,
but then it would have to be made of materials that Wildepad was trying
to avoid in the first place.

Suppose the tether is whizzing past at Low Earth Orbit speed, and we
want to limit the stress to 5 g, then it takes about 2.5 minutes to
accelerate the payload to that speed. During those 2.5 minutes, the
accelerating payload moves 360 miles (s=ut+0.5at^2), and the CoG of the
tether moves 720 miles (s=vt).

--
Mike Williams
Gentleman of Leisure
.

Relevant Pages

  • Different approach to tethers? (was Re: Low cost access to space via tethers)
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    (sci.space.policy)
  • Jonathans Space Report No. 530
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  • Re: Hypersonic skyhook
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    (rec.arts.sf.science)