Re: Space Elevator (was Space Shuttle

Andrew Swallow wrote:
> Christophe Bachmann wrote:
>
>> Matt Ion wrote:
>>
>>> Andrew Swallow wrote:
>>>
>>>> Christophe Bachmann wrote:
>>>>
>>>>
>>>>> Andrew Swallow wrote:
>>>>>
>>>>>
>>>>>> Andre Lieven wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Josh Hill (usereplyto@xxxxxxxxx) writes:
>>>>>>
>>>>>>
>>>>>> [snip]
>>>>>>
>>>>>>
>>>>>>
>>>>>>>> Hello? All but the space elevator, which can't be built until
>>>>>>>> the structural materials are perfected, are already in the
>>>>>>>> budget,
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> No, they've been *proposed* by the President; But the Pres
>>>>>>> doesn't write and pass the Budget...
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> and the space elevator appears to be economically feasible.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> " appears to be " is the operative phrase. VentureStar's fuel
>>>>>>> tanks appeared " feasable " at one time, too.
>>>>>>
>>>>>>
>>>>>> Can we practice the space elevator by running a capsule
>>>>>> from a wire up the side of a mountain? Capsule and wire
>>>>>> are not allowed to touch the mountain except at the top
>>>>>> and bottom. Use a mountain with a (near) cliff face.
>>>>>>
>>>>>> Andrew Swallow
>>>>>
>>>>>
>>>>>
>>>>> I'm sorry to say that even the highest montain is only 9 km high,
>>>>> a whole lot away from the 36000 km of geosynchrone orbit, and we
>>>>> have a whole lot of experience building cable cars strong enough
>>>>> to do that. I'd rather think that lab tests stressing the
>>>>> material enough would be better, but I could be wrong.
>>>>>
>>>>
>>>> True. Things happen in real life that do not happen in
>>>> lab tests.
>>>>
>>>> Many cable car routes are longer than 9 km but they have
>>>> supporting towers. The trick is to do it without
>>>> supporting towers in the middle.
>>>
>>> Plus, in most cable-car designs, the cars aren't self-powered: the
>>> car clamps onto the cable, which is then pulled (in a loop) from
>>> motors at BOTH end.
>>>
>>>
>>
>> I totally agree but that is not my point, my point is that the one
>> big problem we have for the space elevator is the strength of the
>> cable, and we know how to make a cable that has a 9 km strength, but
>> AFAIK we don't yet have a cable with a 36000 km strength but carbon
>> nanotubes are the way to go, and to stress a cable for 36000 km you
>> need a lab test. See :
>> http://www.liftport.com/files/521Edwards.pdf
>>
>> for the state of the art in space elevator research.
>>
>>
> Major tests need performing in the laboratory and I would not
> get into one of the climbers until the cable had passed
> these tests.
>
> The cable is not the only thing that needs testing. The
> climbers and power transmitters also need testing. A 9 km
> test track with wind, rain, cloud and lightning will
> do nicely.
>
Very true, and that will give us valuable insights, even if we will
never have 9 km of tracks because the mountainsides don't spring
straight from the sea. But rain clouds and lightning will be problemns
only for the first ten kilometers of the elevator, the 35990 km beyond
will have to cope with such things as variable gravity, power
transmission, micrometeorits, the radiation belts, and so on that can't
be adequately simulaed on earth.

> The side of a sky scraper may also be needed to help
> debug the cable assembly process. We have never make
> anything large in space so there are bound to be unknown
> problems. We can send engineers up a sky scraper to
> investigate the problems. This is hard when in space.
>
> The nearest thing I can think of to rolling out the ribbon
> cable from space is when a metal cable was strung between
> two satellites to generate electricity. The winch jammed.
>
The winch jammed because of microgravity, and that can't be adequately
tested anywhere on earth, and will need an orbital platform to debug.

> Lets get all (most) of those problems fixed on earth and
> using aircraft before we try in space. Fortunately many
> of these things can be done in parallel.

I agree with you that we should debug everything we can in parallel and
that full scale earth testing will be needed, as outlined in the
http://www.elevator2010.org/site/ elevator 2010 competition, and their
successors but a lot of things can't be tested on earth and will need
orbital testbeds.

--
Salutations, Greetings
Guiraud Belissen, Château du Ciel, Drachenwald
Christophe Bachmann, Rennes, France



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