If I recall correctly, the time to GEO on a space
elevator would be about eight days. Of course,
multiple payloads coule be making the trip at the same
time, at different altitudes, as long as the total
downward force doesn't exceed the tension.
elevator is the material. We basically need a way to
form nanotubes into rings that can be linked like
chainmail; that way no single nanotube would be very
long. Certainly none of them would need to be
macroscopic, although nanotubes have been made at
centimeter-scale lengths already. The trick is to get
a whole bunch of small nanotubes to curl around on
themselves and self-assemble into a chainmail
arrangment, which could then be made arbitrarily
large. Think of it as a 3D chainmail ribbon 1mm
thick, 1m wide, and O[10^8m] long, with each link
probably measuring no more than a micrometer in
diameter.
Such an arrangement would moot Pugno's objections, as
there wouldn't be a requirement for perfect nanotubes
tens of thousands of kilometers long, only perfect
nanotube rings on the order of 10^-5m in
circumference.
Ed
--- Xenophile wrote:
> About how long would a SE trip take? Discovery
> Networks is running
> this ad that talks about months of elevator music,
> but is that real?
>
> How about starting with a wimpy SE, that can only
> haul up a little
> payload, and using that to haul up little bit of
> tether to make it a
> little bit stronger? Do that enough times, and you
> have a beefy SE,
> but only one rocket launch. Aries V (or even
> Shuttle, maybe) could do it.
>
http://en.wikipedia.org/wiki/Space_elevator#Brad_Edwards.27_proposal
--- In spacesettlers, Ed Minchau wrote:
> would be about eight days.
That's no good for tourism. Should work for many types of cargo.
--- In spacesettlers@yahoogroups.com, "Xenophile"
>
> --- In spacesettlers, Ed Minchau wrote:
>
> > If I recall correctly, the time to GEO on a space elevator
> > would be about eight days.
>
> That's no good for tourism. Should work for many types of cargo.
>
This is a little off point in regard to space elevators, but it
has to do with the Discovery show about the Orion CEV and the
proposed trip to Mars. In that show they depicted the Orion
spacecraft detaching from the booster stage and, by means of a
tether, rotating about a common center of "gravity" with it.
Assuming a tether of approximately a mile in length (1600
meters+), and assuming current technology (no exotic yet-to-be-
developed materials), and assuming the cable components could be put
into orbit by multiple heavy lift rocket launches, is there a
practical limit to how much tension ("weight' or mass) a fabricated
cable of this length could safely sustain 1G of pseudogravity for two
modules?
In this context I'm thinking of the type of cables fabricated on-
site for suspension bridges like the Golden Gate Bridge. I'm also
thinking of the upper practical limit for the size (mass) of the
first space hotels/space construction work camps. I think for safety
there would need to be two cables (each capable of sustaining the
full load) in case there would be a failure in one of the cables.
Also, would such a (metal) cable generate unwanted (or usable)
electrical potential orbiting in Earth's magnetic field?
Anyone have any thoughts on this?
Chris
> From: Chris Smyth
> Assuming a tether of approximately a mile in length (1600
> meters+)
though to hang ocean liners off the end you would need a rather thick cable.
The long version (along with lots of fun mathematics) can be found here:
http://en.wikipedia.org/wiki/Tensile_strength
> Also, would such a (metal) cable generate unwanted (or usable)
> electrical potential orbiting in Earth's magnetic field?
It would generate an alternating current if rotation was parallel to the
axis of the Earth's magnetosphere. On a gut fielding, I don't think one mile
would generate enough power to be worth collecting, dangerous, or difficult
to insulate from, or heating efects.
John
--- In spacesettlers@yahoogroups.com, "ANTIcarrot"
wrote:
>
> > From: Chris Smyth
> > Assuming a tether of approximately a mile in length (1600
> > meters+)
>
> No, at one mile there is no limit to the weight that could be
supported; though to hang ocean liners off the end you would need a
rather thick cable.
>
> The long version (along with lots of fun mathematics) can be found
here: http://en.wikipedia.org/wiki/Tensile_strength
>
Thanks for the link - it has a lot of interesting and useful
information for a layman like myself. As a follow-up to my post, I'm
wondering: is a "tethered space hotel" a likely first generation
configuration for a commercial presence in space?
The reason I ask this is that astronauts returning from long stays
on the ISS tend to suffer from loss of muscle and bone density which
they mitigate by a rather rigorous regimen of exercise. I don't
see "civilians" - particularly tourists - being receptive to these
health effects (even if only temporary) or to the daily exercise
required to counteract them.
If a "tethered" configuration is used, would it require a central
hub for docking? Also, would it require a sort of pressurized
"elevator" to "lower" passengers and supplies along the cable to the
habitats at each end? If so, assuming redundant cables to each
habitat, would one pair of "elevators' running on one cable have
to "ascend" to the hub while another set of "elevators"
simutaneously "descended" on the other cable to each of the habitats
in order for the whole complex to maintain rotational stability?
Finally, is this whole idea of a "tethered" space hotel too
complicated? Would it be easier to just build an "I" shaped structure
with a central hub as a first generation space hotel?
Anyone have any thoughts on this?
Chris
--- In spacesettlers@yahoogroups.com, "Chris Smyth" wrote:
>
> --- In spacesettlers@yahoogroups.com, "ANTIcarrot"
> wrote:
> >
> > > From: Chris Smyth
> > > Assuming a tether of approximately a mile in length (1600
> > > meters+)
> >
> > No, at one mile there is no limit to the weight that could be
> supported; though to hang ocean liners off the end you would need a
> rather thick cable.
> >
> > The long version (along with lots of fun mathematics) can be found
> here: http://en.wikipedia.org/wiki/Tensile_strength
> >
> Hi John,
>
> Thanks for the link - it has a lot of interesting and useful
> information for a layman like myself. As a follow-up to my post, I'm
> wondering: is a "tethered space hotel" a likely first generation
> configuration for a commercial presence in space?
>
> The reason I ask this is that astronauts returning from long stays
> on the ISS tend to suffer from loss of muscle and bone density which
> they mitigate by a rather rigorous regimen of exercise. I don't
> see "civilians" - particularly tourists - being receptive to these
> health effects (even if only temporary) or to the daily exercise
> required to counteract them.
>
a rotating barbell arrangement where the 'gravity' comes from
centriptal acceleration or are you describing a long tether where
gravity is based on the fact that one end is not moving at orbital
speed. (For the purest out there, I realize that this is the same
effect with vastly different radius.)
If it is the first case, all the dynamics of a space habitats apply.
If the later it would be necessary to develop a model for the dymanics
before being able to discuss this rationally.
> If a "tethered" configuration is used, would it require a central
> hub for docking? Also, would it require a sort of pressurized
> "elevator" to "lower" passengers and supplies along the cable to the
> habitats at each end? If so, assuming redundant cables to each
> habitat, would one pair of "elevators' running on one cable have
> to "ascend" to the hub while another set of "elevators"
> simutaneously "descended" on the other cable to each of the habitats
> in order for the whole complex to maintain rotational stability?
Any configuration would require a 'central hub' for docking. The space
ship needs to dock with the space structure with zero delta V.
Rotational velocity can most easiest be matched where the structure is
moving the least.
In the case of the elevator, the answer depends on the mass of the
elevator. If the elevator mass is a substanial fraction of the mass of
the entire structure, then moving it down will destablize the
structure. If the elevator mass is a small percentage of the the
total, it will produce a small wobble, which could be cancelled by
having active mass that can be moved a small amount to cancel the wobble.
>
> Finally, is this whole idea of a "tethered" space hotel too
> complicated? Would it be easier to just build an "I" shaped structure
> with a central hub as a first generation space hotel?
>
> Anyone have any thoughts on this?
>
I think the I shaped structure is the way to go.
Bill
--- In spacesettlers@yahoogroups.com, "Bill" wrote:
>
> I think the I shaped structure is the way to go.
>
> Bill
>
In answer to your question I was thinking of a rotating barbell type
structure. My thinking was that the components (hub, habitats, cables,
and hub-to-habitat "elevators") could be individually launched by heavy
lift rockets and assembled in orbit. I was wondering if this dual-
habitat rotating around a central hub via cables arrangement might be
more do-able as a first (or second) generation space hotel than trying
to construct a mile-long cylinder to connect the two habitats.
Chris
Bypassing rotating structures for the moment...
completely zero G, for reasons of cost, complexity, and because zero G is
THE selling point of the entire holiday. :P
Chances are Bigalow will be the first to have a hotel up there:
http://www.bigelowaerospace.com/out_there/complex_modules_size_up.php
Though I am sure follow on designs will have rotating sections. If nothing
else it makes the plumbing so much simplier.
John
I agree, the first space hotels will likely be zero
gee. The stays are not going to be very long, and any
detrimental effects will be minimal. Once one starts
talking about long-term stays in orbit though, six
months or more, then there will likely need to be some
sort of artificial gravity (i.e. spinning). I could
see the Bigelow modules being used as construction
shacks for much larger structures though, such as a
space island:
Ed
--- ANTIcarrot wrote:
> Bypassing rotating structures for the moment...
>
> With reguards to a *first* generation space hotel,
> it's likely to be
> completely zero G, for reasons of cost, complexity,
> and because zero G is
> THE selling point of the entire holiday. :P
>
> Chances are Bigalow will be the first to have a
> hotel up there:
>
http://www.bigelowaerospace.com/out_there/complex_modules_size_up.php
Zero G might be the selling point, but if they aren't comfortable they won't be coming back..
Bypassing rotating structures for the moment...
With reguards to a *first* generation space hotel, it's likely to be
completely zero G, for reasons of cost, complexity, and because zero G is
THE selling point of the entire holiday. :P
Chances are Bigalow will be the first to have a hotel up there:
http://www.bigelowaerospace.com/out_there/complex_modules_size_up.php
Though I am sure follow on designs will have rotating sections. If nothing
else it makes the plumbing so much simplier.
John