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Question on the space elevator



 
 
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  #31  
Old April 9th 04, 10:23 PM
Andromeda et Julie
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Default Question on the space elevator

to me to even consider the energy stored in the
pressurisation.

My point was simply that the material that made the beanstalk feasible
compared to conventional rocketry would help make rocketry more competitive
against a beanstalk.


certainly, very resistant and light material may lead to much
simplified design , for tanks and engines (a hose that would not breaak
whatever the way you plug it..etc..), and maybe (??) pressurized tanks
would get rid of the pumps

in this way , a rocket may be assembled within a few weeks and ready to
launch with reduced infrastructure ..

then the cost of the fuel may become a concern ... which is not today,
compared to the overall costs of launches

building an elevator would anyway requires some conventionnal launches
..


we may never get this magic material for the elevator , though it seems
now not completely impossible

I read somewhere that the resistance achieved and tested for carbon
nanotube/epoxy composite was half way to the required strentgh .. with
hopes to do better

the price of the material may now be over ¤/$ 1000 per gram ...

IF someone finds a way to produce nanotubes by the ton , then many
things may have to be reconsidered !!

that may be tomorrow , that may be never ...

I am very amused by the perspective of building bridges unwinding
something that looks like scoth tape ;-)

more than this, some people seems no to believe (or make others believe
they believe) in the space elevator

example:

http://www.liftport.com/
(they even have a date for it : Countdown to Lift: April 12, 2018 ;-)

or
http://www.highliftsystems.com/



(or maybe this one ;-) : http://www.spaceelevator.ca/ when everything
else fails ;-)

--
Julie
"please save Yuri"
http://membres.lycos.fr/andromedanews

  #32  
Old April 9th 04, 11:35 PM
Steve Willner
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"David M. Palmer" wrote in message ...
... think of
the energy wasted as you drop the ash from your fuel over the side and
let it just fall back to Earth. (If you could use it as a
counterweight to pull you up, then you'd be better off.)


Are counterweights crazy? Obviously so if the "rope" has to run the
whole length of the beanstalk, but what if it runs only 100 km or so?
Attach a car at each end, one goes up while the other goes down. When
the cars are at the extreme positions, they change over to a different
pair of ropes. (Or the cargo moves to another car on a higher or
lower rope.)

This arrangement means there have to be two cars every 100 km or 500
on the beanstalk at all times, and they have to run on a schedule or
all stop and wait for delays to be sorted out. That's a nuisance, but
this scheme might reduce power requirements quite a lot. Are there
any show stoppers? I've just guessed at a likely length of the rope;
would a different guess have been better?
  #33  
Old April 10th 04, 02:06 AM
Gordon D. Pusch
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nafod40 writes:

Gordon D. Pusch wrote:

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.


Does the beanstalk have to be straight up and down?


Pretty much so. (It is under an =ENORMOUS= amount of tension!)


If canted so as to lag the Earth's rotation (at least during a climb
maneuver) how would that make a difference?


It wouldn't. Since gravitation is a conservative force, the amount of work
required to climb to a given distance from the Earth against the force of
gravity is independent of the path along which one climbs.

Also, please be careful not to confuse "velocity" with "force" --- the two
are entirely different concepts, with no direct relationship to each other.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'


  #34  
Old June 27th 04, 10:51 AM
Simon Peacock
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Why not use the power naturally developed in the cable? ... see the NASA
teather experiment no details :-)


"Makhno" wrote in message
...
The current answer to the last question isn't magnets but .. lasers.
Free Electron lasers beam power to the climber, which converts the
energy into mechanical energy (wheels or treads). IIRC, a FEL has
been designed that can do the job.


There's a lot of traffic in this thread about powering the climber. Why
can't it simply have a diesel/gasoline engine with its own oxygen supply?
Or run electrical cables up the elevator to power an electric motor?

Why make things more complicated than they need to be?




  #35  
Old June 29th 04, 02:04 AM
Paul F. Dietz
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Simon Peacock wrote:

Why not use the power naturally developed in the cable?


Because the cable isn't moving w.r.t. the magnetosphere.

Paul
  #36  
Old June 29th 04, 02:20 PM
nafod40
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Default Question on the space elevator

"Makhno" wrote

The current answer to the last question isn't magnets but .. lasers.
Free Electron lasers beam power to the climber, which converts the
energy into mechanical energy (wheels or treads). IIRC, a FEL has
been designed that can do the job.


If the elevator continues to stretch out way beyond the balance point,
at a certain length if we cut the anchors on Earth, it would float out
away from Earth, wouldn't it? If the center of mass is at escape
velocity for it's orbit altitude, the whole thing will float away.

So we can use that capability by just tossing off mass at a much greater
altitude (thereby slowing the Earth's rotation) and using that to lift
the elevator. via a long cable loop. We could toss off bags of water, or
something else that would disperse and cause no harm.

  #37  
Old July 3rd 04, 03:00 AM
Simon Peacock
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Default Question on the space elevator

but isn't the magnetosphere constantly moving.. and the cable stationary ?


"Paul F. Dietz" wrote in message
...
Simon Peacock wrote:

Why not use the power naturally developed in the cable?


Because the cable isn't moving w.r.t. the magnetosphere.

Paul



  #38  
Old July 4th 04, 02:10 PM
Andromeda et Julie
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Default Question on the space elevator

Simon Peacock a écrit :
but isn't the magnetosphere constantly moving.. and the cable stationary ?


I dont think it s moving this fast as compared to much fasters orbit
(LEO)



Why not use the power naturally developed in the cable?


the cable , ribbon, would have to be very thin to exist so it would not
be able to carry much power without dammage (?)

the (I think) only (now) conceivable way to build it is to produce a
composite (epoxy ..)with short carbon nanotubes .. it's not expected to
be conductive

--
Julie
"please save Yuri"
http://membres.lycos.fr/andromedanews

 




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