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Towards routine, reusable space launch.



 
 
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  #121  
Old June 26th 18, 10:14 PM posted to sci.space.policy
Scott M. Kozel[_2_]
external usenet poster
 
Posts: 160
Default Towards routine, reusable space launch.

On Tuesday, June 26, 2018 at 7:29:31 AM UTC-4, Jeff Findley wrote:
In article ,
says...

So virtual thing made of unobtainium and which has elements without any
mass.


I see you didn't comprehend what you're reading. Try again. Note in
the above quote that the "heavy tether of circular cross-section" is
modeled "as a set of massive points". These points, that have mass, are
"connected by massless viscoelastic bars"


Since the material is still theoretical, it would be hard to estimate
the tether cross-section.

What might it be? 1/16"? 1/8"? 1/4"? Or thinner or thicker?



The mass is modeled as points. This is a common simplification in an
analysis such as this.

hyperbolic. For lower part numerical simulations show
that the aerodynamic force changes significantly the tether
behavior. After the tether enters the atmosphere, most of
it slows down and falls smoothly;



The simulation showed the upper sections of the tether where it broke
off near geostationary altitude. It showed it snaking, floating in space.

Meaningful atmosphere is roughly 20m in altitude, or if you want to
include stratosphere, 50km in altitude.

So, in the cable falling because it broke at geostationary orbit
scenario, you have some lateral forces in the first 50km and eventually,
so air resistance to the structure falling sideways or diagonally with
perhaps a terminal velocity.

But it will fall, and it will pull down on all the rest of the 39,000 of
cable. But that cable will first and foremost be affected by orbital
mechanics since it is way above atmosphere. And pulling down an object
that has forwrad motion causes it to accelerate that forward motion.

So in space, that should be the primary factor to affect cable
behaviour. And since the cable is going down, any motion imparted in the
first 50km of cable will be 1-dampened by the anchor point (or drag on
ground) 2- have very little chance of "snaking up" the whole length of
the 39,000km of the cable.

Once the cable has mostly fallen to the ground and all you got left is a
few hundred km of cable left, then yeah, atmopshere will play a large
role because it affects a large part of the cable.


I see that it's pointless trying to give you an actual acedemic paper
describing an actual analysis performed by actual qualified researchers.
You clearly don't understand what was presented and go right back to the
handwavium. Ugh.

Hopefully other readers will get more out of the link I posted.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.


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  #123  
Old August 20th 18, 11:47 PM posted to sci.space.policy
[email protected]
external usenet poster
 
Posts: 5
Default Towards routine, reusable space launch.

On Thursday, June 21, 2018 at 5:57:15 PM UTC-7, Alain Fournier wrote:
On Jun/21/2018 at 1:35 PM, JF Mezei wrote :
On 2018-06-21 06:26, Jeff Findley wrote:

http://gassend.net/spaceelevator/breaks/index.html



Looked at "breaks at counter weight" (longest section of cable that
falls down with only counter weight going away)

Why would the falling cable become "loose" and snake ?

Since the top most portions, when being pulled down, would accelerate
more that portions below it, wouldn't the cable remain raughts and thus
no slack that allows snaking ?


Because of elasticity. I don't know how they chose a value for the
elasticity of the cable. It is very difficult to know how elastic a
cable will be if you don't know how the cable will be built. But I would
expect that a space elevator cable would become loose after snapping.

Why would it break up in space as it falls?


Take a strand of spaghetti (not fresh spaghetti, the dried variety you
will find in a grocery store) hold one end in your left hand the other
end in your right hand and bend until it snaps. You should do this over
a counter with a wall behind. After the spaghetti snaps you will have
one piece in your right hand, another piece in your left hand. But look,
you will see there is a third piece that went flying into the wall and
is now on the counter. Take another strand try again, you will get the
same result. If you repeat several times you might get a different
result once or twice, but almost every time it will break in three pieces.

When you bend a strand of spaghetti until is snaps, it will snap into
two pieces, then the whiplash will break it once more. A space elevator
cable would have much a more complex whiplash than a strand of
spaghetti. So breaking into multiple pieces isn't impossible.

Once again that will depend on the physical properties of the cable. If
instead of breaking spaghetti you tried doing the same with pieces of
wood, you wouldn't get three pieces. But if you don't use fresh pasta
and you didn't get three pieces while breaking your spaghetti, remind me
to bring my own pasta if I ever go dining at your place.

If you did multiple spaghetti breaking tests, let me propose that you
pick up all the pieces. Boil them until al dente. Strain them. Do not
rinse in cold water. Then either mix them with pesto verde or put
St-Jacques sauce over it. Delicious. If you need a recipe for the pesto
verde or the St-Jacques sauce you can send me a private e-mail.


Alain Fournier


I tried snapping spaghetti, 3 times, and 3 times in a row I ended up with 2 pieces. Maybe my spaghetti was too stale.

OB space elevators. If there's any asteroid mining going on, you could have climbers go up and down, put heavier cargo in them going down (from mining), and use the weight differential to power the up-climbers. No lasers required.
  #124  
Old August 21st 18, 12:37 AM posted to sci.space.policy
Alain Fournier[_3_]
external usenet poster
 
Posts: 356
Default Towards routine, reusable space launch.

On Aug/20/2018 at 6:47 PM, wrote :
On Thursday, June 21, 2018 at 5:57:15 PM UTC-7, Alain Fournier wrote:
On Jun/21/2018 at 1:35 PM, JF Mezei wrote :
On 2018-06-21 06:26, Jeff Findley wrote:

http://gassend.net/spaceelevator/breaks/index.html


Looked at "breaks at counter weight" (longest section of cable that
falls down with only counter weight going away)

Why would the falling cable become "loose" and snake ?

Since the top most portions, when being pulled down, would accelerate
more that portions below it, wouldn't the cable remain raughts and thus
no slack that allows snaking ?


Because of elasticity. I don't know how they chose a value for the
elasticity of the cable. It is very difficult to know how elastic a
cable will be if you don't know how the cable will be built. But I would
expect that a space elevator cable would become loose after snapping.

Why would it break up in space as it falls?


Take a strand of spaghetti (not fresh spaghetti, the dried variety you
will find in a grocery store) hold one end in your left hand the other
end in your right hand and bend until it snaps. You should do this over
a counter with a wall behind. After the spaghetti snaps you will have
one piece in your right hand, another piece in your left hand. But look,
you will see there is a third piece that went flying into the wall and
is now on the counter. Take another strand try again, you will get the
same result. If you repeat several times you might get a different
result once or twice, but almost every time it will break in three pieces.

When you bend a strand of spaghetti until is snaps, it will snap into
two pieces, then the whiplash will break it once more. A space elevator
cable would have much a more complex whiplash than a strand of
spaghetti. So breaking into multiple pieces isn't impossible.

Once again that will depend on the physical properties of the cable. If
instead of breaking spaghetti you tried doing the same with pieces of
wood, you wouldn't get three pieces. But if you don't use fresh pasta
and you didn't get three pieces while breaking your spaghetti, remind me
to bring my own pasta if I ever go dining at your place.

If you did multiple spaghetti breaking tests, let me propose that you
pick up all the pieces. Boil them until al dente. Strain them. Do not
rinse in cold water. Then either mix them with pesto verde or put
St-Jacques sauce over it. Delicious. If you need a recipe for the pesto
verde or the St-Jacques sauce you can send me a private e-mail.


Alain Fournier


I tried snapping spaghetti, 3 times, and 3 times in a row I ended up with 2 pieces. Maybe my spaghetti was too stale.


If it's dried spaghetti and you where holding the strands by the ends I
am very surprised by your result. I have never ended up with 2 pieces.
Maybe you don't use the same brand as I do. If that's the difference,
you should try another brand, maybe you will start loving spaghetti.

OB space elevators. If there's any asteroid mining going on, you could have climbers go up and down, put heavier cargo in them going down (from mining), and use the weight differential to power the up-climbers. No lasers required.


And how will you transfer the energy from the climbers going down
(descenders) to the climbers going up. This is not a regular elevator
with a cable moving around a pulley. The cable has to be tapered, so if
it is mobile it is difficult to keep the thickest part at geosynchronous
altitude and the thinnest part near the ground. It isn't totally
impossible to do if you have multiple sections with pulleys between each
section. But it makes a very difficult engineering project much more
difficult.


Alain Fournier
  #125  
Old August 21st 18, 07:23 PM posted to sci.space.policy
Bob Jenkins
external usenet poster
 
Posts: 5
Default Towards routine, reusable space launch.

On Monday, August 20, 2018 at 4:37:29 PM UTC-7, Alain Fournier wrote:
On Aug/20/2018 at 6:47 PM, wrote :

OB space elevators. If there's any asteroid mining going on, you could have climbers go up and down, put heavier cargo in them going down (from mining), and use the weight differential to power the up-climbers. No lasers required.


And how will you transfer the energy from the climbers going down
(descenders) to the climbers going up. This is not a regular elevator
with a cable moving around a pulley. The cable has to be tapered, so if
it is mobile it is difficult to keep the thickest part at geosynchronous
altitude and the thinnest part near the ground. It isn't totally
impossible to do if you have multiple sections with pulleys between each
section. But it makes a very difficult engineering project much more
difficult.


Alain Fournier


Two cables, one up one down, with occasional spacers in between, and C-shaped cars centered on the cables but missing the spacers. Down-cars use regenerative braking, generating electricity, which you run along the spacers, to power up-cars like a rail gun. Neither side should actually touch the cable. I haven't tried to measure how much heavier down-cars have to be than up-cars for this to work out. Cars are reloaded at either end then transferred to the other cable.

Another thing, once you're out of the atmosphere (or the thick part of the atmosphere), up-cars should accelerate to as fast as feasible (and down-cars, the reverse). That way cars are much further spaced above the first 5km or so, so don't add as much total weight, so you can afford to have more of them, plus you reach geosynchronous orbit in hours instead of weeks.
  #126  
Old August 22nd 18, 06:43 PM posted to sci.space.policy
Bob Jenkins
external usenet poster
 
Posts: 5
Default Towards routine, reusable space launch.

On Tuesday, August 21, 2018 at 11:23:36 AM UTC-7, Bob Jenkins wrote:
On Monday, August 20, 2018 at 4:37:29 PM UTC-7, Alain Fournier wrote:
On Aug/20/2018 at 6:47 PM, wrote :

OB space elevators. If there's any asteroid mining going on, you could have climbers go up and down, put heavier cargo in them going down (from mining), and use the weight differential to power the up-climbers. No lasers required.


And how will you transfer the energy from the climbers going down
(descenders) to the climbers going up. This is not a regular elevator
with a cable moving around a pulley. The cable has to be tapered, so if
it is mobile it is difficult to keep the thickest part at geosynchronous
altitude and the thinnest part near the ground. It isn't totally
impossible to do if you have multiple sections with pulleys between each
section. But it makes a very difficult engineering project much more
difficult.


Alain Fournier


Two cables, one up one down, with occasional spacers in between, and C-shaped cars centered on the cables but missing the spacers. Down-cars use regenerative braking, generating electricity, which you run along the spacers, to power up-cars like a rail gun. Neither side should actually touch the cable. I haven't tried to measure how much heavier down-cars have to be than up-cars for this to work out. Cars are reloaded at either end then transferred to the other cable.

Another thing, once you're out of the atmosphere (or the thick part of the atmosphere), up-cars should accelerate to as fast as feasible (and down-cars, the reverse). That way cars are much further spaced above the first 5km or so, so don't add as much total weight, so you can afford to have more of them, plus you reach geosynchronous orbit in hours instead of weeks.


Although I know electromagnetic propulsion can do that, I don't know what weight it would have to add to the car and the cable.
 




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