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Towards routine, reusable space launch.



 
 
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  #81  
Old June 19th 18, 09:58 PM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Sergio
external usenet poster
 
Posts: 37
Default Towards routine, reusable space launch.

On 6/19/2018 2:45 AM, Fred J. McCall wrote:
Sergio wrote on Mon, 18 Jun 2018 22:17:21 -0500:

On 6/18/2018 8:06 PM, Alain Fournier wrote:
On Jun/18/2018 at 2:45 PM, Sergio wrote :
On 6/16/2018 8:54 AM, Alain Fournier wrote:
On Jun/15/2018 at 11:34 PM, Fred J. McCall wrote :
JF Mezei wrote on Fri, 15 Jun 2018
22:13:01 -0400:

On 2018-06-15 19:21, Alain Fournier wrote:

Yes. But I think I am a little less optimistic than you about it
becoming practical in the future. If we have fantastic materials
in the
future, maybe an elevator will become more practical,


Apart from lifting geostationary satellites to just below orbit and
then
let them use their own thrusters to position to their assigned
slot/longitude, what other use would a space elevator have ?


You go above the GEO point on the cable and get flung on
interplanetary trajectories.

Yes!

You would also likely put at least one cable above GEO rotating in a
plane perpendicular to the main cable. So you can give an extra push for
interplanetary trajectories and to fine tune in which direction you
depart for said trajectories.

You can also jump off at an altitude of about 15000 km (that figure is
from the top of my head, it might be more or might be less). From there
after a few passes of aero-braking you can reach LEO with very small
thrusters.

For polar orbits, you use the rotating cable above GEO mentioned above.
But instead of using it for extra push you get off while it is
subtracting some speed but not quite in the direction of rotation of the
cable. So you subtract some speed in the direction of rotation of the
cable and give some speed in the north-south axis. You then use
aero-braking again to lower apogee, and a small thruster to raise
perigee. Note however that using the elevator to reach polar orbits in
this way isn't obvious. You would want a long and fast rotating cable
and you would want it far above GEO, it might not be practical to do so.

Building an elevator, with current technologies, is outrageously
expensive. But if you have one, it can be very useful.


we don't have one, and never will.Â* It is a joke among Engineers.

What would is the monthly insurance payment for it?Â* if it fell over ?

You put the cable on an east coast. You also put a system to cut the
cable at something like 10000 km high. If the cable breaks below that
10000 km the upper part doesn't fall it goes up, the bottom part falls
in the ocean, where it isn't likely to cause damage. If the cable breaks
higher than 10000 km, you cut it at 10000 km, the bottom 10000 km falls
once again in the ocean. The two other parts won't fall to the ground,
the lower part will probably be in an elliptical orbit, the higher part
might be in an escape trajectory. So the damage from a cable breaking
doesn't have to be high. It might be a little difficult to explain that
to an insurance company, but if you can pay for the cable, you should be
able to cover the damages.


how much does 10,000 of cable weigh? 100,000 #
the center of gravity is directly over the support, so you have 100,000#
of steel cable crashing onto it.


Nope. The Earth spins, you know. And STEEL? That's cute.


earth spin is red herring, do the math.
what else are you going to use besides steel ?
NOTHING can support its own weight of 10,000 km of it.

go ahead, NAME what you propose to use.



nothing will go into orbit as the accelleration vector is stright down,
gravity.


Well, no. When whole, the cable is under tension, not compression.
Remove weight from the bottom or break the tether point and it goes UP
above the break, not down.


no, gravity wins over whatever transitory events.




how many miles would the top swing back and forth ?

Why do you care?


I asking to see if you know what you are talking about. 20,000 km is
12,427 miles, if you support the tower it will swing at least 2 degrees
sin 2 degrees = 0.035 times 12427 = *434 miles*

does the tip swinging wider than most states bother you ??


You're not smart enough to be asking questions. It's not a 'tower'.


what do you propose ?



How much sideways force is pushed on it by a 20 mph wind ?

Why do you care?


...to evaporate your imagination with facts.


That would be refreshing. When are you going to start?


what are you proposing ?




how much does one guy wire weigh ? (assume 20,000 km elevator height)

Why would you put a guy wire? Don't assume 20,000 km elevator height,
assume 70,000 km, you want the top of the cable to pull up the bottom of
the cable, so you have to go beyond GEO height.


so what is the weight of 70,000 km of cable to support 500# ?


That rather depends on what it's made of.


you wont name anything, because it is all too heavy.

got anything ?



[there is no cable that will support itself 70,000 km, darling)


There is no cable that will support its own weight like that YET. You
really need to STFU until you educate yourself.


and there never will be. do the math. check the materials, imaginarium
won't work either.




how much does one copper cable weigh if moving 200 amps ?

Don't put a copper cable. Send energy to the climber using some kind of
beamed energy. (A laser on the ground, maybe another one in
geosynchronous orbit, and photocells on the climber to convert back to
electricity. Or something of that kind.)


Use McGinn's patented plasma's and water vapor it up. What happens
when you use a 1000 watt laser to shoot power to it ? the beam heats up
the air and defocuses the beam and the power splinters out, the power
does not get there.

there is no know laser that can meet the dispersion requirements either
(google dispersion laser)


Hogwash.


afraid to google for it ? why doen't the army shoot down missles with
lasers ? -- dispersion and defocusing --





What voltage is needed at the ground to feed the copper wires ?Â* assume
500 V AC needed at the top.

How much does the tower weigh counting only the copper wires, main
cable, and guy wires ?

The copper wires and guy wires are nonexistent and therefore weigh
nothing. As for the main cable, it weighs way too much. That is why I
said in the message to which you are replying that "Building an
elevator, with current technologies, is outrageously expensive." I don't
think we will ever have one.


it is joke bate by Engineers,


You wouldn't know an engineer if you tripped over one.


and you have no real facts for your "space elevator".





  #82  
Old June 19th 18, 10:38 PM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Towards routine, reusable space launch.

Sergio wrote on Tue, 19 Jun 2018 15:58:10 -0500:

On 6/19/2018 2:45 AM, Fred J. McCall wrote:
Sergio wrote on Mon, 18 Jun 2018 22:17:21 -0500:

On 6/18/2018 8:06 PM, Alain Fournier wrote:
On Jun/18/2018 at 2:45 PM, Sergio wrote :
On 6/16/2018 8:54 AM, Alain Fournier wrote:
On Jun/15/2018 at 11:34 PM, Fred J. McCall wrote :
JF Mezei wrote on Fri, 15 Jun 2018
22:13:01 -0400:

On 2018-06-15 19:21, Alain Fournier wrote:

Yes. But I think I am a little less optimistic than you about it
becoming practical in the future. If we have fantastic materials
in the
future, maybe an elevator will become more practical,


Apart from lifting geostationary satellites to just below orbit and
then
let them use their own thrusters to position to their assigned
slot/longitude, what other use would a space elevator have ?


You go above the GEO point on the cable and get flung on
interplanetary trajectories.

Yes!

You would also likely put at least one cable above GEO rotating in a
plane perpendicular to the main cable. So you can give an extra push for
interplanetary trajectories and to fine tune in which direction you
depart for said trajectories.

You can also jump off at an altitude of about 15000 km (that figure is
from the top of my head, it might be more or might be less). From there
after a few passes of aero-braking you can reach LEO with very small
thrusters.

For polar orbits, you use the rotating cable above GEO mentioned above.
But instead of using it for extra push you get off while it is
subtracting some speed but not quite in the direction of rotation of the
cable. So you subtract some speed in the direction of rotation of the
cable and give some speed in the north-south axis. You then use
aero-braking again to lower apogee, and a small thruster to raise
perigee. Note however that using the elevator to reach polar orbits in
this way isn't obvious. You would want a long and fast rotating cable
and you would want it far above GEO, it might not be practical to do so.

Building an elevator, with current technologies, is outrageously
expensive. But if you have one, it can be very useful.


we don't have one, and never will.* It is a joke among Engineers.

What would is the monthly insurance payment for it?* if it fell over ?

You put the cable on an east coast. You also put a system to cut the
cable at something like 10000 km high. If the cable breaks below that
10000 km the upper part doesn't fall it goes up, the bottom part falls
in the ocean, where it isn't likely to cause damage. If the cable breaks
higher than 10000 km, you cut it at 10000 km, the bottom 10000 km falls
once again in the ocean. The two other parts won't fall to the ground,
the lower part will probably be in an elliptical orbit, the higher part
might be in an escape trajectory. So the damage from a cable breaking
doesn't have to be high. It might be a little difficult to explain that
to an insurance company, but if you can pay for the cable, you should be
able to cover the damages.


how much does 10,000 of cable weigh? 100,000 #
the center of gravity is directly over the support, so you have 100,000#
of steel cable crashing onto it.


Nope. The Earth spins, you know. And STEEL? That's cute.


earth spin is red herring, do the math.


You do the math.


what else are you going to use besides steel ?


Almost anything.


NOTHING can support its own weight of 10,000 km of it.


False. You really need to do some research.


go ahead, NAME what you propose to use.


Carbon nanotubes.




nothing will go into orbit as the accelleration vector is stright down,
gravity.


Well, no. When whole, the cable is under tension, not compression.
Remove weight from the bottom or break the tether point and it goes UP
above the break, not down.


no, gravity wins over whatever transitory events.


Don't look now, but I think you just claimed that space satellites and
the Moon are impossible.





how many miles would the top swing back and forth ?

Why do you care?


I asking to see if you know what you are talking about. 20,000 km is
12,427 miles, if you support the tower it will swing at least 2 degrees
sin 2 degrees = 0.035 times 12427 = *434 miles*

does the tip swinging wider than most states bother you ??


You're not smart enough to be asking questions. It's not a 'tower'.


what do you propose ?


And in that question you demonstrate just how clueless you are.




How much sideways force is pushed on it by a 20 mph wind ?

Why do you care?

...to evaporate your imagination with facts.


That would be refreshing. When are you going to start?


what are you proposing ?


I'm proposing you start making sense (but I'm not holding my breath).





how much does one guy wire weigh ? (assume 20,000 km elevator height)

Why would you put a guy wire? Don't assume 20,000 km elevator height,
assume 70,000 km, you want the top of the cable to pull up the bottom of
the cable, so you have to go beyond GEO height.

so what is the weight of 70,000 km of cable to support 500# ?


That rather depends on what it's made of.


you wont name anything, because it is all too heavy.

got anything ?


Jesus, go learn something. Right now you just sound abysmally stupid.




[there is no cable that will support itself 70,000 km, darling)


There is no cable that will support its own weight like that YET. You
really need to STFU until you educate yourself.


and there never will be. do the math. check the materials, imaginarium
won't work either.


I'm sorry you're clueless.





how much does one copper cable weigh if moving 200 amps ?

Don't put a copper cable. Send energy to the climber using some kind of
beamed energy. (A laser on the ground, maybe another one in
geosynchronous orbit, and photocells on the climber to convert back to
electricity. Or something of that kind.)

Use McGinn's patented plasma's and water vapor it up. What happens
when you use a 1000 watt laser to shoot power to it ? the beam heats up
the air and defocuses the beam and the power splinters out, the power
does not get there.

there is no know laser that can meet the dispersion requirements either
(google dispersion laser)


Hogwash.


afraid to google for it ? why doen't the army shoot down missles with
lasers ? -- dispersion and defocusing --


Uh, you haven't been paying attention, have you?




What voltage is needed at the ground to feed the copper wires ?* assume
500 V AC needed at the top.

How much does the tower weigh counting only the copper wires, main
cable, and guy wires ?

The copper wires and guy wires are nonexistent and therefore weigh
nothing. As for the main cable, it weighs way too much. That is why I
said in the message to which you are replying that "Building an
elevator, with current technologies, is outrageously expensive." I don't
think we will ever have one.

it is joke bate by Engineers,


You wouldn't know an engineer if you tripped over one.


and you have no real facts for your "space elevator".


Go educate yourself and get back to us.


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson
  #83  
Old June 20th 18, 12:45 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default Towards routine, reusable space launch.

On Jun/18/2018 at 11:00 PM, Fred J. McCall wrote :
Alain Fournier wrote on Mon, 18 Jun 2018
21:06:46 -0400:


You put the cable on an east coast.


Uh, do you mean west coast? If the thing falls isn't it going to lay
out along the direction of spin, which means it falls to the west.


Uh, no I meant east coast.

At least one of the two of us is making a very silly mistake here. So
I'm going to say some very obvious things, I don't know where the very
silly mistake is but it should be among these obvious things.

The Sun rises in the morning towards the east and sets in the evening in
towards the west. But it isn't really the Sun that is making an east to
west journey, the perceived motion of the Sun is caused by the rotation
of Earth in the opposite direction. So the direction of Earth's spin is
eastward. If a space elevator is anchored to Earth near the equator, it
will necessarily spin with Earth, the direction of spin of the elevator
is also eastward. So yes as you said the elevator is going to lay out
along the direction of spin, but that is eastward not westward. If the
elevator cable breaks, the bottom part will start falling while spinning
eastward, at first spinning at 1 revolution per day, just like Earth. So
at first in the rotating reference frame of the ground it is just going
down. When you tighten up something that is rotating, like a figure
skater pulling in their arms, that increases the rotation rate. So the
cable will be going eastward faster than Earth.


Alain Fournier
  #85  
Old June 20th 18, 04:35 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Greg Goss
external usenet poster
 
Posts: 169
Default Towards routine, reusable space launch.

Sergio wrote:



Nope. The Earth spins, you know. And STEEL? That's cute.


earth spin is red herring, do the math.
what else are you going to use besides steel ?
NOTHING can support its own weight of 10,000 km of it.

go ahead, NAME what you propose to use.


You're not hanging a simple cable. It tapers. The taper amount
depends on the material. So they talk about boron filaments or
buckeytubes. Still not there, but they make steel look "cute".


I asking to see if you know what you are talking about. 20,000 km is
12,427 miles, if you support the tower it will swing at least 2 degrees
sin 2 degrees = 0.035 times 12427 = *434 miles*

does the tip swinging wider than most states bother you ??


You're not smart enough to be asking questions. It's not a 'tower'.


what do you propose ?


"If you support the tower" shows that you don't even understand the
proposal. Nobody here is saying that any currently known material is
practical for this, but you're clearly not even in the ballpark.

--
We are geeks. Resistance is voltage over current.
  #86  
Old June 20th 18, 09:42 PM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Sergio
external usenet poster
 
Posts: 37
Default Towards routine, reusable space launch.

On 6/19/2018 4:38 PM, Fred J. McCall wrote:
Sergio wrote on Tue, 19 Jun 2018 15:58:10 -0500:

On 6/19/2018 2:45 AM, Fred J. McCall wrote:
Sergio wrote on Mon, 18 Jun 2018 22:17:21 -0500:

On 6/18/2018 8:06 PM, Alain Fournier wrote:
On Jun/18/2018 at 2:45 PM, Sergio wrote :
On 6/16/2018 8:54 AM, Alain Fournier wrote:
On Jun/15/2018 at 11:34 PM, Fred J. McCall wrote :
JF Mezei wrote on Fri, 15 Jun 2018
22:13:01 -0400:

On 2018-06-15 19:21, Alain Fournier wrote:

Yes. But I think I am a little less optimistic than you about it
becoming practical in the future. If we have fantastic materials
in the
future, maybe an elevator will become more practical,


Apart from lifting geostationary satellites to just below orbit and
then
let them use their own thrusters to position to their assigned
slot/longitude, what other use would a space elevator have ?


You go above the GEO point on the cable and get flung on
interplanetary trajectories.

Yes!

You would also likely put at least one cable above GEO rotating in a
plane perpendicular to the main cable. So you can give an extra push for
interplanetary trajectories and to fine tune in which direction you
depart for said trajectories.

You can also jump off at an altitude of about 15000 km (that figure is
from the top of my head, it might be more or might be less). From there
after a few passes of aero-braking you can reach LEO with very small
thrusters.

For polar orbits, you use the rotating cable above GEO mentioned above.
But instead of using it for extra push you get off while it is
subtracting some speed but not quite in the direction of rotation of the
cable. So you subtract some speed in the direction of rotation of the
cable and give some speed in the north-south axis. You then use
aero-braking again to lower apogee, and a small thruster to raise
perigee. Note however that using the elevator to reach polar orbits in
this way isn't obvious. You would want a long and fast rotating cable
and you would want it far above GEO, it might not be practical to do so.

Building an elevator, with current technologies, is outrageously
expensive. But if you have one, it can be very useful.


we don't have one, and never will.Â* It is a joke among Engineers.

What would is the monthly insurance payment for it?Â* if it fell over ?

You put the cable on an east coast. You also put a system to cut the
cable at something like 10000 km high. If the cable breaks below that
10000 km the upper part doesn't fall it goes up, the bottom part falls
in the ocean, where it isn't likely to cause damage. If the cable breaks
higher than 10000 km, you cut it at 10000 km, the bottom 10000 km falls
once again in the ocean. The two other parts won't fall to the ground,
the lower part will probably be in an elliptical orbit, the higher part
might be in an escape trajectory. So the damage from a cable breaking
doesn't have to be high. It might be a little difficult to explain that
to an insurance company, but if you can pay for the cable, you should be
able to cover the damages.


how much does 10,000 of cable weigh? 100,000 #
the center of gravity is directly over the support, so you have 100,000#
of steel cable crashing onto it.


Nope. The Earth spins, you know. And STEEL? That's cute.


earth spin is red herring, do the math.


You do the math.


you gave up.



what else are you going to use besides steel ?


Almost anything.


like what ? anything real ?



NOTHING can support its own weight of 10,000 km of it.


False. You really need to do some research.


name it, else you are lying.



go ahead, NAME what you propose to use.


Carbon nanotubes.


they are held in a matrix of epoxy glue. your 10,000 km of glue wont
support itself.





nothing will go into orbit as the accelleration vector is stright down,
gravity.


Well, no. When whole, the cable is under tension, not compression.
Remove weight from the bottom or break the tether point and it goes UP
above the break, not down.


no, gravity wins over whatever transitory events.


Don't look now, but I think you just claimed that space satellites and
the Moon are impossible.


those are your words, now try to refocus on the topic, If your space
elevator is a cable in orbit, atmospheric drag ruins it.







how many miles would the top swing back and forth ?

Why do you care?


I asking to see if you know what you are talking about. 20,000 km is
12,427 miles, if you support the tower it will swing at least 2 degrees
sin 2 degrees = 0.035 times 12427 = *434 miles*

does the tip swinging wider than most states bother you ??


You're not smart enough to be asking questions. It's not a 'tower'.


what do you propose ?


And in that question you demonstrate just how clueless you are.


again, no info from you. Because you have no idea what you are typing
about.





How much sideways force is pushed on it by a 20 mph wind ?

Why do you care?

...to evaporate your imagination with facts.


That would be refreshing. When are you going to start?


what are you proposing ?


I'm proposing you start making sense (but I'm not holding my breath).


so you propose nothing, and state nothing, and know nothing.







how much does one guy wire weigh ? (assume 20,000 km elevator height)

Why would you put a guy wire? Don't assume 20,000 km elevator height,
assume 70,000 km, you want the top of the cable to pull up the bottom of
the cable, so you have to go beyond GEO height.

so what is the weight of 70,000 km of cable to support 500# ?


That rather depends on what it's made of.


you wont name anything, because it is all too heavy.

got anything ?


Jesus, go learn something. Right now you just sound abysmally stupid.


no reason to bring God into this, he cant help you.





[there is no cable that will support itself 70,000 km, darling)


There is no cable that will support its own weight like that YET. You
really need to STFU until you educate yourself.


and there never will be. do the math. check the materials, imaginarium
won't work either.


I'm sorry you're clueless.


and you still have nothing, as it does not exist.






how much does one copper cable weigh if moving 200 amps ?

Don't put a copper cable. Send energy to the climber using some kind of
beamed energy. (A laser on the ground, maybe another one in
geosynchronous orbit, and photocells on the climber to convert back to
electricity. Or something of that kind.)

Use McGinn's patented plasma's and water vapor it up. What happens
when you use a 1000 watt laser to shoot power to it ? the beam heats up
the air and defocuses the beam and the power splinters out, the power
does not get there.

there is no know laser that can meet the dispersion requirements either
(google dispersion laser)


Hogwash.


afraid to google for it ? why doen't the army shoot down missles with
lasers ? -- dispersion and defocusing --


Uh, you haven't been paying attention, have you?


Just testing your depth of knowledge in the subject and it is 1/32 inch
deep. just another troll on the internet.






What voltage is needed at the ground to feed the copper wires ?Â* assume
500 V AC needed at the top.

How much does the tower weigh counting only the copper wires, main
cable, and guy wires ?

The copper wires and guy wires are nonexistent and therefore weigh
nothing. As for the main cable, it weighs way too much. That is why I
said in the message to which you are replying that "Building an
elevator, with current technologies, is outrageously expensive." I don't
think we will ever have one.

it is joke bate by Engineers,


You wouldn't know an engineer if you tripped over one.


and you have no real facts for your "space elevator".


Go educate yourself and get back to us.


no need, you have demonstrated you know nothing in this thread.

you know nothing.

  #87  
Old June 21st 18, 01:07 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Towards routine, reusable space launch.

Sergio wrote on Wed, 20 Jun 2018 15:42:56 -0500:

On 6/19/2018 4:38 PM, Fred J. McCall wrote:
Sergio wrote on Tue, 19 Jun 2018 15:58:10 -0500:

On 6/19/2018 2:45 AM, Fred J. McCall wrote:
Sergio wrote on Mon, 18 Jun 2018 22:17:21 -0500:

On 6/18/2018 8:06 PM, Alain Fournier wrote:
On Jun/18/2018 at 2:45 PM, Sergio wrote :
On 6/16/2018 8:54 AM, Alain Fournier wrote:
On Jun/15/2018 at 11:34 PM, Fred J. McCall wrote :
JF Mezei wrote on Fri, 15 Jun 2018
22:13:01 -0400:

On 2018-06-15 19:21, Alain Fournier wrote:

Yes. But I think I am a little less optimistic than you about it
becoming practical in the future. If we have fantastic materials
in the
future, maybe an elevator will become more practical,


Apart from lifting geostationary satellites to just below orbit and
then
let them use their own thrusters to position to their assigned
slot/longitude, what other use would a space elevator have ?


You go above the GEO point on the cable and get flung on
interplanetary trajectories.

Yes!

You would also likely put at least one cable above GEO rotating in a
plane perpendicular to the main cable. So you can give an extra push for
interplanetary trajectories and to fine tune in which direction you
depart for said trajectories.

You can also jump off at an altitude of about 15000 km (that figure is
from the top of my head, it might be more or might be less). From there
after a few passes of aero-braking you can reach LEO with very small
thrusters.

For polar orbits, you use the rotating cable above GEO mentioned above.
But instead of using it for extra push you get off while it is
subtracting some speed but not quite in the direction of rotation of the
cable. So you subtract some speed in the direction of rotation of the
cable and give some speed in the north-south axis. You then use
aero-braking again to lower apogee, and a small thruster to raise
perigee. Note however that using the elevator to reach polar orbits in
this way isn't obvious. You would want a long and fast rotating cable
and you would want it far above GEO, it might not be practical to do so.

Building an elevator, with current technologies, is outrageously
expensive. But if you have one, it can be very useful.


we don't have one, and never will.* It is a joke among Engineers.

What would is the monthly insurance payment for it?* if it fell over ?

You put the cable on an east coast. You also put a system to cut the
cable at something like 10000 km high. If the cable breaks below that
10000 km the upper part doesn't fall it goes up, the bottom part falls
in the ocean, where it isn't likely to cause damage. If the cable breaks
higher than 10000 km, you cut it at 10000 km, the bottom 10000 km falls
once again in the ocean. The two other parts won't fall to the ground,
the lower part will probably be in an elliptical orbit, the higher part
might be in an escape trajectory. So the damage from a cable breaking
doesn't have to be high. It might be a little difficult to explain that
to an insurance company, but if you can pay for the cable, you should be
able to cover the damages.


how much does 10,000 of cable weigh? 100,000 #
the center of gravity is directly over the support, so you have 100,000#
of steel cable crashing onto it.


Nope. The Earth spins, you know. And STEEL? That's cute.


earth spin is red herring, do the math.


You do the math.


you gave up.


On you? Yes, I certainly did. You're far too adamantly stupid.


--
"Ordinarily he is insane. But he has lucid moments when he is
only stupid."
-- Heinrich Heine
  #88  
Old June 21st 18, 01:13 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Towards routine, reusable space launch.

Alain Fournier wrote on Tue, 19 Jun 2018
19:45:53 -0400:

On Jun/18/2018 at 11:00 PM, Fred J. McCall wrote :
Alain Fournier wrote on Mon, 18 Jun 2018
21:06:46 -0400:


You put the cable on an east coast.


Uh, do you mean west coast? If the thing falls isn't it going to lay
out along the direction of spin, which means it falls to the west.


Uh, no I meant east coast.

At least one of the two of us is making a very silly mistake here.


That would be me, although the 'obvious things' you mentioned were no
help at all.

For some reason known only to my tiny mind it was thinking of the
tether structure as having zero tangential velocity. That meant that
as it fell the Earth would rotate out from under it, leading to a fall
to anti-spinward.

Of course, that's absolutely wrong, since the further up the cable you
go the higher the tangential velocity has to be for the thing to stay
radially 'still'. That means as it falls the upper portions of the
cable will 'outrun' the surface of the Earth and it will fall to
spinward (to the East), which is what you said.

DOH!


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #89  
Old June 21st 18, 01:21 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default Towards routine, reusable space launch.

On Jun/19/2018 at 10:12 PM, JF Mezei wrote :
On 2018-06-19 19:45, Alain Fournier wrote:


at first in the rotating reference frame of the ground it is just going
down. When you tighten up something that is rotating, like a figure
skater pulling in their arms, that increases the rotation rate. So the
cable will be going eastward faster than Earth.


Would such a system be planned with enough "counterweight" above
geostationary orbit to pull the cable up enough such that its weight at
altitude 0 would be 0 ?


A little more counterweight than that. You want the cable to be taut.

Does this mean tensile stress would max out at geostationary altitude
where a force equal to the total weight of the cable below it would be felt?


The tensile stress has to max out at geostationary altitude. Everything
higher pulls up, everything lower pulls down. The stress at
geostationary altitude is a little more than the "weight" of the cable
below because you want the cable to be taut. That is if you use a
definition of "weight" that takes into account the centrifugal force,
that is mass multiplied by local gravitational force minus r
(pi/953882)^2, where r is the distance to the centre of Earth, the
pi/953882 part is Earth's rotation (sidereal) rate in radian/s. If you
compute the "weight" above geostationary altitude (it will be negative,
the centrifugal force being stronger than gravity) you will get the
maximal tensile stress (this time you don't have to add a little because
you want the cable to be taut, the small difference between the forces
above and below and above geostationary altitude is what keeps the cable
taut).

In just a case, would the most likely break point be at geostationalry
orbit, allowing nearly 36,000km of cable to fall down?


No. The cable is tapered, so it is stronger at geostationary altitude.
The most likely reason for the cable to break is if it is hit by
something. The cable being very big at geostationary altitude (and most
likely multi-stranded) it is probably more likely to survive a hit there.

Considering the top most portion of the falling cable was going at
9369km/h and that it would further accelerate as it drops altitude,
woudln't there a great big force to pull the whole cable eastward,
causing portions already on ground to drag?

I assume that as more and more cable drags on ground, the drag force
would eventually exceed cable strength and cable would snap, allowing
the still" flyinG" cab;le to move forward some and stary layiong cable
on ground and drag it until that force again exceed the cable strength
(lather, rinse repeat) ?


Would the portions of cable at near geostationary orbit accelerate
enough as it falls that upon reaching entry interface, would burn up?


That depends on the physical properties of the cable. We don't know what
are the physical properties of a cable made of an unknown material. But,
as I said in another post, I think they would put some kind of mechanism
to cut the cable in case of an emergency. If you do so only a relatively
small portion of the cable would fall to the ground.

If you don't cut the cable and most of it comes down, as I said the
outcome depends on the physical properties of the cable, but burning up
in the atmosphere seems to me as a reasonable outcome, especially if it
is multi-stranded. As for dragging and snapping, maybe it would snap at
or near the attach point to the anchor (where the cable is thinnest) but
after that, I wouldn't think so. It must be a very strong cable. But
once again this is just speculation on my part, I don't know how would
behave a cable of unknown material.


Alain Fournier
  #90  
Old June 21st 18, 01:34 AM posted to sci.space.policy,sci.physics,rec.arts.sf.science
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default Towards routine, reusable space launch.

On Jun/20/2018 Ã* 8:13 PM, Fred J. McCall wrote :
Alain Fournier wrote on Tue, 19 Jun 2018
19:45:53 -0400:

On Jun/18/2018 at 11:00 PM, Fred J. McCall wrote :
Alain Fournier wrote on Mon, 18 Jun 2018
21:06:46 -0400:


You put the cable on an east coast.


Uh, do you mean west coast? If the thing falls isn't it going to lay
out along the direction of spin, which means it falls to the west.


Uh, no I meant east coast.

At least one of the two of us is making a very silly mistake here.


That would be me, although the 'obvious things' you mentioned were no
help at all.

For some reason known only to my tiny mind it was thinking of the
tether structure as having zero tangential velocity. That meant that
as it fell the Earth would rotate out from under it, leading to a fall
to anti-spinward.

Of course, that's absolutely wrong, since the further up the cable you
go the higher the tangential velocity has to be for the thing to stay
radially 'still'. That means as it falls the upper portions of the
cable will 'outrun' the surface of the Earth and it will fall to
spinward (to the East), which is what you said.

DOH!


Ouf! That is an error, but it I can understand making such a mistake.
From what you wrote it seemed to me that your reasoning was based on
Earth spinning westward. I couldn't understand how you could possibly
had made such a mistake. So I knew something was fishy. I was hoping I
hadn't forgotten something obvious.


Alain Fournier
 




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