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#91
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Towards routine, reusable space launch.
On Wednesday, June 20, 2018 at 8:21:31 PM UTC-4, Alain Fournier wrote:
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. Sooner or later an aircraft will blunder into the area and hit the cable and break it. Is there any way to prevent that? |
#92
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Towards routine, reusable space launch.
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#94
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Towards routine, reusable space launch.
On Thursday, June 21, 2018 at 6:26:58 AM UTC-4, Jeff Findley wrote:
It's kind of terrifying what the thing does. And where it breaks has a huge impact on what it does as it falls. http://gassend.net/spaceelevator/breaks/index.html Plus having to rebuild the whole thing, that would be expensive. |
#95
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Towards routine, reusable space launch.
"Jeff Findley" wrote in message
... In article , says... On Wednesday, June 20, 2018 at 8:21:31 PM UTC-4, Alain Fournier wrote: 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. Sooner or later an aircraft will blunder into the area and hit the cable and break it. Is there any way to prevent that? Also orbital debris. ISS maneuvers to avoid large bits. Not sure how you could do that with the space elevator. Jeff The answer I've seen is you intentionally cause a "wave" to occur in the cable to that the peak of the wave moves the cable out of the way of the debris. I find that... questionable.... I love the idea of a space elevator, but I sure do question the details. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#96
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Towards routine, reusable space launch.
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 |
#97
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Towards routine, reusable space launch.
On 6/21/2018 7:57 PM, 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 Alains idea to make a "space elevator" out of al dente spehetti is an amazing idea. Who bring the meat ball ? |
#98
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Towards routine, reusable space launch.
On 6/20/2018 7:07 PM, Fred J. McCall wrote:
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.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. On you? Yes, I certainly did. You're far too adamantly stupid. no worries! I'll do it for you, since you are new to math and materials. |
#99
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Towards routine, reusable space launch.
Sergio wrote on Thu, 21 Jun 2018 23:24:53 -0500:
On 6/20/2018 7:07 PM, Fred J. McCall wrote: 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. no worries! I'll do it for you, since you are new to math and materials. Gee, let's not tell the university. They might ask for my degree in mathematics back. And certainly let's not tell Texas Instruments or Raytheon, as they might want some of that salary back that they paid me for being an engineer all those years. -- "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 |
#100
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Towards routine, reusable space launch.
In article ,
says... 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 ? Because it's flexible, duh. Imagine that you took 10 meters of fishing line with a weight at the bottom then cut it in the middle. Would it stay straight as it fell? Try it! I majored in dynamics and control at Purdue. This stuff is *not* intuitive, but it can be simulated and verified experimentally. 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 ? Why would it break up in space as it falls? To put it simply, it breaks when the stress at a point exceeds the material strength. Again, the dynamics of the falling tether is not intuitive. That's why we perform simulations like this. Why did the Tacoma Narrows Bridge break up due to *wind*? https://en.wikipedia.org/wiki/Tacoma...s_Bridge_(1940) https://www.youtube.com/watch?v=j-zczJXSxnw Again, this stuff isn't intuitive. The bridge designers, at the time, simply didn't take into account the dynamics of the bridge in a strong wind. 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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