|
|
Thread Tools | Display Modes |
#121
|
|||
|
|||
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. |
#123
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Reusable Launch Vehicles - When? | [email protected] | Policy | 4 | November 30th 09 11:10 PM |
AFRL To Develop Reusable Launch Capabilities | [email protected] | Policy | 1 | December 21st 07 04:03 AM |
Is anything on this new launch system reusable? | Ron Bauer | Policy | 10 | September 22nd 05 08:25 PM |
Suborbital Reusable Launch Vehicles and Emerging Markets | Neil Halelamien | Policy | 5 | February 24th 05 05:18 AM |
Space becomes routine. | Ian Stirling | Policy | 24 | July 5th 04 11:21 PM |