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#71
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Towards routine, reusable space launch.
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 ? how many miles would the top swing back and forth ? How much sideways force is pushed on it by a 20 mph wind ? how much does one guy wire weigh ? (assume 20,000 km elevator height) how much does one copper cable weigh if moving 200 amps ? 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 ? Alain Fournier |
#72
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Towards routine, reusable space launch.
At least three observatories with seven telescopes in active use will
be surprised to learn [that making a 6.5-m primary mirror is impossible] That should have been five observatories and ten telescopes. I forgot some. I won't swear I'm not still forgetting others. In article , Fred J. McCall writes: You can do things with earthbound scopes that you cannot do with something you're going to shoot into space. How does that apply to the current discussion? Launching a 6.5-m mirror monolithic should in principle be easier than having the same size mirror deploy to the required precision. The problem is making it fit into the payload fairing. I wouldn't be surprised if there are "black" programs with the same difficulty. Nope. They use a mirror roughly the size of Hubble's. The ones we know about used mirrors that size. Anyone who actually knows the current situation -- I don't -- wouldn't be allowed to say. Remember, they're looking at something relatively close as such things go. 6.5-m mirrors would have advantages over smaller ones. (I don't see what distance has to do with anything.) I've seen hints that some have been built and deployed, but that may be salemanship. Companies vying for the JWST contract would have had an incentive to drop such hints whether true or not. The point is that a balloon does NOT replace a 'first stage'. We agree on that. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#73
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Towards routine, reusable space launch.
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 many miles would the top swing back and forth ? Why do you care? How much sideways force is pushed on it by a 20 mph wind ? Why do you care? 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. 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.) 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. Alain Fournier |
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Towards routine, reusable space launch.
JF Mezei wrote on Mon, 18 Jun 2018
14:27:11 -0400: On 2018-06-18 03:05, Fred J. McCall wrote: You also claimed that what they built and tested wasn't representative of what they intend to build as a final article and fly, which is just a stupid assertion. I did no such thing. I claimed that it was not necessarily what the final would be because during testing, they discovery problems that require changes. Of course you did. You said that they built their test tank out of existing resins using existing processes but that would not be what they built the 'real' tank using. Just because they only told you about two tests doesn't mean they didn't do any others. And just because of that, you can't claim they performed those tests succesfully either. My point is that you can't claim "mission accomplished" on those tanks just because of 2 tests that SpaceX chose to make public. They've made more than two of them public. Your perpetual underinformed state is your personal problem. -- "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 |
#75
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Towards routine, reusable space launch.
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#76
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Towards routine, reusable space launch.
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. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Dryden |
#77
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Towards routine, reusable space launch.
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. nothing will go into orbit as the accelleration vector is stright down, gravity. 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 ?? How much sideways force is pushed on it by a 20 mph wind ? Why do you care? ....to evaporate your imagination with facts. 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# ? [there is no cable that will support itself 70,000 km, darling) 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) 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, Alain Fournier |
#78
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Towards routine, reusable space launch.
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. 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. 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'. 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? 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. [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. 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. 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. -- "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 |
#79
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Towards routine, reusable space launch.
Sergio schrieb:
On 6/16/2018 8:54 AM, Alain Fournier wrote: 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. Well, I did like the space elevator in "Red Mars". Spoiler: When it fell, Mars finally acquired a visible equator... it came down as some sort of continuous meteor. |
#80
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Towards routine, reusable space launch.
In article , Sergio wrote:
how about a Space Slingshot ? Do you mean a rotating skyhook? Some of those ideas are ... intriguing. And have much less stringent requirements on materials. -- Mike Van Pelt | "I don't advise it unless you're nuts." mvp at calweb.com | -- Ray Wilkinson, after riding out Hurricane KE6BVH | Ike on Surfside Beach in Galveston |
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