XPost: sci.space.policy, sci.physics   
   From: invalid@invalid.com   
      
   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.   
      
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