XPost: sci.space.policy, sci.physics   
   From: fjmccall@gmail.com   
      
   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   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)