XPost: sci.space.policy, sci.physics   
   From: fjmccall@gmail.com   
      
   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   
      
   --- SoupGate-Win32 v1.05   
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