Re: shuttle disaster

[Gary Turner <kk5st@sbcglobal.net>]

Paul E Condon wrote:

>Gary Turner wrote:
>
>>John Hasler wrote:
>>
>>>Pigeon writes:
>>>    
>>>>It would be under tension, because the upper station is outside the
>>>>geosynchronous orbit. So the bit above the break would fly off into
>>>>space, and the lower bit would fall back.
>>>>
>>>The tension would taper from nominally zero at the base to maximum at the
>>>attachment to the counterweight.
>>
>>Actually, maximum tension occurs at the CG, with minimums at the ends.
>>Forces are reversed, maximum at the ends, and minimum (balanced) at the
>>CG.  These are tidal forces.  A single point counter-weight, as opposed
>>to distributed, will cause a discontinuity in the function, but the
>>function holds true on either side of the break.
>>
>Center of gravity (CG) is of doubtful value in thinking about this 
>problem. The object extends over a region in which substantially 
>different gravitational accelerations occur, and is at rest in a 
>reference frame in which there is significant centrifugal force.

More correctly, center of mass.  But the effect is the same.
>
>The rules of the space elevator game, as I understand them, are
>1 a vertical tension member
>2 mass at upper end is at higher altitude than geostationary orbit
>3 mass at lower end is close to the surface of the Earth
>4 the whole thing is stationary with respect to the Earth as a reference 
>frame.
>
>5 Adjust unspecified parameters so that it stays put without very large 
>rockets or other cheats.

This tidal dependent structure is inherently stable.

Some kind of accommodations will likely be needed.  Atmospheric
conditions can exhibit tremendous lateral forces.
>
>These conditions imply that maximum tension is at geosychronous orbit 
>altitude. Below that altitude tension is increasing with altitude. Above 
>that altitude tension is decreasing with increase in altitude.

For an interesting application of these principles, read Larry Niven's
"The Integral Trees".
--
gt                  kk5st@sbcglobal.net
 If someone tells you---
 "I have a sense of humor, but that's not funny." 
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