dietz%usc-cse%USC-ECL%SRI-NIC@sri-unix.UUCP (11/03/83)
The space elevator will be a pure tension structure (so it won't topple). In a constant gravity field the cable would taper exponentially, thick end at the top. However, since the cable will be rotating and because gravity is inverse square the taper isn't so fast near the top. There was a diagram plus some mathematics in an issue of DESTINIES (a now defunct SF book-a-zine). Tensile strength/weight ratios required are beyond current materials (but graphite is very close). The biggest problem with the elevator is, again, orbital debris. Back of the envelope calculations tell be that the mean time between debris impacts will be on the order of hours. An elevator from L1 or L2 to the moon or in mars-synchronous orbit is feasible with current materials (but you still have to solve the debris problem).