dietz@SLB-DOLL.CSNET (Paul Dietz) (01/07/86)
Using the data on Kevlar and on Phobos's orbit, I got the following numbers: a 3000 km long kevlar cable stretched out from Phobos will accelerate payloads to ~ 1 km/sec after escape from Mars's gravity well. Even with a safety factor of 2, the cable will have a taper of less than 2:1. A cable 7500 km long will accelerate payloads to 3.1 km/sec after escape, and will have a taper of 25:1 with a safety factor of two. Injection into a Hohmann orbit from Mars to Earth would require 2.63 km/sec velocity change if Mars and Earth were in circular orbits and in the correct positions (they aren't, but I'll ignore that). However, such an injection would require a velocity change nearly parallel to the ecliptic; Phobos's orbit is inclined 25 degrees. The direction of the orbit can be modified by throwing the payload into a Mars intersecting orbit and using the subsequent encounter to fix the orbit's inclination.